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Hartwig A, Arand M, Epe B, Guth S, Jahnke G, Lampen A, Martus HJ, Monien B, Rietjens IMCM, Schmitz-Spanke S, Schriever-Schwemmer G, Steinberg P, Eisenbrand G. Mode of action-based risk assessment of genotoxic carcinogens. Arch Toxicol 2020; 94:1787-1877. [PMID: 32542409 PMCID: PMC7303094 DOI: 10.1007/s00204-020-02733-2] [Citation(s) in RCA: 79] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 03/31/2020] [Indexed: 12/16/2022]
Abstract
The risk assessment of chemical carcinogens is one major task in toxicology. Even though exposure has been mitigated effectively during the last decades, low levels of carcinogenic substances in food and at the workplace are still present and often not completely avoidable. The distinction between genotoxic and non-genotoxic carcinogens has traditionally been regarded as particularly relevant for risk assessment, with the assumption of the existence of no-effect concentrations (threshold levels) in case of the latter group. In contrast, genotoxic carcinogens, their metabolic precursors and DNA reactive metabolites are considered to represent risk factors at all concentrations since even one or a few DNA lesions may in principle result in mutations and, thus, increase tumour risk. Within the current document, an updated risk evaluation for genotoxic carcinogens is proposed, based on mechanistic knowledge regarding the substance (group) under investigation, and taking into account recent improvements in analytical techniques used to quantify DNA lesions and mutations as well as "omics" approaches. Furthermore, wherever possible and appropriate, special attention is given to the integration of background levels of the same or comparable DNA lesions. Within part A, fundamental considerations highlight the terms hazard and risk with respect to DNA reactivity of genotoxic agents, as compared to non-genotoxic agents. Also, current methodologies used in genetic toxicology as well as in dosimetry of exposure are described. Special focus is given on the elucidation of modes of action (MOA) and on the relation between DNA damage and cancer risk. Part B addresses specific examples of genotoxic carcinogens, including those humans are exposed to exogenously and endogenously, such as formaldehyde, acetaldehyde and the corresponding alcohols as well as some alkylating agents, ethylene oxide, and acrylamide, but also examples resulting from exogenous sources like aflatoxin B1, allylalkoxybenzenes, 2-amino-3,8-dimethylimidazo[4,5-f] quinoxaline (MeIQx), benzo[a]pyrene and pyrrolizidine alkaloids. Additionally, special attention is given to some carcinogenic metal compounds, which are considered indirect genotoxins, by accelerating mutagenicity via interactions with the cellular response to DNA damage even at low exposure conditions. Part C finally encompasses conclusions and perspectives, suggesting a refined strategy for the assessment of the carcinogenic risk associated with an exposure to genotoxic compounds and addressing research needs.
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Affiliation(s)
- Andrea Hartwig
- Department of Food Chemistry and Toxicology, Institute of Applied Biosciences (IAB), Karlsruhe Institute of Technology (KIT), Adenauerring 20a, 76131, Karlsruhe, Germany.
| | - Michael Arand
- Institute of Pharmacology and Toxicology, University of Zurich, 8057, Zurich, Switzerland
| | - Bernd Epe
- Institute of Pharmacy and Biochemistry, University of Mainz, 55099, Mainz, Germany
| | - Sabine Guth
- Department of Toxicology, IfADo-Leibniz Research Centre for Working Environment and Human Factors, TU Dortmund, Ardeystr. 67, 44139, Dortmund, Germany
| | - Gunnar Jahnke
- Department of Food Chemistry and Toxicology, Institute of Applied Biosciences (IAB), Karlsruhe Institute of Technology (KIT), Adenauerring 20a, 76131, Karlsruhe, Germany
| | - Alfonso Lampen
- Department of Food Safety, German Federal Institute for Risk Assessment (BfR), 10589, Berlin, Germany
| | - Hans-Jörg Martus
- Novartis Institutes for BioMedical Research, 4002, Basel, Switzerland
| | - Bernhard Monien
- Department of Food Safety, German Federal Institute for Risk Assessment (BfR), 10589, Berlin, Germany
| | - Ivonne M C M Rietjens
- Division of Toxicology, Wageningen University, Stippeneng 4, 6708 WE, Wageningen, The Netherlands
| | - Simone Schmitz-Spanke
- Institute and Outpatient Clinic of Occupational, Social and Environmental Medicine, University of Erlangen-Nuremberg, Henkestr. 9-11, 91054, Erlangen, Germany
| | - Gerlinde Schriever-Schwemmer
- Department of Food Chemistry and Toxicology, Institute of Applied Biosciences (IAB), Karlsruhe Institute of Technology (KIT), Adenauerring 20a, 76131, Karlsruhe, Germany
| | - Pablo Steinberg
- Max Rubner-Institut, Federal Research Institute of Nutrition and Food, Haid-und-Neu-Str. 9, 76131, Karlsruhe, Germany
| | - Gerhard Eisenbrand
- Retired Senior Professor for Food Chemistry and Toxicology, Kühler Grund 48/1, 69126, Heidelberg, Germany.
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Kobets T, Iatropoulos MJ, Williams GM. Mechanisms of DNA-reactive and epigenetic chemical carcinogens: applications to carcinogenicity testing and risk assessment. Toxicol Res (Camb) 2019; 8:123-145. [PMID: 30997017 PMCID: PMC6417487 DOI: 10.1039/c8tx00250a] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2018] [Accepted: 12/18/2018] [Indexed: 01/03/2023] Open
Abstract
Chemicals with carcinogenic activity in either animals or humans produce increases in neoplasia through diverse mechanisms. One mechanism is reaction with nuclear DNA. Other mechanisms consist of epigenetic effects involving either modifications of regulatory macromolecules or perturbation of cellular regulatory processes. The basis for distinguishing between carcinogens that have either DNA reactivity or an epigenetic activity as their primary mechanism of action is detailed in this review. In addition, important applications of information on these mechanisms of action to carcinogenicity testing and human risk assessment are discussed.
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Affiliation(s)
- Tetyana Kobets
- Department of Pathology , New York Medical College , Valhalla , NY 10595 , USA . ; ; Tel: +1 914-594-3105
| | - Michael J Iatropoulos
- Department of Pathology , New York Medical College , Valhalla , NY 10595 , USA . ; ; Tel: +1 914-594-3105
| | - Gary M Williams
- Department of Pathology , New York Medical College , Valhalla , NY 10595 , USA . ; ; Tel: +1 914-594-3105
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Galloway SM. International regulatory requirements for genotoxicity testing for pharmaceuticals used in human medicine, and their impurities and metabolites. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2017; 58:296-324. [PMID: 28299826 DOI: 10.1002/em.22077] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 02/05/2017] [Indexed: 06/06/2023]
Abstract
The process of developing international (ICH) guidelines is described, and the main guidelines reviewed are the ICH S2(R1) guideline that includes the genotoxicity test battery for human pharmaceuticals, and the ICH M7 guideline for assessing and limiting potentially mutagenic impurities and degradation products in drugs. Key aspects of the guidelines are reviewed in the context of drug development, for example the incorporation of genotoxicity assessment into non-clinical toxicity studies, and ways to develop and assess weight of evidence. In both guidelines, the existence of "thresholds" or non-linear dose responses for genotoxicity plays a part in the strategies. Differences in ICH S2(R1) protocol recommendations from OECD guidelines are highlighted and rationales explained. The use of genotoxicity data during clinical development and in assessment of carcinogenic potential is also described. There are no international guidelines on assessment of potentially genotoxic metabolites, but some approaches to safety assessment are discussed for these. Environ. Mol. Mutagen. 58:296-324, 2017. © 2017 Wiley Periodicals, Inc.
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Williams GM, Duan JD, Iatropoulos MJ, Kobets T. A no observed adverse effect level for DNA adduct formation in rat liver with prolonged dosing of the hepatocarcinogen 2-acetylaminofluorene. Toxicol Res (Camb) 2015. [DOI: 10.1039/c4tx00126e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Administration of AAF by gavage to male rats resulted in formation of several DNA adducts in liver, the pattern of which changed over time and with repair. The cumulative dose of 0.125 mg kg−1 AAF achieved in repeated doses for 16 weeks was a NOAEL for DNA adducts.
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Affiliation(s)
- Gary M. Williams
- Department of Pathology
- BSB 413
- New York Medical College
- Valhalla
- USA
| | - Jian-Dong Duan
- Department of Pathology
- BSB 413
- New York Medical College
- Valhalla
- USA
| | | | - Tetyana Kobets
- Department of Pathology
- BSB 413
- New York Medical College
- Valhalla
- USA
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Boobis A, Flari V, Gosling JP, Hart A, Craig P, Rushton L, Idahosa-Taylor E. Interpretation of the margin of exposure for genotoxic carcinogens – Elicitation of expert knowledge about the form of the dose response curve at human relevant exposures. Food Chem Toxicol 2013; 57:106-18. [DOI: 10.1016/j.fct.2013.03.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Revised: 02/06/2013] [Accepted: 03/02/2013] [Indexed: 01/08/2023]
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Iatropoulos MJ, Duan JD, Jeffrey AM, Leach MW, Hayes AN, Stedman NL, Williams GM. Hepatocellular proliferation and hepatocarcinogen bioactivation in mice with diet-induced fatty liver and obesity. ACTA ACUST UNITED AC 2012; 65:451-6. [PMID: 22459205 DOI: 10.1016/j.etp.2012.01.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 01/11/2012] [Accepted: 01/25/2012] [Indexed: 01/06/2023]
Abstract
Human liver cancer is in part associated with obesity and related metabolic diseases. The present study was undertaken in a mouse model of diet-induced obesity (DIO) and hepatic steatosis, conditions which can be associated with hepatic neoplasia, to determine whether the rates of cell proliferation or hepatocarcinogen bioactivation were altered in ways which could facilitate hepatocarcinogenesis. DIO mice were generated by feeding C57BL/6 (B6) male mice a high-fat diet beginning at 4 weeks of age; age-matched conventional lean (LEAN) B6 mice fed a low fat diet (10% Kcal from fat) were used for comparison. Groups of 28 week old DIO and LEAN mice were dosed with the bioactivation-dependent DNA-reactive hepatocarcinogen 2-acetylaminofluorene (AAF), at 2.24 or 22.4 mg/kg, given by gavage 3 times per week for 31 days, or received no treatment (DIO and LEAN control groups). Compared with the LEAN control group, the DIO control group had a higher mean body weight (16.5 g), higher mean absolute (1.4 g) and mean relative (25.5%) liver weights, higher (394%) liver triglyceride concentrations, and an increased incidence and severity of hepatocellular steatosis at the end of the dosing phase. The DIO control group also had a higher mean hepatocellular replicating fraction (31% increase, determined by proliferating cell nuclear antigen immunohistochemistry). Hepatocarcinogen bioactivation, based on formation of AAF DNA adducts as measured by nucleotide (32)P-postlabeling, was similar in both DIO and LEAN AAF-dosed groups. Thus, hepatocellular proliferation, but not hepatocarcinogen bioactivation, was identified as an alteration in livers of DIO mice which could contribute to their susceptibility to hepatocarcinogenesis.
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Affiliation(s)
- M J Iatropoulos
- Department of Pathology, New York Medical College, Valhalla, NY, USA
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Platel A, Nesslany F, Gervais V, Marzin D. Study of oxidative DNA damage in TK6 human lymphoblastoid cells by use of the in vitro micronucleus test: Determination of No-Observed-Effect Levels. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2009; 678:30-7. [DOI: 10.1016/j.mrgentox.2009.06.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Revised: 04/22/2009] [Accepted: 06/05/2009] [Indexed: 11/29/2022]
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O'Brien J, Renwick AG, Constable A, Dybing E, Müller DJG, Schlatter J, Slob W, Tueting W, van Benthem J, Williams GM, Wolfreys A. Approaches to the risk assessment of genotoxic carcinogens in food: A critical appraisal. Food Chem Toxicol 2006; 44:1613-35. [PMID: 16887251 DOI: 10.1016/j.fct.2006.07.004] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2006] [Revised: 07/07/2006] [Accepted: 07/10/2006] [Indexed: 11/18/2022]
Abstract
The present paper examines the particular difficulties presented by low levels of food-borne DNA-reactive genotoxic carcinogens, some of which may be difficult to eliminate completely from the diet, and proposes a structured approach for the evaluation of such compounds. While the ALARA approach is widely applicable to all substances in food that are both carcinogenic and genotoxic, it does not take carcinogenic potency into account and, therefore, does not permit prioritisation based on potential risk or concern. In the absence of carcinogenicity dose-response data, an assessment based on comparison with an appropriate threshold of toxicological concern may be possible. When carcinogenicity data from animal bioassays are available, a useful analysis is achieved by the calculation of margins of exposure (MOEs), which can be used to compare animal potency data with human exposure scenarios. Two reference points on the dose-response relationship that can be used for MOE calculation were examined; the T25 value, which is derived from linear extrapolation, and the BMDL10, which is derived from mathematical modelling of the dose-response data. The above approaches were applied to selected food-borne genotoxic carcinogens. The proposed approach is applicable to all substances in food that are DNA-reactive genotoxic carcinogens and enables the formulation of appropriate semi-quantitative advice to risk managers.
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Affiliation(s)
- J O'Brien
- Food Safety Authority of Ireland, Abbey Court, Lower Abbey Street, Dublin 1, Ireland
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