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Sinha BK, Bortner CD, Jarmusch AK, Tokar EJ, Murphy C, Wu X, Winter H, Cannon RE. Ferroptosis-Mediated Cell Death Induced by NCX4040, The Non-Steroidal Nitric Oxide Donor, in Human Colorectal Cancer Cells: Implications in Therapy. Cells 2023; 12:1626. [PMID: 37371096 DOI: 10.3390/cells12121626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Revised: 06/02/2023] [Accepted: 06/08/2023] [Indexed: 06/29/2023] Open
Abstract
Our recent studies show that the treatment of human ovarian tumor cells with NCX4040 results in significant depletions of cellular glutathione, the formation of reactive oxygen/nitrogen species and cell death. NCX4040 is also cytotoxic to several human colorectal cancer (CRC) cells in vitro and in vivo. Here, we examined the ferroptosis-dependent mechanism(s) of cytotoxicity of NCX4040 in HT-29 and K-RAS mutant HCT 116 colon cell lines. Ferroptosis is characterized by the accumulation of reactive oxygen species (ROS) within the cell, leading to an iron-dependent oxidative stress-mediated cell death. However, its relevance in the mechanism of NCX4040 cytotoxicity in CRCs is not known. We found that NCX4040 generates ROS in CRC cells without any depletion of cellular GSH. Combinations of NCX4040 with erastin (ER) or RSL3 (RAS-selective lethal 3), known inducers of ferroptosis, enhanced CRC death. In contrast, ferrostatin-1, an inhibitor of ferroptosis, significantly inhibited NCX4040-induced cell death. Treatment of CRC cells with NCX4040 resulted in the induction of lipid peroxidation in a dose- and time-dependent manner. NCX4040 treatment induced several genes related to ferroptosis (e.g., CHAC1, GPX4 and NOX4) in both cell lines. Metabolomic studies also indicated significant increases in both lipid and energy metabolism following the drug treatment in HT-29 and HCT 116 cells. These observations strongly suggest that NCX4040 causes the ferroptosis-mediated cell death of CRC cells. Furthermore, combinations of NCX4040 and ER or RSL3 may contribute significantly to the treatment of CRC, including those that are difficult to treat due to the presence of Ras mutations in the clinic. NCX4040-induced ferroptosis may also be a dynamic form of cell death for the treatment of other cancers.
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Affiliation(s)
- Birandra K Sinha
- Mechanistic Toxicology Branch, Division of Translational Toxicology, National Institute of Environmental Health Sciences, Research Triangle Park, Durham, NC 27709, USA
| | - Carl D Bortner
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, Research Triangle Park, Durham, NC 27709, USA
| | - Alan K Jarmusch
- Immunity, Inflammation, and Disease Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, Durham, NC 27709, USA
| | - Erik J Tokar
- Mechanistic Toxicology Branch, Division of Translational Toxicology, National Institute of Environmental Health Sciences, Research Triangle Park, Durham, NC 27709, USA
| | - Carri Murphy
- Mechanistic Toxicology Branch, Division of Translational Toxicology, National Institute of Environmental Health Sciences, Research Triangle Park, Durham, NC 27709, USA
| | - Xian Wu
- Mechanistic Toxicology Branch, Division of Translational Toxicology, National Institute of Environmental Health Sciences, Research Triangle Park, Durham, NC 27709, USA
| | - Heather Winter
- Immunity, Inflammation, and Disease Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, Durham, NC 27709, USA
| | - Ronald E Cannon
- Mechanistic Toxicology Branch, Division of Translational Toxicology, National Institute of Environmental Health Sciences, Research Triangle Park, Durham, NC 27709, USA
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Cattley RC, Kromhout H, Sun M, Tokar EJ, Abdallah MAE, Bauer AK, Broadwater KR, Campo L, Corsini E, Houck KA, Ichihara G, Matsumoto M, Morais S, Mráz J, Nomiyama T, Ryan K, Shen H, Toyoda T, Vähäkangas K, Yakubovskaya MG, Yu IJ, DeBono NL, de Conti A, El Ghissassi F, Madia F, Mattock H, Pasqual E, Suonio E, Wedekind R, Benbrahim-Tallaa L, Schubauer-Berigan MK. Carcinogenicity of anthracene, 2-bromopropane, butyl methacrylate, and dimethyl hydrogen phosphite. Lancet Oncol 2023; 24:431-432. [PMID: 36966774 DOI: 10.1016/s1470-2045(23)00141-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/13/2023]
Affiliation(s)
| | - Hans Kromhout
- International Agency for Research on Cancer, Lyon, France
| | - Meng Sun
- International Agency for Research on Cancer, Lyon, France
| | - Erik J Tokar
- International Agency for Research on Cancer, Lyon, France
| | | | - Alison K Bauer
- International Agency for Research on Cancer, Lyon, France
| | | | - Laura Campo
- International Agency for Research on Cancer, Lyon, France
| | | | - Keith A Houck
- International Agency for Research on Cancer, Lyon, France
| | - Gaku Ichihara
- International Agency for Research on Cancer, Lyon, France
| | | | - Simone Morais
- International Agency for Research on Cancer, Lyon, France
| | - Jaroslav Mráz
- International Agency for Research on Cancer, Lyon, France
| | | | - Kristen Ryan
- International Agency for Research on Cancer, Lyon, France
| | - Huizhong Shen
- International Agency for Research on Cancer, Lyon, France
| | - Takeshi Toyoda
- International Agency for Research on Cancer, Lyon, France
| | | | | | - Il Je Yu
- International Agency for Research on Cancer, Lyon, France
| | | | - Aline de Conti
- International Agency for Research on Cancer, Lyon, France
| | | | - Federica Madia
- International Agency for Research on Cancer, Lyon, France
| | - Heidi Mattock
- International Agency for Research on Cancer, Lyon, France
| | - Elisa Pasqual
- International Agency for Research on Cancer, Lyon, France
| | - Eero Suonio
- International Agency for Research on Cancer, Lyon, France
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Wu X, Chen Y, Luz A, Hu G, Tokar EJ. Cardiac Development in the Presence of Cadmium: An in Vitro Study Using Human Embryonic Stem Cells and Cardiac Organoids. Environ Health Perspect 2022; 130:117002. [PMID: 36321828 PMCID: PMC9628677 DOI: 10.1289/ehp11208] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 09/21/2022] [Accepted: 10/03/2022] [Indexed: 05/24/2023]
Abstract
BACKGROUND Exposure to cadmium (Cd) is associated with cardiovascular diseases. Maternal Cd exposure is a significant risk factor for congenital heart disease. However, mechanisms of Cd on developmental cardiotoxicity are not well defined. OBJECTIVES We evaluated the effects of Cd on the different stages (mesoderm, cardiac induction, cardiac function) of cardiac development using an early embryo development in vitro model and two- or three-dimensional (2- or 3D) cardiomyocyte and cardiac organoid formation models mimicking early cardiac development. METHODS Embryonic stem cells (ESCs) form 3D aggregates, called embryoid bodies, that recapitulate events involved with early embryogenesis (e.g., germ layer formation). This model was used for early germ layer formation and signaling pathway identification. The 2D cardiomyocyte differentiation from the NKX2-5eGFP/w human ESCs model was used to explore the effects of Cd exposure on cardiomyocyte formation and to model mesoderm differentiation and cardiac induction, allowing us to explore different developmental windows of Cd toxicity. The 3D cardiac organoid model was used in evaluating the effects of Cd exposure on contractility and cardiac development. RESULTS Cd (0.6μM; 110 ppb) lowered the differentiation of embryoid bodies to mesoderm via suppression of Wnt/β-catenin-signaling pathways. During early mesoderm induction, the mesoderm-associated transcription factors MESP1 and EOMES showed a transient up-regulation, which decreased later in the cardiac induction stage. Cd (0.15μM) lowered mesoderm formation and cardiac induction through suppression of the transcription factors and mesoderm marker genes HAND1, SNAI2, HOPX, and the cardiac-specific genes NKX2-5, GATA4, troponin T, and alpha-actinin. In addition, Cd-induced histone modifications for both gene activation (H3K4me3) and repression (H3K27me3), which play vital roles in regulating mesoderm commitment markers. The effects of Cd inhibition on cardiomyocyte differentiation were confirmed in 3D cardiac organoids. DISCUSSION In conclusion, using a human ESC-derived 2D/3D in vitro differentiation model system and cardiac organoids, we demonstrated that low-dose Cd suppressed mesoderm formation through mesoderm gene histone modification, thus inhibiting cardiomyocyte differentiation and cardiac induction. The studies provide valuable insights into cellular events and molecular mechanisms associated with Cd-induced congenital heart disease. https://doi.org/10.1289/EHP11208.
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Affiliation(s)
- Xian Wu
- Mechanistic Toxicology Branch, Division of the National Toxicology Program, National Institute for Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Department of Health and Human Services (DHHS), Research Triangle Park, North Carolina, USA
| | - Yichang Chen
- Mechanistic Toxicology Branch, Division of the National Toxicology Program, National Institute for Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Department of Health and Human Services (DHHS), Research Triangle Park, North Carolina, USA
| | - Anthony Luz
- Mechanistic Toxicology Branch, Division of the National Toxicology Program, National Institute for Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Department of Health and Human Services (DHHS), Research Triangle Park, North Carolina, USA
| | - Guang Hu
- Epigenetics and Stem Cell Biology Laboratory, Division of Intramural Research, NIEHS, NIH, DHHS, Research Triangle Park, North Carolina, USA
| | - Erik J. Tokar
- Mechanistic Toxicology Branch, Division of the National Toxicology Program, National Institute for Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Department of Health and Human Services (DHHS), Research Triangle Park, North Carolina, USA
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Sinha BK, Tokar EJ, Bortner CD. Molecular Mechanisms of Cytotoxicty of NCX4040, the Non-Steroidal Anti-Inflammatory NO-Donor, in Human Ovarian Cancer Cells. Int J Mol Sci 2022; 23:ijms23158611. [PMID: 35955744 PMCID: PMC9369271 DOI: 10.3390/ijms23158611] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 07/29/2022] [Accepted: 07/29/2022] [Indexed: 02/04/2023] Open
Abstract
NCX4040, the non-steroidal anti-inflammatory-NO donor, is cytotoxic to several human tumors, including ovarian tumor cells. We have found that NCX4040 is also cytotoxic against both OVCAR-8 and its adriamycin resistant (NCI/ADR-RES) tumor cell lines. Here, we have examined mechanism(s) for the cytotoxicity of NCX4040 in OVCAR-8 and NCI/ADR-RES cell lines. We found that NCX4040 induced significant apoptosis in both cell lines. Furthermore, NCX4040 treatment caused significant depletion of cellular glutathione, causing oxidative stress due to the formation of reactive oxygen/nitrogen species (ROS/RNS). Significantly more ROS/RNS were detected in OVCAR-8 cells than in NCI/ADR-RES cells which may have resulted from increased activities of SOD, glutathione peroxidase and transferases expressed in NCI/ADR-RES cells. NCX4040 treatment resulted in the formation of double-strand DNA breaks in both cells; however, more of these DNA breaks were detected in OVCAR-8 cells. RT-PCR studies indicated that NCX4040-induced DNA damage was not repaired as efficiently in NCI/ADR-RES cells as in OVCAR-8 cells which may lead to a differential cell death. Pretreatment of OVCAR-8 cells with N-acetylcysteine (NAC) significantly decreased cytotoxicity of NCX4040 in OVCAR-8 cells; however, NAC had no effects on NCX4040 cytotoxicity in NCI/ADR-RES cells. In contrast, FeTPPS, a peroxynitrite scavenger, completely blocked NCX4040-induced cell death in both cells, suggesting that NCX4040-induced cell death could be mediated by peroxynitrite formed from NCX4040 following cellular metabolism.
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Affiliation(s)
- Birandra K. Sinha
- Mechanistic Toxicology Branch, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA;
- Correspondence: ; Tel.: +1-984-287-3382
| | - Erik J. Tokar
- Mechanistic Toxicology Branch, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA;
| | - Carl D. Bortner
- Laboratory of Signal Transduction, Division of Intramural Research, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA;
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Zhan L, Zhang H, Zhang Q, Woods CG, Chen Y, Xue P, Dong J, Tokar EJ, Xu Y, Hou Y, Fu J, Yarborough K, Wang A, Qu W, Waalkes MP, Andersen ME, Pi J. Corrigendum to "Regulatory role of KEAP1 and NRF2 in PPARg expression and chemoresistance in human non-small-cell lung carcinoma cells" [Free Radic Biol Med. 53 (2012) 758-68. doi: 10.1016/j.freeradbiomed.2012.05.041. Epub 2012 Jun 7. PMID: 22684020]. Free Radic Biol Med 2022; 179:418-419. [PMID: 34857443 DOI: 10.1016/j.freeradbiomed.2021.11.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- Lijuan Zhan
- Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China; Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC, 27709, USA
| | - Hao Zhang
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC, 27709, USA; School of Public Health, Fudan University, Shanghai, China
| | - Qiang Zhang
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC, 27709, USA.
| | - Courtney G Woods
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC, 27709, USA
| | - Yanyan Chen
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC, 27709, USA; School of First Clinical Sciences, China Medical University, Shenyang, China
| | - Peng Xue
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC, 27709, USA
| | - Jian Dong
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC, 27709, USA
| | - Erik J Tokar
- National Toxicology Program Laboratories, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC, 27709, USA
| | - Yuanyuan Xu
- National Toxicology Program Laboratories, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC, 27709, USA
| | - Yongyong Hou
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC, 27709, USA
| | - Jingqi Fu
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC, 27709, USA
| | - Kathy Yarborough
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC, 27709, USA
| | - Aiping Wang
- Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Weidong Qu
- School of Public Health, Fudan University, Shanghai, China
| | - Michael P Waalkes
- National Toxicology Program Laboratories, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC, 27709, USA
| | - Melvin E Andersen
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC, 27709, USA
| | - Jingbo Pi
- Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
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Alvarado-Morales I, Olivares-Illana V, Arenas-Huertero C, Reynaga-Hernández E, Layseca-Espinosa E, Tokar EJ, Escudero-Lourdes C. Human prostate epithelial cells and prostate-derived stem cells malignantly transformed in vitro with sodium arsenite show impaired Toll like receptor -3 (TLR3)-associated anti-tumor pathway. Toxicol Lett 2021; 350:185-193. [PMID: 34303791 PMCID: PMC8410676 DOI: 10.1016/j.toxlet.2021.07.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 07/13/2021] [Accepted: 07/19/2021] [Indexed: 02/08/2023]
Abstract
A therapeutic strategy for prostate cancer (PCa) involves the use of 9-cis-retinoic acid (9cRA) to induce cancer stem cells (CSCs) differentiation and apoptosis. Polyinosinic:polycytidylic acid (PIC) is a Toll-like receptor 3 (TLR3) agonist that induces tumor cells apoptosis after activation. PIC+9cRA combination activates retinoic acid receptor β (RARβ) re-expression, leading to CSC differentiation and growth arrest. Since inorganic arsenic (iAs) targets prostatic stem cells (SCs), we hypothesized that arsenic-transformed SCs (As-CSCs) show an impaired TLR3-associated anti-tumor pathway and, therefore, are unresponsive to PIC activation. We evaluated TLR3-mediated activation of anti-tumor pathway based in RARβ expression, on As-CSC and iAs-transformed epithelial cells (CAsE-PE). As-CSCs and CAsE-PE showed lower TLR3 and RARβ basal expression compared to their respective isogenic controls WPE-Stem and RWPE-1. Also, iAs transformants showed reduced expression of mediators in TLR3 pathway. Importantly, As-CSCs were irresponsive to PIC+9cRA in terms of increased RARβ and decreased SC-markers expression, while CAsE-PE, a heterogeneous cell line having a small SC population, were partially responsive. These observations indicate that iAs can impair TLR3 expression and anti-tumor pathway activated by PIC+9cRA in SCs and prostatic epithelial cells. These findings suggest that TLR3-activation based therapy may be an ineffective therapeutic alternative for iAs-associated PCa.
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Affiliation(s)
- I Alvarado-Morales
- Laboratorio de Inmunotoxicología. Facultad de Ciencias Químicas, Universidad Autónoma de San Luis Potosí, Manuel Nava 6, Zona Universitaria, 78290, SLP, Mexico
| | - V Olivares-Illana
- Laboratorio de Interacciones Biomoleculares y Cáncer, Instituto de Física, Universidad Autónoma de San Luis Potosí, Manuel Nava 6, Zona Universitaria, 78290, SLP, Mexico
| | - C Arenas-Huertero
- Laboratorio de Biología, Facultad de Ciencias, Universidad Autónoma de San Luis Potosí. Av, Chapultepec, 1570. 78295, SLP, Mexico
| | - E Reynaga-Hernández
- Laboratorio de Inmunotoxicología. Facultad de Ciencias Químicas, Universidad Autónoma de San Luis Potosí, Manuel Nava 6, Zona Universitaria, 78290, SLP, Mexico
| | - E Layseca-Espinosa
- Centro de Investigación en Biomedicina y Salud, Facultad de Medicina, Universidad autónoma de San Luis Potosí, Sierra Leona 550 Lomas de San Luis, 78210, SLP, Mexico
| | - E J Tokar
- National Toxicology Program Laboratory, NTP. National Institutitute of Environmental Health Sciences, NIEHS, Durham, NC, 27709, United States
| | - C Escudero-Lourdes
- Laboratorio de Inmunotoxicología. Facultad de Ciencias Químicas, Universidad Autónoma de San Luis Potosí, Manuel Nava 6, Zona Universitaria, 78290, SLP, Mexico.
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Xu Y, Tokar EJ, Pi J. Arsenic as an environmental toxicant and a therapeutic agent: Foe and friend. Toxicol Appl Pharmacol 2021; 415:115438. [PMID: 33548274 DOI: 10.1016/j.taap.2021.115438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- Yuanyuan Xu
- Laboratory of Chronic Diseases and Environmental Genetics, School of Public Health, China Medical University, No. 77 Puhe Road, Shenyang North New Area, Shenyang, Liaoning Province 110122, PR China.
| | - Erik J Tokar
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, NIEHS, 111 TW Alexander Drive, Building 101, Room E-105, RTP, NC 27709, USA.
| | - Jingbo Pi
- Program of Environmental Toxicology, School of Public Health, China Medical University, No. 77 Puhe Road, Shenyang North New Area, Shenyang, Liaoning Province 110122, PR China.
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Upson K, O’Brien KM, Hall JE, Tokar EJ, Baird DD. Cadmium Exposure and Ovarian Reserve in Women Aged 35-49 Years: The Impact on Results From the Creatinine Adjustment Approach Used to Correct for Urinary Dilution. Am J Epidemiol 2021; 190:116-124. [PMID: 32242622 PMCID: PMC7946799 DOI: 10.1093/aje/kwaa037] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 08/19/2019] [Accepted: 10/09/2019] [Indexed: 12/19/2022] Open
Abstract
Cadmium is toxic to the ovaries in animal studies, but its association with diminished ovarian reserve in women is not established. We investigated urinary cadmium, a biomarker of long-term exposure, in relation to diminished ovarian reserve, as indicated by elevated serum follicle-stimulating hormone concentrations (≥10 IU/L), in women aged 35-49 years (unweighted n = 1,681). Using data from the Third National Health and Nutrition Examination Survey (1988-1994), we conducted Poisson regression to estimate adjusted relative risks and 95% confidence intervals. Because the best approach to correcting for urinary dilution in spot samples with creatinine remains controversial, we employed 3 approaches: standardization, covariate adjustment, and covariate-adjusted standardization. Our data suggested a modest association with standardization (highest quartile vs. lowest: relative risk (RR) = 1.3, 95% confidence interval (CI): 0.8, 1.9; P for trend = 0.06) and covariate-adjusted standardization (highest quartile vs. lowest: RR = 1.3, 95% CI: 0.9, 1.9; P for trend = 0.05) and a stronger association with covariate adjustment (highest quartile vs. lowest: RR = 1.8, 95% CI: 1.2, 2.9; P for trend = 0.01). The stronger association with covariate adjustment may reflect bias from conditioning on urinary creatinine, a collider in the hypothesized causal pathway. We conclude that cadmium may contribute to ovarian aging in women and that careful consideration of the creatinine adjustment approach is needed to minimize bias.
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Affiliation(s)
- Kristen Upson
- Correspondence to Dr. Kristen Upson, Department of Epidemiology and Biostatistics, College of Human Medicine, Michigan State University, 909 Wilson Road, Room B601, East Lansing, MI 48824 (e-mail: )
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Upson K, Harmon QE, Heffron R, Hall JE, Wise LA, Wegienka G, Tokar EJ, Baird DD. Depot Medroxyprogesterone Acetate Use and Blood Lead Levels in a Cohort of Young Women. Environ Health Perspect 2020; 128:117004. [PMID: 33206002 PMCID: PMC7673223 DOI: 10.1289/ehp7017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 09/28/2020] [Accepted: 10/23/2020] [Indexed: 06/11/2023]
Abstract
BACKGROUND Injectable contraceptive use is common, with 74 million users worldwide. Use of the injectable contraceptive depot medroxyprogesterone acetate (DMPA) is associated with bone mineral density loss. We hypothesize that increased bone resorption with DMPA use allows for mobilization of the toxic metal lead stored in bone to blood, presenting users with increased systemic exposure to lead. OBJECTIVE The objective of our study was to investigate the association between current DMPA use and blood lead concentrations. METHODS We conducted a cross-sectional analysis using enrollment data from the Study of Environment, Lifestyle & Fibroids (SELF), a cohort of 1,693 African-American women who were 23-35 years of age. Data on DMPA use were collected by computer-assisted telephone interview. Blood lead concentrations were measured in whole blood samples among 1,548 participants (91% of cohort). We estimated the adjusted percent difference in blood lead concentrations and 95% confidence intervals (CI) between current DMPA users and nonusers using multivariable linear regression. RESULTS Geometric mean blood lead concentration was 0.69 μ g / dL (95% CI: 0.67, 0.71). After adjustment, current DMPA users (7% of cohort) had blood lead concentrations that were 18% higher than those of nonusers (95% CI: 8%, 29%). Similar associations were observed with additional analyses to assess for potential bias from smoking, DMPA-induced amenorrhea, use of estrogen-containing contraceptives, having given birth in the prior year, and history of medical conditions or current medication use associated with bone loss. DISCUSSION Our results indicate that current DMPA use is associated with increased blood lead concentrations. Further research, particularly in populations highly exposed to lead, is warranted to consider tradeoffs between the adverse effects of lead on human health and the importance of DMPA as a contraceptive option to prevent unintended pregnancy. https://doi.org/10.1289/EHP7017.
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Affiliation(s)
- Kristen Upson
- Department of Epidemiology and Biostatistics, College of Human Medicine, Michigan State University, East Lansing, Michigan, USA
| | - Quaker E. Harmon
- Epidemiology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
| | - Renee Heffron
- Department of Global Health, University of Washington, Seattle, Washington, USA
- Department of Epidemiology, University of Washington, Seattle, Washington, USA
| | - Janet E. Hall
- Clinical Research Branch, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
| | - Lauren A. Wise
- Department of Epidemiology, Boston University School of Public Health, Boston, Massachusetts, USA
| | - Ganesa Wegienka
- Department of Public Health Sciences, Henry Ford Health System, Detroit, Michigan, USA
| | - Erik J. Tokar
- Stem Cells Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
| | - Donna D. Baird
- Epidemiology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
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Sinha BK, Tokar EJ, Bushel PR. Elucidation of Mechanisms of Topotecan-Induced Cell Death in Human Breast MCF-7 Cancer Cells by Gene Expression Analysis. Front Genet 2020; 11:775. [PMID: 32765594 PMCID: PMC7379903 DOI: 10.3389/fgene.2020.00775] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Accepted: 06/30/2020] [Indexed: 12/14/2022] Open
Abstract
Topotecan is a clinically active anticancer agent for the management of various human tumors. While the principal mechanism of tumor cell killing by topotecan is due to its interactions with topoisomerase I and formation of DNA double-strand breaks, recent studies suggest that mechanisms involving generation of reactive free radicals and induction of oxidative stress may play a significant role in topotecan-dependent tumor cell death. We have shown that topotecan generates a topotecan radical following one-electron oxidation by a peroxidase-hydrogen peroxide system which reacts with reduced glutathione and cysteine, forming the glutathiyl and cysteinyl radicals, respectively. While little is known how these events are involved in topotecan-induced tumor cell death, we have now examined the effects of topotecan short (1 h) and long (24 h) exposure on global gene expression patterns using gene expression microarray analysis in human breast MCF-7 cancer cells, a wild-type p53 containing cell line. We show here that topotecan treatment significantly down-regulated estrogen receptor alpha (ERα/ESR1) and antiapoptotic BCL2 genes in addition to many other p53-regulated genes. Furthermore, 8-oxoguanine DNA glycosylase (OGG1), ferredoxin reductase (FDXR), methionine sulfoxide reductase (MSR), glutathione peroxidases (GPx), and glutathione reductase (GSR) genes were also differentially expressed by topotecan treatment. The differential expression of these genes was observed in a wild-type p53-containing breast ZR-75-1 tumor cell line following topotecan treatment. The involvement of reactive oxygen free radical sensor genes, the oxidative DNA damage (OGG1) repair gene and induction of pro-apoptotic genes suggest that reactive free radical species play a role in topotecan-induced tumor cell death.
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Affiliation(s)
- Birandra K Sinha
- Immunity, Inflammation, and Disease Laboratory, National Institute of Environmental Health Sciences, Durham, NC, United States
| | - Erik J Tokar
- National Toxicology Program, National Institute of Environmental Health Sciences, Durham, NC, United States
| | - Pierre R Bushel
- Biostatistics and Computational Biology Branch, National Institute of Environmental Health Sciences, Durham, NC, United States
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11
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Merrick BA, Phadke DP, Bostrom MA, Shah RR, Wright GM, Wang X, Gordon O, Pelch KE, Auerbach SS, Paules RS, DeVito MJ, Waalkes MP, Tokar EJ. KRAS-retroviral fusion transcripts and gene amplification in arsenic-transformed, human prostate CAsE-PE cancer cells. Toxicol Appl Pharmacol 2020; 397:115017. [PMID: 32344290 PMCID: PMC7606314 DOI: 10.1016/j.taap.2020.115017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 04/16/2020] [Accepted: 04/19/2020] [Indexed: 01/03/2023]
Abstract
CAsE-PE cells are an arsenic-transformed, human prostate epithelial line containing oncogenic mutations in KRAS compared to immortalized, normal KRAS parent cells, RWPE-1. We previously reported increased copy number of mutated KRAS in CAsE-PE cells, suggesting gene amplification. Here, KRAS flanking genomic and transcriptomic regions were sequenced in CAsE-PE cells for insight into KRAS amplification. Comparison of DNA-Seq and RNA-Seq showed increased reads from background aligning to all KRAS exons in CAsE-PE cells, while a uniform DNA-Seq read distribution occurred in RWPE-1 cells with normal transcript expression. We searched for KRAS fusions in DNA and RNA sequencing data finding a portion of reads aligning to KRAS and viral sequence. After generation of cDNA from total RNA, short and long KRAS probes were generated to hybridize cDNA and KRAS enriched fragments were PacBio sequenced. More KRAS reads were captured from CAsE-PE cDNA versus RWPE-1 by each probe set. Only CAsE-PE cDNA showed KRAS viral fusion transcripts, primarily mapping to LTR and endogenous retrovirus sequences on either 5'- or 3'-ends of KRAS. Most KRAS viral fusion transcripts contained 4 to 6 exons but some PacBio sequences were in unusual orientations, suggesting viral insertions within the gene body. Additionally, conditioned media was extracted for potential retroviral particles. RNA-Seq of culture media isolates identified KRAS retroviral fusion transcripts in CAsE-PE media only. Truncated KRAS transcripts suggested multiple retroviral integration sites occurred within the KRAS gene producing KRAS retroviral fusions of various lengths. Findings suggest activation of endogenous retroviruses in arsenic carcinogenesis should be explored.
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Affiliation(s)
- B Alex Merrick
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States.
| | - Dhiral P Phadke
- Sciome, LLC, Research Triangle Park, North Carolina, United States
| | - Meredith A Bostrom
- David H. Murdock Research Institute, Kannapolis, North Carolina, United States
| | - Ruchir R Shah
- Sciome, LLC, Research Triangle Park, North Carolina, United States
| | - Garron M Wright
- David H. Murdock Research Institute, Kannapolis, North Carolina, United States
| | - Xinguo Wang
- David H. Murdock Research Institute, Kannapolis, North Carolina, United States
| | - Oksana Gordon
- David H. Murdock Research Institute, Kannapolis, North Carolina, United States
| | - Katherine E Pelch
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States
| | - Scott S Auerbach
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States
| | - Richard S Paules
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States
| | - Michael J DeVito
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States
| | - Michael P Waalkes
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States
| | - Erik J Tokar
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States
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12
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Merrick BA, Phadke DP, Bostrom MA, Shah RR, Wright GM, Wang X, Gordon O, Pelch KE, Auerbach SS, Paules RS, DeVito MJ, Waalkes MP, Tokar EJ. Arsenite malignantly transforms human prostate epithelial cells in vitro by gene amplification of mutated KRAS. PLoS One 2019; 14:e0215504. [PMID: 31009485 PMCID: PMC6476498 DOI: 10.1371/journal.pone.0215504] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Accepted: 04/04/2019] [Indexed: 12/20/2022] Open
Abstract
Inorganic arsenic is an environmental human carcinogen of several organs including the urinary tract. RWPE-1 cells are immortalized, non-tumorigenic, human prostate epithelia that become malignantly transformed into the CAsE-PE line after continuous in vitro exposure to 5μM arsenite over a period of months. For insight into in vitro arsenite transformation, we performed RNA-seq for differential gene expression and targeted sequencing of KRAS. We report >7,000 differentially expressed transcripts in CAsE-PE cells compared to RWPE-1 cells at >2-fold change, q<0.05 by RNA-seq. Notably, KRAS expression was highly elevated in CAsE-PE cells, with pathway analysis supporting increased cell proliferation, cell motility, survival and cancer pathways. Targeted DNA sequencing of KRAS revealed a mutant specific allelic imbalance, ‘MASI’, frequently found in primary clinical tumors. We found high expression of a mutated KRAS transcript carrying oncogenic mutations at codons 12 and 59 and many silent mutations, accompanied by lower expression of a wild-type allele. Parallel cultures of RWPE-1 cells retained a wild-type KRAS genotype. Copy number analysis and sequencing showed amplification of the mutant KRAS allele. KRAS is expressed as two splice variants, KRAS4a and KRAS4b, where variant 4b is more prevalent in normal cells compared to greater levels of variant 4a seen in tumor cells. 454 Roche sequencing measured KRAS variants in each cell type. We found KRAS4a as the predominant transcript variant in CAsE-PE cells compared to KRAS4b, the variant expressed primarily in RWPE-1 cells and in normal prostate, early passage, primary epithelial cells. Overall, gene expression data were consistent with KRAS-driven proliferation pathways found in spontaneous tumors and malignantly transformed cell lines. Arsenite is recognized as an important environmental carcinogen, but it is not a direct mutagen. Further investigations into this in vitro transformation model will focus on genomic events that cause arsenite-mediated mutation and overexpression of KRAS in CAsE-PE cells.
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Affiliation(s)
- B. Alex Merrick
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States of America
- * E-mail:
| | - Dhiral P. Phadke
- Sciome, LLC, Research Triangle Park, North Carolina, United States of America
| | - Meredith A. Bostrom
- David H. Murdock Research Institute, Kannapolis, North Carolina, United States of America
| | - Ruchir R. Shah
- Sciome, LLC, Research Triangle Park, North Carolina, United States of America
| | - Garron M. Wright
- David H. Murdock Research Institute, Kannapolis, North Carolina, United States of America
| | - Xinguo Wang
- David H. Murdock Research Institute, Kannapolis, North Carolina, United States of America
| | - Oksana Gordon
- David H. Murdock Research Institute, Kannapolis, North Carolina, United States of America
| | - Katherine E. Pelch
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States of America
| | - Scott S. Auerbach
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States of America
| | - Richard S. Paules
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States of America
| | - Michael J. DeVito
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States of America
| | - Michael P. Waalkes
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States of America
| | - Erik J. Tokar
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States of America
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13
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Abstract
Millions of children are born each year with a birth defect. Many of these defects are caused by environmental factors, although the underlying etiology is often unknown. In vivo mammalian models are frequently used to determine if a chemical poses a risk to the developing fetus. However, there are over 80 000 chemicals registered for use in the United States, many of which have undergone little safety testing, necessitating the need for higher-throughput methods to assess developmental toxicity. Pluripotent stem cells (PSCs) are an ideal in vitro model to investigate developmental toxicity as they possess the capacity to differentiate into nearly any cell type in the human body. Indeed, a burst of research has occurred in the field of stem cell toxicology over the past decade, which has resulted in numerous methodological advances that utilize both mouse and human PSCs, as well as cutting-edge technology in the fields of metabolomics, transcriptomics, transgenics, and high-throughput imaging. Here, we review the wide array of approaches used to detect developmental toxicants, suggest areas for further research, and highlight critical aspects of stem cell biology that should be considered when utilizing PSCs in developmental toxicity testing.
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Affiliation(s)
- Anthony L Luz
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
| | - Erik J Tokar
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
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14
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Ngalame NNO, Luz AL, Makia N, Tokar EJ. Arsenic Alters Exosome Quantity and Cargo to Mediate Stem Cell Recruitment Into a Cancer Stem Cell-Like Phenotype. Toxicol Sci 2018; 165:40-49. [PMID: 30169766 PMCID: PMC6111788 DOI: 10.1093/toxsci/kfy176] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Inorganic arsenic is a human carcinogen that can target the prostate. Accumulating evidence suggests arsenic can disrupt stem cell (SC) dynamics during the carcinogenic process. Previous work demonstrated arsenic-transformed prostate epithelial (CAsE-PE) cells can recruit prostate SCs into rapidly acquiring a cancer SC (CSC) phenotype via the secretion of soluble factors. Exosomes are small, membrane-derived vesicles that contain lipids, RNA, and proteins, and actively contribute to cancer initiation and progression when taken up by target cells. Here we hypothesized that CAsE-PE cells are recruiting SCs to a CSC-like phenotype via exosomal signaling. CAsE-PE cells secreted 700% more exosomes than parental RWPE-1 cells. CAsE-PE exosomes were enriched with oncogenic factors, including oncogenes (KRAS, NRAS, VEFGA, MYB, and EGFR), inflammation-related (cyclooxygenase-2, interleukin 1B (IL1B), IL6, transforming growth factor-β, and tumor necrosis factor-A), and apoptosis-related (CASP7, CASP9, and BCL2) transcripts, and oncogenesis-associated microRNAs. When compared with SCs cultured in exosome-depleted conditioned medium (CM), SCs cultured in CM containing CAsE-PE-derived exosomes showed increased (198%) matrix metalloproteinase activity and underwent an epithelial-to-mesenchymal transition in morphology, suggesting an exosome-mediated transformation. KRAS plays an important role in arsenic carcinogenesis. Although KRAS transcript (>24 000%) and protein (866%) levels were elevated in CAsE-PE exosomes, knock-down of KRAS in these cells only partially mitigated the CSC-like phenotype in cocultured SCs. Collectively, these results suggest arsenic impacts both exosomal quantity and cargo. Exosomal KRAS is only minimally involved in this recruitment, and additional factors (eg, cancer-associated miRNAs) likely also play a role. This work furthers our mechanistic understanding of how arsenic disrupts SC dynamics and influences the tumor microenvironment during carcinogenesis.
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Affiliation(s)
- Ntube N O Ngalame
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
| | - Anthony L Luz
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
| | - Ngome Makia
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
| | - Erik J Tokar
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
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15
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Nachman KE, Punshon T, Rardin L, Signes-Pastor AJ, Murray CJ, Jackson BP, Guerinot ML, Burke TA, Chen CY, Ahsan H, Argos M, Cottingham KL, Cubadda F, Ginsberg GL, Goodale BC, Kurzius-Spencer M, Meharg AA, Miller MD, Nigra AE, Pendergrast CB, Raab A, Reimer K, Scheckel KG, Schwerdtle T, Taylor VF, Tokar EJ, Warczak TM, Karagas MR. Opportunities and Challenges for Dietary Arsenic Intervention. Environ Health Perspect 2018; 126:84503. [PMID: 30235424 PMCID: PMC6375412 DOI: 10.1289/ehp3997] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2018] [Revised: 07/16/2018] [Accepted: 07/20/2018] [Indexed: 05/18/2023]
Abstract
The diet is emerging as the dominant source of arsenic exposure for most of the U.S. population. Despite this, limited regulatory efforts have been aimed at mitigating exposure, and the role of diet in arsenic exposure and disease processes remains understudied. In this brief, we discuss the evidence linking dietary arsenic intake to human disease and discuss challenges associated with exposure characterization and efforts to quantify risks. In light of these challenges, and in recognition of the potential longer-term process of establishing regulation, we introduce a framework for shorter-term interventions that employs a field-to-plate food supply chain model to identify monitoring, intervention, and communication opportunities as part of a multisector, multiagency, science-informed, public health systems approach to mitigation of dietary arsenic exposure. Such an approach is dependent on coordination across commodity producers, the food industry, nongovernmental organizations, health professionals, researchers, and the regulatory community. https://doi.org/10.1289/EHP3997.
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Affiliation(s)
- Keeve E Nachman
- Risk Sciences and Public Policy Institute, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA
- Department of Environmental Health and Engineering, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA
- Department of Health Policy and Management, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA
- Johns Hopkins Center for a Livable Future, Johns Hopkins University, Baltimore, Maryland, USA
| | - Tracy Punshon
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, USA
- Dartmouth Superfund Research Program, Hanover, New Hampshire, USA
- Dartmouth Children's Environmental Health and Disease Prevention Research Center, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, USA
| | - Laurie Rardin
- Dartmouth Superfund Research Program, Hanover, New Hampshire, USA
| | - Antonio J Signes-Pastor
- Dartmouth Superfund Research Program, Hanover, New Hampshire, USA
- Dartmouth Children's Environmental Health and Disease Prevention Research Center, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, USA
- Department of Epidemiology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
| | - Carolyn J Murray
- Dartmouth Children's Environmental Health and Disease Prevention Research Center, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, USA
| | - Brian P Jackson
- Dartmouth Superfund Research Program, Hanover, New Hampshire, USA
- Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire, USA
| | - Mary Lou Guerinot
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, USA
| | - Thomas A Burke
- Risk Sciences and Public Policy Institute, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA
- Department of Health Policy and Management, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA
| | - Celia Y Chen
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, USA
- Dartmouth Superfund Research Program, Hanover, New Hampshire, USA
| | - Habibul Ahsan
- Department of Public Health Sciences, University of Chicago, Chicago, Illinois, USA
| | - Maria Argos
- Department of Public Health Sciences, University of Chicago, Chicago, Illinois, USA
| | - Kathryn L Cottingham
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, USA
- Dartmouth Children's Environmental Health and Disease Prevention Research Center, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, USA
| | - Francesco Cubadda
- Department of Food Safety, Nutrition and Veterinary Public Health, Istituto Superiore di Sanità - Italian National Institute of Health, Rome, Italy
| | - Gary L Ginsberg
- Yale School of Public Health, 60 College St, New Haven, Connecticut, USA
| | - Britton C Goodale
- Dartmouth Superfund Research Program, Hanover, New Hampshire, USA
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
| | - Margaret Kurzius-Spencer
- Department of Pediatrics, College of Medicine, University of Arizona, Tucson, Arizona, USA
- Department of Community, Environment and Policy, Mel & Enid College of Public Health, University of Arizona, Tucson, Arizona, USA
| | - Andrew A Meharg
- Institute for Global Food Security, Queen's University Belfast, David Keir Building, Malone Road, Belfast, BT9 5BN, Northern Ireland, UK
| | - Mark D Miller
- Western States Pediatric Environmental Health Specialty Unit, University of California, San Francisco, San Francisco, California, USA
| | - Anne E Nigra
- Department of Environmental Health Sciences, Columbia University Mailman School of Public Health, New York, New York, USA
| | | | - Andrea Raab
- Department of Chemistry, University of Aberdeen, Aberdeen, UK
| | - Ken Reimer
- Royal Military College, Kingston, Ontario, Canada
| | - Kirk G Scheckel
- Land and Materials Management Division, National Risk Management Research Laboratory, United States Environmental Protection Agency, Cincinnati, Ohio, USA
| | - Tanja Schwerdtle
- Institute of Nutritional Sciences, University of Potsdam, Germany
| | - Vivien F Taylor
- Dartmouth Superfund Research Program, Hanover, New Hampshire, USA
- Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire, USA
| | - Erik J Tokar
- National Toxicology Program Laboratory, National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
| | - Todd M Warczak
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, USA
| | - Margaret R Karagas
- Dartmouth Superfund Research Program, Hanover, New Hampshire, USA
- Dartmouth Children's Environmental Health and Disease Prevention Research Center, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, USA
- Department of Epidemiology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
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17
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Ganini D, Leinisch F, Kumar A, Jiang J, Tokar EJ, Malone CC, Petrovich RM, Mason RP. Fluorescent proteins such as eGFP lead to catalytic oxidative stress in cells. Redox Biol 2017; 12:462-468. [PMID: 28334681 PMCID: PMC5362137 DOI: 10.1016/j.redox.2017.03.002] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 03/03/2017] [Indexed: 12/11/2022] Open
Abstract
Fluorescent proteins are an important tool that has become omnipresent in life sciences research. They are frequently used for localization of proteins and monitoring of cells [1,2]. Green fluorescent protein (GFP) was the first and has been the most used fluorescent protein. Enhanced GFP (eGFP) was optimized from wild-type GFP for increased fluorescence yield and improved expression in mammalian systems [3]. Many GFP-like fluorescent proteins have been discovered, optimized or created, such as the red fluorescent protein TagRFP [4]. Fluorescent proteins are expressed colorless and immature and, for eGFP, the conversion to the fluorescent form, mature, is known to produce one equivalent of hydrogen peroxide (H2O2) per molecule of chromophore [5,6]. Even though it has been proposed that this process is non-catalytic and generates nontoxic levels of H2O2 [6], this study investigates the role of fluorescent proteins in generating free radicals and inducing oxidative stress in biological systems. Immature eGFP and TagRFP catalytically generate the free radical superoxide anion (O2•-) and H2O2 in the presence of NADH. Generation of the free radical O2•- and H2O2 by eGFP in the presence of NADH affects the gene expression of cells. Many biological pathways are altered, such as a decrease in HIF1α stabilization and activity. The biological pathways altered by eGFP are known to be implicated in the pathophysiology of many diseases associated with oxidative stress; therefore, it is critical that such experiments using fluorescent proteins are validated with alternative methodologies and the results are carefully interpreted. Since cells inevitably experience oxidative stress when fluorescent proteins are expressed, the use of this tool for cell labeling and in vivo cell tracing also requires validation using alternative methodologies.
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Affiliation(s)
- Douglas Ganini
- Free Radical Biology, Immunity, Inflammation & Disease Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Fabian Leinisch
- Free Radical Biology, Immunity, Inflammation & Disease Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Ashutosh Kumar
- Free Radical Biology, Immunity, Inflammation & Disease Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - JinJie Jiang
- Free Radical Biology, Immunity, Inflammation & Disease Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Erik J Tokar
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Christine C Malone
- Protein Expression Core Facility, Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Robert M Petrovich
- Protein Expression Core Facility, Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Ronald P Mason
- Free Radical Biology, Immunity, Inflammation & Disease Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
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18
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Ren NSX, Ji M, Tokar EJ, Busch EL, Xu X, Lewis D, Li X, Jin A, Zhang Y, Wu WKK, Huang W, Li L, Fargo DC, Keku TO, Sandler RS, Li X. Haploinsufficiency of SIRT1 Enhances Glutamine Metabolism and Promotes Cancer Development. Curr Biol 2017; 27:483-494. [PMID: 28162896 DOI: 10.1016/j.cub.2016.12.047] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 10/31/2016] [Accepted: 12/20/2016] [Indexed: 01/05/2023]
Abstract
SIRT1, the most conserved mammalian NAD+-dependent protein deacetylase, plays a vital role in the regulation of metabolism, stress responses, and genome stability. However, the role of SIRT1 in the multi-step process leading to transformation and/or tumorigenesis, as either a tumor suppressor or tumor promoter, is complex and may be dependent upon the context in which SIRT1 activity is altered, and the role of SIRT1 in tumor metabolism is unknown. Here, we demonstrate that SIRT1 dose-dependently regulates cellular glutamine metabolism and apoptosis, which in turn differentially impact cell proliferation and cancer development. Heterozygous deletion of Sirt1 induces c-Myc expression, enhancing glutamine metabolism and subsequent proliferation, autophagy, stress resistance, and cancer formation. In contrast, homozygous deletion of Sirt1 triggers cellular apoptotic pathways, increases cell death, diminishes autophagy, and reduces cancer formation. Consistent with the observed dose dependence in cells, intestine-specific Sirt1 heterozygous mice have enhanced intestinal tumor formation, whereas intestine-specific Sirt1 homozygous knockout mice have reduced development of colon cancer. Furthermore, SIRT1 reduction, but not deletion, is associated with human colorectal tumors, and colorectal cancer patients with low protein expression of SIRT1 have a poor prognosis. Taken together, our findings indicate that the dose-dependent regulation of tumor metabolism and possibly apoptosis by SIRT1 mechanistically contribute to the observed dual roles of SIRT1 in tumorigenesis. Our study highlights the importance of maintenance of a suitable SIRT1 dosage for metabolic and tissue homeostasis, which will have important implications in SIRT1-small-molecule-activator/inhibitor-based therapeutic strategies for cancers.
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Affiliation(s)
- Natalie S X Ren
- Signal Transduction Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Ming Ji
- Signal Transduction Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Erik J Tokar
- Stem Cell Toxicology Group, National Toxicology Program, Research Triangle Park, NC 27709, USA
| | - Evan L Busch
- Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Xiaojiang Xu
- Integrative Bioinformatics Branch, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - DeAsia Lewis
- Signal Transduction Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Xiangchun Li
- Department of Anaesthesia and Intensive Care, Institute of Digestive Disease and State Key Laboratory of Digestive Disease, The Chinese University of Hong Kong, Hong Kong, China
| | - Aiwen Jin
- Department of Radiation Oncology and Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Yanping Zhang
- Department of Radiation Oncology and Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - William K K Wu
- Department of Anaesthesia and Intensive Care, Institute of Digestive Disease and State Key Laboratory of Digestive Disease, The Chinese University of Hong Kong, Hong Kong, China
| | - Weichun Huang
- Biostatistics and Computational Biology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Leping Li
- Biostatistics and Computational Biology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - David C Fargo
- Integrative Bioinformatics Branch, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Temitope O Keku
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Robert S Sandler
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Xiaoling Li
- Signal Transduction Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA.
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19
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Abstract
Cadmium (Cd) is a potential human prostate carcinogen. Chronic Cd exposure malignantly transforms RWPE-1 human prostate epithelial cells into CTPE cells by an unclear mechanism. Previous studies show that RWPE-1 can also be malignantly transformed by arsenic, and KRAS activation is key to causation and maintenance of this phenotype. Although Cd and arsenic can both transform prostate epithelial cells, it is uncertain whether their mechanisms are similar. Thus, here we determined whether KRAS activation is critical in causing and maintaining Cd-induced malignant transformation in CTPE cells. Expression of KRAS, miRNAs, and other genes of interest was analyzed by Western blot and RT-PCR. Following stable KRAS knockdown (KD) by RNA interference using shRNAmir, the malignant phenotype was assessed by various physical and genetic parameters. CTPE cells greatly overexpressed KRAS by 20-fold, indicating a likely role in Cd transformation. Thus, we attempted to reverse the malignant phenotype via KRAS KD. Two weeks after shRNAmir transduction, KRAS protein was undetectable in CTPE KD cells, confirming stable KD. KRAS KD reduced stimulated RAS/ERK and PI3K/AKT signaling pathways and markedly mitigated multiple physical and molecular malignant cell characteristics including: hypersecretion of MMP-2, colony formation, cell survival, and expression of cancer-relevant genes (reduced proliferation and cell cycle-related genes; activated tumor suppressor PTEN). However, KRAS KD did not reverse miRNA expression originally down-regulated by Cd transformation. These data strongly suggest KRAS is a key gene in development and maintenance of the Cd-induced malignant phenotype, at least in the prostate. It is not, however, the only genetic factor sustaining this phenotype.
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Affiliation(s)
- Ntube N O Ngalame
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences , Research Triangle Park, North Carolina 27709, United States
| | - Michael P Waalkes
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences , Research Triangle Park, North Carolina 27709, United States
| | - Erik J Tokar
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences , Research Triangle Park, North Carolina 27709, United States
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Carlin DJ, Naujokas MF, Bradham KD, Cowden J, Heacock M, Henry HF, Lee JS, Thomas DJ, Thompson C, Tokar EJ, Waalkes MP, Birnbaum LS, Suk WA. Arsenic and Environmental Health: State of the Science and Future Research Opportunities. Environ Health Perspect 2016; 124:890-9. [PMID: 26587579 PMCID: PMC4937867 DOI: 10.1289/ehp.1510209] [Citation(s) in RCA: 181] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 11/10/2015] [Indexed: 05/20/2023]
Abstract
BACKGROUND Exposure to inorganic and organic arsenic compounds is a major public health problem that affects hundreds of millions of people worldwide. Exposure to arsenic is associated with cancer and noncancer effects in nearly every organ in the body, and evidence is mounting for health effects at lower levels of arsenic exposure than previously thought. Building from a tremendous knowledge base with > 1,000 scientific papers published annually with "arsenic" in the title, the question becomes, what questions would best drive future research directions? OBJECTIVES The objective is to discuss emerging issues in arsenic research and identify data gaps across disciplines. METHODS The National Institutes of Health's National Institute of Environmental Health Sciences Superfund Research Program convened a workshop to identify emerging issues and research needs to address the multi-faceted challenges related to arsenic and environmental health. This review summarizes information captured during the workshop. DISCUSSION More information about aggregate exposure to arsenic is needed, including the amount and forms of arsenic found in foods. New strategies for mitigating arsenic exposures and related health effects range from engineered filtering systems to phytogenetics and nutritional interventions. Furthermore, integration of omics data with mechanistic and epidemiological data is a key step toward the goal of linking biomarkers of exposure and susceptibility to disease mechanisms and outcomes. CONCLUSIONS Promising research strategies and technologies for arsenic exposure and adverse health effect mitigation are being pursued, and future research is moving toward deeper collaborations and integration of information across disciplines to address data gaps. CITATION Carlin DJ, Naujokas MF, Bradham KD, Cowden J, Heacock M, Henry HF, Lee JS, Thomas DJ, Thompson C, Tokar EJ, Waalkes MP, Birnbaum LS, Suk WA. 2016. Arsenic and environmental health: state of the science and future research opportunities. Environ Health Perspect 124:890-899; http://dx.doi.org/10.1289/ehp.1510209.
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Affiliation(s)
- Danielle J. Carlin
- Superfund Research Program, National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Department of Health and Human Services (DHHS), Research Triangle Park, North Carolina, USA
| | | | - Karen D. Bradham
- Human Exposure & Atmospheric Science Division, National Exposure Research Laboratory, U.S. Environmental Protection Agency (EPA), Research Triangle Park, North Carolina, USA
| | - John Cowden
- National Center for Computational Toxicology, and
| | - Michelle Heacock
- Superfund Research Program, National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Department of Health and Human Services (DHHS), Research Triangle Park, North Carolina, USA
| | - Heather F. Henry
- Superfund Research Program, National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Department of Health and Human Services (DHHS), Research Triangle Park, North Carolina, USA
| | - Janice S. Lee
- National Center for Environmental Assessment, Office of Research and Development (ORD), U.S. EPA, Research Triangle Park, North Carolina, USA
| | - David J. Thomas
- Integrated Systems Toxicology Division, National Human and Environmental Health Effects Research Laboratory, ORD, U.S. EPA, Research Triangle Park, North Carolina, USA
| | | | - Erik J. Tokar
- National Toxicology Program, NIEHS, NIH, DHHS, Research Triangle Park, North Carolina, USA
| | - Michael P. Waalkes
- National Toxicology Program, NIEHS, NIH, DHHS, Research Triangle Park, North Carolina, USA
| | - Linda S. Birnbaum
- National Toxicology Program, NIEHS, NIH, DHHS, Research Triangle Park, North Carolina, USA
- NIEHS, NIH, DHHS, Research Triangle Park, North Carolina, USA
| | - William A. Suk
- Superfund Research Program, National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Department of Health and Human Services (DHHS), Research Triangle Park, North Carolina, USA
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Kumar A, Ehrenshaft M, Tokar EJ, Mason RP, Sinha BK. Nitric oxide inhibits topoisomerase II activity and induces resistance to topoisomerase II-poisons in human tumor cells. Biochim Biophys Acta 2016; 1860:1519-27. [PMID: 27095671 PMCID: PMC4909546 DOI: 10.1016/j.bbagen.2016.04.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 04/11/2016] [Accepted: 04/13/2016] [Indexed: 01/18/2023]
Abstract
BACKGROUND Etoposide and doxorubicin, topoisomerase II poisons, are important drugs for the treatment of tumors in the clinic. Topoisomerases contain several free sulfhydryl groups which are important for their activity and are also potential targets for nitric oxide (NO)-induced nitrosation. NO, a physiological signaling molecule nitrosates many cellular proteins, causing altered protein and cellular functions. METHODS Here, we have evaluated the roles of NO/NO-derived species in the activity/stability of topo II both in vitro and in human tumor cells, and in the cytotoxicity of topo II-poisons, etoposide and doxorubicin. RESULTS Treatment of purified topo IIα with propylamine propylamine nonoate (PPNO), an NO donor, resulted in inhibition of both the catalytic and relaxation activity in vitro, and decreased etoposide-dependent cleavable complex formation in both human HT-29 colon and MCF-7 breast cancer cells. PPNO treatment also induced significant nitrosation of topo IIα protein in these human tumor cells. These events, taken together, caused a significant resistance to etoposide in both cell lines. However, PPNO had no effect on doxorubicin-induced cleavable complex formation, or doxorubicin cytotoxicity in these cell lines. CONCLUSION Inhibition of topo II function by NO/NO-derived species induces significant resistance to etoposide, without affecting doxorubicin cytotoxicity in human tumor cells. GENERAL SIGNIFICANCE As tumors express inducible nitric oxide synthase and generate significant amounts of NO, modulation of topo II functions by NO/NO-derived species could render tumors resistant to certain topo II-poisons in the clinic.
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Affiliation(s)
- Ashutosh Kumar
- Immunity, Inflammation and Disease Laboratory, NIH, Research Triangle Park, North Carolina, USA
| | - Marilyn Ehrenshaft
- Immunity, Inflammation and Disease Laboratory, NIH, Research Triangle Park, North Carolina, USA
| | - Erik J Tokar
- National Toxicology Program National Institute of Environmental Health Sciences, NIH, Research Triangle Park, North Carolina, USA
| | - Ronald P Mason
- Immunity, Inflammation and Disease Laboratory, NIH, Research Triangle Park, North Carolina, USA
| | - Birandra K Sinha
- Immunity, Inflammation and Disease Laboratory, NIH, Research Triangle Park, North Carolina, USA.
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Bailey KA, Smith AH, Tokar EJ, Graziano JH, Kim KW, Navasumrit P, Ruchirawat M, Thiantanawat A, Suk WA, Fry RC. Mechanisms Underlying Latent Disease Risk Associated with Early-Life Arsenic Exposure: Current Research Trends and Scientific Gaps. Environ Health Perspect 2016; 124:170-5. [PMID: 26115410 PMCID: PMC4749078 DOI: 10.1289/ehp.1409360] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Accepted: 06/23/2015] [Indexed: 05/04/2023]
Abstract
BACKGROUND Millions of individuals worldwide, particularly those living in rural and developing areas, are exposed to harmful levels of inorganic arsenic (iAs) in their drinking water. Inorganic As exposure during key developmental periods is associated with a variety of adverse health effects, including those that are evident in adulthood. There is considerable interest in identifying the molecular mechanisms that relate early-life iAs exposure to the development of these latent diseases, particularly in relationship to cancer. OBJECTIVES This work summarizes research on the molecular mechanisms that underlie the increased risk of cancer development in adulthood that is associated with early-life iAs exposure. DISCUSSION Epigenetic reprogramming that imparts functional changes in gene expression, the development of cancer stem cells, and immunomodulation are plausible underlying mechanisms by which early-life iAs exposure elicits latent carcinogenic effects. CONCLUSIONS Evidence is mounting that relates early-life iAs exposure and cancer development later in life. Future research should include animal studies that address mechanistic hypotheses and studies of human populations that integrate early-life exposure, molecular alterations, and latent disease outcomes.
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Affiliation(s)
- Kathryn A. Bailey
- Department of Environmental Sciences and Engineering, UNC Gillings School of Global Public Health, Chapel Hill, North Carolina, USA
| | - Allan H. Smith
- Arsenic Health Effects Research Program, School of Public Health, University of California, Berkeley, Berkeley, California, USA
| | - Erik J. Tokar
- National Toxicology Program, National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Department of Health and Human Services (DHHS), Research Triangle Park, North Carolina, USA
| | - Joseph H. Graziano
- Department of Environmental Health Sciences, Columbia University Mailman School of Public Health, New York, New York, USA
| | - Kyoung-Woong Kim
- School of Environmental Science and Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - Panida Navasumrit
- Laboratory of Environmental Toxicology, Chulabhorn Research Institute, Bangkok, Thailand
| | - Mathuros Ruchirawat
- Laboratory of Environmental Toxicology, Chulabhorn Research Institute, Bangkok, Thailand
| | - Apinya Thiantanawat
- Laboratory of Environmental Toxicology, Chulabhorn Research Institute, Bangkok, Thailand
| | - William A. Suk
- Superfund Research Program, NIEHS, NIH, DHHS, Research Triangle Park, North Carolina, USA
| | - Rebecca C. Fry
- Department of Environmental Sciences and Engineering, UNC Gillings School of Global Public Health, Chapel Hill, North Carolina, USA
- Address correspondence to R.C. Fry, Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, 135 Dauer Dr., CB 7431, University of North Carolina, Chapel Hill, NC 27599-7295 USA. Telephone: (919) 843-6864. E-mail:
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Ngalame NNO, Makia NL, Waalkes MP, Tokar EJ. Mitigation of arsenic-induced acquired cancer phenotype in prostate cancer stem cells by miR-143 restoration. Toxicol Appl Pharmacol 2015; 312:11-18. [PMID: 26721309 DOI: 10.1016/j.taap.2015.12.013] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 12/17/2015] [Accepted: 12/18/2015] [Indexed: 12/22/2022]
Abstract
Inorganic arsenic, an environmental contaminant and a human carcinogen is associated with prostate cancer. Emerging evidence suggests that cancer stem cells (CSCs) are the driving force of carcinogenesis. Chronic arsenic exposure malignantly transforms the human normal prostate stem/progenitor cell (SC) line, WPE-stem to arsenic-cancer SCs (As-CSCs), through unknown mechanisms. MicroRNAs (miRNAs) are small, non-coding RNAs that negatively regulate gene expression at the posttranscriptional level. In prior work, miR-143 was markedly downregulated in As-CSCs, suggesting a role in arsenic-induced malignant transformation. In the present study, we investigated whether loss of miR-143 expression is important in arsenic-induced transformation of prostate SCs. Restoration of miR-143 in As-CSCs was achieved by lentivirus-mediated miR-143 overexpression. Cells were assessed bi-weekly for up to 30weeks to examine mitigation of cancer phenotype. Secreted matrix metalloproteinase (MMP) activity was increased by arsenic-induced malignant transformation, but miR-143 restoration decreased secreted MMP-2 and MMP-9 enzyme activities compared with scramble controls. Increased cell proliferation and apoptotic resistance, two hallmarks of cancer, were decreased upon miR-143 restoration. Increased apoptosis was associated with decreased BCL2 and BCL-XL expression. miR-143 restoration dysregulated the expression of SC/CSC self-renewal genes including NOTCH-1, BMI-1, OCT4 and ABCG2. The anticancer effects of miR-143 overexpression appeared to be mediated by targeting and inhibiting LIMK1 protein, and the phosphorylation of cofilin, a LIMK1 substrate. These findings clearly show that miR-143 restoration mitigated multiple cancer characteristics in the As-CSCs, suggesting a potential role in arsenic-induced transformation of prostate SCs. Thus, miR-143 is a potential biomarker and therapeutic target for arsenic-induced prostate cancer.
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Affiliation(s)
- Ntube N O Ngalame
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA.
| | - Ngome L Makia
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA.
| | - Michael P Waalkes
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA.
| | - Erik J Tokar
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA.
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Sharma NK, Kumar A, Kumari A, Tokar EJ, Waalkes MP, Bortner CD, Williams J, Ehrenshaft M, Mason RP, Sinha BK. Nitric Oxide Down-Regulates Topoisomerase I and Induces Camptothecin Resistance in Human Breast MCF-7 Tumor Cells. PLoS One 2015; 10:e0141897. [PMID: 26540186 PMCID: PMC4635000 DOI: 10.1371/journal.pone.0141897] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 10/14/2015] [Indexed: 11/19/2022] Open
Abstract
Camptothecin (CPT), a topoisomerase I poison, is an important drug for the treatment of solid tumors in the clinic. Nitric oxide (·NO), a physiological signaling molecule, is involved in many cellular functions, including cell proliferation, survival and death. We have previously shown that ·NO plays a significant role in the detoxification of etoposide (VP-16), a topoisomerase II poison in vitro and in human melanoma cells. ·NO/·NO-derived species are reported to modulate activity of several important cellular proteins. As topoisomerases contain a number of free sulfhydryl groups which may be targets of ·NO/·NO-derived species, we have investigated the roles of ·NO/·NO-derived species in the stability and activity of topo I. Here we show that ·NO/·NO-derived species induces a significant down-regulation of topoisomerase I protein via the ubiquitin/26S proteasome pathway in human colon (HT-29) and breast (MCF-7) cancer cell lines. Importantly, ·NO treatment induced a significant resistance to CPT only in MCF-7 cells. This resistance to CPT did not result from loss of topoisomerase I activity as there were no differences in topoisomerase I-induced DNA cleavage in vitro or in tumor cells, but resulted from the stabilization/induction of bcl2 protein. This up-regulation of bcl2 protein in MCF-7 cells was wtp53 dependent as pifithrine-α, a small molecule inhibitor of wtp53 function, completely reversed CPT resistance, suggesting that wtp53 and bcl2 proteins played important roles in CPT resistance. Because tumors in vivo are heterogeneous and contaminated by infiltrating macrophages, ·NO-induced down-regulation of topoisomerase I protein combined with bcl2 protein stabilization could render certain tumors highly resistant to CPT and drugs derived from it in the clinic.
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Affiliation(s)
- Nilesh K. Sharma
- Immunity, Inflammation and Disease Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle, Park, Durham, North Carolina, United States of America
| | - Ashutosh Kumar
- Immunity, Inflammation and Disease Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle, Park, Durham, North Carolina, United States of America
| | - Amrita Kumari
- Immunity, Inflammation and Disease Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle, Park, Durham, North Carolina, United States of America
| | - Erik J. Tokar
- National Toxicology Program, National Institute of Environmental Health Sciences, NIH, Research Triangle, Park, Durham, North Carolina, United States of America
| | - Michael P. Waalkes
- National Toxicology Program, National Institute of Environmental Health Sciences, NIH, Research Triangle, Park, Durham, North Carolina, United States of America
| | - Carl D. Bortner
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, Research Triangle, Park, Durham, North Carolina, United States of America
| | - Jason Williams
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences, NIH, Research Triangle, Park, Durham, North Carolina, United States of America
| | - Marilyn Ehrenshaft
- Immunity, Inflammation and Disease Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle, Park, Durham, North Carolina, United States of America
| | - Ronald P. Mason
- Immunity, Inflammation and Disease Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle, Park, Durham, North Carolina, United States of America
| | - Birandra K. Sinha
- Immunity, Inflammation and Disease Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle, Park, Durham, North Carolina, United States of America
- * E-mail:
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25
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Pelch KE, Tokar EJ, Merrick BA, Waalkes MP. Differential DNA methylation profile of key genes in malignant prostate epithelial cells transformed by inorganic arsenic or cadmium. Toxicol Appl Pharmacol 2015; 286:159-67. [PMID: 25922126 PMCID: PMC4461502 DOI: 10.1016/j.taap.2015.04.011] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 04/16/2015] [Accepted: 04/20/2015] [Indexed: 12/11/2022]
Abstract
Previous work shows altered methylation patterns in inorganic arsenic (iAs)- or cadmium (Cd)-transformed epithelial cells. Here, the methylation status near the transcriptional start site was assessed in the normal human prostate epithelial cell line (RWPE-1) that was malignantly transformed by 10μM Cd for 11weeks (CTPE) or 5μM iAs for 29weeks (CAsE-PE), at which time cells showed multiple markers of acquired cancer phenotype. Next generation sequencing of the transcriptome of CAsE-PE cells identified multiple dysregulated genes. Of the most highly dysregulated genes, five genes that can be relevant to the carcinogenic process (S100P, HYAL1, NTM, NES, ALDH1A1) were chosen for an in-depth analysis of the DNA methylation profile. DNA was isolated, bisulfite converted, and combined bisulfite restriction analysis was used to identify differentially methylated CpG sites, which was confirmed with bisulfite sequencing. Four of the five genes showed differential methylation in transformants relative to control cells that was inversely related to altered gene expression. Increased expression of HYAL1 (>25-fold) and S100P (>40-fold) in transformants was correlated with hypomethylation near the transcriptional start site. Decreased expression of NES (>15-fold) and NTM (>1000-fold) in transformants was correlated with hypermethylation near the transcriptional start site. ALDH1A1 expression was differentially expressed in transformed cells but was not differentially methylated relative to control. In conclusion, altered gene expression observed in Cd and iAs transformed cells may result from altered DNA methylation status.
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Affiliation(s)
- Katherine E Pelch
- National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Erik J Tokar
- National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - B Alex Merrick
- Molecular Toxicology and Informatics Group, Biomolecular Screening Branch, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Morrisville, NC 27560, USA
| | - Michael P Waalkes
- National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA.
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26
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Person RJ, Ngalame NNO, Makia NL, Bell MW, Waalkes MP, Tokar EJ. Chronic inorganic arsenic exposure in vitro induces a cancer cell phenotype in human peripheral lung epithelial cells. Toxicol Appl Pharmacol 2015; 286:36-43. [PMID: 25804888 PMCID: PMC4444387 DOI: 10.1016/j.taap.2015.03.014] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 03/10/2015] [Accepted: 03/12/2015] [Indexed: 02/07/2023]
Abstract
Inorganic arsenic is a human lung carcinogen. We studied the ability of chronic inorganic arsenic (2 μM; as sodium arsenite) exposure to induce a cancer phenotype in the immortalized, non-tumorigenic human lung peripheral epithelial cell line, HPL-1D. After 38 weeks of continuous arsenic exposure, secreted matrix metalloproteinase-2 (MMP2) activity increased to over 200% of control, levels linked to arsenic-induced cancer phenotypes in other cell lines. The invasive capacity of these chronic arsenic-treated lung epithelial (CATLE) cells increased to 320% of control and colony formation increased to 280% of control. CATLE cells showed enhanced proliferation in serum-free media indicative of autonomous growth. Compared to control cells, CATLE cells showed reduced protein expression of the tumor suppressor gene PTEN (decreased to 26% of control) and the putative tumor suppressor gene SLC38A3 (14% of control). Morphological evidence of epithelial-to-mesenchymal transition (EMT) occurred in CATLE cells together with appropriate changes in expression of the EMT markers vimentin (VIM; increased to 300% of control) and e-cadherin (CDH1; decreased to 16% of control). EMT is common in carcinogenic transformation of epithelial cells. CATLE cells showed increased KRAS (291%), ERK1/2 (274%), phosphorylated ERK (p-ERK; 152%), and phosphorylated AKT1 (p-AKT1; 170%) protein expression. Increased transcript expression of metallothioneins, MT1A and MT2A and the stress response genes HMOX1 (690%) and HIF1A (247%) occurred in CATLE cells possibly in adaptation to chronic arsenic exposure. Thus, arsenic induced multiple cancer cell characteristics in human peripheral lung epithelial cells. This model may be useful to assess mechanisms of arsenic-induced lung cancer.
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Affiliation(s)
- Rachel J Person
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
| | - Ntube N Olive Ngalame
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
| | - Ngome L Makia
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
| | - Matthew W Bell
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
| | - Michael P Waalkes
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
| | - Erik J Tokar
- Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA.
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27
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Severson PL, Tokar EJ, Vrba L, Waalkes MP, Futscher BW. Abstract 5448: Common targets of epigenetic dysfunction in distinct target tissues of arsenic and cadmium induced malignant transformation. Carcinogenesis 2014. [DOI: 10.1158/1538-7445.am2012-5448] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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28
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Ngalame NNO, Tokar EJ, Person RJ, Waalkes MP. Silencing KRAS overexpression in arsenic-transformed prostate epithelial and stem cells partially mitigates malignant phenotype. Toxicol Sci 2014; 142:489-96. [PMID: 25273566 DOI: 10.1093/toxsci/kfu201] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Inorganic arsenic is a human carcinogen that likely targets the prostate. Chronic arsenic exposure malignantly transforms the RWPE-1 human prostate epithelial line to chronic arsenic exposed-prostate epithelial (CAsE-PE) cells, and a derivative normal prostate stem cell (SC) line, WPE-stem to arsenic-cancer SCs (As-CSCs). The KRAS oncogene is highly overexpressed in CAsE-PE cells and activation precedes transformation, inferring mechanistic significance. As-CSCs also highly overexpress KRAS. Thus, we hypothesize KRAS activation is key in causing and maintaining an arsenic-induced malignant phenotype, and hence, KRAS knockdown (KD) may reverse this malignant phenotype. RNA interference using shRNAmirs to obtain KRAS KD was used in CAsE-PE and As-CSC cells. Cells analyzed 2 weeks post transduction showed KRAS protein decreased to 5% of control after KD, confirming stable KD. KRAS KD decreased phosphorylated ERK, indicating inhibition of RAS/ERK signaling, a proliferation/survival pathway activated with arsenic transformation. Secreted metalloproteinase (MMP) activity was increased by arsenic-induced malignant transformation, but KRAS KD from 4 weeks on decreased secreted MMP-9 activity by 50% in As-CSCs. Colony formation, a characteristic of cancer cells, was decreased in both KRAS KD transformants. KRAS KD also decreased the invasive capacity of both cell types. KRAS KD decreased proliferation in As-CSCs, consistent with loss of rapid tumor growth. Genes predicted to impact cell proliferation (eg, Cyclin D1, p16, and p21) changed accordingly in both KD cell types. Thus, KRAS silencing impacts aspects of arsenic-induced malignant phenotype, inducing loss of many typical cancer characteristics particularly in As-CSCs.
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Affiliation(s)
- Ntube N O Ngalame
- Inorganic Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
| | - Erik J Tokar
- Inorganic Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
| | - Rachel J Person
- Inorganic Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
| | - Michael P Waalkes
- Inorganic Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
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Waalkes MP, Qu W, Tokar EJ, Kissling GE, Dixon D. Lung tumors in mice induced by "whole-life" inorganic arsenic exposure at human-relevant doses. Arch Toxicol 2014; 88:1619-29. [PMID: 25005685 PMCID: PMC4130362 DOI: 10.1007/s00204-014-1305-8] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 06/23/2014] [Indexed: 01/08/2023]
Abstract
In mice, inorganic arsenic in the drinking water in the parts per million range via the dam during in utero life or with whole-life exposure is a multi-site carcinogen in the offspring. However, human arsenic exposure is typically in the parts per billion (ppb) range. Thus, we studied "whole-life" inorganic arsenic carcinogenesis in mice at levels more relevant to humans. Breeder male and female CD1 mice were exposed to 0, 50, 500 or 5,000 ppb arsenic (as sodium arsenite) in the drinking water for 3 weeks prior to breeding, during pregnancy and lactation, and after weaning (at week 3) groups of male and female offspring (initial n = 40) were exposed for up to 2 years. Tumors were assessed in these offspring. Arsenic exposure had no effect on pregnant dam weights or water consumption, litter size, offspring birthweight or weight at weaning compared to control. In male offspring mice, arsenic exposure increased (p < 0.05) bronchiolo-alveolar tumor (adenoma or carcinoma) incidence at 50-ppb group (51 %) and 500-ppb group (54 %), but not at 5,000-ppb group (28 %) compared to control (22 %). These arsenic-induced bronchiolo-alveolar tumors included increased (p < 0.05) carcinoma at 50-ppb group (27 %) compared to controls (8 %). An increase (p < 0.05) in lung adenoma (25 %) in the 50-ppb group compared to control (11 %) occurred in female offspring. Thus, in CD1 mice whole-life arsenic exposure induced lung tumors at human-relevant doses (i.e., 50 and 500 ppb).
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Affiliation(s)
- Michael P Waalkes
- Inorganic Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, 111 Alexander Drive, MD E1-07, P.O. Box 12233, Research Triangle Park, NC, 27709, USA,
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Ngalame NNO, Tokar EJ, Person RJ, Xu Y, Waalkes MP. Aberrant microRNA expression likely controls RAS oncogene activation during malignant transformation of human prostate epithelial and stem cells by arsenic. Toxicol Sci 2014; 138:268-77. [PMID: 24431212 PMCID: PMC3968309 DOI: 10.1093/toxsci/kfu002] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Accepted: 12/20/2013] [Indexed: 11/13/2022] Open
Abstract
Inorganic arsenic (iAs), a human carcinogen, potentially targets the prostate. iAs malignantly transforms the RWPE-1 human prostate epithelial line to CAsE-PE cells, and a derivative normal stem cell (SC) line, WPE-stem, to As-Cancer SC (As-CSC) line. MicroRNAs (miRNA) are noncoding but exert negative control on expression by degradation or translational repression of target mRNAs. Aberrant miRNA expression is important in carcinogenesis. A miRNA array of CAsE-PE and As-CSC revealed common altered expression in both for pathways concerning oncogenesis, miRNA biogenesis, cell signaling, proliferation, and tumor metastasis and invasion. The KRAS oncogene is overexpressed in CAsE-PE cells but not by mutation or promoter hypomethylation, and is intensely overexpressed in As-CSC cells. In both transformants, decreased miRNAs targeting KRAS and RAS superfamily members occurred. Reduced miR-134, miR-373, miR-155, miR-138, miR-205, miR-181d, miR-181c, and let-7 in CAsE-PE cells correlated with increased target RAS oncogenes, RAN, RAB27A, RAB22A mRNAs, and KRAS protein. Reduced miR-143, miR-34c-5p, and miR-205 in As-CSC correlated with increased target RAN mRNA, and KRAS, NRAS, and RRAS proteins. The RAS/ERK and PI3K/PTEN/AKT pathways control cell survival, differentiation, and proliferation, and when dysregulated promote a cancer phenotype. iAs transformation increased expression of activated ERK kinase in both transformants and altered components of the PI3K/PTEN/AKT pathway including decreased PTEN and increases in BCL2, BCL-XL, and VEGF in the absence of AKT activation. Thus, dysregulated miRNA expression may be linked to RAS activation in both transformants.
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Affiliation(s)
- Ntube N. O. Ngalame
- Inorganic Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
| | - Erik J. Tokar
- Inorganic Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
| | - Rachel J. Person
- Inorganic Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
| | - Yuanyuan Xu
- Inorganic Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
| | - Michael P. Waalkes
- Inorganic Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
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Tokar EJ, Kojima C, Waalkes MP. Methylarsonous acid causes oxidative DNA damage in cells independent of the ability to biomethylate inorganic arsenic. Arch Toxicol 2014; 88:249-61. [PMID: 24091636 PMCID: PMC3946729 DOI: 10.1007/s00204-013-1141-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 09/23/2013] [Indexed: 10/26/2022]
Abstract
Inorganic arsenic (iAs) and its toxic methylated metabolite, methylarsonous acid (MMA(III)), both have carcinogenic potential. Prior study shows iAs-induced malignant transformation in both arsenic methylation-proficient (liver) and methylation-deficient (prostate) cells, but only methylation-proficient cells show oxidative DNA damage (ODD) during this transformation. To further define whether arsenic methylation is necessary for transformation or ODD induction, here we chronically exposed these same liver or prostate cell lines to MMA(III) (0.25-1.0 μM) and tested for acquired malignant phenotype. Various metrics of oncogenic transformation were periodically assessed along with ODD during chronic MMA(III) exposure. Methylation-deficient and methylation-proficient cells both acquired a cancer phenotype with MMA(III) exposure at about 20 weeks, based on increased matrix metalloproteinase secretion, colony formation, and invasion. In contrast, prior work showed iAs-induced transformation took longer in biomethylation-deficient cells (~30 weeks) than in biomethylation-proficient cells (~18 weeks). In the present study, MMA(III) caused similar peak ODD levels at similar concentrations and at similar exposure times (18-22 weeks) in both cell types. At the approximate peak of ODD production, both cell types showed similar alterations in arsenic and oxidative stress adaptation factors (i.e., ABCC1, ABCC2, GST-π, SOD-1). Thus, MMA(III) causes oncogenic transformation associated with ODD in methylation-deficient cells, indicating that further methylation is not required to induce ODD. Together, these results show that MMA(III) and iAs cause an acquired malignant phenotype in methylation-deficient cells, yet iAs does not induce ODD. This indicates iAs likely has both genotoxic and non-genotoxic mechanisms dictated by the target cell's ability to methylate arsenic.
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Affiliation(s)
- Erik J. Tokar
- National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709
| | - Chikara Kojima
- National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709
| | - Michael P. Waalkes
- National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709
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Xu Y, Tokar EJ, Waalkes MP. Arsenic-induced cancer cell phenotype in human breast epithelia is estrogen receptor-independent but involves aromatase activation. Arch Toxicol 2014; 88:263-74. [PMID: 24068038 PMCID: PMC3946706 DOI: 10.1007/s00204-013-1131-4] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 09/11/2013] [Indexed: 01/12/2023]
Abstract
Accumulating data suggest arsenic may be an endocrine disruptor and tentatively linked to breast cancer by some studies. Therefore, we tested the effects of chronic inorganic arsenic exposure on the normal estrogen receptor (ER)-negative breast epithelial cell line, MCF-10A. Cells were chronically exposed to a low-level arsenite (500 nM) for up to 24 weeks. Markers of cancer cell phenotype and the expression of critical genes relevant to breast cancer or stem cells (SCs) were examined. After 24 weeks, chronic arsenic-exposed breast epithelial (CABE) cells showed increases in secreted MMP activity, colony formation, invasion, and proliferation rate, indicating an acquired cancer cell phenotype. These CABE cells presented with basal-like breast cancer characteristics, including ER-α, HER-2, and progesterone receptor negativity, and overexpression of K5 and p63. Putative CD44(+)/CD24(-/low) breast SCs were increased to 80 % over control in CABE cells. CABE cells also formed multilayer cell mounds, indicative of loss of contact inhibition. These mounds showed high levels of K5 and p63, indicating the potential presence of cancer stem cells (CSCs). Epithelial-to-mesenchymal transition occurred during arsenic exposure. Overexpression of aromatase, a key rate-limiting enzyme in estrogen synthesis, occurred with arsenic starting early on in exposure. Levels of 17β-estradiol increased in CABE cells and their conditioned medium. The aromatase inhibitor letrozole abolished arsenic-induced increases in 17β-estradiol production and reversed cancer cell phenotype. Thus, chronic arsenic exposure drives human breast epithelia into a cancer cell phenotype with an apparent overabundance of putative CSCs. Arsenic appears to transform breast epithelia through overexpression of aromatase, thereby activating oncogenic processes independent of ER.
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Affiliation(s)
- Yuanyuan Xu
- National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
| | - Erik J. Tokar
- National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
| | - Michael P. Waalkes
- National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
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Person RJ, Tokar EJ, Xu Y, Orihuela R, Olive Ngalame NN, Waalkes MP. Chronic cadmium exposure in vitro induces cancer cell characteristics in human lung cells. Toxicol Appl Pharmacol 2013; 273:281-8. [PMID: 23811327 PMCID: PMC3863781 DOI: 10.1016/j.taap.2013.06.013] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 06/13/2013] [Accepted: 06/18/2013] [Indexed: 01/22/2023]
Abstract
Cadmium is a known human lung carcinogen. Here, we attempt to develop an in vitro model of cadmium-induced human lung carcinogenesis by chronically exposing the peripheral lung epithelia cell line, HPL-1D, to a low level of cadmium. Cells were chronically exposed to 5 μM cadmium, a noncytotoxic level, and monitored for acquired cancer characteristics. By 20 weeks of continuous cadmium exposure, these chronic cadmium treated lung (CCT-LC) cells showed marked increases in secreted MMP-2 activity (3.5-fold), invasion (3.4-fold), and colony formation in soft agar (2-fold). CCT-LC cells were hyperproliferative, grew well in serum-free media, and overexpressed cyclin D1. The CCT-LC cells also showed decreased expression of the tumor suppressor genes p16 and SLC38A3 at the protein levels. Also consistent with an acquired cancer cell phenotype, CCT-LC cells showed increased expression of the oncoproteins K-RAS and N-RAS as well as the epithelial-to-mesenchymal transition marker protein Vimentin. Metallothionein (MT) expression is increased by cadmium, and is typically overexpressed in human lung cancers. The major MT isoforms, MT-1A and MT-2A were elevated in CCT-LC cells. Oxidant adaptive response genes HO-1 and HIF-1A were also activated in CCT-LC cells. Expression of the metal transport genes ZNT-1, ZNT-5, and ZIP-8 increased in CCT-LC cells culminating in reduced cadmium accumulation, suggesting adaptation to the metal. Overall, these data suggest that exposure of human lung epithelial cells to cadmium causes acquisition of cancer cell characteristics. Furthermore, transformation occurs despite the cell's ability to adapt to chronic cadmium exposure.
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Affiliation(s)
- Rachel J. Person
- Inorganic Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
| | - Erik J. Tokar
- Inorganic Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
| | - Yuanyuan Xu
- Inorganic Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
| | - Ruben Orihuela
- Inorganic Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
| | - Ntube N. Olive Ngalame
- Inorganic Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
| | - Michael P. Waalkes
- Inorganic Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
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Severson PL, Tokar EJ, Vrba L, Waalkes MP, Futscher BW. Coordinate H3K9 and DNA methylation silencing of ZNFs in toxicant-induced malignant transformation. Epigenetics 2013; 8:1080-8. [PMID: 23974009 PMCID: PMC3891689 DOI: 10.4161/epi.25926] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Genome-wide disruption of the epigenetic code is a hallmark of malignancy that encompasses many distinct, highly interactive modifications. Delineating the aberrant epigenome produced during toxicant-mediated malignant transformation will help identify the underlying epigenetic drivers of environmental toxicant-induced carcinogenesis. Gene promoter DNA methylation and gene expression profiling of arsenite-transformed prostate epithelial cells showed a negative correlation between gene expression changes and DNA methylation changes; however, less than 10% of the genes with increased promoter methylation were downregulated. Studies described herein confirm that a majority of the DNA hypermethylation events occur at H3K27me3 marked genes that were already transcriptionally repressed. In contrast to aberrant DNA methylation targeting H3K27me3 pre-marked silent genes, we found that actively expressed C2H2 zinc finger genes (ZNFs) marked with H3K9me3 on their 3′ ends, were the favored targets of DNA methylation linked gene silencing. DNA methylation coupled, H3K9me3 mediated gene silencing of ZNF genes was widespread, occurring at individual ZNF genes on multiple chromosomes and across ZNF gene family clusters. At ZNF gene promoters, H3K9me3 and DNA hypermethylation replaced H3K4me3, resulting in a widespread downregulation of ZNF gene expression, which accounted for 8% of all the downregulated genes in the arsenical-transformed cells. In summary, these studies associate toxicant exposure with widespread silencing of ZNF genes by DNA hypermethylation-linked H3K9me3 spreading, further implicating epigenetic dysfunction as a driver of toxicant associated carcinogenesis.
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Affiliation(s)
- Paul L Severson
- Department of Pharmacology and Toxicology; College of Pharmacy; University of Arizona; Tucson, AZ USA
| | - Erik J Tokar
- National Toxicology Program Laboratory; National Institute of Environmental Health Sciences; Research Triangle Park, NC USA
| | - Lukas Vrba
- University of Arizona Cancer Center; Tucson, AZ USA
| | - Michael P Waalkes
- National Toxicology Program Laboratory; National Institute of Environmental Health Sciences; Research Triangle Park, NC USA
| | - Bernard W Futscher
- Department of Pharmacology and Toxicology; College of Pharmacy; University of Arizona; Tucson, AZ USA; University of Arizona Cancer Center; Tucson, AZ USA
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Xu Y, Tokar EJ, Person RJ, Orihuela RG, Ngalame NNO, Waalkes MP. Recruitment of normal stem cells to an oncogenic phenotype by noncontiguous carcinogen-transformed epithelia depends on the transforming carcinogen. Environ Health Perspect 2013; 121:944-950. [PMID: 23687063 PMCID: PMC3734505 DOI: 10.1289/ehp.1306714] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Accepted: 05/16/2013] [Indexed: 06/02/2023]
Abstract
BACKGROUND Cancer stem cells (CSCs) drive tumor initiation, progression, and metastasis. The microenvironment is critical to the fate of CSCs. We have found that a normal stem cell (NSC) line from human prostate (WPE-stem) is recruited into CSC-like cells by nearby, but noncontiguous, arsenic-transformed isogenic malignant epithelial cells (MECs). OBJECTIVE It is unknown whether this recruitment of NSCs into CSCs by noncontact co-culture is specific to arsenic-transformed MECs. Thus, we used co-culture to examine the effects of neighboring noncontiguous cadmium-transformed MECs (Cd-MECs) and N-methyl-N-nitrosourea-transformed MECs (MNU-MECs) on NSCs. RESULTS After 2 weeks of noncontact Cd-MEC co-culture, NSCs showed elevated metalloproteinase-9 (MMP-9) and MMP-2 secretion, increased invasiveness, increased colony formation, decreased PTEN expression, and formation of aggressive, highly branched duct-like structures from single cells in Matrigel, all characteristics typical of cancer cells. These oncogenic characteristics did not occur in NSCs co-cultured with MNU-MECs. The NSCs co-cultured with Cd-MECs retained self-renewal capacity, as evidenced by multiple passages (> 3) of structures formed in Matrigel. Cd-MEC-co-cultured NSCs also showed molecular (increased VIM, SNAIL1, and TWIST1 expression; decreased E-CAD expression) and morphologic evidence of epithelial-to-mesenchymal transition typical for conversion to CSCs. Dysregulated expression of SC-renewal genes, including ABCG2, OCT-4, and WNT-3, also occurred in NSCs during oncogenic transformation induced by noncontact co-culture with Cd-MECs. CONCLUSIONS These data indicate that Cd-MECs can recruit nearby NSCs into a CSC-like phenotype, but MNU-MECs do not. Thus, the recruitment of NSCs into CSCs by nearby MECs is dependent on the carcinogen originally used to malignantly transform the MECs.
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Affiliation(s)
- Yuanyuan Xu
- National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina, USA
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Das S, Kumar A, Seth RK, Tokar EJ, Kadiiska MB, Waalkes MP, Mason RP, Chatterjee S. Proinflammatory adipokine leptin mediates disinfection byproduct bromodichloromethane-induced early steatohepatitic injury in obesity. Toxicol Appl Pharmacol 2013; 269:297-306. [PMID: 23438451 PMCID: PMC3654077 DOI: 10.1016/j.taap.2013.02.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 02/05/2013] [Accepted: 02/06/2013] [Indexed: 12/17/2022]
Abstract
Today's developed world faces a major public health challenge in the rise in the obese population and the increased incidence in fatty liver disease. There is a strong association among diet induced obesity, fatty liver disease and development of nonalcoholic steatohepatitis but the environmental link to disease progression remains unclear. Here we demonstrate that in obesity, early steatohepatitic lesions induced by the water disinfection byproduct bromodichloromethane are mediated by increased oxidative stress and leptin which act in synchrony to potentiate disease progression. Low acute exposure to bromodichloromethane (BDCM), in diet-induced obesity produced oxidative stress as shown by increased lipid peroxidation, protein free radical and nitrotyrosine formation and elevated leptin levels. Exposed obese mice showed histopathological signs of early steatohepatitic injury and necrosis. Spontaneous knockout mice for leptin or systemic leptin receptor knockout mice had significantly decreased oxidative stress and TNF-α levels. Co-incubation of leptin and BDCM caused Kupffer cell activation as shown by increased MCP-1 release and NADPH oxidase membrane assembly, a phenomenon that was decreased in Kupffer cells isolated from leptin receptor knockout mice. In obese mice that were BDCM-exposed, livers showed a significant increase in Kupffer cell activation marker CD68 and, increased necrosis as assessed by levels of isocitrate dehydrogenase, events that were decreased in the absence of leptin or its receptor. In conclusion, our results show that exposure to the disinfection byproduct BDCM in diet-induced obesity augments steatohepatitic injury by potentiating the effects of leptin on oxidative stress, Kupffer cell activation and cell death in the liver.
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Affiliation(s)
- Suvarthi Das
- Environmental Health and Disease Laboratory, Department of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia SC 29208
| | - Ashutosh Kumar
- Free Radical Metabolism Group, Laboratory of Toxicology and Pharmacology, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709
| | - Ratanesh Kumar Seth
- Environmental Health and Disease Laboratory, Department of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia SC 29208
| | - Erik J Tokar
- Inorganic Toxicology Group, National Toxicology Program Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709
| | - Maria B. Kadiiska
- Free Radical Metabolism Group, Laboratory of Toxicology and Pharmacology, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709
| | - Michael P Waalkes
- Inorganic Toxicology Group, National Toxicology Program Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709
| | - Ronald P Mason
- Free Radical Metabolism Group, Laboratory of Toxicology and Pharmacology, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709
| | - Saurabh Chatterjee
- Environmental Health and Disease Laboratory, Department of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia SC 29208
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Chatterjee S, Ganini D, Tokar EJ, Kumar A, Das S, Corbett J, Kadiiska MB, Waalkes MP, Diehl AM, Mason RP. Leptin is key to peroxynitrite-mediated oxidative stress and Kupffer cell activation in experimental non-alcoholic steatohepatitis. J Hepatol 2013; 58. [PMID: 23207144 PMCID: PMC3596459 DOI: 10.1016/j.jhep.2012.11.035] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND & AIMS Progression from steatosis to steatohepatitic lesions is hypothesized to require a second hit. These lesions have been associated with increased oxidative stress, often ascribed to high levels of leptin and other proinflammatory mediators. Here we have examined the role of leptin in inducing oxidative stress and Kupffer cell activation in CCl4-mediated steatohepatitic lesions of obese mice. METHODS Male C57BL/6 mice fed with a high-fat diet (60%kcal) at 16 weeks were administered CCl₄ to induce steatohepatitic lesions. Approaches included use of immuno-spin trapping for measuring free radical stress, gene-deficient mice for leptin, p47 phox, iNOS and adoptive transfer of leptin primed macrophages in vivo. RESULTS Diet-induced obese (DIO) mice, treated with CCl4 increased serum leptin levels. Oxidative stress was significantly elevated in the DIO mouse liver, but not in ob/ob mice, or in DIO mice treated with leptin antibody. In ob/ob mice, leptin supplementation restored markers of free radical generation. Markers of free radical formation were significantly decreased by the peroxynitrite decomposition catalyst FeTPPS, the iNOS inhibitor 1400W, the NADPH oxidase inhibitor apocynin, or in iNOS or p47 phox-deficient mice. These results correlated with the decreased expression of TNF-alpha and MCP-1. Kupffer cell depletion eliminated oxidative stress and inflammation, whereas in macrophage-depleted mice, the adoptive transfer of leptin-primed macrophages significantly restored inflammation. CONCLUSIONS These results, for the first time, suggest that leptin action in macrophages of the steatotic liver, through induction of iNOS and NADPH oxidase, causes peroxynitrite-mediated oxidative stress thus activating Kupffer cells.
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Affiliation(s)
- Saurabh Chatterjee
- Environmental Health and Disease Laboratory, Department of Environmental Health Sciences, University of South Carolina, Columbia, SC 29208, USA.
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Orihuela R, Kojima C, Tokar EJ, Person RJ, Xu Y, Qu W, Waalkes MP. Oxidative DNA damage after acute exposure to arsenite and monomethylarsonous acid in biomethylation-deficient human cells. Toxicol Mech Methods 2013; 23:389-95. [PMID: 23301828 DOI: 10.3109/15376516.2012.762570] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The carcinogen inorganic arsenic (iAs) undergoes biomethylation (BMT) in some cells. The methylated metabolite, monomethylarsonous (MMA(3+)), may cause oxidative DNA damage (ODD). With chronic iAs exposure, BMT-competent cells show ODD while BMT-deficient do not. To further define these events, we studied ODD produced by acute iAs or MMA(3+) in the BMT-deficient human prostate cell line, RWPE-1. ODD, measured by the immuno-spin trapping method, was assessed after exposure to iAs or MMA(3+) alone, with the arsenic BMT inhibitor selenite or after glutathione (GSH) depletion. The expression of oxidative stress-related genes (HO-1, SOD-1, SOD-2, Nrf2 and Keap-1) was also assessed. Exposure to iAs at 24 h (0-20 µM), stimulated ODD only at levels above the LC50 of a 48 h exposure (17 µM). If iAs induced ODD, it also activated oxidative stress-related genes. Selenium did not alter iAs-induced ODD. MMA(3+) at 24 h (0-0.5 µM) caused ODD at levels below the LC50 of a 48 h exposure (1.5 µM), which were greatly increased by GSH depletion but not selenite. MMA(3+) induced ODD at levels not activating oxidant stress response genes. Overall, iAs induced ODD in BMT-deficient cells only at toxic levels. MMA(3+) caused ODD at non-toxic levels, independently of cellular BMT capacity and in a fashion not requiring further BMT.
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Affiliation(s)
- Ruben Orihuela
- Inorganic Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
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Abstract
Inorganic arsenic in the drinking water is a multisite human carcinogen that potentially targets the kidney. Recent evidence also indicates that developmental arsenic exposure impacts renal carcinogenesis in humans and mice. Emerging theory indicates that cancer may be a disease of stem cells (SCs) and that there are abundant active SCs during early life. Therefore, we hypothesized that inorganic arsenic targets SCs, or partially differentiated progenitor cells (PCs), for oncogenic transformation. Thus, a rat kidney SC/PC cell line, RIMM-18, was chronically exposed to low-level arsenite (500 nM) for up to 28 weeks. Multiple markers of acquired cancer phenotype were assessed biweekly during arsenic exposure, including secreted matrix metalloproteinase (MMP) activity, proliferation rate, colony formation in soft agar, and cellular invasiveness. Arsenic exposure by 10 weeks and after also induced marked and sustained increases in colony formation, indicative of the loss of contact inhibition, and increased invasiveness, both cancer cell characteristics. Compared to the passage-matched control, chronic arsenic exposure caused exposure-duration dependent increases in secreted MMP-2 and MMP-9 activity, Cox-2 expression, and more rapid proliferation (all >2-fold), characteristics typical of cancer cells. Dysregulation of SC maintenance genes and signaling pathways are common during oncogenesis. During arsenite exposure, expression of several genes associated with normal kidney development and SC regulation and differentiation (i.e., Wt-1, Wnt-4, Bmp-7, etc.) were aberrantly altered. Arsenic-exposed renal SCs produced more nonadherent spheroid bodies that grew much more aggressively in Matrigel, typical of cancer SCs (CSCs). The transformed cells also showed gene overexpression typical of renal SCs/CSCs (CD24, Osr1, Ncam) and arsenic adaptation such as overexpression of Mt-1, Mt2, Sod-1, and Abcc2. These data suggest that inorganic arsenic induced an acquired cancer phenotype in vitro in these rat kidney SCs potentially forming CSCs and, consistent with data in vivo, indicate that these multipotent SCs may be targets of arsenic during renal carcinogenesis.
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Affiliation(s)
- Erik J. Tokar
- National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, United States
| | - Rachel J. Person
- National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, United States
| | - Yang Sun
- National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, United States
| | - Alan O. Perantoni
- Cancer and Developmental Biology Laboratory, National Cancer Institute at Frederick, Frederick, Maryland 21702, United States
| | - Michael P. Waalkes
- National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, United States
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Severson PL, Tokar EJ, Vrba L, Waalkes MP, Futscher BW. Agglomerates of aberrant DNA methylation are associated with toxicant-induced malignant transformation. Epigenetics 2012; 7:1238-48. [PMID: 22976526 PMCID: PMC3499325 DOI: 10.4161/epi.22163] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Epigenetic dysfunction is a known contributor in carcinogenesis, and is emerging as a mechanism involved in toxicant-induced malignant transformation for environmental carcinogens such as arsenicals or cadmium. In addition to aberrant DNA methylation of single genes, another manifestation of epigenetic dysfunction in cancer is agglomerative DNA methylation, which can participate in long-range epigenetic silencing that targets many neighboring genes and has been shown to occur in several types of clinical cancers. Using in vitro model systems of toxicant-induced malignant transformation, we found hundreds of aberrant DNA methylation events that emerge during malignant transformation, some of which occur in an agglomerative fashion. In an arsenite-transformed prostate epithelial cell line, the protocadherin (PCDH), HOXC and HOXD gene family clusters are targeted for agglomerative DNA methylation. The agglomerative DNA methylation changes induced by arsenicals appear to be common and clinically relevant events, since they occur in other human cancer cell lines and models of malignant transformation, as well as clinical cancer specimens. Aberrant DNA methylation in general occurred more often within histone H3 lysine-27 trimethylation stem cell domains. We found a striking association between enrichment of histone H3 lysine-9 trimethylation stem cell domains and toxicant-induced agglomerative DNA methylation, suggesting these epigenetic modifications may become aberrantly linked during malignant transformation. In summary, we found an association between toxicant-induced malignant transformation and agglomerative DNA methylation, which lends further support to the hypothesis that epigenetic dysfunction plays an important role in toxicant-induced malignant transformation.
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Affiliation(s)
- Paul L Severson
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, AZ, USA
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Qu W, Tokar EJ, Kim AJ, Bell MW, Waalkes MP. Chronic cadmium exposure in vitro causes acquisition of multiple tumor cell characteristics in human pancreatic epithelial cells. Environ Health Perspect 2012; 120:1265-71. [PMID: 22626610 PMCID: PMC3440134 DOI: 10.1289/ehp.1205082] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Accepted: 05/24/2012] [Indexed: 05/12/2023]
Abstract
BACKGROUND Cancer may be a stem cell (SC)-based disease involving formation of cancer SCs (CSCs) potentially arising from transformation of normal SCs. Cadmium has been linked to human pancreatic cancer. OBJECTIVE We studied cadmium exposure of human pancreatic ductal epithelial (HPDE) cells and whether SCs may be targeted in this process. METHODS We chronically exposed HPDE cells to low level cadmium (1 μM) for ≤ 29 weeks. Nonadherent spheroid formation was used to indicate CSC-like cell production, and we assessed tumor cell characteristics in such spheres. Assessed tumor cell characteristics including secretion of matrix metalloproteinase-9 (MMP-9), invasion, and colony formation were fortified by evaluating expression of relevant genes by real-time reverse transcription polymerase chain reaction and by Western blot. RESULTS Increased MMP-9 secretion and overexpression of the pancreatic cancer marker S100P occurred in chronic (29 weeks of exposure) cadmium-exposed (CCE) cells. CCE cells also showed markedly higher colony formation and invasion, typical of cancer cells. Floating "spheres" of viable cells, known to contain an abundance of normal SCs or CSCs, form in vitro with many cell types. CCE cells produced 3-fold more spheres than control cells and were more invasive, secreted more MMP-9, and overexpressed markers for pancreatic SCs/CSCs (i.e., CXCR4, OCT4, CD44) and S100P, a marker for pancreatic cancer. CCE-derived spheres rapidly produced aggressive, highly branched, and poorly differentiated glandular-like structures in Matrigel. CONCLUSIONS Chronic cadmium exposure produced multiple tumor cell characteristics in HPDE cells and CCE cell-derived spheres. These data support the plausibility of cadmium as a human pancreatic carcinogen.
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Affiliation(s)
- Wei Qu
- Inorganic Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina, USA
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Zhan L, Zhang H, Zhang Q, Woods CG, Chen Y, Xue P, Dong J, Tokar EJ, Xu Y, Hou Y, Fu J, Yarborough K, Wang A, Qu W, Waalkes MP, Andersen ME, Pi J. Regulatory role of KEAP1 and NRF2 in PPARγ expression and chemoresistance in human non-small-cell lung carcinoma cells. Free Radic Biol Med 2012; 53:758-68. [PMID: 22684020 PMCID: PMC3418425 DOI: 10.1016/j.freeradbiomed.2012.05.041] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Revised: 05/17/2012] [Accepted: 05/27/2012] [Indexed: 12/21/2022]
Abstract
The nuclear factor-E2-related factor 2 (NRF2) serves as a master regulator in cellular defense against oxidative stress and chemical detoxification. However, persistent activation of NRF2 resulting from mutations in NRF2 and/or downregulation of or mutations in its suppressor, Kelch-like ECH-associated protein 1 (KEAP1), is associated with tumorigenicity and chemoresistance of non-small-cell lung carcinomas (NSCLCs). Thus, inhibiting the NRF2-mediated adaptive antioxidant response is widely considered a promising strategy to prevent tumor growth and reverse chemoresistance in NSCLCs. Unexpectedly, stable knockdown of KEAP1 by lentiviral shRNA sensitized three independent NSCLC cell lines (A549, HTB-178, and HTB-182) to multiple chemotherapeutic agents, including arsenic trioxide (As(2)O(3)), etoposide, and doxorubicin, despite moderately increased NRF2 levels. In lung adenocarcinoma epithelial A549 cells, silencing of KEAP1 augmented the expression of peroxisome proliferator-activated receptor γ (PPARγ) and genes associated with cell differentiation, including E-cadherin and gelsolin. In addition, KEAP1-knockdown A549 cells displayed attenuated expression of the proto-oncogene cyclin D1 and markers for cancer stem cells (CSCs) and reduced nonadherent sphere formation. Moreover, deficiency of KEAP1 led to elevated induction of PPARγ in response to As(2)O(3). Pretreatment of A549 cells with PPARγ agonists activated PPARγ and augmented the cytotoxicity of As(2)O(3). A mathematical model was formulated to advance a hypothesis that differential regulation of PPARγ and detoxification enzymes by KEAP1 and NRF2 may underpin the observed landscape changes in chemosensitivity. Collectively, suppression of KEAP1 expression in human NSCLC cells resulted in sensitization to chemotherapeutic agents, which may be attributed to activation of PPARγ and subsequent alterations in cell differentiation and CSC abundance.
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Affiliation(s)
- Lijuan Zhan
- Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC 27709
| | - Hao Zhang
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC 27709
- School of Public Health, Fudan University, Shanghai, China
| | - Qiang Zhang
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC 27709
| | - Courtney G. Woods
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC 27709
| | - Yanyan Chen
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC 27709
- School of First Clinical Sciences andc College of Basic Medical Sciences, China Medical University, Shenyang, China
| | - Peng Xue
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC 27709
| | - Jian Dong
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC 27709
| | - Erik J. Tokar
- National Toxicology Program Laboratories, Division of the National Toxicology Program, National Institutes of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Yuanyuan Xu
- National Toxicology Program Laboratories, Division of the National Toxicology Program, National Institutes of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Yongyong Hou
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC 27709
| | - Jingqi Fu
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC 27709
| | - Kathy Yarborough
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC 27709
| | - Aiping Wang
- Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China
| | - Weidong Qu
- School of Public Health, Fudan University, Shanghai, China
| | - Michael P. Waalkes
- National Toxicology Program Laboratories, Division of the National Toxicology Program, National Institutes of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Melvin E. Andersen
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC 27709
| | - Jingbo Pi
- Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, NC 27709
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Xu Y, Tokar EJ, Sun Y, Waalkes MP. Arsenic-transformed malignant prostate epithelia can convert noncontiguous normal stem cells into an oncogenic phenotype. Environ Health Perspect 2012; 120:865-71. [PMID: 22472196 PMCID: PMC3385457 DOI: 10.1289/ehp.1204987] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Accepted: 03/27/2012] [Indexed: 05/19/2023]
Abstract
BACKGROUND Cancer stem cells (CSCs) are likely critical to carcinogenesis, and, like normal stem cells (NSCs), are affected by microenvironmental factors. Malignant cells release extracellular factors, modifying tumor behavior. Inorganic arsenic, a human carcinogen, is associated with an overproduction of CSCs in various model systems of carcinogenesis. OBJECTIVE We aimed to determine if NSCs are influenced by nearby arsenic-transformed malignant epithelial cells (MECs) as a possible factor in arsenic-associated CSC overabundance. METHODS Transwell noncontact co-culture allowed the study of the effects of non-contiguous, arsenic-transformed prostate MECs on the isogenic human prostate NSC line, WPE-stem. Cancer phenotype was assessed by evaluating secreted matrix metalloproteinases (MMPs), invasiveness, colony formation, and spheroid formation. Gene expression was assessed at the protein (Western blot) or mRNA (real-time reverse transcription-polymerase chain reaction) levels. RESULTS Noncontact co-culture of MECs and NSCs rapidly (≤ 3 weeks) caused hypersecretion of MMPs and marked suppression of the tumor suppressor gene PTEN in NSCs. NSCs co-cultured with MECs also showed increased invasiveness and clonogenicity and formed more free-floating spheroids and highly branched ductal-like structures in Matrigel, all typical for CSCs. MEC co-culture caused dysregulated self-renewal and differentiation-related gene expression patterns and epithelial-to-mesenchymal transition in NSCs consistent with an acquired cancer phenotype. Interleukin-6 (IL-6), a cytokine involved in tumor microenvironment control, was hypersecreted by MECs, and IL-6 exposure of NSCs resulted in the duplication of several responses in NSCs of conversion to CSCs via MEC co-culture (e.g., MMP hypersecretion, decreased PTEN). CONCLUSIONS Arsenic-transformed MECs recruit nearby NSCs into a cancer phenotype, thereby potentially increasing CSC number. This may be a factor in arsenic-induced CSC overabundance seen in multiple model systems.
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Affiliation(s)
- Yuanyuan Xu
- National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina, USA
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Tokar EJ, Diwan BA, Thomas DJ, Waalkes MP. Tumors and proliferative lesions in adult offspring after maternal exposure to methylarsonous acid during gestation in CD1 mice. Arch Toxicol 2012; 86:975-82. [PMID: 22398986 PMCID: PMC3459060 DOI: 10.1007/s00204-012-0820-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Accepted: 02/14/2012] [Indexed: 01/28/2023]
Abstract
Developmental exposure to inorganic arsenic is carcinogenic in humans and mice, and adult offspring of mice exposed to inorganic arsenic can develop tumors of the lung, liver, adrenal, uterus, and ovary. It has been suggested that methylarsonous acid (MMA3+), a product of the biological methylation of inorganic arsenic, could be a key carcinogenic species. Thus, pregnant CD1 mice were provided drinking water containing MMA3+ at 0 (control), 12.5, or 25 parts per million (ppm) from gestational days 8 to 18. Tumors were assessed in groups of male or female (initial n = 25) offspring up to 2 years of age. In utero treatment had no effect on survival or body weights. Female offspring exhibited increases in total epithelial uterine tumors (control 0%; 12.5 ppm 26%; 25 ppm 30%), oviduct hyperplasia (control 4%; 12.5 ppm 35%; 25 ppm 43%), adrenal cortical adenoma at 25 ppm (control 0%; 12.5 ppm 9%; 25 ppm 26%), and total epithelial ovarian tumors (control 0%; 12.5 ppm 39%; 25 ppm 26%). Male offspring showed dose-related increases in hepatocellular carcinoma (control 0%; 12.5 ppm 12%; 25 ppm 22%), adrenal adenoma (control 0%; 12.5 ppm 28%; 25 ppm 17%), and lung adenocarcinoma (control 17%; 12.5 ppm 44%). Male offspring had unusual testicular lesions, including two rete testis carcinomas, two adenomas, and three interstitial cell tumors. Overall, maternal consumption of MMA3+ during pregnancy in CD1 mice produced some similar proliferative lesions as gestationally applied inorganic arsenic in the offspring during adulthood.
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Affiliation(s)
- Erik J. Tokar
- Inorganic Toxicology Group, National Toxicology Program Laboratory Branch, Division of the National Toxicology Program, the National Institute of Environmental Health Sciences, Research Triangle Park, NC, and Inorganic Carcinogenesis Section, Laboratory of Comparative Carcinogenesis, National Cancer Institute at the National Institute of Environmental Health Sciences, Research Triangle Park, NC
| | - Bhalchandra A. Diwan
- Basic Research Program, SAIC-Frederick, National Cancer Institute at Frederick, Frederick, MD (retired)
| | - David J. Thomas
- Integrated Systems Toxicology Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC
| | - Michael P. Waalkes
- Inorganic Toxicology Group, National Toxicology Program Laboratory Branch, Division of the National Toxicology Program, the National Institute of Environmental Health Sciences, Research Triangle Park, NC, and Inorganic Carcinogenesis Section, Laboratory of Comparative Carcinogenesis, National Cancer Institute at the National Institute of Environmental Health Sciences, Research Triangle Park, NC
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Tokar EJ, Diwan BA, Waalkes MP. Renal, hepatic, pulmonary and adrenal tumors induced by prenatal inorganic arsenic followed by dimethylarsinic acid in adulthood in CD1 mice. Toxicol Lett 2012; 209:179-85. [PMID: 22230260 PMCID: PMC3285471 DOI: 10.1016/j.toxlet.2011.12.016] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Revised: 12/21/2011] [Accepted: 12/22/2011] [Indexed: 12/22/2022]
Abstract
Inorganic arsenic, an early life carcinogen in humans and mice, can initiate lesions promotable by other agents in later life. The biomethylation product of arsenic, dimethylarsinic acid (DMA), is a multi-site tumor promoter. Thus, pregnant CD1 mice were given drinking water (0 ppm or 85 ppm arsenic) from gestation day 8 to 18 and after weaning male offspring received DMA (0 ppm or 200 ppm; drinking water) for up to 2 years. No renal tumors occurred in controls or DMA alone treated mice while gestational arsenic exposure plus later DMA induced a significant renal tumor incidence of 17% (primarily renal cell carcinoma). Arsenic plus DMA or arsenic alone also increased renal hyperplasia over control but DMA alone did not. Arsenic alone, DMA alone and arsenic plus DMA all induced urinary bladder hyperplasia (33-35%) versus control (2%). Compared to control (6%), arsenic alone tripled hepatocellular carcinoma (20%), and arsenic plus DMA doubled this rate again (43%), but DMA alone had no effect. DMA alone, arsenic alone, and arsenic plus DMA increased lung adenocarcinomas and adrenal adenomas versus control. Overall, DMA in adulthood promoted tumors/lesions initiated by prenatal arsenic in the kidney and liver, but acted independently in the urinary bladder, lung and adrenal.
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Affiliation(s)
- Erik J. Tokar
- Inorganic Toxicology Group, National Toxicology Program Laboratory Branch, Division of the National Toxicology Program, the National Institute of Environmental Health Sciences, Research Triangle Park, NC, and the National Cancer Institute at Frederick, Frederick, MD
| | - Bhalchandra A. Diwan
- Basic Research Program, SAIC-Frederick, National Cancer Institute at Frederick, Frederick, MD
| | - Michael P. Waalkes
- Inorganic Toxicology Group, National Toxicology Program Laboratory Branch, Division of the National Toxicology Program, the National Institute of Environmental Health Sciences, Research Triangle Park, NC, and the National Cancer Institute at Frederick, Frederick, MD
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Sun Y, Tokar EJ, Waalkes MP. Overabundance of putative cancer stem cells in human skin keratinocyte cells malignantly transformed by arsenic. Toxicol Sci 2011; 125:20-9. [PMID: 22011395 DOI: 10.1093/toxsci/kfr282] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Arsenic is a human skin carcinogen. Cancer is probably a disease driven by stem cells (SCs), and SCs are likely a key target during arsenic oncogenesis. In utero arsenic exposure predisposes mice to skin cancers that overproduce cancer SCs (CSCs) and have distorted CSC signaling and population dynamics. Therefore, we hypothesized CSC accumulation may occur during arsenic-induced malignant transformation in vitro of human skin keratinocytes. Thus, the HaCaT cell line, malignantly transformed by arsenite (100 nM, 30 weeks; termed As-TM cells) in prior work, was further studied for the quantity and nature of SCs after this transformation. SCs were isolated from passage-matched control and As-TM cells by a magnetic bead system that enriches for CD34-positive cells. There were 2.5 times more SCs isolated from As-TM cells than control. Holoclone production from As-TM putative CSCs was 2.5-fold higher by 1 week and 3.5-fold higher by 2 weeks than control SCs. Potential malignant phenotype was assessed in isolated SC/CSCs. Transcript level of SC/CSC markers were elevated in both isolated As-TM CSCs and control SCs compared with parental cells, but compared with control SCs, As-TM putative CSCs had elevated CD34, K5, K14, K15, and K19 transcripts and dramatically stronger staining for p63, Rac1, K5, Notch1, and K19. As-TM putative CSCs also showed markedly elevated MMP-9 secretion and colony formation, indicators of cancer phenotype, even compared with total population of As-TM cells. Thus, malignant phenotype is particularly pronounced in CSCs after arsenic-induced transformation of human skin cells and occurs concurrently with a potential overproduction of these cells.
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Affiliation(s)
- Yang Sun
- National Toxicology Program Laboratory, Inorganic Toxicology Group, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA
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Shpyleva SI, Muskhelishvili L, Tryndyak VP, Koturbash I, Tokar EJ, Waalkes MP, Beland FA, Pogribny IP. Chronic administration of 2-acetylaminofluorene alters the cellular iron metabolism in rat liver. Toxicol Sci 2011; 123:433-40. [PMID: 21785164 DOI: 10.1093/toxsci/kfr193] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Dysregulated intracellular iron homeostasis has been found not only in rodent and human hepatocellular carcinomas but also in several preneoplastic pathological states associated with hepatocarcinogenesis; however, the precise underlying mechanisms of metabolic iron disturbances in preneoplastic liver and the role of these disturbances remain unexplored. In the present study, using an in vivo model of rat hepatocarcinogenesis induced by 2-acetylaminofluorene, we found extensive alterations in cellular iron metabolism at preneoplastic stages of liver carcinogenesis. These were characterized by a substantial decrease in the levels of cytoplasmic non-heme iron in foci of initiated hepatocytes and altered expression of the major genes responsible for the proper maintenance of intracellular iron homeostasis. Gene expression analysis revealed that the decreased intracellular levels of iron in preneoplastic foci might be attributed to increased iron export from the cells, driven by upregulation of ferroportin (Fpn1), the only known non-heme iron exporter. Likewise, increased Fpn1 gene expression was found in vitro in TRL1215 rat liver cells with an acquired malignant phenotype, suggesting that upregulation of Fpn1 might be a specific feature of neoplastically transformed cells. Other changes observed in vivo included the downregulation of hepcidin (Hamp) gene, a key regulator of Fpn1, and this was accompanied by decreased levels of CCAAT/enhancer binding proteins alpha and beta, especially at the Hamp promoter. In conclusion, our results demonstrate the significance of altered intracellular iron metabolism in the progression of liver carcinogenesis and suggest that correction of these alterations could possibly affect liver cancer development.
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Affiliation(s)
- Svitlana I Shpyleva
- Division of Biochemical Toxicology, National Center for Toxicological Research, Jefferson, Arkansas 72079, USA
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Tokar EJ, Qu W, Waalkes MP. Arsenic, stem cells, and the developmental basis of adult cancer. Toxicol Sci 2011; 120 Suppl 1:S192-203. [PMID: 21071725 PMCID: PMC3043086 DOI: 10.1093/toxsci/kfq342] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Accepted: 11/08/2010] [Indexed: 12/18/2022] Open
Abstract
That chemical insults or nutritive changes during in utero and/or postnatal life can emerge as diseases much later in life are now being accepted as a recurring phenomenon. In this regard, inorganic arsenic is a multisite human carcinogen found at high levels in the drinking water of millions of people, although it has been difficult until recently to produce tumors in rodents with this metalloid. A mouse transplacental model has been developed where maternal exposure to inorganic arsenic either acts as a complete carcinogen or enhances carcinogenic response to other agents given subsequently in the offspring, producing tumors during adulthood. Similarly, human data now have emerged showing that arsenic exposure during the in utero period and/or in early life is associated with cancer in adulthood. The mouse arsenic transplacental model produces tumors or enhances response to other agents in multiple strains and tissues, including sites concordant with human targets of arsenic carcinogenesis. It is now believed that cancer often is a stem cell (SC)-based disease, and there is no reason to think cancer induced by developmental chemical exposure is any different. Indeed, arsenic impacts human SC population dynamics in vitro by blocking exit into differentiation pathways and whereby creating more key targets for transformation. In fact, during in vitro malignant transformation, arsenic causes a remarkable survival selection of SCs, creating a marked overabundance of cancer SCs (CSCs) compared with other carcinogens once a cancer phenotype is obtained. In addition, skin cancers produced following in utero arsenic exposure in mice are highly enriched in CSCs. Thus, arsenic impacts key, long-lived SC populations as critical targets to cause or facilitate later oncogenic events in adulthood as a possible mechanism of developmental basis of adult disease.
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Affiliation(s)
| | | | - Michael P. Waalkes
- National Toxicology Program Laboratories, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina
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Tokar EJ, Diwan BA, Ward JM, Delker DA, Waalkes MP. Carcinogenic effects of "whole-life" exposure to inorganic arsenic in CD1 mice. Toxicol Sci 2011; 119:73-83. [PMID: 20937726 PMCID: PMC3003832 DOI: 10.1093/toxsci/kfq315] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Accepted: 10/06/2010] [Indexed: 01/21/2023] Open
Abstract
In a previously developed mouse model, arsenic exposure in utero induces tumors at multiple sites in the offspring as adults, often duplicating human targets. However, human environmental inorganic arsenic exposure occurs during the entire life span, not just part of gestation. Thus, "whole-life" inorganic arsenic carcinogenesis in mice was studied. CD1 mice were exposed to 0, 6, 12, or 24 ppm arsenic in the drinking water 2 weeks prior to breeding, during pregnancy, lactation, and after weaning through adulthood. Tumors were assessed in offspring until 2 years of age. Arsenic induced dose-related increases in lung adenocarcinoma (both sexes), hepatocellular carcinoma (both sexes), gallbladder tumors (males), and uterine carcinomas. Arsenic induced dose-related increases in ovarian tumors (including carcinomas) starting with the lowest dose. Adrenal tumors increased at all doses (both sexes). Arsenic-induced lung and liver cancers were highly enriched for cancer stem cells, consistent with prior work with skin cancers stimulated by prenatal arsenic. Reproductive tract tumors overexpressed cyclooxygenase-2 and estrogen receptor-α. Arsenic target sites were remarkably similar to prior transplacental studies, although tumors from whole-life exposure were generally more aggressive and frequent. This may indicate that arsenic-induced events in utero dictate target site in some tissues, whereas other exposure periods of arsenic enhance incidence or progression, though other factors could be at play, like cumulative dose. Whole-life arsenic exposure induced tumors at dramatically lower external doses than in utero arsenic only while more realistically duplicating human exposure.
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Affiliation(s)
- Erik J. Tokar
- Laboratory of Comparative Carcinogenesis, National Cancer Institute at the National Institute of Environmental Health Sciences, and National Toxicology Program, The National Institute of Environmental Health Sciences, Research Triangle Park, Raleigh, North Carolina 27709
| | - Bhalchandra A. Diwan
- Basic Research Program, SAIC-Frederick, National Cancer Institute at Frederick, Frederick, Maryland 21773
| | | | - Don A. Delker
- University of Utah, School of Medicine, 30 North 1900 East, Salt Lake City, Utah 84132
| | - Michael P. Waalkes
- Laboratory of Comparative Carcinogenesis, National Cancer Institute at the National Institute of Environmental Health Sciences, and National Toxicology Program, The National Institute of Environmental Health Sciences, Research Triangle Park, Raleigh, North Carolina 27709
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Tokar EJ, Benbrahim-Tallaa L, Waalkes MP. Metal ions in human cancer development. Met Ions Life Sci 2011; 8:375-401. [PMID: 21473387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Metals have been in the environment during the entire evolution of man and the use of metals is key to human civilization. None-the-less, several very toxic species are included in the metallic elements and compounds either widely used by man and/or widely found in the human environment. This includes the five metallic agents considered human carcinogens, namely arsenic and arsenic compounds, beryllium and beryllium compounds, cadmium and cadmium compounds, chromium(VI) compounds, and nickel compounds, all of which are proven carcinogens in laboratory animals as well. There is significant human exposure to these carcinogenic inorganics, either occupationally, through the environment, or both. Inhalation is typical in the workplace while inhalation or ingestion occurs from environmental sources. Human metallic carcinogens frequently cause tumors at the portal of entry and lung cancers are the most common tumor after inhalation. Agent-specific tumors occur as well, like urinary bladder tumors after arsenic exposure, which are due to biokinetics or mechanisms that are specific to arsenic. Even in their simplest elemental form, metals are not inert, and they have biological activity. However, it should be kept in mind that these inorganic carcinogens, when in the atomic form, cannot be broken down into less toxic subunits, and this, in part, is why they are so important as environmental human carcinogens. This chapter focuses on the metallic agents that are known human carcinogens.
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Affiliation(s)
- Erik J Tokar
- Inorganic Carcinogenesis Section, Laboratory of Comparative Carcinogenesis, National Cancer Institute at the National Institute of Environmental Health Sciences, Alexander Drive, Research Triangle Park, NC 27709, USA
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