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Yari F, Ashoub MH, Amirizadeh N, Nikougoftar M, Valandani HM, Khalilabadi RM. Differential Expression of the hTERT Gene in Umbilical Cord-Derived Mesenchymal Stem Cells Cocultured with B Cell Precursor Leukemia Cell Microparticles or CD41 +/CD61 + Platelet Microparticles. Biochem Genet 2023:10.1007/s10528-023-10565-9. [PMID: 38019337 DOI: 10.1007/s10528-023-10565-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 10/26/2023] [Indexed: 11/30/2023]
Abstract
Several investigations are being done to increase the short lifetime of mesenchymal stem cells (MSCs). One of the crucial genes involved in the immortalization of MSCs, hTERT (human telomerase reverse transcriptase), is activated in most publications using viral-based techniques. In this work, we investigated the use of platelet-derived (PMPs) and B cell precursor leukemia-derived microparticles as a nonviral method to trigger and compare the expression of the hTERT gene in MSCs. MSCs were extracted from the umbilical cord for the current investigation and identified using a flow cytometry approach and an inverted microscope. The Nalm-6 cell line and platelet concentrate were used to isolate microparticles (MPs). MSCs and MPs were cocultured for 14 days at 25-, 50-, and 100 μg/ml concentrations. qRT-PCR was used to research the expression of the hTERT gene. SPSS 26.0's t test was used to compare the outcomes. After coculture with platelet MPs, MSCs had higher levels of hTERT gene expression than the control group. In contrast, this gene's expression was concurrently decreased in MSCs exposed to MPs generated from Nalm-6. We demonstrated that following 14-day treatment, PMP significantly boosted the hTERT gene expression in MSCs, while the Nalm-6 MPs lowered the gene expression. However, additional studies are necessary due to the stability of hTERT gene expression and the immortalization of MSCs following exposure.
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Affiliation(s)
- Fatemeh Yari
- Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine, Tehran, Iran
| | - Muhammad Hossein Ashoub
- Department of Hematology and Medical Laboratory Sciences, Faculty of Allied Medicine, Kerman University of Medical Sciences, Kerman, Iran
| | - Naser Amirizadeh
- Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine, Tehran, Iran
| | - Mahin Nikougoftar
- Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine, Tehran, Iran
| | - Hajar Mardani Valandani
- Department of Hematology and Medical Laboratory Sciences, Faculty of Allied Medicine, Kerman University of Medical Sciences, Kerman, Iran
| | - Roohollah Mirzaee Khalilabadi
- Department of Hematology and Medical Laboratory Sciences, Faculty of Allied Medicine, Kerman University of Medical Sciences, Kerman, Iran.
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Fontaine M, Bartolami E, Prono M, Béal D, Blosi M, Costa AL, Ravagli C, Baldi G, Sprio S, Tampieri A, Fenoglio I, Tran L, Fadeel B, Carriere M. Nanomaterial genotoxicity evaluation using the high-throughput p53-binding protein 1 (53BP1) assay. PLoS One 2023; 18:e0288737. [PMID: 37713377 PMCID: PMC10503773 DOI: 10.1371/journal.pone.0288737] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 07/04/2023] [Indexed: 09/17/2023] Open
Abstract
Toxicity evaluation of engineered nanomaterials is challenging due to the ever increasing number of materials and because nanomaterials (NMs) frequently interfere with commonly used assays. Hence, there is a need for robust, high-throughput assays with which to assess their hazard potential. The present study aimed at evaluating the applicability of a genotoxicity assay based on the immunostaining and foci counting of the DNA repair protein 53BP1 (p53-binding protein 1), in a high-throughput format, for NM genotoxicity assessment. For benchmarking purposes, we first applied the assay to a set of eight known genotoxic agents, as well as X-ray irradiation (1 Gy). Then, a panel of NMs and nanobiomaterials (NBMs) was evaluated with respect to their impact on cell viability and genotoxicity, and to their potential to induce reactive oxygen species (ROS) production. The genotoxicity recorded using the 53BP1 assay was confirmed using the micronucleus assay, also scored via automated (high-throughput) microscopy. The 53BP1 assay successfully identified genotoxic compounds on the HCT116 human intestinal cell line. None of the tested NMs showed any genotoxicity using the 53BP1 assay, except the positive control consisting in (CoO)(NiO) NMs, while only TiO2 NMs showed positive outcome in the micronucleus assay. Only Fe3O4 NMs caused significant elevation of ROS, not correlated to DNA damage. Therefore, owing to its adequate predictivity of the genotoxicity of most of the tested benchmark substance and its ease of implementation in a high throughput format, the 53BP1 assay could be proposed as a complementary high-throughput screening genotoxicity assay, in the context of the development of New Approach Methodologies.
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Affiliation(s)
- Maelle Fontaine
- CEA, CNRS, IRIG, SyMMES-CIBEST, Univ. Grenoble Alpes, Grenoble, France
| | - Eline Bartolami
- CEA, CNRS, IRIG, SyMMES-CIBEST, Univ. Grenoble Alpes, Grenoble, France
| | - Marion Prono
- CEA, CNRS, IRIG, SyMMES-CIBEST, Univ. Grenoble Alpes, Grenoble, France
| | - David Béal
- CEA, CNRS, IRIG, SyMMES-CIBEST, Univ. Grenoble Alpes, Grenoble, France
| | - Magda Blosi
- National Research Council, Institute of Science, Technology and Sustainability for Ceramic Materials ISSMC-CNR (Former ISTEC-CNR), Faenza, Italy
| | - Anna L. Costa
- National Research Council, Institute of Science, Technology and Sustainability for Ceramic Materials ISSMC-CNR (Former ISTEC-CNR), Faenza, Italy
| | - Costanza Ravagli
- Ce.Ri.Col, Colorobbia Consulting S.R.L, Sovigliana-Vinci, Firenze, Italy
| | - Giovanni Baldi
- Ce.Ri.Col, Colorobbia Consulting S.R.L, Sovigliana-Vinci, Firenze, Italy
| | - Simone Sprio
- National Research Council, Institute of Science, Technology and Sustainability for Ceramic Materials ISSMC-CNR (Former ISTEC-CNR), Faenza, Italy
| | - Anna Tampieri
- National Research Council, Institute of Science, Technology and Sustainability for Ceramic Materials ISSMC-CNR (Former ISTEC-CNR), Faenza, Italy
| | - Ivana Fenoglio
- Department of Chemistry, University of Turin, Turin, Italy
| | - Lang Tran
- Institute of Occupational Medicine, Edinburgh, Midlothian, United Kingdom
| | - Bengt Fadeel
- Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Marie Carriere
- CEA, CNRS, IRIG, SyMMES-CIBEST, Univ. Grenoble Alpes, Grenoble, France
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3
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Cruz B, Balderas I, Gómez I. Aqueous synthesis of red fluorescent l-cysteine functionalized Cu 2S quantum dots with potential application as an As(iii) aptasensor. RSC Adv 2023; 13:18946-18952. [PMID: 37362604 PMCID: PMC10286222 DOI: 10.1039/d3ra02886k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Accepted: 06/14/2023] [Indexed: 06/28/2023] Open
Abstract
Water-stable Cu2S quantum dots were obtained by applying l-cysteine as a Cu(ii) to Cu(i) reducer and stabilizer in water and using an inert atmosphere at ambient temperature. The obtained quantum dots were characterized by STEM, XRD, FT-IR, UV-Vis, Raman, and fluorescence spectroscopy. The synthesis was optimized to achieve Cu2S quantum dots with an average diameter of about 9 nm that show red fluorescence emission. l-cysteine stabilization mediates crystallite growth, avoids aggregation of the quantum dots, and allows water solubility through polar functional groups, improving the fluorescence. The fluorometric test in the presence of the aptamer showed a shift in fluorescence intensity when an aliquot of As(iii) with a concentration of 100 pmol l-1 is incorporated because As(iii) and the used aptamer make a complex, leaving free the quantum dots and recovering their fluorescence response. The developed Cu2S quantum dots open possibilities for fluorescent detection of different analytes by simply changing aptamers according to the analyte to be detected.
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Affiliation(s)
- Brandon Cruz
- Laboratorio de Materiales I, Universidad Autónoma de Nuevo León San Nicolás de los Garza Mexico
| | - Isaías Balderas
- Laboratorio de Ingeniería Genética y Genómica, Universidad Autónoma de Nuevo León San Nicolás de los Garza Mexico
| | - Idalia Gómez
- Laboratorio de Materiales I, Universidad Autónoma de Nuevo León San Nicolás de los Garza Mexico
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4
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Pikula K, Johari SA, Santos-Oliveira R, Golokhvast K. The Comparative Toxic Impact Assessment of Carbon Nanotubes, Fullerene, Graphene, and Graphene Oxide on Marine Microalgae Porphyridium purpureum. TOXICS 2023; 11:491. [PMID: 37368591 DOI: 10.3390/toxics11060491] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 05/29/2023] [Accepted: 05/29/2023] [Indexed: 06/29/2023]
Abstract
The growing production and application of carbon-based nanomaterials (CNMs) represent possible risks for aquatic systems. However, the variety of CNMs with different physical and chemical properties and different morphology complicate the understanding of their potential toxicity. This paper aims to evaluate and compare the toxic impact of the four most common CNMs, namely multiwalled carbon nanotubes (CNTs), fullerene (C60), graphene (Gr), and graphene oxide (GrO) on the marine microalgae Porphyridium purpureum. The microalgae cells were exposed to the CNMs for 96 h and measured by flow cytometry. Based on the obtained results, we determined no observed effect level (NOEL), and calculated EC10 and EC50 concentrations for growth rate inhibition, esterase activity, membrane potential, and reactive oxygen species (ROS) generation changes for each tested CNM. According to the sensitivity (growth rate inhibition) of P. purpureum, the used CNMs can be listed in the following order (EC50 in mg/L, 96 h): CNTs (2.08) > GrO (23.37) > Gr (94.88) > C60 (>131.0). The toxicity of CNTs was significantly higher than the toxic effect of the other used CNMs, and only this sample caused an increase in ROS generation in microalgae cells. This effect was apparently caused by the high affinity between particles and microalgae associated with the presence of exopolysaccharide coverage on P. purpureum cells.
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Affiliation(s)
- Konstantin Pikula
- Polytechnical Institute, Far Eastern Federal University, 10 Ajax Bay, Russky Island, Vladivostok 690922, Russia
| | - Seyed Ali Johari
- Department of Fisheries, Faculty of Natural Resources, University of Kurdistan, Pasdaran St, Sanandaj 66177-15175, Iran
| | - Ralph Santos-Oliveira
- Laboratory of Nanoradiopharmaceuticals and Synthesis of Novel Radiopharmaceuticals, Nuclear Engineering Institute, Brazilian Nuclear Energy Commission, Rua Hélio de Almeida 75, Rio de Janeiro 21941906, Brazil
- Laboratory of Nanoradiopharmaceuticals and Radiopharmacy, Rio de Janeiro State University, R. São Francisco Xavier, 524, Rio de Janeiro 23070200, Brazil
| | - Kirill Golokhvast
- Polytechnical Institute, Far Eastern Federal University, 10 Ajax Bay, Russky Island, Vladivostok 690922, Russia
- Siberian Federal Scientific Center of Agrobiotechnology RAS, Centralnaya Str., Presidium, Krasnoobsk 633501, Russia
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5
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Guth S, Baum M, Cartus AT, Diel P, Engel KH, Engeli B, Epe B, Grune T, Haller D, Heinz V, Hellwig M, Hengstler JG, Henle T, Humpf HU, Jäger H, Joost HG, Kulling SE, Lachenmeier DW, Lampen A, Leist M, Mally A, Marko D, Nöthlings U, Röhrdanz E, Roth A, Spranger J, Stadler R, Steinberg P, Vieths S, Wätjen W, Eisenbrand G. Evaluation of the genotoxic potential of acrylamide: Arguments for the derivation of a tolerable daily intake (TDI value). Food Chem Toxicol 2023; 173:113632. [PMID: 36708862 DOI: 10.1016/j.fct.2023.113632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 01/09/2023] [Accepted: 01/19/2023] [Indexed: 01/26/2023]
Abstract
This opinion of the Senate Commission on Food Safety (SKLM) of the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) presents arguments for an updated risk assessment of diet-related exposure to acrylamide (AA), based on a critical review of scientific evidence relevant to low dose exposure. The SKLM arrives at the conclusion that as long as an appropriate exposure limit for AA is not exceeded, genotoxic effects resulting in carcinogenicity are unlikely to occur. Based on the totality of the evidence, the SKLM considers it scientifically justified to derive a tolerable daily intake (TDI) as a health-based guidance value.
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Affiliation(s)
- Sabine Guth
- Leibniz Research Centre for Working Environment and Human Factors (IfADo), Ardeystr. 67, 44139, Dortmund, Germany.
| | - Matthias Baum
- Solenis Germany Industries GmbH, Fütingsweg 20, 47805 Krefeld, Germany.
| | | | - Patrick Diel
- Department of Molecular and Cellular Sports Medicine, Institute of Cardiovascular Research and Sports Medicine, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933, Cologne, Germany.
| | - Karl-Heinz Engel
- Technical University of Munich, Maximus-von-Imhof-Forum 2, 85354, Freising, Germany.
| | - Barbara Engeli
- Federal Food Safety and Veterinary Office (FSVO), Risk Assessment Division, Schwarzenburgstrasse 155, 3003, Bern, Switzerland.
| | - Bernd Epe
- Institute of Pharmaceutical and Biomedical Sciences, University of Mainz, Staudinger Weg 5, 55128, Mainz, Germany.
| | - Tilman Grune
- Department of Molecular Toxicology, German Institute of Human Nutrition (DIfE), Arthur-Scheunert-Allee 114-116, 14558, Nuthetal, Germany.
| | - Dirk Haller
- ZIEL - Institute for Food & Health, Technical University of Munich, 85354, Freising, Germany; Technical University of Munich, Gregor-Mendel-Str. 2, 85354, Freising, Germany.
| | - Volker Heinz
- German Institute of Food Technologies (DIL), Prof.-von-Klitzing-Str. 7, 49610, Quakenbrück, Germany.
| | - Michael Hellwig
- Technische Universität Dresden, Bergstraße 66, 01062, Dresden, Germany.
| | - Jan G Hengstler
- Leibniz Research Centre for Working Environment and Human Factors (IfADo), Ardeystr. 67, 44139, Dortmund, Germany.
| | - Thomas Henle
- Department of Food Chemistry, TU Dresden, Bergstrasse 66, 01062, Dresden, Germany.
| | - Hans-Ulrich Humpf
- Institute of Food Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstraße 45, 48149, Münster, Germany.
| | - Henry Jäger
- Institute of Food Technology, University of Natural Resources and Life Sciences (BOKU), Muthgasse 18, 1190, Vienna, Austria.
| | - Hans-Georg Joost
- Department of Experimental Diabetology, German Institute of Human Nutrition (DIfE), Arthur-Scheunert-Allee 114-116, 14558, Nuthetal, Germany.
| | - Sabine E Kulling
- Department of Safety and Quality of Fruit and Vegetables, Max Rubner-Institut, Federal Research Institute of Nutrition and Food, Haid-und-Neu-Straße 9, 76131, Karlsruhe, Germany.
| | - Dirk W Lachenmeier
- Chemisches und Veterinäruntersuchungsamt Karlsruhe, Weißenburger Str. 3, 76187, Karlsruhe, Germany.
| | - Alfonso Lampen
- University of Veterinary Medicine Hannover, Institute for Food Quality and Food Safety, Bischofsholer Damm 15, 30173, Hannover, Germany.
| | - Marcel Leist
- In Vitro Toxicology and Biomedicine, Department Inaugurated By the Doerenkamp-Zbinden Foundation, University of Konstanz, Box 657, 78457, Konstanz, Germany.
| | - Angela Mally
- Department of Toxicology, University of Würzburg, Versbacher Str. 9, 97078, Würzburg, Germany.
| | - Doris Marko
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Währinger Straße 38, 1090, Vienna, Austria.
| | - Ute Nöthlings
- Department of Nutrition and Food Sciences, Nutritional Epidemiology, Rheinische Friedrich-Wilhelms University Bonn, Friedrich-Hirzebruch-Allee 7, 53115, Bonn, Germany.
| | - Elke Röhrdanz
- Unit Reproductive and Genetic Toxicology, Federal Institute for Drugs and Medical Devices (BfArM), Kurt-Georg-Kiesinger Allee 3, 53175, Bonn, Germany.
| | - Angelika Roth
- Leibniz Research Centre for Working Environment and Human Factors (IfADo), Ardeystr. 67, 44139, Dortmund, Germany.
| | - Joachim Spranger
- Department of Endocrinology and Metabolic Medicine, Campus Benjamin Franklin, Charité University Medicine, Hindenburgdamm 30, 12200, Berlin, Germany.
| | - Richard Stadler
- Institute of Food Safety and Analytical Sciences, Nestlé Research Centre, Route du Jorat 57, 1000, Lausanne, 26, Switzerland.
| | - Pablo Steinberg
- Max Rubner-Institut, Federal Research Institute of Nutrition and Food, Haid-und-Neu-Str. 9, 76131, Karlsruhe, Germany.
| | - Stefan Vieths
- Paul-Ehrlich-Institut, Paul-Ehrlich-Straße 51-59, 63225, Langen, Germany.
| | - Wim Wätjen
- Institut für Agrar- und Ernährungswissenschaften, Martin-Luther-Universität Halle-Wittenberg, Weinbergweg 22, 06120, Halle (Saale), Germany.
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6
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Zeng Z, Huo J, Zhu X, Liu Y, Li R, Chen Y, Zhang L, Chen J. Characterization of benzo[ a]pyrene and colchicine based on an in vivo repeat-dosing multi-endpoint genotoxicity quantitative assessment platform. Mutagenesis 2022; 37:213-225. [PMID: 35869703 DOI: 10.1093/mutage/geac012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 07/06/2022] [Indexed: 11/13/2022] Open
Abstract
Abstract
Two prototypical genotoxicants, benzo[a]pyrene (B[a]P) and colchicine (COL), were selected as model compounds to deduce their quantitative genotoxic dose–response relationship at low doses in a multi-endpoint genotoxicity assessment platform. Male Sprague-Dawley rats were treated with B[a]P (2.5–80 mg/kg bw/day) and COL (0.125–2 mg/kg bw/day) daily for 28 days. The parameters included were as follows: comet assay in the peripheral blood and liver, Pig-a gene mutation assay in the peripheral blood, and micronucleus test in the peripheral blood and bone marrow. A significant increase was observed in Pig-a mutant frequency in peripheral blood for B[a]P (started at 40 mg/kg bw/day on Day 14, started at 20 mg/kg bw/day on Day 28), whereas no statistical difference for COL was observed. Micronucleus frequency in reticulocytes of the peripheral blood and bone marrow increased significantly for B[a]P (80 mg/kg bw/day on Day 4, started at 20 mg/kg bw/day on Days 14 and 28 in the blood; started at 20 mg/kg bw/day on Day 28 in the bone marrow) and COL (started at 2 mg/kg bw/day on Day 14, 1 mg/kg bw/day on Day 28 in the blood; started at 1 mg/kg bw/day on Day 28 in the bone marrow). No statistical variation was found in indexes of comet assay at all time points for B[a]P and COL in the peripheral blood and liver. The dose–response relationships of Pig-a and micronucleus test data were analyzed for possible point of departures using three quantitative approaches, i.e., the benchmark dose, breakpoint dose, and no observed genotoxic effect level. The practical thresholds of the genotoxicity of B[a]P and COL estimated in this study were 0.122 and 0.0431 mg/kg bw/day, respectively, and our results also provided distinct genotoxic mode of action of the two chemicals.
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Affiliation(s)
- Zhu Zeng
- Department of Clinical Nutrition, Chengdu Fifth People’s Hospital , Chengdu, Sichuan , China
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University , Chengdu, Sichuan , China
| | - Jiao Huo
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University , Chengdu, Sichuan , China
- Department of Nutrition and Food Safety, Chongqing Center for Disease Control and Prevention , Chongqing , China
| | - Xuejiao Zhu
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University , Chengdu, Sichuan , China
- West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University , Chengdu, Sichuan , China
| | - Yunjie Liu
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University , Chengdu, Sichuan , China
- West China School of Public Health, Sichuan University , Chengdu, Sichuan , China
| | - Ruirui Li
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University , Chengdu, Sichuan , China
- Food Safety Monitoring and Risk Assessment Key Laboratory of Sichuan Province , Chengdu, Sichuan , China
| | - Yiyi Chen
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University , Chengdu, Sichuan , China
- Infections Disease Prevention and Immunization Program Office, ChengHua Center for Disease Control and Prevention , Chengdu, Sichuan , China
| | - Lishi Zhang
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University , Chengdu, Sichuan , China
- Food Safety Monitoring and Risk Assessment Key Laboratory of Sichuan Province , Chengdu, Sichuan , China
| | - Jinyao Chen
- Department of Nutrition, Food Safety and Toxicology, West China School of Public Health, Sichuan University , Chengdu, Sichuan , China
- Food Safety Monitoring and Risk Assessment Key Laboratory of Sichuan Province , Chengdu, Sichuan , China
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7
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Hill P, Zellmann F, Vukova T, Marini F, Kolmar S, Kaina B, Hofmann TG, Nikolova T. Dose response to methylating agents in the γH2AX, SCE and colony formation assays: Effect of MGMT and MPG overexpression. MUTATION RESEARCH. GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2022; 876-877:503462. [PMID: 35483785 DOI: 10.1016/j.mrgentox.2022.503462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 11/29/2021] [Accepted: 02/01/2022] [Indexed: 06/14/2023]
Abstract
Cells have developed diverse protective mechanisms that enable them to tolerate low doses of genotoxic compounds. DNA repair processes attenuate the mutagenic and carcinogenic effects of alkylating agents, and multiple studies indicate a key role of specific DNA repair factors and pathways in establishing non-linear dose response relationships. Using an overexpression approach, we investigated the impact of O6-methylguanine-DNA-methyltransferase (MGMT), which repairs O6-methylguanine (O6MeG) in a damage reversal reaction, and N-methylpurine-DNA glycosylase (MPG), which acts as an apical enzyme in the BER pathway, on the DNA damage response to the alkylating agents MNNG and MMS. Our data indicate a clear protective effect of MGMT against MNNG-induced nuclear γH2AX foci formation, sister chromatid exchanges (SCE) and cytotoxicity, as determined in the colony formation assay. MGMT protected with similar efficiency against MMS-induced cytotoxicity and γH2AX foci formation, but suppressed SCE induction only weakly, which indicates that recombination events induced by MMS result from other lesions than O6MeG. In contrast, overexpression of MPG had only a very mild protective effect on the cellular defense against MMS and MNNG. Collectively, our data indicate that overexpression of MGMT results in non-linear DNA damage responses to O6MeG inducers. In contrast, MPG overexpression has only minor impact on the DNA damage response to alkylating drugs, indicating that other downstream enzymes in the BER pathway are limiting.
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Affiliation(s)
- Philipp Hill
- Institute of Toxicology, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - Felix Zellmann
- Institute of Toxicology, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - Tsvetomira Vukova
- Institute of Toxicology, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - Federico Marini
- Institute of Medical Biostatistics, Epidemiology and Informatics (IMBEI), University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - Sarah Kolmar
- Institute of Toxicology, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - Bernd Kaina
- Institute of Toxicology, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - Thomas G Hofmann
- Institute of Toxicology, University Medical Center of the Johannes Gutenberg University, Mainz, Germany
| | - Teodora Nikolova
- Institute of Toxicology, University Medical Center of the Johannes Gutenberg University, Mainz, Germany.
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8
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Kumaravel TS, Sathya TN, Balaje R, Pradeepa P, Yogaraj D, Murali MR, Navaneethakrishnan KR, Murugan S, Jha AN. Genotoxicity evaluation of medical devices: A regulatory perspective. MUTATION RESEARCH. REVIEWS IN MUTATION RESEARCH 2022; 789:108407. [PMID: 35690410 DOI: 10.1016/j.mrrev.2021.108407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 11/22/2021] [Accepted: 11/29/2021] [Indexed: 06/15/2023]
Abstract
This review critically evaluates our current regulatory understanding of genotoxicity testing and risk assessment of medical devices. Genotoxicity risk assessment of these devices begins with the evaluation of materials of construction, manufacturing additives and all residual materials for potential to induce DNA damage. This is followed by extractable and/or leachable (E&L) studies to understand the worst case and/or clinical exposures, coupled with risk assessment of extractables or leachables. The TTC (Threshold of Toxicological Concern) approach is used to define acceptable levels of genotoxic chemicals, when identified. Where appropriate, in silico predictions may be used to evaluate the genotoxic potentials of identifiable chemicals with limited toxicological data and above the levels defined by TTC. Devices that could not be supported by E&L studies are evaluated by in vitro genotoxicity studies conducted in accordance with ISO10993-3 and 33. Certain endpoints such as 'site of contact genotoxicity' that are specific for certain classes of medical devices are currently not addressed in the current standards. The review also illustrates the potential uses of recent advances to achieve the goal of robust genotoxicity assessment of medical devices which are being increasingly used for health benefits. The review also highlights the gaps for genotoxicity risk assessment of medical devices and suggests possible approaches to address them taking into consideration the recent advances in genotoxicity testing including their potential uses in biocompatibility assessment.
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Affiliation(s)
- Tirukalikundram S Kumaravel
- GLR Laboratories (Europe) Pvt. Ltd., Sharnbrook, MK44 1LZ, United Kingdom; GLR Laboratories Pvt Ltd, Chennai, 600068, India.
| | | | | | | | | | | | | | - Sivasubramanian Murugan
- GLR Laboratories (Europe) Pvt. Ltd., Sharnbrook, MK44 1LZ, United Kingdom; GLR Laboratories Pvt Ltd, Chennai, 600068, India
| | - Awadhesh N Jha
- School of Biological and Marine Sciences, University of Plymouth, Plymouth, PL4 8AA, United Kingdom
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9
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Effects of Manganese on Genomic Integrity in the Multicellular Model Organism Caenorhabditis elegans. Int J Mol Sci 2021; 22:ijms222010905. [PMID: 34681565 PMCID: PMC8535284 DOI: 10.3390/ijms222010905] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2021] [Revised: 09/24/2021] [Accepted: 09/30/2021] [Indexed: 12/30/2022] Open
Abstract
Although manganese (Mn) is an essential trace element, overexposure is associated with Mn-induced toxicity and neurological dysfunction. Even though Mn-induced oxidative stress is discussed extensively, neither the underlying mechanisms of the potential consequences of Mn-induced oxidative stress on DNA damage and DNA repair, nor the possibly resulting toxicity are characterized yet. In this study, we use the model organism Caenorhabditis elegans to investigate the mode of action of Mn toxicity, focusing on genomic integrity by means of DNA damage and DNA damage response. Experiments were conducted to analyze Mn bioavailability, lethality, and induction of DNA damage. Different deletion mutant strains were then used to investigate the role of base excision repair (BER) and dePARylation (DNA damage response) proteins in Mn-induced toxicity. The results indicate a dose- and time-dependent uptake of Mn, resulting in increased lethality. Excessive exposure to Mn decreases genomic integrity and activates BER. Altogether, this study characterizes the consequences of Mn exposure on genomic integrity and therefore broadens the molecular understanding of pathways underlying Mn-induced toxicity. Additionally, studying the basal poly(ADP-ribosylation) (PARylation) of worms lacking poly(ADP-ribose) glycohydrolase (PARG) parg-1 or parg-2 (two orthologue of PARG), indicates that parg-1 accounts for most of the glycohydrolase activity in worms.
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Hirabayashi Y, Maki K, Kinoshita K, Nakazawa T, Obika S, Naota M, Watanabe K, Suzuki M, Arato T, Fujisaka A, Fueki O, Ito K, Onodera H. Considerations of the Japanese Research Working Group for the ICH S6 & Related Issues Regarding Nonclinical Safety Assessments of Oligonucleotide Therapeutics: Comparison with Those of Biopharmaceuticals. Nucleic Acid Ther 2021; 31:114-125. [PMID: 33470890 PMCID: PMC7997717 DOI: 10.1089/nat.2020.0879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
This white paper summarizes the current consensus of the Japanese Research Working Group for the ICH S6 & Related Issues (WGS6) on strategies for the nonclinical safety assessment of oligonucleotide-based therapeutics (ONTs), specifically focused on the similarities and differences to biotechnology-derived pharmaceuticals (biopharmaceuticals). ONTs, like biopharmaceuticals, have high species and target specificities. However, ONTs have characteristic off-target effects that clearly differ from those of biopharmaceuticals. The product characteristics of ONTs necessitate specific considerations when planning nonclinical studies. Some ONTs have been approved for human use and many are currently undergoing nonclinical and/or clinical development. However, as ONTs are a rapidly evolving class of drugs, there is still much to learn to achieve optimal strategies for the development of ONTs. There are no formal specific guidelines, so safety assessments of ONTs are principally conducted by referring to published white papers and conventional guidelines for biopharmaceuticals and new chemical entities, and each ONT is assessed on a case-by-case basis. The WGS6 expects that this report will be useful in considering nonclinical safety assessments and developing appropriate guidelines specific for ONTs.
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Affiliation(s)
| | - Kazushige Maki
- Pharmaceuticals and Medical Devices Agency (PMDA), Chiyoda-ku, Japan
| | - Kiyoshi Kinoshita
- The Japan Pharmaceutical Manufacturers Association (JPMA), Chuo-ku, Japan
| | | | - Satoshi Obika
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan
| | - Misaki Naota
- Pharmaceuticals and Medical Devices Agency (PMDA), Chiyoda-ku, Japan
| | - Kazuto Watanabe
- The Japan Pharmaceutical Manufacturers Association (JPMA), Chuo-ku, Japan
| | - Mutsumi Suzuki
- The Japan Pharmaceutical Manufacturers Association (JPMA), Chuo-ku, Japan
| | - Teruyo Arato
- Clinical Research and Medical Innovation Center, Hokkaido University Hospital, Sapporo, Japan
| | - Aki Fujisaka
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan.,Faculty of Pharmacy, Osaka Ohtani University, Tondabayashi, Japan
| | - Osamu Fueki
- Pharmaceuticals and Medical Devices Agency (PMDA), Chiyoda-ku, Japan
| | - Kosuke Ito
- Pharmaceuticals and Medical Devices Agency (PMDA), Chiyoda-ku, Japan
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11
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Chiara F, Indraccolo S, Trevisan A. Filling the gap between risk assessment and molecular determinants of tumor onset. Carcinogenesis 2020; 42:507-516. [PMID: 33319226 DOI: 10.1093/carcin/bgaa135] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 11/22/2020] [Accepted: 12/11/2020] [Indexed: 12/30/2022] Open
Abstract
In the past two decades, a ponderous epidemiological literature has causally linked tumor onset to environmental exposure to carcinogens. As consequence, risk assessment studies have been carried out with the aim to identify both predictive models of estimating cancer risks within exposed populations and establishing rules for minimizing hazard when handling carcinogenic compounds. The central assumption of these works is that neoplastic transformation is directly related to the mutational burden of the cell without providing further mechanistic clues to explain increased cancer onset after carcinogen exposure. Nevertheless, in the last few years, a growing number of studies have implemented the traditional models of cancer etiology, proposing that neoplastic transformation is a complex process in which several parameters and crosstalk between tumor and microenvironmental cells must be taken into account and integrated with mutagenesis. In this conceptual framework, the current strategies of risk assessment that are solely based on the 'mutator model' require an urgent update and revision to keep pace with advances in our understanding of cancer biology. We will approach this topic revising the most recent theories on the biological mechanisms involved in tumor formation in order to envision a roadmap leading to a future regulatory framework for a new, protective policy of risk assessment.
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Affiliation(s)
- Federica Chiara
- Department of Surgery, Oncology and Gastroenterology, University of Padova, Via Giustiniani, Padua, Italy
| | | | - Andrea Trevisan
- Department of Cardiac, Thoracic, Vascular Sciences and Public Health, University of Padova, Via Giustiniani, Padua, Italy
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12
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Modes of action considerations in threshold expectations for health effects of benzene. Toxicol Lett 2020; 334:78-86. [DOI: 10.1016/j.toxlet.2020.09.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 09/05/2020] [Accepted: 09/10/2020] [Indexed: 01/21/2023]
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13
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Wei J, Hao Q, Chen C, Li J, Han X, Lei Z, Wang T, Wang Y, You X, Chen X, Li H, Ding Y, Huang W, Hu Y, Lin S, Shen H, Lin Y. Epigenetic repression of miR-17 contributed to di(2-ethylhexyl) phthalate-triggered insulin resistance by targeting Keap1-Nrf2/miR-200a axis in skeletal muscle. Am J Cancer Res 2020; 10:9230-9248. [PMID: 32802189 PMCID: PMC7415800 DOI: 10.7150/thno.45253] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Accepted: 07/13/2020] [Indexed: 12/15/2022] Open
Abstract
Rationale: Skeletal muscle insulin resistance is detectable before type 2 diabetes is diagnosed. Exposure to di(2-ethylhexyl) phthalate (DEHP), a typical environmental endocrine-disrupting chemical, is a novel risk factor for insulin resistance and type 2 diabetes. This study aimed to explore insulin signaling regulatory pathway in skeletal muscle of the DEHP-induced insulin-resistant mice and to investigate potential therapeutic strategies for treating insulin resistance. Methods: C57BL/6J male mice were exposed to 2 mg/kg/day DEHP for 15 weeks. Whole-body glucose homeostasis, oxidative stress and deregulated miRNA-mediated molecular transduction in skeletal muscle were examined. microRNA (miRNA) interventions based on lentiviruses and adeno-associated viruses 9 (AAV9) were performed. Results: Dnmt3a-dependent promoter methylation and lncRNA Malat1-related sponge functions cooperatively downregulated miR-17 in DEHP-exposed skeletal muscle cells. DEHP suppressed miR-17 to disrupt the Keap1-Nrf2 redox system and to activate oxidative stress-responsive Txnip in skeletal muscle. Oxidative stress upregulated miR-200a, which directly targets the 3'UTR of Insr and Irs1, leading to hindered insulin signaling and impaired insulin-dependent glucose uptake in skeletal muscle, ultimately promoting the development of insulin resistance. AAV9-induced overexpression of miR-17 and lentivirus-mediated silencing of miR-200a in skeletal muscle ameliorated whole-body insulin resistance in DEHP-exposed mice. Conclusions: The miR-17/Keap1-Nrf2/miR-200a axis contributed to DEHP-induced insulin resistance. miR-17 is a positive regulator, whereas miR-200a is a negative regulator of insulin signaling in skeletal muscle, and both miRNAs have the potential to become therapeutic targets for preventing and treating insulin resistance or type 2 diabetes.
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Helm JS, Rudel RA. Adverse outcome pathways for ionizing radiation and breast cancer involve direct and indirect DNA damage, oxidative stress, inflammation, genomic instability, and interaction with hormonal regulation of the breast. Arch Toxicol 2020. [PMID: 32399610 DOI: 10.1007/s00204-020-02752-z)] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
Abstract
Knowledge about established breast carcinogens can support improved and modernized toxicological testing methods by identifying key mechanistic events. Ionizing radiation (IR) increases the risk of breast cancer, especially for women and for exposure at younger ages, and evidence overall supports a linear dose-response relationship. We used the Adverse Outcome Pathway (AOP) framework to outline and evaluate the evidence linking ionizing radiation with breast cancer from molecular initiating events to the adverse outcome through intermediate key events, creating a qualitative AOP. We identified key events based on review articles, searched PubMed for recent literature on key events and IR, and identified additional papers using references. We manually curated publications and evaluated data quality. Ionizing radiation directly and indirectly causes DNA damage and increases production of reactive oxygen and nitrogen species (RONS). RONS lead to DNA damage and epigenetic changes leading to mutations and genomic instability (GI). Proliferation amplifies the effects of DNA damage and mutations leading to the AO of breast cancer. Separately, RONS and DNA damage also increase inflammation. Inflammation contributes to direct and indirect effects (effects in cells not directly reached by IR) via positive feedback to RONS and DNA damage, and separately increases proliferation and breast cancer through pro-carcinogenic effects on cells and tissue. For example, gene expression changes alter inflammatory mediators, resulting in improved survival and growth of cancer cells and a more hospitable tissue environment. All of these events overlap at multiple points with events characteristic of "background" induction of breast carcinogenesis, including hormone-responsive proliferation, oxidative activity, and DNA damage. These overlaps make the breast particularly susceptible to ionizing radiation and reinforce that these biological activities are important characteristics of carcinogens. Agents that increase these biological processes should be considered potential breast carcinogens, and predictive methods are needed to identify chemicals that increase these processes. Techniques are available to measure RONS, DNA damage and mutation, cell proliferation, and some inflammatory proteins or processes. Improved assays are needed to measure GI and chronic inflammation, as well as the interaction with hormonally driven development and proliferation. Several methods measure diverse epigenetic changes, but it is not clear which changes are relevant to breast cancer. In addition, most toxicological assays are not conducted in mammary tissue, and so it is a priority to evaluate if results from other tissues are generalizable to breast, or to conduct assays in breast tissue. Developing and applying these assays to identify exposures of concern will facilitate efforts to reduce subsequent breast cancer risk.
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Affiliation(s)
- Jessica S Helm
- Silent Spring Institute, 320 Nevada Street, Suite 302, Newton, MA, 02460, USA
| | - Ruthann A Rudel
- Silent Spring Institute, 320 Nevada Street, Suite 302, Newton, MA, 02460, USA.
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15
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Helm JS, Rudel RA. Adverse outcome pathways for ionizing radiation and breast cancer involve direct and indirect DNA damage, oxidative stress, inflammation, genomic instability, and interaction with hormonal regulation of the breast. Arch Toxicol 2020; 94:1511-1549. [PMID: 32399610 PMCID: PMC7261741 DOI: 10.1007/s00204-020-02752-z] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 04/16/2020] [Indexed: 12/15/2022]
Abstract
Knowledge about established breast carcinogens can support improved and modernized toxicological testing methods by identifying key mechanistic events. Ionizing radiation (IR) increases the risk of breast cancer, especially for women and for exposure at younger ages, and evidence overall supports a linear dose-response relationship. We used the Adverse Outcome Pathway (AOP) framework to outline and evaluate the evidence linking ionizing radiation with breast cancer from molecular initiating events to the adverse outcome through intermediate key events, creating a qualitative AOP. We identified key events based on review articles, searched PubMed for recent literature on key events and IR, and identified additional papers using references. We manually curated publications and evaluated data quality. Ionizing radiation directly and indirectly causes DNA damage and increases production of reactive oxygen and nitrogen species (RONS). RONS lead to DNA damage and epigenetic changes leading to mutations and genomic instability (GI). Proliferation amplifies the effects of DNA damage and mutations leading to the AO of breast cancer. Separately, RONS and DNA damage also increase inflammation. Inflammation contributes to direct and indirect effects (effects in cells not directly reached by IR) via positive feedback to RONS and DNA damage, and separately increases proliferation and breast cancer through pro-carcinogenic effects on cells and tissue. For example, gene expression changes alter inflammatory mediators, resulting in improved survival and growth of cancer cells and a more hospitable tissue environment. All of these events overlap at multiple points with events characteristic of "background" induction of breast carcinogenesis, including hormone-responsive proliferation, oxidative activity, and DNA damage. These overlaps make the breast particularly susceptible to ionizing radiation and reinforce that these biological activities are important characteristics of carcinogens. Agents that increase these biological processes should be considered potential breast carcinogens, and predictive methods are needed to identify chemicals that increase these processes. Techniques are available to measure RONS, DNA damage and mutation, cell proliferation, and some inflammatory proteins or processes. Improved assays are needed to measure GI and chronic inflammation, as well as the interaction with hormonally driven development and proliferation. Several methods measure diverse epigenetic changes, but it is not clear which changes are relevant to breast cancer. In addition, most toxicological assays are not conducted in mammary tissue, and so it is a priority to evaluate if results from other tissues are generalizable to breast, or to conduct assays in breast tissue. Developing and applying these assays to identify exposures of concern will facilitate efforts to reduce subsequent breast cancer risk.
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Affiliation(s)
- Jessica S Helm
- Silent Spring Institute, 320 Nevada Street, Suite 302, Newton, MA, 02460, USA
| | - Ruthann A Rudel
- Silent Spring Institute, 320 Nevada Street, Suite 302, Newton, MA, 02460, USA.
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16
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Martus HJ, Froetschl R, Gollapudi B, Honma M, Marchetti F, Pfuhler S, Schoeny R, Uno Y, Yauk C, Kirkland DJ. Summary of major conclusions from the 7th International Workshop on Genotoxicity Testing (IWGT), Tokyo, Japan. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2020; 852:503134. [PMID: 32265038 DOI: 10.1016/j.mrgentox.2020.503134] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Hans-Joerg Martus
- Novartis Institutes for BioMedical Research, Preclinical Safety, 4002 Basel, Switzerland.
| | - Roland Froetschl
- BfArM Federal Institute for Drugs and Medical Devices, Bonn, Germany
| | - Bhaskar Gollapudi
- Exponent, Inc., Center for Health Sciences, 1800 Diagonal Road, Alexandria, VA, 22314, USA
| | - Masamitsu Honma
- National Institute of Health Sciences, Division of Genetics & Mutagenesis, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo, 158-8501, Japan
| | - Francesco Marchetti
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, K1A 0K9, Canada
| | - Stefan Pfuhler
- Global Product Stewardship- Human Safety, Procter & Gamble, Mason, OH, USA
| | - Rita Schoeny
- Rita Schoeny LLC, Washington DC, 20002, United States
| | | | - Carole Yauk
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, K1A 0K9, Canada
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17
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White PA, Long AS, Johnson GE. Quantitative Interpretation of Genetic Toxicity Dose-Response Data for Risk Assessment and Regulatory Decision-Making: Current Status and Emerging Priorities. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2020; 61:66-83. [PMID: 31794061 DOI: 10.1002/em.22351] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 11/27/2019] [Accepted: 11/30/2019] [Indexed: 06/10/2023]
Abstract
The screen-and-bin approach for interpretation of genotoxicity data is predicated on three false assumptions: that genotoxicants are rare, that genotoxicity dose-response functions do not contain a low-dose region mechanistically characterized by zero-order kinetics, and that genotoxicity is not a bona fide toxicological endpoint. Consequently, there is a need to develop and implement quantitative methods to interpret genotoxicity dose-response data for risk assessment and regulatory decision-making. Standardized methods to analyze dose-response data, and determine point-of-departure (PoD) metrics, have been established; the most robust PoD is the benchmark dose (BMD). However, there are no standards for regulatory interpretation of mutagenicity BMDs. Although 5-10% is often used as a critical effect size (CES) for BMD determination, values for genotoxicity endpoints have not been established. The use of BMDs to determine health-based guidance values (HBGVs) requires assessment factors (AFs) to account for interspecies differences and variability in human sensitivity. Default AFs used for other endpoints may not be appropriate for interpretation of in vivo mutagenicity BMDs. Analyses of published dose-response data showing the effects of compensatory pathway deficiency indicate that AFs for sensitivity differences should be in the range of 2-20. Additional analyses indicate that the AF to compensate for short treatment durations should be in the range of 5-15. Future work should use available data to empirically determine endpoint-specific CES values; similarly, to determine AF values for BMD adjustment. Future work should also evaluate the ability to use in vitro dose-response data for risk assessment, and the utility of probabilistic methods for determination of mutagenicity HBGVs. Environ. Mol. Mutagen. 61:66-83, 2020. © 2019 Her Majesty the Queen in Right of Canada.
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Affiliation(s)
- Paul A White
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, Canada
| | - Alexandra S Long
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario, Canada
| | - George E Johnson
- Swansea University Medical School, Swansea, Wales, United Kingdom
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18
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Klapacz J, Gollapudi BB. Considerations for the Use of Mutation as a Regulatory Endpoint in Risk Assessment. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2020; 61:84-93. [PMID: 31301246 DOI: 10.1002/em.22318] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 07/08/2019] [Accepted: 07/10/2019] [Indexed: 06/10/2023]
Abstract
Assessment of a chemical's potential to cause permanent changes in the genetic code has been a common practice in the industry and regulatory settings for decades. Furthermore, the genetic toxicity battery of tests has typically been employed during the earliest stages of the research and development programs of new product development. A positive outcome from such battery has a major impact on the chemical's utility, industrial hygiene, product stewardship practices, and product life cycle analysis, among many other decisions that need to be taken by the industry, even before the registration of a chemical is undertaken. Under the prevailing regulatory paradigm, the dichotomous (yes/no) evaluation of the chemical's genotoxic potential leads to a conservative, linear no-threshold (LNT) risk assessment, unless compelling and undeniable data to the contrary can be provided to satisfy regulators, typically in a number of different global jurisdictions. With the current advent of predictive methods, new testing paradigms, mode-of-action/adverse outcome pathways, and quantitative risk assessment approaches, various stakeholders are starting to employ these state-of-the-science methodologies to further the conversation on decision making and advance the regulatory paradigm beyond the dominant LNT status quo. This commentary describes these novel methodologies, relevant biological responses, and how these can affect internal and regulatory risk assessment approaches. Environ. Mol. Mutagen. 61:84-93, 2020. © 2019 Wiley Periodicals, Inc.
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Affiliation(s)
- Joanna Klapacz
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland, Michigan
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Sasaki JC, Allemang A, Bryce SM, Custer L, Dearfield KL, Dietz Y, Elhajouji A, Escobar PA, Fornace AJ, Froetschl R, Galloway S, Hemmann U, Hendriks G, Li HH, Luijten M, Ouedraogo G, Peel L, Pfuhler S, Roberts DJ, Thybaud V, van Benthem J, Yauk CL, Schuler M. Application of the adverse outcome pathway framework to genotoxic modes of action. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2020; 61:114-134. [PMID: 31603995 DOI: 10.1002/em.22339] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 09/17/2019] [Accepted: 09/23/2019] [Indexed: 05/22/2023]
Abstract
In May 2017, the Health and Environmental Sciences Institute's Genetic Toxicology Technical Committee hosted a workshop to discuss whether mode of action (MOA) investigation is enhanced through the application of the adverse outcome pathway (AOP) framework. As AOPs are a relatively new approach in genetic toxicology, this report describes how AOPs could be harnessed to advance MOA analysis of genotoxicity pathways using five example case studies. Each of these genetic toxicology AOPs proposed for further development includes the relevant molecular initiating events, key events, and adverse outcomes (AOs), identification and/or further development of the appropriate assays to link an agent to these events, and discussion regarding the biological plausibility of the proposed AOP. A key difference between these proposed genetic toxicology AOPs versus traditional AOPs is that the AO is a genetic toxicology endpoint of potential significance in risk characterization, in contrast to an adverse state of an organism or a population. The first two detailed case studies describe provisional AOPs for aurora kinase inhibition and tubulin binding, leading to the common AO of aneuploidy. The remaining three case studies highlight provisional AOPs that lead to chromosome breakage or mutation via indirect DNA interaction (inhibition of topoisomerase II, production of cellular reactive oxygen species, and inhibition of DNA synthesis). These case studies serve as starting points for genotoxicity AOPs that could ultimately be published and utilized by the broader toxicology community and illustrate the practical considerations and evidence required to formalize such AOPs so that they may be applied to genetic toxicity evaluation schemes. Environ. Mol. Mutagen. 61:114-134, 2020. © 2019 Wiley Periodicals, Inc.
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Affiliation(s)
| | | | | | - Laura Custer
- Bristol-Myers Squibb Company, Drug Safety Evaluation, New Brunswick, New Jersey
| | | | - Yasmin Dietz
- Sanofi-Aventis Deutschland GmbH, Frankfurt, Germany
| | | | | | | | | | | | | | | | - Heng-Hong Li
- Georgetown University, Washington, District of Columbia
| | - Mirjam Luijten
- National Institute for Public Health and the Environment, Bilthoven, The Netherlands
| | | | - Lauren Peel
- Health and Environmental Sciences Institute, Washington, District of Columbia
| | | | | | - Véronique Thybaud
- Sanofi, Research and Development, Preclinical Safety, Vitry-sur-Seine, France
| | - Jan van Benthem
- National Institute for Public Health and the Environment, Bilthoven, The Netherlands
| | - Carole L Yauk
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, Canada
| | - Maik Schuler
- Pfizer Inc, World Wide Research and Development, Groton, Connecticut
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Zeller A, Brigo A, Brink A, Guerard M, Lang D, Muster W, Runge F, Sutter A, Vock E, Wichard J, Schadt S. Genotoxicity Assessment of Drug Metabolites in the Context of MIST and Beyond. Chem Res Toxicol 2019; 33:10-19. [DOI: 10.1021/acs.chemrestox.9b00348] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Andreas Zeller
- Roche Pharmaceutical Research & Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd., Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Alessandro Brigo
- Roche Pharmaceutical Research & Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd., Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Andreas Brink
- Roche Pharmaceutical Research & Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd., Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Melanie Guerard
- Roche Pharmaceutical Research & Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd., Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Dieter Lang
- Bayer AG, Pharmaceuticals, Research Center Aprath, 42096 Wuppertal, Germany
| | - Wolfgang Muster
- Roche Pharmaceutical Research & Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd., Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Frank Runge
- Boehringer Ingelheim Pharma GmbH & Co. KG, Birkendorfer Strasse 65, 88400 Biberach, Germany
| | - Andreas Sutter
- Bayer AG, Pharmaceuticals, Research Center Aprath, 42096 Wuppertal, Germany
| | - Esther Vock
- Boehringer Ingelheim Pharma GmbH & Co. KG, Birkendorfer Strasse 65, 88400 Biberach, Germany
| | - Jörg Wichard
- Bayer AG, Pharmaceuticals, Research Center Aprath, 42096 Wuppertal, Germany
| | - Simone Schadt
- Roche Pharmaceutical Research & Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd., Grenzacherstrasse 124, 4070 Basel, Switzerland
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Evaluation of mutagenic activity of platinum complexes in somatic cells of Drosophila melanogaster. Food Chem Toxicol 2019; 133:110782. [PMID: 31465821 DOI: 10.1016/j.fct.2019.110782] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 08/19/2019] [Accepted: 08/21/2019] [Indexed: 01/03/2023]
Abstract
Cisplatin, carboplatin, and oxaliplatin are some of the most often used alkylating chemotherapeutic agents. In view of the paucity of data on the genotoxicity of oxaliplatin, this study compares the mutagenic activity of cisplatin (0.006, 0.012, 0.025, 0.05 mM), carboplatin (0.1, 0.2, 0,5, 1.0 mM), and oxaliplatin (0.1, 0.2, 0,5, 1.0 mM) using the somatic mutation and recombination test (SMART) in Drosophila melanogaster. Standard and high-bioactivation crosses of the drosophilid were used, which present basal and high levels of cytochrome P450 (CYP450) metabolization enzymes, respectively. All concentrations of cisplatin and carboplatin induced lesions in genetic material in both crosses, while oxaliplatin was mutagenic only to high bioactivation flies treated with 0.1, 0.5 and 1 mM of the compound. No significant differences were observed between genotoxicity values of cisplatin and carboplatin. However, CYP450 enzymes may have affected the mutagenic action of oxaliplatin. Carboplatin induced mainly mutation events, while cisplatin triggered mostly mutation and recombination events when low and high doses were used. Most events induced by oxaliplatin were generated by somatic recombination. Important differences were observed in genotoxic potential of platinum chemotherapeutic compounds, possibly due to the origin and type of the lesions induced in DNA and the repair mechanisms involved.
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Itoh K, Masumori S, Mukai D, Sakakibara H, Yasuda M, Shimoi K. Dosage time affects alkylating agents induced micronuclei in mouse peripheral blood reticulocytes through the function of erythropoietin. J Toxicol Sci 2019; 44:273-282. [PMID: 30944280 DOI: 10.2131/jts.44.273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Previously, we reported that the frequency of micronucleated reticulocytes (MNRETs) in the peripheral blood of male C3H/He mice intraperitoneally administered ethylnitrosourea (ENU) (25 mg/kg body weight) in the dark period (zeitgeber time, ZT15) was higher than in the light period (ZT3). In this study, to clarify the mechanism underlying this phenomenon, we investigated the differences in micronucleus (MN) induction observed between ZT3 and ZT15 using five chemicals, methylnitrosourea (MNU), ethylmethane sulfonate (EMS), mitomycin C, cyclophosphamide and vincristin. MNU and EMS, monofunctional alkylating agents, showed higher frequencies of MNRETs in the ZT15 than the ZT3 treatment similar to ENU. However, no differences were observed for the other chemicals. In the comet assay, more DNA damage was induced by ENU in the ZT15 than the ZT3 treatment. Furthermore, the plasma erythropoietin (EPO) level, a known effector of MN induction with anti-apoptotic activity mediated by Bcl-xL expression, was higher in the dark than in the light period. EPO did not increase the frequency of MNRETs. However, in the ENU treatment group at ZT3 following EPO injection a significant increase of MNRETs was observed similar to the ZT15 treatment. Higher expression of apoptosis-related genes such as Bcl-xL was induced in bone marrow cells from mice treated with ENU at ZT15 compared with ZT3. From these results, it was speculated that the differences in MN induction in the peripheral blood of mice exposed to monofunctional alkylating agents such as ENU depend on apoptotic or anti-apoptotic conditions related to the circadian rhythms of EPO in bone marrow.
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Affiliation(s)
- Keiichi Itoh
- Graduate School of Integrated Pharmaceutical and Nutritional Science, University of Shizuoka.,Biosafety Research Center Inc. (BSRC)
| | | | | | | | - Michiko Yasuda
- Department of Human Nutrition, Sugiyama Jogakuen University
| | - Kayoko Shimoi
- Graduate School of Integrated Pharmaceutical and Nutritional Science, University of Shizuoka
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Spassova MA. Statistical Approach to Identify Threshold and Point of Departure in Dose-Response Data. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2019; 39:940-956. [PMID: 30253453 DOI: 10.1111/risa.13191] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 08/09/2018] [Accepted: 08/18/2018] [Indexed: 06/08/2023]
Abstract
The study presents an integrated, rigorous statistical approach to define the likelihood of a threshold and point of departure (POD) based on dose-response data using nested family of bent-hyperbola models. The family includes four models: the full bent-hyperbola model, which allows for transition between two linear regiments with various levels of smoothness; a bent-hyperbola model reduced to a spline model, where the transition is fixed to a knot; a bent-hyperbola model with a restricted negative asymptote slope of zero, named hockey-stick with arc (HS-Arc); and spline model reduced further to a hockey-stick type model (HS), where the first linear segment has a slope of zero. A likelihood-ratio test is used to discriminate between the models and determine if the more flexible versions of the model provide better or significantly better fit than a hockey-stick type model. The full bent-hyperbola model can accommodate both threshold and nonthreshold behavior, can take on concave up and concave down shapes with various levels of curvature, can approximate the biochemically relevant Michaelis-Menten model, and even be reduced to a straight line. Therefore, with the use of this model, the presence or absence of a threshold may even become irrelevant and the best fit of the full bent-hyperbola model be used to characterize the dose-response behavior and risk levels, with no need for mode of action (MOA) information. Point of departure (POD), characterized by exposure level at which some predetermined response is reached, can be defined using the full model or one of the better fitting reduced models.
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Wilde S, Queisser N, Holz C, Raschke M, Sutter A. Differentiation of Aneugens and Clastogens in the In Vitro Micronucleus Test by Kinetochore Scoring Using Automated Image Analysis. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2019; 60:227-242. [PMID: 30561837 DOI: 10.1002/em.22259] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2018] [Revised: 09/30/2018] [Accepted: 10/06/2018] [Indexed: 06/09/2023]
Abstract
The in vitro micronucleus test according to OECD Test Guideline 487 (TG 487) is widely used to investigate the genotoxic potential of drugs. Besides the identification of in vitro genotoxicants, the assay can be complemented with kinetochore staining for the differentiation between clastogens and aneugens. This differentiation constitutes a major contribution to risk assessment as especially aneugens show a threshold response. Thus, a novel method for automated MN plus kinetochore (k+) scoring by image analysis was developed based on the OECD TG 487. Compound-induced increases in MN frequency can be detected using the cytokinesis-block (cytochalasin B) method in V79 cells after 24 h in a 96-well format. Nuclei, MN, and kinetochores were labeled with nuclear counterstain and anti-kinetochore antibodies, respectively, to score MN in binuclear or multinuclear cells and to differentiate compound-induced MN by the presence of kinetochores. First, a reference data set was created by manual scoring using two clastogens and aneugens. After developing the automated scoring process, a set of 14 reference genotoxicants were studied. The automated image analysis yielded the expected results: 5/5 clastogens and 6/6 aneugens (sensitivity: 100%) as well as 3/3 non-genotoxicants (specificity: 100%) were correctly identified. Further, a threshold was determined for identifying aneugens. Based on the data for our internally characterized reference compounds, unknown compounds that induce ≥53.8% k+ MN are classified as aneugens. The current data demonstrate excellent specificity and sensitivity and the methodology is superior to manual microscopic analysis in terms of speed and throughput as well as the absence of human bias. Environ. Mol. Mutagen. 60:227-242, 2019. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Sabrina Wilde
- Bayer AG, Investigational Toxicology, Berlin, Germany
- Fraunhofer ITEM, Preclinical Pharmacology and In Vitro Toxicology, Hannover, Germany
| | - Nina Queisser
- Bayer AG, Investigational Toxicology, Berlin, Germany
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Wilde S, Dambowsky M, Hempt C, Sutter A, Queisser N. Classification of in vitro genotoxicants using a novel multiplexed biomarker assay compared to the flow cytometric micronucleus test. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2017; 58:662-677. [PMID: 28940655 DOI: 10.1002/em.22130] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 07/26/2017] [Accepted: 07/28/2017] [Indexed: 06/07/2023]
Abstract
Regulatory in vitro genotoxicity testing exhibits shortcomings in specificity and mode of action (MoA) information. Thus, the aim of this work was to evaluate the performance of the novel MultiFlow® assay composed of mechanistic biomarkers quantified in TK6 cells after treatment (4 and 24 hr): γH2AX (DNA double strand breaks), phosphorylated H3 (mitotic cells), translocated p53 (genotoxicity), and cleaved PARP1 (apoptosis). A reference dataset of 31 compounds with well-established MoA was studied using the MicroFlow® micronucleus assay. A positive call was raised following the earlier published criteria from Litron Laboratories. In the light of our data, these evaluation criteria should probably be adjusted since only 8/11 (73%) nongenotoxicants and 18/20 (90%) genotoxicants were correctly identified. Moreover, there is a need for new in vitro tools to delineate the predominant MoA as in the MicroFlow® assay only 5/9 (56%) aneugens and 4/11 (36%) clastogens were correctly classified. In contrast, the MultiFlow® assay provides more in-depth information about the MoA and therefore reliably discriminates clastogens, aneugens, and nongenotoxicants. By using a lab-specific, practical threshold for the aforementioned biomarkers, 10/11 (91%) nongenotoxicants and 19/20 genotoxicants (95%), 9/11 (82%) clastogens, and 8/9 (89%) aneugens were correctly categorized, suggesting a clear improvement over the MicroFlow® . Furthermore, the MultiFlow markers were benchmarked against established methods to assess the validity of the data. Altogether, these findings demonstrated good agreement between the MultiFlow® assay and the benchmarking methods. Finally, p21 may improve class discrimination given the correct identification of 4/4 (100%) aneugens and 2/5 (40%) clastogens. Environ. Mol. Mutagen. 58:662-677, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Sabrina Wilde
- Investigational Toxicology, Bayer AG, Berlin, Germany
| | | | - Claudia Hempt
- Investigational Toxicology, Bayer AG, Berlin, Germany
| | | | - Nina Queisser
- Investigational Toxicology, Bayer AG, Berlin, Germany
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Guérard M, Andreas Z, Erich K, Christine M, Martina MB, Christian W, Franz S, Thomas S, Yann T. Locked nucleic acid (LNA): Based single-stranded oligonucleotides are not genotoxic. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2017; 58:112-121. [PMID: 28295562 DOI: 10.1002/em.22076] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Revised: 01/30/2017] [Accepted: 01/31/2017] [Indexed: 06/06/2023]
Abstract
Over the last decade, single stranded oligonucleotides (ON) have gained increased attention as a new drug modality. Because the assessment of genotoxicity risk during early development of pharmaceuticals is essential, we evaluated the potential of locked nucleic acids (LNA)-ONs to induce DNA damage in L5178Y tk+/- cells both with the mouse lymphoma assay (MLA) and the micronucleus test (MNT). Further, the MLA was performed to assess gene and chromosome mutation over 3 and 24h (± metabolic activation). In addition, the MNT was performed to assess, in addition, a potential aneugenic liability. None of the experiments demonstrated a genotoxic effect for the five tested LNA-ONs. We further show data from four proprietary LNA-ONs tested in standard genotoxicity assays in vitro and partially in vivo, which were all negative. In addition, cellular and nuclear uptake of LNA-ONs in L5178Y tk+/- cells was demonstrated. Based on the results presented here as well as in the literature about other representatives of this class, we consider LNA-ONs as generally not DNA reactive and question whether genotoxicity testing of this class of ONs should be required. This is in line with recent recommendation made by the OSWG that extensively assessed the genotoxicity of oligonucleotides. Environ. Mol. Mutagen. 58:112-121, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Melanie Guérard
- Pharmaceutical Sciences, Roche Innovation Center Basel, Pharmaceutical Research and Early Development, F. Hoffmann-La Roche, Ltd, Basel, 4070, Switzerland
| | - Zeller Andreas
- Pharmaceutical Sciences, Roche Innovation Center Basel, Pharmaceutical Research and Early Development, F. Hoffmann-La Roche, Ltd, Basel, 4070, Switzerland
| | - Koller Erich
- Pharmaceutical Sciences, Roche Innovation Center Basel, Pharmaceutical Research and Early Development, F. Hoffmann-La Roche, Ltd, Basel, 4070, Switzerland
| | - Marchand Christine
- Pharmaceutical Sciences, Roche Innovation Center Basel, Pharmaceutical Research and Early Development, F. Hoffmann-La Roche, Ltd, Basel, 4070, Switzerland
| | - Müller B Martina
- Pharmaceutical Sciences, Roche Innovation Center Basel, Pharmaceutical Research and Early Development, F. Hoffmann-La Roche, Ltd, Basel, 4070, Switzerland
| | - Weile Christian
- Roche Innovation Center Copenhagen A/S, Pharmaceutical Research and Early Development, F. Hoffmann-La Roche, Ltd, Hørsholm, 2970, Denmark
| | - Schuler Franz
- Pharmaceutical Sciences, Roche Innovation Center Basel, Pharmaceutical Research and Early Development, F. Hoffmann-La Roche, Ltd, Basel, 4070, Switzerland
| | - Singer Thomas
- Pharmaceutical Sciences, Roche Innovation Center Basel, Pharmaceutical Research and Early Development, F. Hoffmann-La Roche, Ltd, Basel, 4070, Switzerland
| | - Tessier Yann
- Roche Innovation Center Copenhagen A/S, Pharmaceutical Research and Early Development, F. Hoffmann-La Roche, Ltd, Hørsholm, 2970, Denmark
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Klaus V, Bastek H, Damme K, Collins LB, Frötschl R, Benda N, Lutter D, Ellinger-Ziegelbauer H, Swenberg JA, Dietrich DR, Stemmer K. Time-matched analysis of DNA adduct formation and early gene expression as predictive tool for renal carcinogenesis in methylazoxymethanol acetate treated Eker rats. Arch Toxicol 2017; 91:3427-3438. [PMID: 28349193 DOI: 10.1007/s00204-017-1953-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Accepted: 03/01/2017] [Indexed: 11/28/2022]
Abstract
Genotoxic carcinogens pose great hazard to human health. Uncertainty of current risk assessment strategies and long latency periods between first carcinogen exposure and diagnosis of tumors have raised interest in predictive biomarkers. Initial DNA adduct formation is a necessary step for genotoxin induced carcinogenesis. However, as DNA adducts not always translate into tumorigenesis, their predictive value is limited. Here we hypothesize that the combined analysis of pro-mutagenic DNA adducts along with time-matched gene expression changes could serve as a superior prediction tool for genotoxic carcinogenesis. Eker rats, heterozygous for the tuberous sclerosis (Tsc2) tumor suppressor gene and thus highly susceptible towards genotoxic renal carcinogens, were continuously treated with the DNA alkylating carcinogen methylazoxymethanol acetate (MAMAc). Two weeks of MAMAc treatment resulted in a time-dependent increase of O6-methylguanine and N7-methylguanine adducts in the kidney cortex, which was however not reflected by significant expression changes of cyto-protective genes involved in DNA repair, cell cycle arrest or apoptosis. Instead, we found a transcriptional regulation of genes involved in the tumor-related MAPK, FoxO and TGF-beta pathways. Continuous MAMAc treatment for up to 6 months resulted in a mild but significant increase of cancerous lesions. In summary, the combined analysis of DNA adducts and early gene expression changes could serve as a suitable predictive tool for genotoxicant-induced carcinogenesis.
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Affiliation(s)
- Valentina Klaus
- Computational Discovery Research, Institute for Diabetes and Obesity, Helmholtz Diabetes Center & German Center for Diabetes Research (DZD), Helmholtz Zentrum München, Neuherberg, Germany
| | - Heinke Bastek
- Human and Environmental Toxicology, University of Konstanz, Konstanz, Germany
| | - Katja Damme
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Leonard B Collins
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Roland Frötschl
- Federal Institute for Drugs and Medical Devices, Bonn, Germany
| | - Norbert Benda
- Federal Institute for Drugs and Medical Devices, Bonn, Germany
| | - Dominik Lutter
- Computational Discovery Research, Institute for Diabetes and Obesity, Helmholtz Diabetes Center & German Center for Diabetes Research (DZD), Helmholtz Zentrum München, Neuherberg, Germany
| | | | - James A Swenberg
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Daniel R Dietrich
- Human and Environmental Toxicology, University of Konstanz, Konstanz, Germany
| | - Kerstin Stemmer
- Metabolism and Cancer, Institute for Diabetes and Obesity, Helmholtz Diabetes Center & German Center for Diabetes Research (DZD), Helmholtz Zentrum München, Neuherberg, Germany.
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Dose–response relationship of temozolomide, determined by the Pig-a, comet, and micronucleus assay. Arch Toxicol 2017; 91:2443-2453. [DOI: 10.1007/s00204-016-1923-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Accepted: 12/20/2016] [Indexed: 11/25/2022]
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Kuempel ED, Jaurand MC, Møller P, Morimoto Y, Kobayashi N, Pinkerton KE, Sargent LM, Vermeulen RCH, Fubini B, Kane AB. Evaluating the mechanistic evidence and key data gaps in assessing the potential carcinogenicity of carbon nanotubes and nanofibers in humans. Crit Rev Toxicol 2017; 47:1-58. [PMID: 27537422 PMCID: PMC5555643 DOI: 10.1080/10408444.2016.1206061] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2015] [Accepted: 06/22/2016] [Indexed: 12/31/2022]
Abstract
In an evaluation of carbon nanotubes (CNTs) for the IARC Monograph 111, the Mechanisms Subgroup was tasked with assessing the strength of evidence on the potential carcinogenicity of CNTs in humans. The mechanistic evidence was considered to be not strong enough to alter the evaluations based on the animal data. In this paper, we provide an extended, in-depth examination of the in vivo and in vitro experimental studies according to current hypotheses on the carcinogenicity of inhaled particles and fibers. We cite additional studies of CNTs that were not available at the time of the IARC meeting in October 2014, and extend our evaluation to include carbon nanofibers (CNFs). Finally, we identify key data gaps and suggest research needs to reduce uncertainty. The focus of this review is on the cancer risk to workers exposed to airborne CNT or CNF during the production and use of these materials. The findings of this review, in general, affirm those of the original evaluation on the inadequate or limited evidence of carcinogenicity for most types of CNTs and CNFs at this time, and possible carcinogenicity of one type of CNT (MWCNT-7). The key evidence gaps to be filled by research include: investigation of possible associations between in vitro and early-stage in vivo events that may be predictive of lung cancer or mesothelioma, and systematic analysis of dose-response relationships across materials, including evaluation of the influence of physico-chemical properties and experimental factors on the observation of nonmalignant and malignant endpoints.
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Affiliation(s)
- Eileen D Kuempel
- a National Institute for Occupational Safety and Health , Cincinnati , OH , USA
| | - Marie-Claude Jaurand
- b Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche , UMR 1162 , Paris , France
- c Labex Immuno-Oncology, Sorbonne Paris Cité, University of Paris Descartes , Paris , France
- d University Institute of Hematology, Sorbonne Paris Cité, University of Paris Diderot , Paris , France
- e University of Paris 13, Sorbonne Paris Cité , Saint-Denis , France
| | - Peter Møller
- f Department of Public Health , University of Copenhagen , Copenhagen , Denmark
| | - Yasuo Morimoto
- g Department of Occupational Pneumology , University of Occupational and Environmental Health , Kitakyushu City , Japan
| | | | - Kent E Pinkerton
- i Center for Health and the Environment, University of California , Davis , California , USA
| | - Linda M Sargent
- j National Institute for Occupational Safety and Health , Morgantown , West Virginia , USA
| | - Roel C H Vermeulen
- k Institute for Risk Assessment Sciences, Utrecht University , Utrecht , The Netherlands
| | - Bice Fubini
- l Department of Chemistry and "G.Scansetti" Interdepartmental Center , Università degli Studi di Torino , Torino , Italy
| | - Agnes B Kane
- m Department of Pathology and Laboratory Medicine , Brown University , Providence , RI , USA
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Banholzer ML, Wandel C, Barrow P, Mannino M, Schmitt G, Guérard M, Müller L, Greig G, Amemiya K, Peck R, Singer T, Doessegger L. Clinical trial considerations on male contraception and collection of pregnancy information from female partner: update. Clin Transl Med 2016; 5:23. [PMID: 27455840 PMCID: PMC4960246 DOI: 10.1186/s40169-016-0103-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 06/24/2016] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND This is an update to our 2012 publication on clinical trial considerations on male contraception and collection of pregnancy information from female partner, after critical review of recent (draft) guidances released by the International Council for Harmonisation [ICH] the Clinical Trial Facilitation Group [CTFG] and the US Food & Drug Administration [FDA]. METHODS Relevant aspects of the new guidance documents are discussed in the context of male contraception and pregnancy reporting from female partner in clinical trials and the approach is updated accordingly. RESULTS Genotoxicity The concept of a threshold is introduced using acceptable daily intake/permissible daily exposure to define genotoxicity requirements, hence highly effective contraception in order to avoid conception. The duration for highly effective contraception has been extended from 74 to 90 days from the end of relevant systemic exposure. Teratogenicity Pharmacokinetic considerations to estimate safety margins have been contextualized with regard to over- and underestimation of the risk of teratogenicity transmitted by a vaginal dose. The duration of male contraception after the last dose takes into account the end of relevant systemic exposure if measured, or a default period of five half-lives after last dose for small molecules and two half-lives for immunoglobulins (mAbs). Measures to prevent exposure of the conceptus via a vaginal dose apply to reproductively competent or vasectomized men, unless measurements fail to detect the compound in seminal fluid. CONCLUSION Critical review of new guidance documents provides a comparison across approaches and resulted in an update of our previous publication. Separate algorithms for small molecules and monoclonal antibodies are proposed to guide the recommendations for contraception for male trial participants and pregnancy reporting from female partners. No male contraception is required if the dose is below a defined threshold for genotoxic concern applicable to small molecules. For men treated with teratogenic mAbs, condom use to prevent exposure of a potentially pregnant partner is unlikely to be recommended because of the minimal female exposure anticipated following a vaginal dose. The proposed safety margins for teratogenicity may evolve with further knowledge.
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Affiliation(s)
- Maria Longauer Banholzer
- Safety Risk Management, Licensing & Early Development, F. Hoffmann-La Roche AG, Basel, Switzerland
| | - Christoph Wandel
- Safety Risk Management, Licensing & Early Development, F. Hoffmann-La Roche AG, Basel, Switzerland
| | - Paul Barrow
- Pharma Research & Early Development, Roche Innovation Center Basel, Pharmaceutical Sciences, F. Hoffmann-La Roche AG, Basel, Switzerland
| | - Marie Mannino
- Safety Risk Management, Licensing & Early Development, F. Hoffmann-La Roche Ltd, New York, NY USA
| | - Georg Schmitt
- Pharma Research & Early Development, Roche Innovation Center Basel, Pharmaceutical Sciences, F. Hoffmann-La Roche AG, Basel, Switzerland
| | - Melanie Guérard
- Pharma Research & Early Development, Roche Innovation Center Basel, Pharmaceutical Sciences, F. Hoffmann-La Roche AG, Basel, Switzerland
| | - Lutz Müller
- Pharma Research & Early Development, Roche Innovation Center Basel, Pharmaceutical Sciences, F. Hoffmann-La Roche AG, Basel, Switzerland
| | - Gerard Greig
- Pharma Research & Early Development, Roche Innovation Center Basel, Clinical Pharmacology, F. Hoffmann-La Roche AG, Basel, Switzerland
| | - Kenjie Amemiya
- Non-Clinical Safety Department, Genentech Inc, South San Francisco, CA USA
| | - Richard Peck
- Pharma Research & Early Development, Roche Innovation Center Basel, Clinical Pharmacology, F. Hoffmann-La Roche AG, Basel, Switzerland
| | - Thomas Singer
- Pharma Research & Early Development, Roche Innovation Center Basel, Pharmaceutical Sciences, F. Hoffmann-La Roche AG, Basel, Switzerland
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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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Lovsin Barle E, Winkler GC, Glowienke S, Elhajouji A, Nunic J, Martus HJ. Setting Occupational Exposure Limits for Genotoxic Substances in the Pharmaceutical Industry. Toxicol Sci 2016; 151:2-9. [PMID: 27207978 PMCID: PMC4914798 DOI: 10.1093/toxsci/kfw028] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
In the pharmaceutical industry, genotoxic drug substances are developed for life-threatening indications such as cancer. Healthy employees handle these substances during research, development, and manufacturing; therefore, safe handling of genotoxic substances is essential. When an adequate preclinical dataset is available, a risk-based decision related to exposure controls for manufacturing is made following a determination of safe health-based limits, such as an occupational exposure limit (OEL). OELs are calculated for substances based on a threshold dose-response once a threshold is identified. In this review, we present examples of genotoxic mechanisms where thresholds can be demonstrated and OELs can be calculated, including a holistic toxicity assessment. We also propose a novel approach for inhalation Threshold of Toxicological Concern (TTC) limit for genotoxic substances in cases where the database is not adequate to determine a threshold.
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Affiliation(s)
| | | | | | | | - Jana Nunic
- Lek Pharmaceuticals D.D, Verovškova 57, 1526 Ljubljana, Slovenia
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Lee SH, Wang TY, Hong JH, Cheng TJ, Lin CY. NMR-based metabolomics to determine acute inhalation effects of nano- and fine-sized ZnO particles in the rat lung. Nanotoxicology 2016; 10:924-34. [DOI: 10.3109/17435390.2016.1144825] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Sheng-Han Lee
- Institute of Environmental Health, College of Public Health, National Taiwan University, Taipei, Taiwan and
| | - Ting-Yi Wang
- Institute of Environmental Health, College of Public Health, National Taiwan University, Taipei, Taiwan and
| | - Jia-Huei Hong
- Institute of Environmental Health, College of Public Health, National Taiwan University, Taipei, Taiwan and
| | - Tsun-Jen Cheng
- Institute of Occupational Medicine and Industrial Hygiene, College of Public Health, National Taiwan University, Taipei, Taiwan
| | - Ching-Yu Lin
- Institute of Environmental Health, College of Public Health, National Taiwan University, Taipei, Taiwan and
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Klapacz J, Pottenger LH, Engelward BP, Heinen CD, Johnson GE, Clewell RA, Carmichael PL, Adeleye Y, Andersen ME. Contributions of DNA repair and damage response pathways to the non-linear genotoxic responses of alkylating agents. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2015; 767:77-91. [PMID: 27036068 DOI: 10.1016/j.mrrev.2015.11.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 11/26/2015] [Accepted: 11/27/2015] [Indexed: 11/27/2022]
Abstract
From a risk assessment perspective, DNA-reactive agents are conventionally assumed to have genotoxic risks at all exposure levels, thus applying a linear extrapolation for low-dose responses. New approaches discussed here, including more diverse and sensitive methods for assessing DNA damage and DNA repair, strongly support the existence of measurable regions where genotoxic responses with increasing doses are insignificant relative to control. Model monofunctional alkylating agents have in vitro and in vivo datasets amenable to determination of points of departure (PoDs) for genotoxic effects. A session at the 2013 Society of Toxicology meeting provided an opportunity to survey the progress in understanding the biological basis of empirically-observed PoDs for DNA alkylating agents. Together with the literature published since, this review discusses cellular pathways activated by endogenous and exogenous alkylation DNA damage. Cells have evolved conserved processes that monitor and counteract a spontaneous steady-state level of DNA damage. The ubiquitous network of DNA repair pathways serves as the first line of defense for clearing of the DNA damage and preventing mutation. Other biological pathways discussed here that are activated by genotoxic stress include post-translational activation of cell cycle networks and transcriptional networks for apoptosis/cell death. The interactions of various DNA repair and DNA damage response pathways provide biological bases for the observed PoD behaviors seen with genotoxic compounds. Thus, after formation of DNA adducts, the activation of cellular pathways can lead to the avoidance of a mutagenic outcome. The understanding of the cellular mechanisms acting within the low-dose region will serve to better characterize risks from exposures to DNA-reactive agents at environmentally-relevant concentrations.
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Affiliation(s)
- Joanna Klapacz
- Toxicology & Environmental Research and Consulting, The Dow Chemical Company, Midland, MI 48674, USA.
| | - Lynn H Pottenger
- Toxicology & Environmental Research and Consulting, The Dow Chemical Company, Midland, MI 48674, USA; Current Address: Olin Corporation, Midland, MI 48674, USA
| | - Bevin P Engelward
- Department of Biological Engineering, MA Institute of Technology, Cambridge, MA 02139, USA
| | - Christopher D Heinen
- Center for Molecular Medicine, Neag Comprehensive Cancer Center, University of CT Health Center, Farmington, CT 06030, USA
| | - George E Johnson
- Institute of Life Science, College of Medicine, Swansea University, SA2 8PP, UK
| | - Rebecca A Clewell
- Hamner Institutes for Health Sciences, Research Triangle Park, NC 27709, USA
| | - Paul L Carmichael
- Unilever, Safety & Environmental Assurance Centre, Colworth Science Park, Sharnbrook, Bedfordshire MK44 1LQ, UK
| | - Yeyejide Adeleye
- Unilever, Safety & Environmental Assurance Centre, Colworth Science Park, Sharnbrook, Bedfordshire MK44 1LQ, UK
| | - Melvin E Andersen
- Hamner Institutes for Health Sciences, Research Triangle Park, NC 27709, USA
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Zeller A, Tang L, Dertinger SD, Funk J, Duran-Pacheco G, Guérard M. A proposal for a novel rationale for critical effect size in dose–response analysis based on a multi-endpointin vivostudy with methyl methanesulfonate. Mutagenesis 2015; 31:239-53. [DOI: 10.1093/mutage/gev077] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Kinetic Modeling Reveals the Roles of Reactive Oxygen Species Scavenging and DNA Repair Processes in Shaping the Dose-Response Curve of KBrO₃-Induced DNA Damage. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2015; 2015:764375. [PMID: 26448819 PMCID: PMC4581570 DOI: 10.1155/2015/764375] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 07/21/2015] [Indexed: 11/24/2022]
Abstract
We have developed a kinetic model to investigate how DNA repair processes and scavengers of reactive oxygen species (ROS) can affect the dose-response shape of prooxidant induced DNA damage. We used as an example chemical KBrO3 which is activated by glutathione and forms reactive intermediates that directly interact with DNA to form 8-hydroxy-2-deoxyguanosine DNA adducts (8-OH-dG). The single strand breaks (SSB) that can result from failed base excision repair of these adducts were considered as an effect downstream from 8-OH-dG. We previously demonstrated that, in the presence of effective base excision repair, 8-OH-dG can exhibit threshold-like dose-response dependence, while the downstream SSB can still exhibit a linear dose-response. Here we demonstrate that this result holds for a variety of conditions, including low levels of GSH, the presence of additional SSB repair mechanisms, or a scavenger. It has been shown that melatonin, a terminal scavenger, inhibits KBrO3-caused oxidative damage. Our modeling revealed that sustained exposure to KBrO3 can lead to fast scavenger exhaustion, in which case the dose-response shapes for both endpoints are not substantially affected. The results are important to consider when forming conclusions on a chemical's toxicity dose dependence based on the dose-response of early genotoxic events.
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Narayan S, Sharma R. Molecular mechanism of adenomatous polyposis coli-induced blockade of base excision repair pathway in colorectal carcinogenesis. Life Sci 2015; 139:145-52. [PMID: 26334567 DOI: 10.1016/j.lfs.2015.08.019] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Revised: 07/31/2015] [Accepted: 08/23/2015] [Indexed: 02/07/2023]
Abstract
Colorectal cancer (CRC) is the third leading cause of death in both men and women in North America. Despite chemotherapeutic efforts, CRC is associated with a high degree of morbidity and mortality. Thus, to develop effective treatment strategies for CRC, one needs knowledge of the pathogenesis of cancer development and cancer resistance. It is suggested that colonic tumors or cell lines harbor truncated adenomatous polyposis coli (APC) without DNA repair inhibitory (DRI)-domain. It is also thought that the product of the APC gene can modulate base excision repair (BER) pathway through an interaction with DNA polymerase β (Pol-β) and flap endonuclease 1 (Fen-1) to mediate CRC cell apoptosis. The proposed therapy with temozolomide (TMZ) exploits this particular pathway; however, a high percentage of colorectal tumors continue to develop resistance to chemotherapy due to mismatch repair (MMR)-deficiency. In the present communication, we have comprehensively reviewed a critical issue that has not been addressed previously: a novel mechanism by which APC-induced blockage of single nucleotide (SN)- and long-patch (LP)-BER play role in DNA-alkylation damage-induced colorectal carcinogenesis.
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Affiliation(s)
- Satya Narayan
- Department of Anatomy and Cell Biology, University of Florida, Gainesville, FL 32610 United States.
| | - Ritika Sharma
- Department of Anatomy and Cell Biology, University of Florida, Gainesville, FL 32610 United States
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Fahrer J, Frisch J, Nagel G, Kraus A, Dörsam B, Thomas AD, Reißig S, Waisman A, Kaina B. DNA repair by MGMT, but not AAG, causes a threshold in alkylation-induced colorectal carcinogenesis. Carcinogenesis 2015; 36:1235-44. [PMID: 26243310 DOI: 10.1093/carcin/bgv114] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 07/27/2015] [Indexed: 12/23/2022] Open
Abstract
Epidemiological studies indicate that N-nitroso compounds (NOC) are causally linked to colorectal cancer (CRC). NOC induce DNA alkylations, including O (6)-methylguanine (O (6)-MeG) and N-methylated purines, which are repaired by O (6)-MeG-DNA methyltransferase (MGMT) and N-alkyladenine-DNA glycosylase (AAG)-initiated base excision repair, respectively. In view of recent evidence of nonlinear mutagenicity for NOC-like compounds, the question arises as to the existence of threshold doses in CRC formation. Here, we set out to determine the impact of DNA repair on the dose-response of alkylation-induced CRC. DNA repair proficient (WT) and deficient (Mgmt (-/-), Aag (-/-) and Mgmt (-/-)/Aag (-/-)) mice were treated with azoxymethane (AOM) and dextran sodium sulfate to trigger CRC. Tumors were quantified by non-invasive mini-endoscopy. A non-linear increase in CRC formation was observed in WT and Aag (-/-) mice. In contrast, a linear dose-dependent increase in tumor frequency was found in Mgmt (-/-) and Mgmt (-/-)/Aag (-/-) mice. The data were corroborated by hockey stick modeling, yielding similar carcinogenic thresholds for WT and Aag (-/-) and no threshold for MGMT lacking mice. O (6)-MeG levels and depletion of MGMT correlated well with the observed dose-response in CRC formation. AOM induced dose-dependently DNA double-strand breaks in colon crypts including Lgr5-positive colon stem cells, which coincided with ATR-Chk1-p53 signaling. Intriguingly, Mgmt (-/-) mice displayed significantly enhanced levels of γ-H2AX, suggesting the usefulness of γ-H2AX as an early genotoxicity marker in the colorectum. This study demonstrates for the first time a non-linear dose-response for alkylation-induced colorectal carcinogenesis and reveals DNA repair by MGMT, but not AAG, as a key node in determining a carcinogenic threshold.
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Affiliation(s)
| | | | | | | | | | | | - Sonja Reißig
- Institute of Molecular Medicine, University Medical Center Mainz, Obere Zahlbacher Str. 67, D-55131 Mainz, Germany
| | - Ari Waisman
- Institute of Molecular Medicine, University Medical Center Mainz, Obere Zahlbacher Str. 67, D-55131 Mainz, Germany
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Thomas AD, Fahrer J, Johnson GE, Kaina B. Theoretical considerations for thresholds in chemical carcinogenesis. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2015; 765:56-67. [PMID: 26281768 DOI: 10.1016/j.mrrev.2015.05.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 05/11/2015] [Accepted: 05/12/2015] [Indexed: 02/08/2023]
Abstract
There is increasing evidence for non-linear relationships for gene mutations, chromosomal aberrations and even tumor incidences in response to low doses of genotoxic carcinogens. To attain the biological relevance of such non-linear responses, there is a need to identify the underlying defense mechanisms that allow tolerance to low doses of genotoxicants. This communication discusses presumptive cancer prevention mechanisms that may contribute to thresholds, i.e. points of departure, for each endpoint, from initial DNA lesion to tumor formation. We discuss a sequential order of genome protection during carcinogenesis where genotoxicant scavenging, cellular efflux, DNA repair, elimination of damaged cells by apoptosis, autophagy, silencing by DNA damage-triggered replicative senescence, and finally, elimination of transformed (premalignant) cells by the immune system are thought to be responsible for a threshold in tumor formation. We highlight DNA repair, for which experimental evidence has been recently provided to dictate a role in PoDs. In conclusion, from a theoretical perspective it is reasonable to posit that tolerance to low dose levels exists for each requisite step of tumor formation and these tolerance mechanisms are critical in determining thresholds in chemical carcinogenesis.
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Affiliation(s)
- Adam D Thomas
- Institute of Toxicology, University Medical Centre, Mainz, Germany
| | - Jörg Fahrer
- Institute of Toxicology, University Medical Centre, Mainz, Germany
| | - George E Johnson
- Institue of Life Science, College of Medicine, Swansea, Wales, United Kingdom
| | - Bernd Kaina
- Institute of Toxicology, University Medical Centre, Mainz, Germany.
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Lairmore MD, Ilkiw J. Animals Used in Research and Education, 1966-2016: Evolving Attitudes, Policies, and Relationships. JOURNAL OF VETERINARY MEDICAL EDUCATION 2015; 42:425-440. [PMID: 26673210 DOI: 10.3138/jvme.0615-087r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Since the inception of the Association of American Veterinary Medical Colleges (AAVMC), the use of animals in research and education has been a central element of the programs of member institutions. As veterinary education and research programs have evolved over the past 50 years, so too have societal views and regulatory policies. AAVMC member institutions have continually responded to these events by exchanging best practices in training their students in the framework of comparative medicine and the needs of society. Animals provide students and faculty with the tools to learn the fundamental knowledge and skills of veterinary medicine and scientific discovery. The study of animal models has contributed extensively to medicine, veterinary medicine, and basic sciences as these disciplines seek to understand life processes. Changing societal views over the past 50 years have provided active examination and continued refinement of the use of animals in veterinary medical education and research. The future use of animals to educate and train veterinarians will likely continue to evolve as technological advances are applied to experimental design and educational systems. Natural animal models of both human and animal health will undoubtedly continue to serve a significant role in the education of veterinarians and in the development of new treatments of animal and human disease. As it looks to the future, the AAVMC as an organization will need to continue to support and promote best practices in the humane care and appropriate use of animals in both education and research.
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MESH Headings
- Animal Experimentation/history
- Animal Experimentation/legislation & jurisprudence
- Animal Use Alternatives/history
- Animal Use Alternatives/legislation & jurisprudence
- Animal Use Alternatives/trends
- Animal Welfare/history
- Animal Welfare/legislation & jurisprudence
- Animals
- Animals, Laboratory
- Education, Veterinary/history
- Education, Veterinary/methods
- Education, Veterinary/trends
- History, 18th Century
- History, 19th Century
- History, 20th Century
- History, 21st Century
- History, Ancient
- Human-Animal Bond
- Humans
- Models, Animal
- United States
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