1
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Hannon SL, Ding X. Assessing cytochrome P450 function using genetically engineered mouse models. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2022; 95:253-284. [PMID: 35953157 PMCID: PMC10544722 DOI: 10.1016/bs.apha.2022.05.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The ability to knock out and/or humanize different genes in experimental animals, globally or in cell- and tissue-specific patterns, has revolutionized scientific research in many areas. Genetically engineered mouse models, including knockout models, transgenic models, and humanized models, have played important roles in revealing the in vivo functions of various cytochrome P450 (CYP) enzymes. These functions are very diverse, ranging from the biotransformation of drugs and other xenobiotics, events that often dictate their pharmacokinetic or toxicokinetic properties and the associated therapeutic or adverse actions, to the metabolism of endogenous compounds, such as steroid hormones and other bioactive substances, that may determine susceptibility to many diseases, such as cancer and metabolic diseases. In this review, we provide a comprehensive list of Cyp-knockout, human CYP-transgenic, and CYP-humanized mouse models that target genes in the CYP1-4 gene families, and highlight their utility in assessing the in vivo metabolism, bioactivation, and toxicity of various xenobiotic compounds, including therapeutic agents and chemical carcinogens. We aim to showcase the advantages of utilizing these mouse models for in vivo drug metabolism and toxicology studies, and to encourage and facilitate greater utility of engineered mouse models to further improve our knowledge of the in vivo functions of various P450 enzymes, which is integral to our ability to develop safer and more effective therapeutics and to identify individuals predisposed to adverse drug reactions or environmental diseases.
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Affiliation(s)
- Sarrah L Hannon
- Department of Pharmacology and Toxicology, Ken R. Coit College of Pharmacy, The University of Arizona, Tucson, AZ, United States
| | - Xinxin Ding
- Department of Pharmacology and Toxicology, Ken R. Coit College of Pharmacy, The University of Arizona, Tucson, AZ, United States.
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2
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Hakura A, Koyama N, Seki Y, Sonoda J, Asakura S. o-Aminoazotoluene, 7,12-dimethylbenz[a]anthracene, and N-ethyl-N-nitrosourea, which are mutagenic but not carcinogenic in the colon, rapidly induce colonic tumors in mice with dextran sulfate sodium-induced colitis. Genes Environ 2022; 44:11. [PMID: 35351212 PMCID: PMC8966303 DOI: 10.1186/s41021-022-00240-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 03/09/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Several rodent models with chemically induced colon cancer have been developed. Among these models, dextran sulfate sodium (DSS), a colitis inducer, combined with azoxymethane as a colon mutagenic carcinogen, is commonly used. We previously reported that although benzo [a] pyrene (BP) is mutagenic but not carcinogenic in the colon, it rapidly develops colon tumors at a high incidence/multiplicity after treatment with DSS. In the present study, we examined whether other colon-mutagenic non-carcinogens (CMNCs) induced colon tumors after treatment with DSS. RESULTS o-Aminoazotoluene, 7,12-dimethylbenz[a]anthracene, and N-ethyl-N-nitrosourea were selected as CMNCs. Male CD2F1 mice were orally administered CMNC for 5 consecutive days. After a 9-day dose-free period, mice were treated with 4% DSS in drinking water for 1 week. Three months after DSS treatment, colon samples were collected for histopathology and β-catenin immunohistochemistry analyses. All CMNCs in combination with DSS induced colonic adenocarcinomas at a high incidence/multiplicity in the distal and middle parts of the colon, coinciding with the location of colitis. Unlike in normal cells where β-catenin is exclusively located on the cell membrane, in adenocarcinoma cells, it was translocated to both the nucleus and cytoplasm or only to cytoplasm. The translocation of β-catenin is closely associated with colon carcinogenesis in rodents and humans. No colonic tumors or dysplastic lesions were found after exposure to either CMNC or DSS alone. CONCLUSION We provided further evidence clearly showing that CMNCs can rapidly induce colonic tumors in mice with DSS-induced colitis, even if they are not colonic carcinogens.
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Affiliation(s)
- Atsushi Hakura
- Global Drug Safety, Eisai Co., Ltd., 5-1-3 Tokodai, Tsukuba, Ibaraki, 300-2635, Japan.
| | - Naoki Koyama
- Global Drug Safety, Eisai Co., Ltd., 5-1-3 Tokodai, Tsukuba, Ibaraki, 300-2635, Japan
| | - Yuki Seki
- Global Drug Safety, Eisai Co., Ltd., 5-1-3 Tokodai, Tsukuba, Ibaraki, 300-2635, Japan
| | - Jiro Sonoda
- Global Drug Safety (present affiliation, Advanced Data Assurance), Eisai Co., Ltd., 5-1-3 Tokodai, Tsukuba, Ibaraki, 300-2635, Japan
| | - Shoji Asakura
- Global Drug Safety, Eisai Co., Ltd., 5-1-3 Tokodai, Tsukuba, Ibaraki, 300-2635, Japan
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3
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Chi LH, Burrows AD, Anderson RL. Can preclinical drug development help to predict adverse events in clinical trials? Drug Discov Today 2021; 27:257-268. [PMID: 34469805 DOI: 10.1016/j.drudis.2021.08.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 06/03/2021] [Accepted: 08/24/2021] [Indexed: 12/23/2022]
Abstract
The development of novel therapeutics is associated with high rates of attrition, with unexpected adverse events being a major cause of failure. Serious adverse events have led to organ failure, cancer development and deaths that were not expected outcomes in clinical trials. These life-threatening events were not identified during therapeutic development due to the lack of preclinical safety tests that faithfully represented human physiology. We highlight the successful application of several novel technologies, including high-throughput screening, organs-on-chips, microbiome-containing drug-testing platforms and humanised mouse models, for mechanistic studies and prediction of toxicity. We propose the incorporation of similar preclinical tests into future drug development to reduce the likelihood of hazardous therapeutics entering later-stage clinical trials.
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Affiliation(s)
- Lap Hing Chi
- Translational Breast Cancer Program, Olivia Newton-John Cancer Research Institute, Heidelberg, Victoria, Australia; School of Cancer Medicine, La Trobe University, Bundoora, Victoria, Australia
| | - Allan D Burrows
- Translational Breast Cancer Program, Olivia Newton-John Cancer Research Institute, Heidelberg, Victoria, Australia; School of Cancer Medicine, La Trobe University, Bundoora, Victoria, Australia
| | - Robin L Anderson
- Translational Breast Cancer Program, Olivia Newton-John Cancer Research Institute, Heidelberg, Victoria, Australia; School of Cancer Medicine, La Trobe University, Bundoora, Victoria, Australia; Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, Victoria, Australia.
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4
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Yang X, Peng H, Luo Z, Luo A, Cai M, Xu L, Wang H. The dietary carcinogen PhIP activates p53-dependent DNA damage response in the colon of CYP1A-humanized mice. Biofactors 2021; 47:612-626. [PMID: 33811687 DOI: 10.1002/biof.1730] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 03/24/2021] [Indexed: 11/09/2022]
Abstract
Species differences in the metabolism of xenobiotics by cytochrome P450 are critical in evaluating the use of experimental animals in studying toxic compounds relevant to human diseases. 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), which is produced by high-temperature cooking of fish and meat, is activated to become a carcinogen by cytochrome P4501A2 (CYP1A2) through N2 -hydroxylation in humans, but is detoxified by Cyp1a2 through 4'-hydroxylation in mice. CYP1A-humanized (hCYP1A) mice, in which mouse Cyp1a is replaced with human CYP1A, show constitutive human xenobiotic metabolism by hCYP1A, thereby serving as a suitable model for studying PhIP. Previous studies have demonstrated that oral administration of PhIP induces colon tumors in hCYP1A mice; however, these studies used a super-high dose, raising concerns regarding the relevance of the mechanism to human cancer. Herein, we systematically investigated PhIP-induced colon carcinogenesis in hCYP1A mice treated with lower doses. We found that a dose 2000 times lower than that used previously, which is comparable to human daily intake levels, could induce colon tumors, albeit at a lower incidence rate. We further investigated the transcriptome changes in the colon of hCYP1A mice treated with PhIP and identified that PhIP treatment increased the expression of Bax, Btg2, Ccng1, Cdkn1a, and Trp53inp1 and decreased the expression of Igf1 and Ccnd1. Since these genes are key components of the p53-dependent DNA damage response, the altered expression patterns indicated PhIP-induced DNA damage in hCYP1A mice. Together, these results prove that hCYP1A mice are suitable for studying PhIP-induced carcinogenesis and show that PhIP is an important colorectal cancer carcinogen in human diet.
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Affiliation(s)
- Xu Yang
- Department of Hematology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, Guangdong, China
| | - Hongxia Peng
- Department of Hematology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, Guangdong, China
| | - Ziyan Luo
- Department of Hematology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, Guangdong, China
| | - Ailing Luo
- Department of Hematology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, Guangdong, China
| | - Mansi Cai
- Department of Hematology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, Guangdong, China
| | - Ling Xu
- Department of Hematology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, Guangdong, China
| | - Hong Wang
- Department of Hematology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, Guangdong, China
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5
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Loke YL, Chew MT, Ngeow YF, Lim WWD, Peh SC. Colon Carcinogenesis: The Interplay Between Diet and Gut Microbiota. Front Cell Infect Microbiol 2020; 10:603086. [PMID: 33364203 PMCID: PMC7753026 DOI: 10.3389/fcimb.2020.603086] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 10/28/2020] [Indexed: 12/24/2022] Open
Abstract
Colorectal cancer (CRC) incidence increases yearly, and is three to four times higher in developed countries compared to developing countries. The well-known risk factors have been attributed to low physical activity, overweight, obesity, dietary consumption including excessive consumption of red processed meats, alcohol, and low dietary fiber content. There is growing evidence of the interplay between diet and gut microbiota in CRC carcinogenesis. Although there appears to be a direct causal role for gut microbes in the development of CRC in some animal models, the link between diet, gut microbes, and colonic carcinogenesis has been established largely as an association rather than as a cause-and-effect relationship. This is especially true for human studies. As essential dietary factors influence CRC risk, the role of proteins, carbohydrates, fat, and their end products are considered as part of the interplay between diet and gut microbiota. The underlying molecular mechanisms of colon carcinogenesis mediated by gut microbiota are also discussed. Human biological responses such as inflammation, oxidative stress, deoxyribonucleic acid (DNA) damage can all influence dysbiosis and consequently CRC carcinogenesis. Dysbiosis could add to CRC risk by shifting the effect of dietary components toward promoting a colonic neoplasm together with interacting with gut microbiota. It follows that dietary intervention and gut microbiota modulation may play a vital role in reducing CRC risk.
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Affiliation(s)
- Yean Leng Loke
- Centre for Biomedical Physics, School of Healthcare and Medical Sciences, Sunway University, Petaling Jaya, Malaysia
| | - Ming Tsuey Chew
- Centre for Biomedical Physics, School of Healthcare and Medical Sciences, Sunway University, Petaling Jaya, Malaysia
| | - Yun Fong Ngeow
- Faculty of Medicine and Health Sciences, Universiti Tunku Abdul Rahman, Kajang, Malaysia.,Centre for Research on Communicable Diseases, Universiti Tunku Abdul Rahman, Kajang, Malaysia
| | - Wendy Wan Dee Lim
- Department of Gastroenterology, Sunway Medical Centre, Petaling Jaya, Malaysia
| | - Suat Cheng Peh
- Ageing Health and Well-Being Research Centre, Sunway University, Petaling Jaya, Malaysia.,Department of Medical Sciences, School of Healthcare and Medical Sciences, Sunway University, Petaling Jaya, Malaysia
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6
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Wang H, Wang DH, Yang X, Sun Y, Yang CS. Colitis-induced IL11 promotes colon carcinogenesis. Carcinogenesis 2020; 42:557-569. [PMID: 33196831 DOI: 10.1093/carcin/bgaa122] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 10/19/2020] [Accepted: 11/09/2020] [Indexed: 12/24/2022] Open
Abstract
Colitis increases the risk of colorectal cancer; however, the mechanism of the association between colitis and cancer remains largely unknown. To identify colitis-associated cancer promoting factors, we investigated gene expression changes caused by dextran sulfate sodium (DSS)-induced colitis in mice. By analyzing gene expression profiles, we found that IL11 was upregulated in DSS-induced colitis tissue and 2-amino-1-methyl-6-phenylimidazo[4,5-b]-pyridine (PhIP)/DSS-induced colon tumours in mice as well as in human colorectal cancer. By characterizing the activation/phosphorylation of STAT3 (pSTAT3), we found that pSTAT3 was induced transiently in colitis, but maintained at higher levels from hyper-proliferative dysplastic lesions to tumours. Using the IL11 receptor (IL11Rα1) knockout mice, we found that pSTAT3 in the newly regenerated crypt epithelial cells in colitis is abolished in IL11Rα1+/- and -/- mice, suggesting that colitis-induced IL11 activates STAT3 in colon crypt epithelial cells. Moreover, colitis-promoted colon carcinogenesis was significantly reduced in IL11Rα1+/- and -/- mice. To determine the roles of the IL11 in colitis, we found that the inhibition of IL11 signalling by recombinant IL11 antagonist mutein during colitis was sufficient to attenuate colitis-promoted carcinogenesis. Together, our results demonstrated that colitis-induced IL11 plays critical roles in creating cancer promoting microenvironment to facilitate the development of colon cancer from dormant premalignant cells.
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Affiliation(s)
- Hong Wang
- Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
| | - David H Wang
- Department of Electrical and Computer Engineering, Ohio State University, Columbus, OH, USA
| | - Xu Yang
- Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
| | - Yuhai Sun
- Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
| | - Chung S Yang
- Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
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7
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Akhtar S, Najafzadeh M, Isreb M, Newton L, Gopalan RC, Anderson D. Ex vivo/in vitro protective effect of myricetin bulk and nano-forms on PhIP-induced DNA damage in lymphocytes from healthy individuals and pre-cancerous MGUS patients. Arch Toxicol 2020; 94:2349-2357. [PMID: 32342131 PMCID: PMC7367907 DOI: 10.1007/s00204-020-02754-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 04/16/2020] [Indexed: 12/12/2022]
Abstract
2-Amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP) is a central dietary mutagen, produced when proteinaceous food is heated at very high temperatures potentially causing DNA strand breaks. This study investigates the protective potential of a well-researched flavonoid, myricetin in its bulk and nano-forms against oxidative stress induced ex vivo/in vitro by PhIP in lymphocytes from pre-cancerous monoclonal gammopathy of undetermined significance (MGUS) patients and those from healthy individuals. The results from the Comet assay revealed that in the presence of myricetin bulk (10 µM) and myricetin nano (20 µM), the DNA damage caused by a high dose of PhIP (100 µM) was significantly (P < 0.001) reduced in both groups. However, nano has shown better protection in lymphocytes from pre-cancerous patients. Consistent results were obtained from the micronucleus assay where micronuclei frequency in binucleated cells significantly decreased upon supplementing PhIP with myricetin bulk (P < 0.01) and myricetin nano (P < 0.001), compared to the PhIP treatment alone. To briefly determine the cellular pathways involved in the protective role of myricetin against PhIP, we studied gene expression of P53 and ATR kinase (ATM- and Rad3-related), using the real-time PCR technique.
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Affiliation(s)
- Shabana Akhtar
- School of Chemistry and Biosciences, University of Bradford, Richmond Building, Bradford, BD7 1DP, UK
| | - Mojgan Najafzadeh
- School of Chemistry and Biosciences, University of Bradford, Richmond Building, Bradford, BD7 1DP, UK
| | - Mohammad Isreb
- School of Pharmacy and Medical Sciences, University of Bradford, Bradford, UK
| | - Lisa Newton
- Bradford Royal Infirmary (BRI), Bradford, UK
| | - Rajendran C Gopalan
- School of Pharmacy and Medical Sciences, University of Bradford, Bradford, UK
| | - Diana Anderson
- School of Chemistry and Biosciences, University of Bradford, Richmond Building, Bradford, BD7 1DP, UK.
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8
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Bürtin F, Mullins CS, Linnebacher M. Mouse models of colorectal cancer: Past, present and future perspectives. World J Gastroenterol 2020; 26:1394-1426. [PMID: 32308343 PMCID: PMC7152519 DOI: 10.3748/wjg.v26.i13.1394] [Citation(s) in RCA: 77] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 03/05/2020] [Accepted: 03/09/2020] [Indexed: 02/06/2023] Open
Abstract
Colorectal cancer (CRC) is the third most common diagnosed malignancy among both sexes in the United States as well as in the European Union. While the incidence and mortality rates in western, high developed countries are declining, reflecting the success of screening programs and improved treatment regimen, a rise of the overall global CRC burden can be observed due to lifestyle changes paralleling an increasing human development index. Despite a growing insight into the biology of CRC and many therapeutic improvements in the recent decades, preclinical in vivo models are still indispensable for the development of new treatment approaches. Since the development of carcinogen-induced rodent models for CRC more than 80 years ago, a plethora of animal models has been established to study colon cancer biology. Despite tenuous invasiveness and metastatic behavior, these models are useful for chemoprevention studies and to evaluate colitis-related carcinogenesis. Genetically engineered mouse models (GEMM) mirror the pathogenesis of sporadic as well as inherited CRC depending on the specific molecular pathways activated or inhibited. Although the vast majority of CRC GEMM lack invasiveness, metastasis and tumor heterogeneity, they still have proven useful for examination of the tumor microenvironment as well as systemic immune responses; thus, supporting development of new therapeutic avenues. Induction of metastatic disease by orthotopic injection of CRC cell lines is possible, but the so generated models lack genetic diversity and the number of suited cell lines is very limited. Patient-derived xenografts, in contrast, maintain the pathological and molecular characteristics of the individual patient’s CRC after subcutaneous implantation into immunodeficient mice and are therefore most reliable for preclinical drug development – even in comparison to GEMM or cell line-based analyses. However, subcutaneous patient-derived xenograft models are less suitable for studying most aspects of the tumor microenvironment and anti-tumoral immune responses. The authors review the distinct mouse models of CRC with an emphasis on their clinical relevance and shed light on the latest developments in the field of preclinical CRC models.
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Affiliation(s)
- Florian Bürtin
- Department of General, Visceral, Vascular and Transplantation Surgery, University Medical Center Rostock, University of Rostock, Rostock 18057, Germany
| | - Christina S Mullins
- Department of Thoracic Surgery, University Medical Center Rostock, University of Rostock, Rostock 18057, Germany
| | - Michael Linnebacher
- Molecular Oncology and Immunotherapy, Department of General, Visceral, Vascular and Transplantation Surgery, University Medical Center Rostock, Rostock 18057, Germany
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9
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New insights of CYP1A in endogenous metabolism: a focus on single nucleotide polymorphisms and diseases. Acta Pharm Sin B 2020; 10:91-104. [PMID: 31998606 PMCID: PMC6984740 DOI: 10.1016/j.apsb.2019.11.016] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 10/13/2019] [Accepted: 10/16/2019] [Indexed: 12/31/2022] Open
Abstract
Cytochrome P450 1A (CYP1A), one of the major CYP subfamily in humans, not only metabolizes xenobiotics including clinical drugs and pollutants in the environment, but also mediates the biotransformation of important endogenous substances. In particular, some single nucleotide polymorphisms (SNPs) for CYP1A genes may affect the metabolic ability of endogenous substances, leading to some physiological or pathological changes in humans. This review first summarizes the metabolism of endogenous substances by CYP1A, and then introduces the research progress of CYP1A SNPs, especially the research related to human diseases. Finally, the relationship between SNPs and diseases is discussed. In addition, potential animal models for CYP1A gene editing are summarized. In conclusion, CYP1A plays an important role in maintaining the health in the body.
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Key Words
- CYP, cytochrome P450
- CYP1A
- EOAs, cis-epoxyoctadecenoics
- Endogenous substances
- FSH, follicle stimulating hormone
- HODEs, hydroxyoctadecdienoic acids
- IQ, 2-amino-3-methylimidazo [4,5-f] quinoline
- KO, knockout
- LIF/STAT3, inhibiting leukemia inhibitory factor/signal transducer and activator of transcription 3
- Metabolism and disease
- PhIP, 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine
- SNPs
- SNPs, single nucleotide polymorphisms
- WT, wild type
- Xenobiotics
- t-RA, all-trans-retinoic acid
- t-ROH, all-trans-retinol
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10
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D'Agostino L, Nie Y, Goswami S, Tong K, Yu S, Bandyopadhyay S, Flores J, Zhang X, Balasubramanian I, Joseph I, Sakamori R, Farrell V, Li Q, Yang CS, Gao B, Ferraris RP, Yehia G, Bonder EM, Goldenring JR, Verzi MP, Zhang L, Ip YT, Gao N. Recycling Endosomes in Mature Epithelia Restrain Tumorigenic Signaling. Cancer Res 2019; 79:4099-4112. [PMID: 31239271 DOI: 10.1158/0008-5472.can-18-4075] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Revised: 05/11/2019] [Accepted: 06/11/2019] [Indexed: 11/16/2022]
Abstract
The effects of polarized membrane trafficking in mature epithelial tissue on cell growth and cancer progression have not been fully explored in vivo. A majority of colorectal cancers have reduced and mislocalized Rab11, a small GTPase dedicated to trafficking of recycling endosomes. Patients with low Rab11 protein expression have poor survival rates. Using genetic models across species, we show that intact recycling endosome function restrains aberrant epithelial growth elicited by APC or RAS mutations. Loss of Rab11 protein led to epithelial dysplasia in early animal development and synergized with oncogenic pathways to accelerate tumor progression initiated by carcinogen, genetic mutation, or aging. Transcriptomic analysis uncovered an immediate expansion of the intestinal stem cell pool along with cell-autonomous Yki/Yap activation following disruption of Rab11a-mediated recycling endosomes. Intestinal tumors lacking Rab11a traffic exhibited marked elevation of nuclear Yap, upd3/IL6-Stat3, and amphiregulin-MAPK signaling, whereas suppression of Yki/Yap or upd3/IL6 reduced gut epithelial dysplasia and hyperplasia. Examination of Rab11a function in enteroids or cultured cell lines suggested that this endosome unit is required for suppression of the Yap pathway by Hippo kinases. Thus, recycling endosomes in mature epithelia constitute key tumor suppressors, loss of which accelerates carcinogenesis. SIGNIFICANCE: Recycling endosome traffic in mature epithelia constitutes a novel tumor suppressing mechanism.
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Affiliation(s)
- Luca D'Agostino
- Department of Biological Sciences, Rutgers University, Newark, New Jersey
| | - Yingchao Nie
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts
| | - Sayantani Goswami
- Department of Biological Sciences, Rutgers University, Newark, New Jersey
| | - Kevin Tong
- Department of Genetics, Rutgers University, Piscataway, New Jersey
| | - Shiyan Yu
- Department of Biological Sciences, Rutgers University, Newark, New Jersey
| | | | - Juan Flores
- Department of Biological Sciences, Rutgers University, Newark, New Jersey
| | - Xiao Zhang
- Department of Biological Sciences, Rutgers University, Newark, New Jersey
| | | | - Ivor Joseph
- Department of Biological Sciences, Rutgers University, Newark, New Jersey
| | - Ryotaro Sakamori
- Department of Biological Sciences, Rutgers University, Newark, New Jersey
| | - Victoria Farrell
- Department of Biological Sciences, Rutgers University, Newark, New Jersey
| | - Qi Li
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts
| | - Chung S Yang
- Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers University, Piscataway, New Jersey
| | - Bin Gao
- Department of Internal Medicine, Taixing Chinese Medicine Hospital, Taixing, Jiangsu, China
| | - Ronaldo P Ferraris
- Department of Pharmacology, Physiology, and Neuroscience, Rutgers New Jersey Medical School, Newark, New Jersey
| | - Ghassan Yehia
- Rutgers Genome Editing Core Facility, Rutgers University, New Brunswick, New Jersey
| | - Edward M Bonder
- Department of Biological Sciences, Rutgers University, Newark, New Jersey
| | - James R Goldenring
- Department of Surgery, Cell and Developmental Biology, and Epithelial Center, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Michael P Verzi
- Department of Genetics, Rutgers University, Piscataway, New Jersey.,Rutgers Cancer Institute of New Jersey, New Brunswick, New Jersey
| | - Lanjing Zhang
- Department of Biological Sciences, Rutgers University, Newark, New Jersey.,Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers University, Piscataway, New Jersey.,Rutgers Cancer Institute of New Jersey, New Brunswick, New Jersey.,Department of Pathology, Princeton Medical Center, Plainsboro, New Jersey
| | - Y Tony Ip
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts.
| | - Nan Gao
- Department of Biological Sciences, Rutgers University, Newark, New Jersey. .,Rutgers Cancer Institute of New Jersey, New Brunswick, New Jersey
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11
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ABC transporters Mdr1a/1b, Bcrp1, Mrp2 and Mrp3 determine the sensitivity to PhIP/DSS-induced colon carcinogenesis and inflammation. Arch Toxicol 2019; 93:775-790. [DOI: 10.1007/s00204-019-02394-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Accepted: 01/10/2019] [Indexed: 12/29/2022]
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12
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Bissig KD, Han W, Barzi M, Kovalchuk N, Ding L, Fan X, Pankowicz FP, Zhang QY, Ding X. P450-Humanized and Human Liver Chimeric Mouse Models for Studying Xenobiotic Metabolism and Toxicity. Drug Metab Dispos 2018; 46:1734-1744. [PMID: 30093418 DOI: 10.1124/dmd.118.083303] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 08/03/2018] [Indexed: 01/01/2023] Open
Abstract
Preclinical evaluation of drug candidates in experimental animal models is an essential step in drug development. Humanized mouse models have emerged as a promising alternative to traditional animal models. The purpose of this mini-review is to provide a brief survey of currently available mouse models for studying human xenobiotic metabolism. Here, we describe both genetic humanization and human liver chimeric mouse models, focusing on the advantages and limitations while outlining their key features and applications. Although this field of biomedical science is relatively young, these humanized mouse models have the potential to transform preclinical drug testing and eventually lead to a more cost-effective and rapid development of new therapies.
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Affiliation(s)
- Karl-Dimiter Bissig
- Baylor College of Medicine, Houston, Texas (K.-D.B., M.B., F.P.P.); and Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona (W.H., N.K., L.D., X.F., Q.-Y.Z., X.D.)
| | - Weiguo Han
- Baylor College of Medicine, Houston, Texas (K.-D.B., M.B., F.P.P.); and Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona (W.H., N.K., L.D., X.F., Q.-Y.Z., X.D.)
| | - Mercedes Barzi
- Baylor College of Medicine, Houston, Texas (K.-D.B., M.B., F.P.P.); and Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona (W.H., N.K., L.D., X.F., Q.-Y.Z., X.D.)
| | - Nataliia Kovalchuk
- Baylor College of Medicine, Houston, Texas (K.-D.B., M.B., F.P.P.); and Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona (W.H., N.K., L.D., X.F., Q.-Y.Z., X.D.)
| | - Liang Ding
- Baylor College of Medicine, Houston, Texas (K.-D.B., M.B., F.P.P.); and Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona (W.H., N.K., L.D., X.F., Q.-Y.Z., X.D.)
| | - Xiaoyu Fan
- Baylor College of Medicine, Houston, Texas (K.-D.B., M.B., F.P.P.); and Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona (W.H., N.K., L.D., X.F., Q.-Y.Z., X.D.)
| | - Francis P Pankowicz
- Baylor College of Medicine, Houston, Texas (K.-D.B., M.B., F.P.P.); and Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona (W.H., N.K., L.D., X.F., Q.-Y.Z., X.D.)
| | - Qing-Yu Zhang
- Baylor College of Medicine, Houston, Texas (K.-D.B., M.B., F.P.P.); and Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona (W.H., N.K., L.D., X.F., Q.-Y.Z., X.D.)
| | - Xinxin Ding
- Baylor College of Medicine, Houston, Texas (K.-D.B., M.B., F.P.P.); and Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona (W.H., N.K., L.D., X.F., Q.-Y.Z., X.D.)
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13
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Lee MJ, Feng W, Yang L, Chen YK, Chi E, Liu A, Yang CS. Methods for efficient analysis of tocopherols, tocotrienols and their metabolites in animal samples with HPLC-EC. J Food Drug Anal 2018; 26:318-329. [PMID: 29389570 PMCID: PMC9332665 DOI: 10.1016/j.jfda.2017.07.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Revised: 07/19/2017] [Accepted: 07/21/2017] [Indexed: 12/14/2022] Open
Abstract
Tocopherols and tocotrienols, collectively known as vitamin E, have received a great deal of attention because of their interesting biological activities. In the present study, we reexamined and improved previous methods of sample preparation and the conditions of high-performance liquid chromatography for more accurate quantification of tocopherols, tocotrienols and their major chain-degradation metabolites. For the analysis of serum tocopherols/tocotrienols, we reconfirmed our method of mixing serum with ethanol followed by hexane extraction. For the analysis of tissue samples, we improved our methods by extracting tocopherols/tocotrienols directly from tissue homogenate with hexane. For the analysis of total amounts (conjugated and unconjugated forms) of side-chain degradation metabolites, the samples need to be deconjugated by incubating with β-glucuronidase and sulfatase; serum samples can be directly used for the incubation, whereas for tissue homogenates a pre-deproteination step is needed. The present methods are sensitive, convenient and are suitable for the determination of different forms of vitamin E and their metabolites in animal and human studies. Results from the analysis of serum, liver, kidney, lung and urine samples from mice that had been treated with mixtures of tocotrienols and tocopherols are presented as examples.
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14
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Turner ND, Lloyd SK. Association between red meat consumption and colon cancer: A systematic review of experimental results. Exp Biol Med (Maywood) 2017; 242:813-839. [PMID: 28205448 PMCID: PMC5407540 DOI: 10.1177/1535370217693117] [Citation(s) in RCA: 74] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
A role for red and processed meat in the development of colorectal cancer has been proposed based largely on evidence from observational studies in humans, especially in those populations consuming a westernized diet. Determination of causation specifically by red or processed meat is contingent upon identification of plausible mechanisms that lead to colorectal cancer. We conducted a systematic review of the available evidence to determine the availability of plausible mechanistic data linking red and processed meat consumption to colorectal cancer risk. Forty studies using animal models or cell cultures met specified inclusion criteria, most of which were designed to examine the role of heme iron or heterocyclic amines in relation to colon carcinogenesis. Most studies used levels of meat or meat components well in excess of those found in human diets. Although many of the experiments used semi-purified diets designed to mimic the nutrient loads in current westernized diets, most did not include potential biologically active protective compounds present in whole foods. Because of these limitations in the existing literature, there is currently insufficient evidence to confirm a mechanistic link between the intake of red meat as part of a healthy dietary pattern and colorectal cancer risk. Impact statement Current recommendations to reduce colon cancer include the reduction or elimination of red or processed meats. These recommendations are based on data from epidemiological studies conducted among cultures where meat consumption is elevated and consumption of fruits, vegetables, and whole grains are reduced. This review evaluated experimental data exploring the putative mechanisms whereby red or processed meats may contribute to colon cancer. Most studies used levels of meat or meat-derived compounds that were in excess of those in human diets, even in cultures where meat intake is elevated. Experiments where protective dietary compounds were used to mitigate the extreme levels of meat and meat-derived compounds showed protection against colon cancer, with some essentially negating the impact of meat in the diet. It is essential that better-designed studies be conducted that use relevant concentrations of meat or meat-derived compounds in complex diets representative of the foods consumed by humans.
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Affiliation(s)
- Nancy D Turner
- Nutrition & Food Science Department, Texas A&M University, TX 77843-2253, USA
- Department of Veterinary Pathobiology, Texas A&M University, TX 77843-2253, USA
| | - Shannon K Lloyd
- Nutrition & Food Science Department, Texas A&M University, TX 77843-2253, USA
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15
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Chen JX, Liu A, Lee MJ, Wang H, Yu S, Chi E, Reuhl K, Suh N, Yang CS. δ- and γ-tocopherols inhibit phIP/DSS-induced colon carcinogenesis by protection against early cellular and DNA damages. Mol Carcinog 2017; 56:172-183. [PMID: 27175800 PMCID: PMC5647579 DOI: 10.1002/mc.22481] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 02/18/2016] [Accepted: 03/01/2016] [Indexed: 12/25/2022]
Abstract
Tocopherols, the major forms of vitamin E, are a family of fat-soluble compounds that exist in alpha (α-T), beta (β-T), gamma (γ-T), and delta (δ-T) variants. A cancer preventive effect of vitamin E is suggested by epidemiological studies. However, past animal studies and human intervention trials with α-T, the most active vitamin E form, have yielded disappointing results. A possible explanation is that the cancer preventive activity of α-T is weak compared to other tocopherol forms. In the present study, we investigated the effects of δ-T, γ-T, and α-T (0.2% in diet) in a novel colon cancer model induced by the meat-derived dietary carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and promoted by dextran sodium sulfate (DSS)-induced colitis in CYP1A-humanized (hCYP1A) mice. PhIP/DSS treatments induced multiple polypoid tumors, mainly tubular adenocarcinomas, in the middle to distal colon of the hCYP1A mice after 10 wk. Dietary supplementation with δ-T and γ-T significantly reduced colon tumor formation and suppressed markers of oxidative and nitrosative stress (i.e., 8-oxo-dG and nitrotyrosine) as well as pro-inflammatory mediators (i.e., NF-κB p65 and p-STAT3) in tumors and adjacent tissues. By administering δ-T at different time periods, we obtained results suggesting that the inhibitory effect of δ-T against colon carcinogenesis is mainly due to protection against early cellular and DNA damages caused by PhIP. α-T was found to be ineffective in inhibiting colon tumors and less effective in attenuating the molecular changes. Altogether, we demonstrated strong cancer preventive effects of δ-T and γ-T in a physiologically relevant model of human colon cancer. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Jayson X. Chen
- Department of Chemical Biology and Center for Cancer Prevention Research, Ernest Mario School of Pharmacy, New Jersey
| | - Anna Liu
- Department of Chemical Biology and Center for Cancer Prevention Research, Ernest Mario School of Pharmacy, New Jersey
| | - Mao-Jung Lee
- Department of Chemical Biology and Center for Cancer Prevention Research, Ernest Mario School of Pharmacy, New Jersey
| | - Hong Wang
- Department of Chemical Biology and Center for Cancer Prevention Research, Ernest Mario School of Pharmacy, New Jersey
| | - Siyuan Yu
- Department of Chemical Biology and Center for Cancer Prevention Research, Ernest Mario School of Pharmacy, New Jersey
| | - Eric Chi
- Department of Chemical Biology and Center for Cancer Prevention Research, Ernest Mario School of Pharmacy, New Jersey
| | - Kenneth Reuhl
- Department of Pharmacology and Toxicology, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Nanjoo Suh
- Department of Chemical Biology and Center for Cancer Prevention Research, Ernest Mario School of Pharmacy, New Jersey
- Cancer Institute of New Jersey, New Brunswick, NJ 08903, USA
| | - Chung S. Yang
- Department of Chemical Biology and Center for Cancer Prevention Research, Ernest Mario School of Pharmacy, New Jersey
- Cancer Institute of New Jersey, New Brunswick, NJ 08903, USA
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16
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Mimmler M, Peter S, Kraus A, Stroh S, Nikolova T, Seiwert N, Hasselwander S, Neitzel C, Haub J, Monien BH, Nicken P, Steinberg P, Shay JW, Kaina B, Fahrer J. DNA damage response curtails detrimental replication stress and chromosomal instability induced by the dietary carcinogen PhIP. Nucleic Acids Res 2016; 44:10259-10276. [PMID: 27599846 PMCID: PMC5137439 DOI: 10.1093/nar/gkw791] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 07/28/2016] [Accepted: 08/27/2016] [Indexed: 11/13/2022] Open
Abstract
PhIP is an abundant heterocyclic aromatic amine (HCA) and important dietary carcinogen. Following metabolic activation, PhIP causes bulky DNA lesions at the C8-position of guanine. Although C8-PhIP-dG adducts are mutagenic, their interference with the DNA replication machinery and the elicited DNA damage response (DDR) have not yet been studied. Here, we analyzed PhIP-triggered replicative stress and elucidated the role of the apical DDR kinases ATR, ATM and DNA-PKcs in the cellular defense response. First, we demonstrate that PhIP induced C8-PhIP-dG adducts and DNA strand breaks. This stimulated ATR-CHK1 signaling, phosphorylation of histone 2AX and the formation of RPA foci. In proliferating cells, PhIP treatment increased the frequency of stalled replication forks and reduced fork speed. Inhibition of ATR in the presence of PhIP-induced DNA damage strongly promoted the formation of DNA double-strand breaks, activation of the ATM-CHK2 pathway and hyperphosphorylation of RPA. The abrogation of ATR signaling potentiated the cell death response and enhanced chromosomal aberrations after PhIP treatment, while ATM and DNA-PK inhibition had only marginal effects. These results strongly support the notion that ATR plays a key role in the defense against cancer formation induced by PhIP and related HCAs.
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Affiliation(s)
| | - Simon Peter
- Department of Toxicology, University Medical Center, Mainz, Germany
| | - Alexander Kraus
- Department of Toxicology, University Medical Center, Mainz, Germany
| | - Svenja Stroh
- Department of Toxicology, University Medical Center, Mainz, Germany
| | - Teodora Nikolova
- Department of Toxicology, University Medical Center, Mainz, Germany
| | - Nina Seiwert
- Department of Toxicology, University Medical Center, Mainz, Germany
| | | | - Carina Neitzel
- Department of Toxicology, University Medical Center, Mainz, Germany
| | - Jessica Haub
- Department of Toxicology, University Medical Center, Mainz, Germany
| | - Bernhard H Monien
- Department of Food Safety, Federal Institute for Risk Assessment (BfR), Berlin, Germany
- Research Group Genotoxic Food Contaminants, German Institute of Human Nutrition (DIfE), Potsdam-Rehbrücke, Germany
| | - Petra Nicken
- Institute for Food Toxicology and Analytical Chemistry, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Pablo Steinberg
- Institute for Food Toxicology and Analytical Chemistry, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Jerry W Shay
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Bernd Kaina
- Department of Toxicology, University Medical Center, Mainz, Germany
| | - Jörg Fahrer
- Department of Toxicology, University Medical Center, Mainz, Germany
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17
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Fahrer J, Kaina B. Impact of DNA repair on the dose-response of colorectal cancer formation induced by dietary carcinogens. Food Chem Toxicol 2016; 106:583-594. [PMID: 27693244 DOI: 10.1016/j.fct.2016.09.029] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 09/10/2016] [Accepted: 09/27/2016] [Indexed: 12/30/2022]
Abstract
Colorectal cancer (CRC) is one of the most frequently diagnosed cancers, which is causally linked to dietary habits, notably the intake of processed and red meat. Processed and red meat contain dietary carcinogens, including heterocyclic aromatic amines (HCAs) and N-nitroso compounds (NOC). NOC are agents that induce various N-methylated DNA adducts and O6-methylguanine (O6-MeG), which are removed by base excision repair (BER) and O6-methylguanine-DNA methyltransferase (MGMT), respectively. HCAs such as the highly mutagenic 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) cause bulky DNA adducts, which are removed from DNA by nucleotide excision repair (NER). Both O6-MeG and HCA-induced DNA adducts are linked to the occurrence of KRAS and APC mutations in colorectal tumors of rodents and humans, thereby driving CRC initiation and progression. In this review, we focus on DNA repair pathways removing DNA lesions induced by NOC and HCA and assess their role in protecting against mutagenicity and carcinogenicity in the large intestine. We further discuss the impact of DNA repair on the dose-response relationship in colorectal carcinogenesis in view of recent studies, demonstrating the existence of 'no effect' point of departures (PoDs), i.e. thresholds for genotoxicity and carcinogenicity. The available data support the threshold concept for NOC with DNA repair being causally involved.
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Affiliation(s)
- Jörg Fahrer
- Department of Toxicology, University Medical Center Mainz, Obere Zahlbacher Strasse 67, D-55131 Mainz, Germany.
| | - Bernd Kaina
- Department of Toxicology, University Medical Center Mainz, Obere Zahlbacher Strasse 67, D-55131 Mainz, Germany.
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18
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Chen JX, Wang H, Liu A, Zhang L, Reuhl K, Yang CS. From the Cover: PhIP/DSS-Induced Colon Carcinogenesis in CYP1A-Humanized Mice and the Possible Role of Lgr5+ Stem Cells. Toxicol Sci 2016; 155:224-233. [PMID: 27664423 DOI: 10.1093/toxsci/kfw190] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
In the past decades, experimental rodent models developed to study the pathogenesis of human colorectal cancer (CRC) generally employed synthetic chemical carcinogens or genetic manipulation. Our lab, in order to establish a more physiologically relevant CRC model, recently developed a colon carcinogenesis model induced by the meat-derived dietary carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), and promoted by dextran sodium sulfate (DSS)-induced colitis in the cytochrome P450 1A-humanized (hCYP1A) mice. The resulting colon tumors shared many histologic and molecular features of human colon cancer. In this study, we characterized the early stages of PhIP/DSS-induced colon carcinogenesis. We found that PhIP/DSS treatments caused rapid destruction of the colon mucosa with severe inflammation, followed by the presence of reactive changes and low-grade dysplastic lesions, and then manifestation of high-grade dysplastic lesions and finally adenocarcinomas. Molecular analysis of the early time-points (ie, days 1, 3, 7, 11, 14, and 21 after DSS exposure) indicates Ctnnb1/β-catenin mutations and β-catenin nuclear accumulation in the high-grade dysplastic lesions, but not low-grade dysplastic lesions or adjacent normal tissues. In addition, we investigated the role of Lgr5+ colon stem cells in the PhIP/DSS-induced colon carcinogenesis and found the presence of Lgr5-enhance green fluorescent protein-expressing cells amidst some ulcerated mucosa, high-grade dysplastic lesions and adenocarcinomas, suggesting a possible role of Lgr5+ stem cells in this dietary carcinogen-induced, inflammation-promoted colon carcinogenesis model. Overall, the findings suggest that PhIP/DSS-induced colon carcinogenesis is likely initiated by dominant active Ctnnb1/β-catenin mutation in residual epithelial cells, which when promoted by colitis, developed into high-grade dysplasia and adenocarcinoma.
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Affiliation(s)
- Jayson X Chen
- Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, New Jersey.,Joint Graduate Program in Toxicology, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Hong Wang
- Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Anna Liu
- Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Lanjing Zhang
- Department of Pathology, University Medical Center of Princeton, Plainsboro, New Jersey
| | - Kenneth Reuhl
- Department of Pharmacology and Toxicology, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Chung S Yang
- Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, New Jersey;
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19
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Zamora R, Hidalgo FJ. The triple defensive barrier of phenolic compounds against the lipid oxidation-induced damage in food products. Trends Food Sci Technol 2016. [DOI: 10.1016/j.tifs.2016.06.006] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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20
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Wang H, Liu A, Kuo Y, Chi E, Yang X, Zhang L, Yang CS. Obesity promotes PhIP-induced small intestinal carcinogenesis in hCYP1A-db/db mice: involvement of mutations and DNA hypermethylation of Apc. Carcinogenesis 2016; 37:723-730. [PMID: 27207656 DOI: 10.1093/carcin/bgw054] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Accepted: 04/17/2016] [Indexed: 12/16/2022] Open
Abstract
Obesity is associated with an increased risk of cancer. To study the promotion of dietary carcinogen-induced gastrointestinal cancer by obesity, we employed 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) to induce intestinal tumorigenesis in CYP1A-humanized (hCYP1A) mice, in which mouse Cyp1a1/1a2 was replaced with human CYP1A1/1A2 Obesity was introduced in hCYP1A mice by breeding with Lepr(db/+) mice to establish the genetically induced obese hCYP1A-Lepr(db/db) mice or by feeding hCYP1A mice a high-fat diet. PhIP induced the formation of small intestinal tumors at the ages of weeks 28-40 in obese hCYP1A mice, but not in lean hCYP1A mice. No tumors were found in colon and other gastrointestinal organs in the lean or obese mice. Using immunohistochemistry (IHC), we found strong positive staining of NF-κB p65, pSTAT3 and COX2 as well as elevated levels of nuclear β-catenin (Ctnnb1) in small intestinal tumors, but not in normal tissues. By sequencing Apc and Ctnnb1 genes, we found that most PhIP-induced small intestinal tumors in obese mice carried only a single heterozygous mutation in Apc By bisulfite-sequencing of CpG islands of Apc, we found DNA hypermethylation in a CpG cluster located in its transcription initiation site, which most likely caused the inactivation of the wild-type Apc allele. Our findings demonstrate that PhIP-induced small intestinal carcinogenesis in hCYP1A-db/db mice is promoted by obesity and involves Apc mutation and inactivation by DNA hypermethylation. This experimental result is consistent with the association of obesity and the increased incidence of small intestinal cancer in humans in recent decades.
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Affiliation(s)
- Hong Wang
- Susan L. Cullman Laboratory for Cancer Research, Department of Chemical Biology and Center for Cancer Prevention Research, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, 164 Frelinghuysen Road, Piscataway, NJ 08854, USA
| | - Anna Liu
- Susan L. Cullman Laboratory for Cancer Research, Department of Chemical Biology and Center for Cancer Prevention Research, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, 164 Frelinghuysen Road, Piscataway, NJ 08854, USA
| | - Yingyi Kuo
- Susan L. Cullman Laboratory for Cancer Research, Department of Chemical Biology and Center for Cancer Prevention Research, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, 164 Frelinghuysen Road, Piscataway, NJ 08854, USA
| | - Eric Chi
- Susan L. Cullman Laboratory for Cancer Research, Department of Chemical Biology and Center for Cancer Prevention Research, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, 164 Frelinghuysen Road, Piscataway, NJ 08854, USA
| | - Xu Yang
- Susan L. Cullman Laboratory for Cancer Research, Department of Chemical Biology and Center for Cancer Prevention Research, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, 164 Frelinghuysen Road, Piscataway, NJ 08854, USA
| | - Lanjing Zhang
- Susan L. Cullman Laboratory for Cancer Research, Department of Chemical Biology and Center for Cancer Prevention Research, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, 164 Frelinghuysen Road, Piscataway, NJ 08854, USA.,Department of Pathology, University Medical Center of Princeton, Plainsboro, NJ 08536, USA and.,Department of Pathology, Robert Wood Johnson Medical School and Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA
| | - Chung S Yang
- Susan L. Cullman Laboratory for Cancer Research, Department of Chemical Biology and Center for Cancer Prevention Research, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, 164 Frelinghuysen Road, Piscataway, NJ 08854, USA
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21
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Bhushan A, Martucci NJ, Usta OB, Yarmush ML. New technologies in drug metabolism and toxicity screening: organ-to-organ interaction. Expert Opin Drug Metab Toxicol 2016; 12:475-7. [PMID: 26940609 DOI: 10.1517/17425255.2016.1162292] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Abhinav Bhushan
- a Department of Biomedical Engineering , Illinois Institute of Technology , Chicago , IL , USA
| | - Nicole J Martucci
- b Department of Biomedical Engineering , Binghamton University , Binghamton , NY , USA
| | - O Berk Usta
- c Center for Engineering in Medicine, Harvard Medical School , Massachusetts General Hospital , Boston , MA , USA
| | - Martin L Yarmush
- c Center for Engineering in Medicine, Harvard Medical School , Massachusetts General Hospital , Boston , MA , USA.,d Department of Biomedical Engineering , Rutgers University , Piscataway , NJ , USA
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22
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Scheer N, Wilson ID. A comparison between genetically humanized and chimeric liver humanized mouse models for studies in drug metabolism and toxicity. Drug Discov Today 2015; 21:250-63. [PMID: 26360054 DOI: 10.1016/j.drudis.2015.09.002] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2015] [Revised: 08/07/2015] [Accepted: 09/01/2015] [Indexed: 12/12/2022]
Abstract
Mice that have been genetically humanized for proteins involved in drug metabolism and toxicity and mice engrafted with human hepatocytes are emerging and promising in vivo models for an improved prediction of the pharmacokinetic, drug-drug interaction and safety characteristics of compounds in humans. The specific advantages and disadvantages of these models should be carefully considered when using them for studies in drug discovery and development. Here, an overview on the corresponding genetically humanized and chimeric liver humanized mouse models described to date is provided and illustrated with examples of their utility in drug metabolism and toxicity studies. We compare the strength and weaknesses of the two different approaches, give guidance for the selection of the appropriate model for various applications and discuss future trends and perspectives.
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Affiliation(s)
| | - Ian D Wilson
- Imperial College London, South Kensington, London SW7 2AZ, UK.
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23
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Wang H, Zhou H, Liu A, Guo X, Yang CS. Genetic analysis of colon tumors induced by a dietary carcinogen PhIP in CYP1A humanized mice: Identification of mutation of β-catenin/Ctnnb1 as the driver gene for the carcinogenesis. Mol Carcinog 2014; 54:1264-74. [PMID: 25131582 DOI: 10.1002/mc.22199] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 05/23/2014] [Accepted: 06/06/2014] [Indexed: 01/08/2023]
Abstract
Replacing mouse Cyp1a with human CYP1A enables the humanized CYP1A mice to mimic human metabolism of the dietary carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), by N(2) -hydroxylation to a proximate carcinogen. Our previous study demonstrated that PhIP, combined with the dextrin sulfate sodium (DSS)-induced colitis, induces colon carcinogenesis in hCYP1A mice. Here, we employed whole exome sequencing and found multiple gene mutations in PhIP/DSS-induced colon tumors. Mutations in the exon 3 of Ctnnb1/β-catenin, however, were the predominant events. We further sequenced the key fragments of Apc, Ctnnb1, and Kras, because mutations of these genes in the humans are commonly found as the drivers of colorectal cancer. Mutations on either codon 32 or 34 in the exon 3 of Ctnnb1 were found in 39 out of 42 tumors, but no mutation was found in either Apc or Kras. The sequence context of codons 32 and 34 suggests that PhIP targets +3G in a TGGA motif of Ctnnb1. Since mutations that activate Wnt signal is a major driving force for human colorectal cancers, we conclude that the mutated β-catenin is the driver in PhIP/DSS-induced colon carcinogenesis. This result suggests that the colon tumors in hCYP1A mice mimic human colorectal carcinogenesis not only in the dietary etiology involving PhIP, but also in the aberrant activation of the Wnt signaling pathway as the driving force.
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Affiliation(s)
- Hong Wang
- Susan L. Cullman Laboratory for Cancer Research, Department of Chemical Biology and Center for Cancer Prevention Research, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Hong Zhou
- Department of Mathematics, University of Saint Joseph, West Hartford, Connecticut
| | - Anna Liu
- Susan L. Cullman Laboratory for Cancer Research, Department of Chemical Biology and Center for Cancer Prevention Research, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Xiangyi Guo
- Susan L. Cullman Laboratory for Cancer Research, Department of Chemical Biology and Center for Cancer Prevention Research, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Chung S Yang
- Susan L. Cullman Laboratory for Cancer Research, Department of Chemical Biology and Center for Cancer Prevention Research, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, New Jersey
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24
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Structural characteristics that determine the inhibitory role of phenolic compounds on 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) formation. Food Chem 2014; 151:480-6. [DOI: 10.1016/j.foodchem.2013.11.105] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Revised: 10/03/2013] [Accepted: 11/19/2013] [Indexed: 12/22/2022]
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Scheer N, Wolf CR. Genetically humanized mouse models of drug metabolizing enzymes and transporters and their applications. Xenobiotica 2013; 44:96-108. [DOI: 10.3109/00498254.2013.815831] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Tang Y, Kassie F, Qian X, Ansha B, Turesky RJ. DNA adduct formation of 2-amino-9H-pyrido[2,3-b]indole and 2-amino-3,4-dimethylimidazo[4,5-f]quinoline in mouse liver and extrahepatic tissues during a subchronic feeding study. Toxicol Sci 2013; 133:248-58. [PMID: 23535364 PMCID: PMC3663563 DOI: 10.1093/toxsci/kft077] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 03/20/2013] [Indexed: 01/01/2023] Open
Abstract
Tobacco smoking is a risk factor for cancers of the liver and gastrointestinal (GI) tract, but the causal agents responsible for these cancers are uncertain. 2-Amino-9H-pyrido[2,3-b]indole (AαC) is an abundant heterocyclic aromatic amine present in tobacco smoke. AαC is a liver carcinogen and both a transgene mutagen and inducer of aberrant crypt foci in the colon of mice. We hypothesize that AαC may contribute to DNA damage and tumorigenesis in these organs of smokers. The potential of AαC to induce DNA adduct formation in liver, organs of the GI tract, lung, and urinary bladder, which are target organs of cancer in smokers, was examined using the C57BL/6 mouse as an animal model. AαC (400 or 800 ppm) and 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) (300 ppm), a liver and colon carcinogen in C57BL/6 mice, were given in the diet for up to 12 weeks. Liquid chromatography/mass spectrometry was employed to measure DNA adducts. The major DNA adducts of both carcinogens were identified as deoxyguanosine-C8 adducts. The levels of formation of AαC- and MeIQ-DNA adducts were similar in liver and extrahepatic tissues when adjusted for dose. The highest levels of adducts occurred in liver, followed by urinary bladder, and then in cecum and colon; lower DNA adduct levels were formed in the lung and pancreas following 12 weeks of feeding. The high levels of AαC adduct formed in liver, GI tract, and bladder of C57BL/6 mice reinforce the notion that AαC may contribute to DNA damage and cancer of these organs in smokers.
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Affiliation(s)
- Yijin Tang
- *Division of Environmental Health Sciences, Wadsworth Center, New York State Department of Health, Albany, New York 12201; and
| | - Fekadu Kassie
- Masonic Cancer Center and
- College of Veterinary Medicine, University of Minnesota, Minneapolis, Minnesota
| | | | | | - Robert J. Turesky
- *Division of Environmental Health Sciences, Wadsworth Center, New York State Department of Health, Albany, New York 12201; and
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Baer-Dubowska W, Szaefer H. Modulation of carcinogen-metabolizing cytochromes P450 by phytochemicals in humans. Expert Opin Drug Metab Toxicol 2013; 9:927-41. [PMID: 23634851 DOI: 10.1517/17425255.2013.795219] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION Cytochrome P450 (CYP) families 1 - 3, besides oxidizing environmental and dietary chemicals, leading to their elimination, catalyze the bioactivation of exogenous as well as endogenous carcinogens. Phytochemicals, particularly those which are active food components, were shown to be able to affect specific CYP expression and/or activity in animal models and in human in vitro systems. Human intervention studies involving healthy volunteers were also performed. This review describes human CYP modulation by naturally occurring phytochemicals which can not only affect carcinogen metabolism in humans, but also change the drug response. AREAS COVERED The authors present an overview of carcinogens metabolizing human CYP modulation in different model systems as well as studies on human dietary intervention. Furthermore, the authors provide examples of the phytochemicals that affect CYP expression and activity. EXPERT OPINION CYP, which are involved in carcinogen activation, can metabolize a range of substrates and inducing CYP by one substrate may also increase the metabolism of another. The ultimate proof of the efficacy of CYP modulation strategy for chemoprevention may be provided by clinical trials involving risk populations, which are difficult to perform. The new human-like models are highly desired for the study of modulation of carcinogen-metabolizing CYP.
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Affiliation(s)
- Wanda Baer-Dubowska
- Poznan University of Medical Sciences, Department of Pharmaceutical Biochemistry, Poznań, Poland.
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Comparative formation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in creatinine/phenylalanine and creatinine/phenylalanine/4-oxo-2-nonenal reaction mixtures. Food Chem 2013; 138:180-5. [DOI: 10.1016/j.foodchem.2012.09.116] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Revised: 08/16/2012] [Accepted: 09/24/2012] [Indexed: 11/18/2022]
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Abstract
Colorectal cancer is one of the most common malignancies in the world. Many mouse models have been developed to evaluate features of colorectal cancer in humans. These can be grouped into genetically-engineered, chemically-induced, and inoculated models. However, none recapitulates all of the characteristics of human colorectal cancer. It is critical to use a specific mouse model to address a particular research question. Here, we review commonly used mouse models for human colorectal cancer.
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Affiliation(s)
- Yunguang Tong
- Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA.
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Abstract
Considerable support exists for the roles of metabolism in modulating the carcinogenic properties of chemicals. In particular, many of these compounds are pro-carcinogens that require activation to electrophilic forms to exert genotoxic effects. We systematically analyzed the existing literature on the metabolism of carcinogens by human enzymes, which has been developed largely in the past 25 years. The metabolism and especially bioactivation of carcinogens are dominated by cytochrome P450 enzymes (66% of bioactivations). Within this group, six P450s--1A1, 1A2, 1B1, 2A6, 2E1, and 3A4--accounted for 77% of the P450 activation reactions. The roles of these P450s can be compared with those estimated for drug metabolism and should be considered in issues involving enzyme induction, chemoprevention, molecular epidemiology, interindividual variations, and risk assessment.
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Li G, Wang H, Liu AB, Cheung C, Reuhl KR, Bosland MC, Yang CS. Dietary carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine-induced prostate carcinogenesis in CYP1A-humanized mice. Cancer Prev Res (Phila) 2012; 5:963-72. [PMID: 22581815 DOI: 10.1158/1940-6207.capr-12-0023] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
To develop a relevant mouse model for prostate cancer prevention research, we administered a dietary carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), to CYP1A-humanized mice. In comparison with mouse Cyp1a2, human CYP1A2 preferentially activates PhIP to a proximate carcinogen. Following a single oral dose of PhIP (200 mg/kg body weight), we observed inflammation, atrophy of acini, low-grade prostatic intraepithelial neoplasia (PIN; after 20 weeks), and high-grade PIN (HgPIN; after 30 to 50 weeks) in dorsolateral, ventral, and coagulating anterior prostate glands of these mice. These lesions were androgen receptor positive and featured the loss of expression of the basal cell marker p63 and the tumor suppressor PTEN. Similar to human prostate carcinogenesis, glutathione S-transferase P1 (GSTP1) expression was lost or partially lost in HgPIN. E-Cadherin expression was also lost in HgPIN. The expression of DNA methyltransferase 1 was elevated, possibly to enhance promoter hypermethylation for the silencing of GSTP1 and E-cadherin. Prostate carcinogenesis was promoted by a high-fat stress diet, resulting in HgPIN that developed earlier and in advanced lesions displayed features consistent with carcinoma in situ. This dietary carcinogen-induced prostate cancer model, recapitulating important features of early human prostate carcinogenesis, constitutes a new experimental system for prostate cancer research.
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Affiliation(s)
- Guangxun Li
- Department of Chemical Biology, Center for Cancer Prevention Research, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA
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Shen HW, Jiang XL, Gonzalez FJ, Yu AM. Humanized transgenic mouse models for drug metabolism and pharmacokinetic research. Curr Drug Metab 2012; 12:997-1006. [PMID: 22023319 DOI: 10.2174/138920011798062265] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Revised: 07/16/2011] [Accepted: 07/20/2011] [Indexed: 02/08/2023]
Abstract
Extrapolation of the metabolic, pharmacokinetic and toxicological data obtained from animals to humans is not always straightforward, given the remarkable species difference in drug metabolism that is due in large part to the differences in drug-metabolizing enzymes between animals and humans. Furthermore, genetic variations in drug-metabolizing enzymes may significantly alter pharmacokinetics, drug efficacy and safety. Thus, humanized transgenic mouse lines, in which the human drug-metabolizing enzymes are expressed in mouse tissues in the presence or absence of mouse orthologues, have been developed to address such challenges. These humanized transgenic mice are valuable animal models in understanding the significance of specific human drug-metabolizing enzymes in drug clearance and pharmacokinetics, as well as in predicting potential drug-drug interactions and chemical toxicity in humans. This review, therefore, aims to summarize the development and application of some humanized transgenic mouse models expressing human drug-metabolizing enzymes. The limitations of these genetically modified mouse models are also discussed.
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Affiliation(s)
- Hong-Wu Shen
- Department of Pharmaceutical Sciences University at Buffalo, The State University of New York, 541 Cooke Hall, Buffalo, NY 14260-1200, USA
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Arlt VM, Singh R, Stiborová M, Gamboa da Costa G, Frei E, Evans JD, Farmer PB, Wolf CR, Henderson CJ, Phillips DH. Effect of hepatic cytochrome P450 (P450) oxidoreductase deficiency on 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine-DNA adduct formation in P450 reductase conditional null mice. Drug Metab Dispos 2011; 39:2169-73. [PMID: 21940903 DOI: 10.1124/dmd.111.041343] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), formed during the cooking of foods, induces colon cancer in rodents. PhIP is metabolically activated by cytochromes P450 (P450s). To evaluate the role of hepatic P450s in the bioactivation of PhIP, we used Reductase Conditional Null (RCN) mice, in which cytochrome P450 oxidoreductase (POR), the unique electron donor to P450s, can be specifically deleted in hepatocytes by pretreatment with 3-methylcholanthrene (3-MC), resulting in the loss of essentially all hepatic P450 function. RCN mice were treated orally with 50 mg/kg b.wt. PhIP daily for 5 days, with and without 3-MC pretreatment. PhIP-DNA adducts (i.e., N-(deoxyguanosin-8-yl)-2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine [dG-C8-PhIP]), measured by liquid chromatography-tandem mass spectrometry, were highest in colon (1362 adducts/10(8) deoxynucleosides), whereas adduct levels in liver were ∼3.5-fold lower. Whereas no differences in PhIP-DNA adduct levels were found in livers with active POR versus inactivated POR, adduct levels were on average ∼2-fold lower in extrahepatic tissues of mice lacking hepatic POR. Hepatic microsomes from RCN mice with or without 3-MC pretreatment were also incubated with PhIP and DNA in vitro. PhIP-DNA adduct formation was ∼8-fold lower with hepatic microsomes from POR-inactivated mice than with those with active POR. Most of the hepatic microsomal activation of PhIP in vitro was attributable to CYP1A. Our results show that PhIP-DNA adduct formation in colon involves hepatic N-oxidation, circulation of activated metabolites via the bloodstream to extrahepatic tissues, and further activation, resulting in the formation of dG-C8-PhIP. Besides hepatic P450s, PhIP may be metabolically activated mainly by a non-P450 pathway in liver.
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Affiliation(s)
- Volker M Arlt
- Section of Molecular Carcinogenesis, Institute of Cancer Research, Brookes Lawley Building, Sutton, Surrey SM2 5NG, UK.
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