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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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Gi M, Fujioka M, Totsuka Y, Matsumoto M, Masumura K, Kakehashi A, Yamaguchi T, Fukushima S, Wanibuchi H. Quantitative analysis of mutagenicity and carcinogenicity of 2-amino-3-methylimidazo[4,5-f]quinoline in F344 gpt delta transgenic rats. Mutagenesis 2020; 34:279-287. [PMID: 31233596 DOI: 10.1093/mutage/gez015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 06/09/2019] [Indexed: 11/13/2022] Open
Abstract
Quantitative analysis of the mutagenicity and carcinogenicity of the low doses of genotoxic carcinogens present in food is of pressing concern. The purpose of the present study was to determine the mutagenicity and carcinogenicity of low doses of the dietary genotoxic carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). Male F344 gpt delta transgenic rats were fed diets supplemented with 0, 0.1, 1, 10 or 100 ppm IQ for 4 weeks. The frequencies of gpt transgene mutations in the liver were significantly increased in the 10 and 100 ppm groups. In addition, the mutation spectra was altered in the 1, 10 and 100 ppm groups: frequencies of G:C to T:A transversion were significantly increased in groups administered 1, 10 and 100 ppm IQ in a dose-dependent manner, and the frequencies of G:C to A:T transitions, A:T to T:A transversions and A:T to C:G transversions were significantly increased in the 100 ppm group. Increased frequencies of single base pair deletions and Spi- mutants in the liver, and an increase in glutathione S-transferase placental form (GST-P)-positive foci, a preneoplastic lesion of the liver in rats, was also observed in the 100 ppm group. In contrast, neither mutations nor mutation spectra or GST-P-positive foci were statistically altered by administration of IQ at 0.1 ppm. We estimated the point of departure for the mutagenicity and carcinogenicity of IQ using the no-observed-effect level approach and the Benchmark dose approach to characterise the dose-response relationship of low doses of IQ. Our findings demonstrate the existence of no effect levels of IQ for both in vivo mutagenicity and hepatocarcinogenicity. The findings of the present study will facilitate an understanding of the carcinogenic effects of low doses of IQ and help to determine a margin of exposure that may be useful for practical human risk assessment.
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Affiliation(s)
- Min Gi
- Department of Molecular Pathology, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka, Japan
| | - Masaki Fujioka
- Department of Molecular Pathology, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka, Japan
| | - Yukari Totsuka
- Division of Carcinogenesis and Cancer Prevention, National Cancer Center Research Institute, Chuo-ku, Tokyo, Japan
| | - Michiharu Matsumoto
- Japan Bioassay Research Center, Japan Organization of Occupational Health and Safety, Hadano, Kanagawa, Japan
| | - Kenichi Masumura
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, Kawasaki-ku, Kawasaki, Kanagawa, Japan
| | - Anna Kakehashi
- Department of Molecular Pathology, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka, Japan
| | - Takashi Yamaguchi
- Department of Molecular Pathology, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka, Japan
| | - Shoji Fukushima
- Japan Bioassay Research Center, Japan Organization of Occupational Health and Safety, Hadano, Kanagawa, Japan.,Association for Promotion of Research on Risk Assessment, Nakagawa-ku, Nagoya, Japan
| | - Hideki Wanibuchi
- Department of Molecular Pathology, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka, Japan
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Fukushima S, Gi M, Fujioka M, Kakehashi A, Wanibuchi H, Matsumoto M. Quantitative Approaches to Assess Key Carcinogenic Events of Genotoxic Carcinogens. Toxicol Res 2018; 34:291-296. [PMID: 30370003 PMCID: PMC6195881 DOI: 10.5487/tr.2018.34.4.291] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 08/20/2018] [Accepted: 08/30/2018] [Indexed: 11/22/2022] Open
Abstract
Chemical carcinogenesis is a multistep process. Genotoxic carcinogens, which are DNA-reactive, induce DNA adduct formation and genetic alterations in target cells, thereby generating mutated cells (initiation). Subsequently, preneoplastic lesions appear through clonal proliferation of the mutated cells and transform into tumors (promotion and progression). Many factors may influence these processes in a dose-dependent manner. Therefore, quantitative analysis plays an important role in studies on the carcinogenic threshold of genotoxic carcinogens. Herein, we present data on the relationship between key carcinogenic events and their deriving point of departure (PoD). Their PoDs were also compared to those of the carcinogenesis pathway. In an experiment, the liver of rats exposed to 2-amino-3,8-dimethylimidazo-(4,5-f)quinoxaline (MeIQx) was examined to determine the formation of MeIQx-DNA adducts, generation of mutations at LacI transgene, and induction of preneoplastic glutathione S-transferase placental form (GST-P)-positive foci and tumors (benign and malignant). The PoDs of the above key events in the carcinogenicity of MeIQx were increased as the carcinogenesis advanced; however, these PoDs were lower than those of tumor induction. Thus, the order of key events during tumor induction in the liver was as follows: formation of DNA adducts << Mutations << GST-positive foci (preneoplasia) << Tumor (adenoma and carcinoma). We also obtained similar data on the genotoxic and carcinogenic PoDs of other hepatocarcinogens, such as 2-amino-3,8-dimethylimidazo(4,5-f)quinoline. These results contribute to elucidating the existence of a genotoxic and carcinogenic threshold.
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Affiliation(s)
- Shoji Fukushima
- Association for Promotion of Research on Risk Assessment, Nakagawa, Nagoya, Japan.,Japan Bioassay Research Center, Hadano, Kanagawa, Japan
| | - Min Gi
- Department of Molecular Pathology, Osaka City University Graduate School of Medicine, Abeno, Osaka, Japan
| | - Masaki Fujioka
- Department of Molecular Pathology, Osaka City University Graduate School of Medicine, Abeno, Osaka, Japan
| | - Anna Kakehashi
- Department of Molecular Pathology, Osaka City University Graduate School of Medicine, Abeno, Osaka, Japan
| | - Hideki Wanibuchi
- Department of Molecular Pathology, Osaka City University Graduate School of Medicine, Abeno, Osaka, Japan
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Gi M, Fujioka M, Kakehashi A, Okuno T, Masumura K, Nohmi T, Matsumoto M, Omori M, Wanibuchi H, Fukushima S. In vivo positive mutagenicity of 1,4-dioxane and quantitative analysis of its mutagenicity and carcinogenicity in rats. Arch Toxicol 2018; 92:3207-3221. [PMID: 30155721 DOI: 10.1007/s00204-018-2282-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 08/02/2018] [Indexed: 12/17/2022]
Abstract
1,4-Dioxane is a widely used synthetic industrial chemical and its contamination of drinking water and food is a potential health concern. It induces liver tumors when administered in the drinking water to rats and mice. However, the mode of action (MOA) of the hepatocarcinogenicity of 1,4-dioxane remains unclear. Importantly, it is unknown if 1,4-dioxane is genotoxic, a key consideration for risk assessment. To determine the in vivo mutagenicity of 1,4-dioxane, gpt delta transgenic F344 rats were administered 1,4-dioxane at various doses in the drinking water for 16 weeks. The overall mutation frequency (MF) and A:T- to -G:C transitions and A:T- to -T:A transversions in the gpt transgene were significantly increased by administration of 5000 ppm 1,4-dioxane. A:T- to -T:A transversions were also significantly increased by administration of 1000 ppm 1,4-dioxane. Furthermore, the DNA repair enzyme MGMT was significantly induced at 5000 ppm 1,4-dioxane, implying that extensive genetic damage exceeded the repair capacity of the cells in the liver and consequently led to liver carcinogenesis. No evidence supporting other MOAs, including induction of oxidative stress, cytotoxicity, or nuclear receptor activation, that could contribute to the carcinogenic effects of 1,4-dioxane were found. These findings demonstrate that 1,4-dioxane is a genotoxic hepatocarcinogen and induces hepatocarcinogenesis through a mutagenic MOA in rats. Because our data indicate that 1,4-dioxane is a genotoxic carcinogen, we estimated the point of departure of the mutagenicity and carcinogenicity of 1,4-dioxane using the no-observed effect-level approach and the Benchmark dose approach to characterize its dose-response relationship at low doses.
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Affiliation(s)
- Min Gi
- Department of Molecular Pathology, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka, 545-8585, Japan
| | - Masaki Fujioka
- Department of Molecular Pathology, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka, 545-8585, Japan
| | - Anna Kakehashi
- Department of Molecular Pathology, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka, 545-8585, Japan
| | - Takahiro Okuno
- Department of Molecular Pathology, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka, 545-8585, Japan
| | - Kenichi Masumura
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, 3-25-26 Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa, 210-9501, Japan
| | - Takehiko Nohmi
- Biological Safety Research Center, National Institute of Health Sciences, 3-25-26 Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa, 210-9501, Japan
| | - Michiharu Matsumoto
- Japan Bioassay Research Center, Japan Organization of Occupational Health and Safety, Hadano, Kanagawa, 257-0015, Japan
| | - Masako Omori
- Association for Promotion of Research on Risk Assessment, Nakagawa-ku, Nagoya, 454-0869, Japan
| | - Hideki Wanibuchi
- Department of Molecular Pathology, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka, 545-8585, Japan
| | - Shoji Fukushima
- Japan Bioassay Research Center, Japan Organization of Occupational Health and Safety, Hadano, Kanagawa, 257-0015, Japan.
- Association for Promotion of Research on Risk Assessment, Nakagawa-ku, Nagoya, 454-0869, Japan.
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Kirkland D, Zeiger E, Madia F, Gooderham N, Kasper P, Lynch A, Morita T, Ouedraogo G, Parra Morte JM, Pfuhler S, Rogiers V, Schulz M, Thybaud V, van Benthem J, Vanparys P, Worth A, Corvi R. Can in vitro mammalian cell genotoxicity test results be used to complement positive results in the Ames test and help predict carcinogenic or in vivo genotoxic activity? I. Reports of individual databases presented at an EURL ECVAM Workshop. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2014; 775-776:55-68. [PMID: 25435356 DOI: 10.1016/j.mrgentox.2014.10.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 10/10/2014] [Accepted: 10/13/2014] [Indexed: 11/28/2022]
Abstract
Positive results in the Ames test correlate well with carcinogenic potential in rodents. This correlation is not perfect because mutations are only one of many stages in tumour development. Also, situations can be envisaged where the mutagenic response may be specific to the bacteria or the test protocol, e.g., bacterial-specific metabolism, exceeding a detoxification threshold, or the induction of oxidative damage to which bacteria may be more sensitive than mammalian cells in vitro or tissues in vivo. Since most chemicals are also tested for genotoxicity in mammalian cells, the pattern of mammalian cell results may help identify whether Ames-positive results predict carcinogenic or in vivo mutagenic activity. A workshop was therefore organised and sponsored by the EU Reference Laboratory for Alternatives to Animal Testing (EURL ECVAM) to investigate this further. Participants presented results from other genotoxicity tests with Ames-positive compounds. Data came from published, regulatory agency, and industry sources. The question was posed whether negative results in mammalian cell tests were associated with absence of carcinogenic or in vivo genotoxic activity despite a positive Ames test. In the limited time available, the presented data were combined and an initial analysis suggested that the association of negative in vitro mammalian cell test results with lack of in vivo genotoxic or carcinogenic activity could have some significance. Possible reasons why a positive Ames test may not be associated with in vivo activity and what additional investigations/tests might contribute to a more robust evaluation were discussed. Because a considerable overlap was identified among the different databases presented, it was recommended that a consolidated database be built, with overlapping chemicals removed, so that a more robust analysis of the predictive capacity for potential carcinogenic and in vivo genotoxic activity could be derived from the patterns of mammalian cell test results obtained for Ames-positive compounds.
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Affiliation(s)
- David Kirkland
- Kirkland Consulting, PO Box 79, Tadcaster LS24 0AS, United Kingdom
| | - Errol Zeiger
- Errol Zeiger Consulting, 800 Indian Springs Rd., Chapel Hill, NC 27514, USA
| | - Federica Madia
- European Union Reference Laboratory for Alternatives to Animal Testing (EURL ECVAM), Systems Toxicology Unit; Institute for Health and Consumer Protection (IHCP), European Commission - Joint Research Centre, TP 126, Via E. Fermi 2749, I-21027 Ispra, Va, Italy
| | - Nigel Gooderham
- Surgery and Cancer, Imperial College London, London SW7 2AZ, United Kingdom
| | - Peter Kasper
- BfArM, Genetic Toxicology, Kurt-George-Kiesinger Allee 3, D-53175 Bonn, Germany
| | - Anthony Lynch
- GlaxoSmithKline R&D, Park Road, Ware, Herts SG12 0DP, England, United Kingdom
| | - Takeshi Morita
- Division of Safety Information on Drug, Food and Chemicals, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan
| | - Gladys Ouedraogo
- L'Oreal 1, Avenue Eugéne Schueller, 93601 Aulnay-sous-Bois, France
| | | | - Stefan Pfuhler
- Procter & Gamble Co., Miami Valley Innovation Center, 11810 East Miami River Road, Cincinnati, OH 45239 8707, USA
| | - Vera Rogiers
- Department of Toxicology, Vrije Universiteit Brussel, Laarbeeklaan 103, 1090 Brussels, Belgium
| | | | - Veronique Thybaud
- Sanofi, 13 Quai Jules Guesde, BP 14, 94403 Vitry-sur-Seine Cedex, France
| | - Jan van Benthem
- National Institute of Public Health and the Environment, Antonie van Leeuwenhoeklaan 9, PO Box 1, 3720 BA Bilthoven, The Netherlands
| | | | - Andrew Worth
- European Union Reference Laboratory for Alternatives to Animal Testing (EURL ECVAM), Systems Toxicology Unit; Institute for Health and Consumer Protection (IHCP), European Commission - Joint Research Centre, TP 126, Via E. Fermi 2749, I-21027 Ispra, Va, Italy
| | - Raffaella Corvi
- European Union Reference Laboratory for Alternatives to Animal Testing (EURL ECVAM), Systems Toxicology Unit; Institute for Health and Consumer Protection (IHCP), European Commission - Joint Research Centre, TP 126, Via E. Fermi 2749, I-21027 Ispra, Va, Italy.
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Salawu SO, Bester MJ, Duodu KG. Phenolic Composition and Bioactive Properties of Cell Wall Preparations and Whole Grains of Selected Cereals and Legumes. J Food Biochem 2013. [DOI: 10.1111/jfbc.12026] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sule O. Salawu
- Department of Food Science; University of Pretoria; Private Bag X20 Hatfield 0028 South Africa
- Department of Biochemistry; Federal University of Technology; Akure Nigeria
| | - Megan J. Bester
- Department of Anatomy; University of Pretoria; Private Bag X20 Hatfield 0028 South Africa
| | - Kwaku G. Duodu
- Department of Food Science; University of Pretoria; Private Bag X20 Hatfield 0028 South Africa
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Wei M, Kakehashi A, Yamano S, Tamano S, Shirai T, Wanibuchi H, Fukushima S. Lack of Hepatocarcinogenicity of Combinations of Low Doses of 2-amino-3, 8-dimethylimidazo[4,5- f ]quinoxaline and Diethylnitrosamine in Rats: Indication for the Existence of a Threshold for Genotoxic Carcinogens. J Toxicol Pathol 2012; 25:209-14. [PMID: 22988339 PMCID: PMC3434336 DOI: 10.1293/tox.25.209] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Accepted: 06/14/2012] [Indexed: 01/20/2023] Open
Abstract
The purposes of the present study were to evaluate the hepatocarcinogenicity of
concurrent treatment of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline
(MeIQx) and diethylnitrosamine (DEN) in rats and to determine whether no effect levels of
combinations of these two different structural categories of genotoxic hepatocarcinogens
exist. Two 16-week rat hepatocarcinogenesis assays were performed using a total of 790
male F344 rats. In experiment 1, we evaluated the effects of concurrent treatment of a
subcarcinogenic dose of DEN on rat hepatocarcinogenesis induced by various doses of MeIQx.
In experiment 2, we determined hepatocarcinogenicities of combinations of MeIQx and DEN at
subcarcinogenic doses, low carcinogenic doses and high carcinogenic doses. Quantitative
analyses of glutathione S-transferase placental form (GST-P)-positive
foci, a preneoplastic lesion of the liver in rats, revealed that concurrent treatment with
subcarcinogenic doses of DEN did not enhance MeIQx-induced rat hepatocarcinogenicity. We
also found that concurrent treatment with combinations of subcarcinogenic doses of DEN and
MeIQx was not hepatocarcinogenic, indicating that the combined effects of subcarcinogenic
doses of DEN and MeIQx were neither additive nor synergistic. Moreover, concurrent
treatment with low carcinogenic doses of these 2 carcinogens did not show additive or
synergistic effects. Synergetic effects were observed only in rats coadministered high
carcinogenic doses of the 2 carcinogens. These results demonstrate the existence of no
effect levels of combinations of these 2 genotoxic hepatocarcinogens, and provide new
evidence supporting our idea that there is a threshold, at least a practical threshold,
that should be considered when evaluating the risk of genotoxic carcinogens.
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Affiliation(s)
- Min Wei
- Department of Pathology, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka 545-8585, Japan
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Piersma AH, Hernandez LG, van Benthem J, Muller JJA, van Leeuwen FR, Vermeire TG, van Raaij MTM. Reproductive toxicants have a threshold of adversity. Crit Rev Toxicol 2011; 41:545-54. [DOI: 10.3109/10408444.2011.554794] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Wei M, Wanibuchi H, Nakae D, Tsuda H, Takahashi S, Hirose M, Totsuka Y, Tatematsu M, Fukushima S. Low-dose carcinogenicity of 2-amino-3-methylimidazo[4,5-f ]quinoline in rats: Evidence for the existence of no-effect levels and a mechanism involving p21(Cip / WAF1). Cancer Sci 2011; 102:88-94. [PMID: 20964789 PMCID: PMC11159129 DOI: 10.1111/j.1349-7006.2010.01761.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The carcinogenicity of the low amounts of genotoxic carcinogens present in food is of pressing concern. The purpose of the present study was to determine the carcinogenicity of low doses of the dietary genotoxic carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and to investigate mechanisms by which IQ exerts its carcinogenic effects. A total of 1595 male F344 rats were divided into seven groups and administered with IQ at doses of 0, 0.001, 0.01, 0.1, 1, 10 and 100 p.p.m. in the diet for 16 weeks. We found that IQ doses of 1 p.p.m. and below did not induce preneoplastic lesions in either the liver or the colon, while IQ doses of 10 and 100 p.p.m. induced preneoplastic lesions in both of these organs. These results demonstrate the presence of no-effect levels of IQ for both liver and colon carcinogenicity in rats. The finding that p21(Cip/WAF1) was significantly induced in the liver at doses well below those required for IQ mediated carcinogenic effects suggests that induction of p21(Cip/WAF1) is one of the mechanisms responsible for the observed no-effect of low doses of IQ. Furthermore, IQ administration caused significant induction of CYP1A2 at doses of 0.01-10 p.p.m., but administration of 100 p.p.m. IQ induced CYP1A1 rather than CYP1A2. This result indicates the importance of dosage when interpreting data on the carcinogenicity and metabolic activation of IQ. Overall, our results suggest the existence of no-effect levels for the carcinogenicity of this genotoxic compound.
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Affiliation(s)
- Min Wei
- Department of Pathology, Osaka City University Medical School, Osaka. Japan
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Wei M, Hamoud AS, Yamaguchi T, Kakehashi A, Morimura K, Doi K, Kushida M, Kitano M, Wanibuchi H, Fukushima S. Potassium bromate enhances N-ethyl-N-hydroxyethylnitrosamine-induced kidney carcinogenesis only at high doses in Wistar rats: indication of the existence of an enhancement threshold. Toxicol Pathol 2010; 37:983-91. [PMID: 19833912 DOI: 10.1177/0192623309351720] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
As susceptibility to carcinogens varies considerably among different strains of experimental animals, evaluation of dose-response relationships for genotoxic carcinogen in different strains is indispensable for risk assessment. Potassium bromate (KBrO(3)) is a genotoxic carcinogen inducing kidney cancers at high doses in male F344 rats, but little is known about its carcinogenic effects in other strains of rats. The purpose of the present study was to determine dose-response relationships for carcinogenic effects of KBrO(3) on N-ethyl-N-hydroxyethylnitrosamine (EHEN)-induced kidney carcinogenesis in male Wistar rats. We found that KBrO(3) showed significant enhancement effects on EHEN-induced kidney carcinogenesis at above 250 ppm but not at doses of 125 ppm and below when evaluated in terms of induction of either preneoplastic lesions or tumors in male Wistar rats. Furthermore, KBrO(3) significantly increased the formation of oxidative DNA damage at doses of 125 and above but not at doses of 30 ppm and below in kidneys. These results demonstrated that low doses of KBrO(3) exert no effects on development of EHEN-initiated kidney lesions and induction of oxidative DNA damage. Taking account of previous similar findings in male F344 rats, it is strongly suggested that a threshold dose exists for enhancement effects of KBrO(3) on kidney carcinogenesis in rats.
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Affiliation(s)
- Min Wei
- Department of Pathology, Osaka City University Medical School, 1-4-3 Asahi-machi, Abeno-ku, Osaka 545-8585, Japan
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