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Chandrasekaran A, Bentley K, McClanahan R, Nallani G. Effects of pethoxamid treatment on the disposition of thyroxine in rats. Toxicol Appl Pharmacol 2024; 487:116959. [PMID: 38734151 DOI: 10.1016/j.taap.2024.116959] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 04/11/2024] [Accepted: 05/08/2024] [Indexed: 05/13/2024]
Abstract
Pethoxamid (PXA) is a chloroacetamide herbicide that works by inhibiting the germination of target weeds in crops. PXA is not a genotoxic agent, however, in a two-year chronic toxicity study, incidence of thyroid follicular cell hyperplasia was observed in male rats treated at a high dose. Many non-mutagenic chemicals, including agrochemicals are known to produce thyroid hyperplasia in rodents through a hepatic metabolizing enzyme induction mode of action (MoA). In this study, the effects of oral gavage PXA treatment at 300 mg/kg for 7 days on the disposition of intravenously (iv) administered radio-labeled thyroxine ([125I]-T4) was assessed in bile-duct cannulated (BDC) rats. Another group of animals were treated with phenobarbital (PB, 100 mg/kg), a known enzyme inducer, serving as a positive control. The results showed significant increase (p < 0.01) in the mean liver weights in the PB and PXA-treated groups relative to the control group. The serum total T4 radioactivity Cmax and AUC0-4 values for PB and PXA-treated groups were lower than for the control group, suggesting increased clearance from serum. The mean percentages of administered radioactivity excreted in bile were 7.96 ± 0.38%, 16.13 ± 5.46%, and 11.99 ± 2.80% for the control, PB and PXA groups, respectively, indicating increased clearance via the bile in the treated animals. These data indicate that PXA can perturb the thyroid hormone homeostasis in rats by increasing T4 elimination in bile, possibly through enzyme induction mechanism similar to PB. In contrast to humans, the lack of high affinity thyroid binding globulin (TBG) in rats perhaps results in enhanced metabolism of T4 by uridine diphosphate glucuronosyl transferase (UGT). Since this liver enzyme induction MoA for thyroid hyperplasia by PB is known to be rodent specific, PXA effects on thyroid can also be considered not relevant to humans. The data from this study also suggest that incorporating a BDC rat model to determine thyroid hormone disposition using [125I]-T4 is valuable in a thyroid mode of action analysis.
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Affiliation(s)
| | - Karin Bentley
- FMC Corporation, 2929 Walnut St, Philadelphia, PA, USA
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2
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Klaunig JE, Bevan C, Gollapudi B. Assessment of the mode of action of perchloroethylene-induced mouse liver tumors. Toxicol Ind Health 2024; 40:272-291. [PMID: 38523547 DOI: 10.1177/07482337241240188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/26/2024]
Abstract
Perchloroethylene (PCE) is used as a solvent and chemical intermediate. Following chronic inhalation exposure, PCE selectively induced liver tumors in mice. Understanding the mode of action (MOA) for PCE carcinogenesis in mice is important in defining its possible human cancer risk. The proposed MOA is based on the extensive examination of the peer-reviewed studies that have assessed the mouse liver effects of PCE and its major oxidative metabolite trichloroacetic acid (TCA). Similar to PCE, TCA has also been demonstrated to liver tumors selectively in mice following chronic exposure. The Key Events (KE) of the proposed PCE MOA involve oxidative metabolism of PCE to TCA [KE 1]; activation of the peroxisome proliferator-activated receptor alpha (PPARα) [KE 2]; alteration in hepatic gene expression including cell growth pathways [KE 3]; increase in cell proliferation [KE 4]; selective clonal expansion of hepatic preneoplastic foci [KE 5]; and formation of hepatic neoplasms [KE 6]. The scientific evidence supporting the PPARα MOA for PCE is strong and satisfies the requirements for a MOA analysis. The PPARα liver tumor MOA in rodents has been demonstrated not to occur in humans; thus, human liver cancer risk to PCE is not likely.
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Affiliation(s)
- James E Klaunig
- School of Public Health, Indiana University, Bloomington, IN, USA
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3
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Sanz-Serrano J, Callewaert E, De Boever S, Drees A, Verhoeven A, Vinken M. Chemical-induced liver cancer: an adverse outcome pathway perspective. Expert Opin Drug Saf 2024; 23:425-438. [PMID: 38430529 DOI: 10.1080/14740338.2024.2326479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Accepted: 02/29/2024] [Indexed: 03/04/2024]
Abstract
INTRODUCTION The evaluation of the potential carcinogenicity is a key consideration in the risk assessment of chemicals. Predictive toxicology is currently switching toward non-animal approaches that rely on the mechanistic understanding of toxicity. AREAS COVERED Adverse outcome pathways (AOPs) present toxicological processes, including chemical-induced carcinogenicity, in a visual and comprehensive manner, which serve as the conceptual backbone for the development of non-animal approaches eligible for hazard identification. The current review provides an overview of the available AOPs leading to liver cancer and discusses their use in advanced testing of liver carcinogenic chemicals. Moreover, the challenges related to their use in risk assessment are outlined, including the exploitation of available data, the need for semantic ontologies, and the development of quantitative AOPs. EXPERT OPINION To exploit the potential of liver cancer AOPs in the field of risk assessment, 3 immediate prerequisites need to be fulfilled. These include developing human relevant AOPs for chemical-induced liver cancer, increasing the number of AOPs integrating quantitative toxicodynamic and toxicokinetic data, and developing a liver cancer AOP network. As AOPs and other areas in the field continue to evolve, liver cancer AOPs will progress into a reliable and robust tool serving future risk assessment and management.
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Affiliation(s)
- Julen Sanz-Serrano
- In Vitro Toxicology and Dermato-Cosmetology Research Group, Vrije Universiteit Brussel, Brussels, Belgium
| | - Ellen Callewaert
- In Vitro Toxicology and Dermato-Cosmetology Research Group, Vrije Universiteit Brussel, Brussels, Belgium
| | - Sybren De Boever
- In Vitro Toxicology and Dermato-Cosmetology Research Group, Vrije Universiteit Brussel, Brussels, Belgium
| | - Annika Drees
- In Vitro Toxicology and Dermato-Cosmetology Research Group, Vrije Universiteit Brussel, Brussels, Belgium
| | - Anouk Verhoeven
- In Vitro Toxicology and Dermato-Cosmetology Research Group, Vrije Universiteit Brussel, Brussels, Belgium
| | - Mathieu Vinken
- In Vitro Toxicology and Dermato-Cosmetology Research Group, Vrije Universiteit Brussel, Brussels, Belgium
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Rusyn I, Wright FA. Ten years of using key characteristics of human carcinogens to organize and evaluate mechanistic evidence in IARC Monographs on the identification of carcinogenic hazards to humans: Patterns and associations. Toxicol Sci 2024; 198:141-154. [PMID: 38141214 PMCID: PMC10901152 DOI: 10.1093/toxsci/kfad134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2023] Open
Abstract
Systematic review and evaluation of mechanistic evidence using the Key Characteristics approach was proposed by the International Agency for Research on Cancer (IARC) in 2012 and used by the IARC Monographs Working Groups since 2015. Key Characteristics are 10 features of agents known to cause cancer in humans. From 2015 to 2022, a total of 19 Monographs (73 agents combined) used Key Characteristics for cancer hazard classification. We hypothesized that a retrospective analysis of applications of the Key Characteristics approach to cancer hazard classification using heterogenous mechanistic data on diverse agents would be informative for systematic reviews in decision-making. We extracted information on the conclusions, data types, and the role mechanistic data played in the cancer hazard classification from each Monograph. Statistical analyses identified patterns in the use of Key Characteristics, as well as trends and correlations among Key Characteristics, data types, and ultimate decisions. Despite gaps in data for many agents and Key Characteristics, several significant results emerged. Mechanistic data from in vivo animal, in vitro animal, and in vitro human studies were most impactful in concluding that an agent could cause cancer via a Key Characteristic. To exclude the involvement of a Key Characteristic, data from large-scale systematic in vitro testing programs such as ToxCast, were most informative. Overall, increased availability of systemized data streams, such as human in vitro data, would provide the basis for more confident and informed conclusions about both positive and negative associations and inform expert judgments on cancer hazard.
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Affiliation(s)
- Ivan Rusyn
- Department of Veterinary Pharmacology and Physiology, Texas A&M University, College Station, Texas 77843, USA
| | - Fred A Wright
- Department of Statistics, Bioinformatics Research Center, North Carolina State University, Raleigh, North Carolina 27606, USA
- Department of Biological Sciences, Bioinformatics Research Center, North Carolina State University, Raleigh, North Carolina 27606, USA
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5
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Duarte Hospital C, Tête A, Debizet K, Imler J, Tomkiewicz-Raulet C, Blanc EB, Barouki R, Coumoul X, Bortoli S. SDHi fungicides: An example of mitotoxic pesticides targeting the succinate dehydrogenase complex. ENVIRONMENT INTERNATIONAL 2023; 180:108219. [PMID: 37778286 DOI: 10.1016/j.envint.2023.108219] [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: 03/11/2023] [Revised: 06/15/2023] [Accepted: 09/18/2023] [Indexed: 10/03/2023]
Abstract
Succinate dehydrogenase inhibitors (SDHi) are fungicides used to control the proliferation of pathogenic fungi in crops. Their mode of action is based on blocking the activity of succinate dehydrogenase (SDH), a universal enzyme expressed by all species harboring mitochondria. The SDH is involved in two interconnected metabolic processes for energy production: the transfer of electrons in the mitochondrial respiratory chain and the oxidation of succinate to fumarate in the Krebs cycle. In humans, inherited SDH deficiencies may cause major pathologies including encephalopathies and cancers. The cellular and molecular mechanisms related to such genetic inactivation have been well described in neuroendocrine tumors, in which it induces an oxidative stress, a pseudohypoxic phenotype, a metabolic, epigenetic and transcriptomic remodeling, and alterations in the migration and invasion capacities of cancer cells, in connection with the accumulation of succinate, an oncometabolite, substrate of the SDH. We will discuss recent studies reporting toxic effects of SDHi in non-target organisms and their implications for risk assessment of pesticides. Recent data show that the SDH structure is highly conserved during evolution and that SDHi can inhibit SDH activity in mitochondria of non-target species, including humans. These observations suggest that SDHi are not specific inhibitors of fungal SDH. We hypothesize that SDHi could have toxic effects in other species, including humans. Moreover, the analysis of regulatory assessment reports shows that most SDHi induce tumors in animals without evidence of genotoxicity. Thus, these substances could have a non-genotoxic mechanism of carcinogenicity that still needs to be fully characterized and that could be related to SDH inhibition. The use of pesticides targeting mitochondrial enzymes encoded by tumor suppressor genes raises questions on the risk assessment framework of mitotoxic pesticides. The issue of SDHi fungicides is therefore a textbook case that highlights the urgent need for changes in regulatory assessment.
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Affiliation(s)
| | - Arnaud Tête
- Université Paris Cité, INSERM UMR-S 1124, T3S, 45 rue des Saints-Pères, 75006 Paris
| | - Kloé Debizet
- Université Paris Cité, INSERM UMR-S 1124, T3S, 45 rue des Saints-Pères, 75006 Paris
| | - Jules Imler
- Université Paris Cité, INSERM UMR-S 1124, T3S, 45 rue des Saints-Pères, 75006 Paris
| | | | - Etienne B Blanc
- Université Paris Cité, INSERM UMR-S 1124, T3S, 45 rue des Saints-Pères, 75006 Paris
| | - Robert Barouki
- Université Paris Cité, INSERM UMR-S 1124, T3S, 45 rue des Saints-Pères, 75006 Paris
| | - Xavier Coumoul
- Université Paris Cité, INSERM UMR-S 1124, T3S, 45 rue des Saints-Pères, 75006 Paris.
| | - Sylvie Bortoli
- Université Paris Cité, INSERM UMR-S 1124, T3S, 45 rue des Saints-Pères, 75006 Paris.
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6
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Pandiri AR, Auerbach SS, Stevens JL, Blomme EAG. Toxicogenomics Approaches to Address Toxicity and Carcinogenicity in the Liver. Toxicol Pathol 2023; 51:470-481. [PMID: 38288963 PMCID: PMC11014763 DOI: 10.1177/01926233241227942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/13/2024]
Abstract
Toxicogenomic technologies query the genome, transcriptome, proteome, and the epigenome in a variety of toxicological conditions. Due to practical considerations related to the dynamic range of the assays, sensitivity, cost, and technological limitations, transcriptomic approaches are predominantly used in toxicogenomics. Toxicogenomics is being used to understand the mechanisms of toxicity and carcinogenicity, evaluate the translational relevance of toxicological responses from in vivo and in vitro models, and identify predictive biomarkers of disease and exposure. In this session, a brief overview of various transcriptomic technologies and practical considerations related to experimental design was provided. The advantages of gene network analyses to define mechanisms were also discussed. An assessment of the utility of toxicogenomic technologies in the environmental and pharmaceutical space showed that these technologies are being increasingly used to gain mechanistic insights and determining the translational relevance of adverse findings. Within the environmental toxicology area, there is a broader regulatory consideration of benchmark doses derived from toxicogenomics data. In contrast, these approaches are mainly used for internal decision-making in pharmaceutical development. Finally, the development and application of toxicogenomic signatures for prediction of apical endpoints of regulatory concern continues to be area of intense research.
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Affiliation(s)
- Arun R Pandiri
- National Institute of Environmental Health Sciences, Durham, North Carolina, USA
| | - Scott S Auerbach
- National Institute of Environmental Health Sciences, Durham, North Carolina, USA
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7
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Felter SP, Ponting DJ, Mudd AM, Thomas R, Oliveira AAF. Maximizing use of existing carcinogenicity data to support acceptable intake levels for mutagenic impurities in pharmaceuticals: Learnings from N-nitrosamine case studies. Regul Toxicol Pharmacol 2023; 143:105459. [PMID: 37474097 DOI: 10.1016/j.yrtph.2023.105459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 06/27/2023] [Accepted: 07/17/2023] [Indexed: 07/22/2023]
Abstract
The unexpected finding of N-nitrosamine (NA) impurities in many pharmaceutical products raised significant challenges for industry and regulators. In addition to well-studied small molecular weight NAs, many of which are potent rodent carcinogens, novel NAs associated with active pharmaceutical ingredients have been found, many of which have limited or no safety data. A tiered approach to establishing Acceptable Intake (AI) limits for NA impurities has been established using chemical-specific data, read-across, or a class-specific TTC limit. There are ∼140 NAs with some rodent carcinogenicity data, but much of it is older and does not meet current guidelines for what constitutes a 'robust' bioassay. Nevertheless, these data are an important source of information to ensure the best science is used for assessing NA impurities and assuring consumer safety while minimizing impact that can lead to drug shortages. We present several strategies to maximize the use of imperfect data including using a lower confidence limit on a rodent TD50, and leveraging data from multiple NAs. Information on the chemical structure known to impact potency can also support development of an AI or potentially conclude that a particular NA does not fall in the cohort of concern for potent carcinogenicity.
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Affiliation(s)
- S P Felter
- Procter & Gamble, Central Product Safety, 8700 Mason-Montgomery Rd, Mason, OH, USA.
| | - D J Ponting
- Lhasa Limited, Granary Wharf House, 2 Canal Wharf, Leeds, LS11 5PS, UK
| | - A M Mudd
- Procter & Gamble, Central Product Safety, 8700 Mason-Montgomery Rd, Mason, OH, USA
| | - R Thomas
- Lhasa Limited, Granary Wharf House, 2 Canal Wharf, Leeds, LS11 5PS, UK
| | - A A F Oliveira
- Lhasa Limited, Granary Wharf House, 2 Canal Wharf, Leeds, LS11 5PS, UK
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8
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De Castelbajac T, Aiello K, Arenas CG, Svingen T, Ramhøj L, Zalko D, Barouki R, Vanhaecke T, Rogiers V, Audebert M, Oelgeschlaeger M, Braeuning A, Blanc E, Tal T, Rüegg J, Fritsche E, Marx-Stoelting P, Rivière G. Innovative tools and methods for toxicity testing within PARC work package 5 on hazard assessment. FRONTIERS IN TOXICOLOGY 2023; 5:1216369. [PMID: 37538785 PMCID: PMC10395075 DOI: 10.3389/ftox.2023.1216369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Accepted: 07/10/2023] [Indexed: 08/05/2023] Open
Abstract
New approach methodologies (NAMs) have the potential to become a major component of regulatory risk assessment, however, their actual implementation is challenging. The European Partnership for the Assessment of Risks from Chemicals (PARC) was designed to address many of the challenges that exist for the development and implementation of NAMs in modern chemical risk assessment. PARC's proximity to national and European regulatory agencies is envisioned to ensure that all the research and innovation projects that are initiated within PARC agree with actual regulatory needs. One of the main aims of PARC is to develop innovative methodologies that will directly aid chemical hazard identification, risk assessment, and regulation/policy. This will facilitate the development of NAMs for use in risk assessment, as well as the transition from an endpoint-based animal testing strategy to a more mechanistic-based NAMs testing strategy, as foreseen by the Tox21 and the EU Chemical's Strategy for Sustainability. This work falls under work package 5 (WP5) of the PARC initiative. There are three different tasks within WP5, and this paper is a general overview of the five main projects in the Task 5.2 'Innovative Tools and methods for Toxicity Testing,' with a focus on Human Health. This task will bridge essential regulatory data gaps pertaining to the assessment of toxicological prioritized endpoints such as non-genotoxic carcinogenicity, immunotoxicity, endocrine disruption (mainly thyroid), metabolic disruption, and (developmental and adult) neurotoxicity, thereby leveraging OECD's and PARC's AOP frameworks. This is intended to provide regulatory risk assessors and industry stakeholders with relevant, affordable and reliable assessment tools that will ultimately contribute to the application of next-generation risk assessment (NGRA) in Europe and worldwide.
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Affiliation(s)
- Thalia De Castelbajac
- French Agency for Food Environmental and Occupational Health and Safety, Maisons-Alfort, France
| | - Kiara Aiello
- German Federal Institute for Risk Assessment, Berlin, Germany
| | | | - Terje Svingen
- National Food Institute, Technical University of Denmark, Kgs Lyngby, Denmark
| | - Louise Ramhøj
- National Food Institute, Technical University of Denmark, Kgs Lyngby, Denmark
| | - Daniel Zalko
- INRAE, Toxalim Research Centre in Food Toxicology, Université de Toulouse, Toulouse, France
| | | | - Tamara Vanhaecke
- Department In Vitro Toxicology and Dermato-Cosmetology (IVTD) at the Faculty of Medicine and Pharmacy of the Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Vera Rogiers
- Department In Vitro Toxicology and Dermato-Cosmetology (IVTD) at the Faculty of Medicine and Pharmacy of the Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Marc Audebert
- INRAE, Toxalim Research Centre in Food Toxicology, Université de Toulouse, Toulouse, France
| | | | | | - Etienne Blanc
- Université Paris Cité, Inserm unit 1124, Paris, France
| | - Tamara Tal
- Helmholtz Centre for Environmental Research, Leipzig, Germany
| | - Joëlle Rüegg
- Department of Organismal Biology, Uppsala University, Uppsala, Sweden
| | - Ellen Fritsche
- Leibniz Research Institute of Environmental Medicine, Düsseldorf, Germany
| | | | - Gilles Rivière
- French Agency for Food Environmental and Occupational Health and Safety, Maisons-Alfort, France
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Rusyn I, Wright FA. Ten Years of Using Key Characteristics of Human Carcinogens to Organize and Evaluate Mechanistic Evidence in IARC Monographs on the Identification of Carcinogenic Hazards to Humans: Patterns and Associations. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.11.548354. [PMID: 37503163 PMCID: PMC10369858 DOI: 10.1101/2023.07.11.548354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Systematic review and evaluation of the mechanistic evidence only recently been instituted in cancer hazard identification step of decision-making. One example of organizing and evaluating mechanistic evidence is the Key Characteristics approach of the International Agency for Research on Cancer (IARC) Monographs on the Identification of Carcinogenic Hazards to Humans. The Key Characteristics of Human Carcinogens were proposed almost 10 years ago and have been used in every IARC Monograph since 2015. We investigated the patterns and associations in the use of Key Characteristics by the independent expert Working Groups. We examined 19 Monographs (2015-2022) that evaluated 73 agents. We extracted information on the conclusions by each Working Group on the strength of evidence for agent-Key Characteristic combinations, data types that were available for decisions, and the role mechanistic data played in the final cancer hazard classification. We conducted both descriptive and association analyses within and across data types. We found that IARC Working Groups were cautious when evaluating mechanistic evidence: for only ∼13% of the agents was strong evidence assigned for any Key Characteristic. Genotoxicity and cell proliferation were most data-rich, while little evidence was available for DNA repair and immortalization Key Characteristics. Analysis of the associations among Key Characteristics revealed that only chemical's metabolic activation was significantly co-occurring with genotoxicity and cell proliferation/death. Evidence from exposed humans was limited, while mechanistic evidence from rodent studies in vivo was often available. Only genotoxicity and cell proliferation/death were strongly associated with decisions on whether mechanistic data was impactful on the final cancer hazard classification. The practice of using the Key Characteristics approach is now well-established at IARC Monographs and other government agencies and the analyses presented herein will inform the future use of mechanistic evidence in regulatory decision-making.
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Dekant W, Dekant R. Mammalian toxicity of trifluoroacetate and assessment of human health risks due to environmental exposures. Arch Toxicol 2023; 97:1069-1077. [PMID: 36800005 DOI: 10.1007/s00204-023-03454-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2022] [Accepted: 02/02/2023] [Indexed: 02/18/2023]
Abstract
While trifluoroacetic acid has limited technical uses, the highly water-soluble trifluoroacetate (TFA) is reported to be present in water bodies at low concentrations. Most of the TFA in the environment is discussed to arise from natural processes, but also with the contribution from decomposition of environmental chemicals. The presence of TFA may result in human exposures. For hazard and risk assessment, the mammalian toxicity of TFA and human exposures are reviewed to assess the margin of exposures (MoE). The potential of TFA to induce acute toxicity is very low and oral repeated dose studies in rats have identified the liver as the target organ with mild liver hypertrophy as the lead effect. Biomarker analyses indicate that TFA is a weak peroxisome proliferator in rats. TFA administered to rats did not induce adverse effects in an extended one-generation study and in a developmental toxicity study or induce genotoxic responses. Based on recent levels of TFA in water and diet, MoEs for human exposures to TFA are well above 100 and do not indicate health risks.
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Affiliation(s)
- Wolfgang Dekant
- Department of Pharmacology and Toxicology, University of Würzburg, Versbacherstr. 9, 97078, Würzburg, Germany.
| | - Raphael Dekant
- Department of Pharmacology and Toxicology, University of Würzburg, Versbacherstr. 9, 97078, Würzburg, Germany
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11
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Zhang X, Felter SP, Api AM, Joshi K, Selechnik D. A Cautionary tale for using read-across for cancer hazard classification: Case study of isoeugenol and methyl eugenol. Regul Toxicol Pharmacol 2022; 136:105280. [DOI: 10.1016/j.yrtph.2022.105280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 09/16/2022] [Accepted: 10/19/2022] [Indexed: 11/06/2022]
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12
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Fukunaga S, Ogata K, Eguchi A, Matsunaga K, Sakurai K, Abe J, Cohen SM, Asano H. Evaluation of the mode of action and human relevance of liver tumors in male mice treated with epyrifenacil. Regul Toxicol Pharmacol 2022; 136:105268. [DOI: 10.1016/j.yrtph.2022.105268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 09/15/2022] [Accepted: 10/01/2022] [Indexed: 11/13/2022]
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13
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Harmon P, Otter R. A review of common non-ortho-phthalate plasticizers for use in food contact materials. Food Chem Toxicol 2022; 164:112984. [PMID: 35452769 DOI: 10.1016/j.fct.2022.112984] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 03/17/2022] [Accepted: 03/31/2022] [Indexed: 10/18/2022]
Abstract
Several non-ortho phthalate plasticizers, including ATBC, DEHA, DINCH, DOTP, and ESBO, are currently used in flexible PVC applications for food packaging and processing. The aim of this review is to summarize the available toxicity, migration, and human biomonitoring data. Available assessments from US CPSC, EFSA, other governmental and non-governmental organizations, and published toxicology studies were used to show that these plasticizers are generally well-studied and demonstrate low toxicity with a focus on potential carcinogenicity, reproductive, developmental, and endocrine related adverse effects as well as biodegradation, aquatic toxicity, and bioaccumulation. Seven other plasticizers, 2EHESBO, ASE, CMCHA, DBT, DEHCH, PETV, and TOTM, have at least some recent but limited food contact clearances; assessments from CPSC, EFSA, and robust summaries in the REACH dossiers were reviewed for these products. Data gaps were found for some of these products; however, there were no concerns raised by the existing data, and they for now have limited use in food contact applications. Migration of ASE, COMGHA, DINCH, DOTP, DEHCH, and TOTM in simulants for aqueous and low alcohol foods ranged from <0.02 to 0.165 mg/kg, which showed they are below established migration limits and well-suited for these applications. Human biomonitoring data are available for DINCH, DOTP, DEHA, DINA, and TOTM, and are essential for determining exposure from all uses.
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Affiliation(s)
- Patrick Harmon
- BASF Corporation, 11750 Katy Freeway, Houston, TX, 77079, United States.
| | - Rainer Otter
- BASF SE, Carl-Bosch-Strasse 38, Ludwigshafen am Rhein, D-67056, Germany
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14
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Felter SP, Bhat VS, Botham PA, Bussard DA, Casey W, Hayes AW, Hilton GM, Magurany KA, Sauer UG, Ohanian EV. Assessing chemical carcinogenicity: hazard identification, classification, and risk assessment. Insight from a Toxicology Forum state-of-the-science workshop. Crit Rev Toxicol 2022; 51:653-694. [DOI: 10.1080/10408444.2021.2003295] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
| | | | | | - David A. Bussard
- U.S. Environmental Protection Agency, Office of the Science Advisor, Policy and Engagement, Washington, DC, USA
| | - Warren Casey
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
| | - A. Wallace Hayes
- University of South Florida College of Public Health, Tampa, FL, USA
| | - Gina M. Hilton
- PETA Science Consortium International e.V., Stuttgart, Germany
| | | | | | - Edward V. Ohanian
- United States Environmental Protection Agency, Office of Water, Washington, DC, USA
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Krishan M, Navarro L, Beck B, Carvajal R, Dourson M. A regulatory relic: After 60 years of research on cancer risk, the Delaney Clause continues to keep us in the past. Toxicol Appl Pharmacol 2021; 433:115779. [PMID: 34737146 DOI: 10.1016/j.taap.2021.115779] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 10/23/2021] [Accepted: 10/25/2021] [Indexed: 11/29/2022]
Abstract
The Delaney Clause of the Federal Food, Drug, and Cosmetic Act became law in 1958 because of concerns that potentially harmful chemicals were finding their way into foods and causing cancer. It states, "[n]o additive shall be deemed to be safe if it is found to induce cancer when ingested by man or animal, or if it is found, after tests which are appropriate for the evaluation of the safety of food additives, to induce cancer in man or animal." The United States Food and Drug Administration (US FDA) and United States Environmental Protection Agency (US EPA, prior to implementation of the Food Quality Protection Act) were charged with implementing this clause. Over 60 years, advances in cancer research have elucidated how chemicals induce cancer. Significant advancements in analytical methodologies have allowed for accurate and progressively lower detection limits, resulting in detection of trace amounts. Based on current scientific knowledge, there is a need to revisit the Delaney Clause's utility. The lack of scientific merit to the Delaney Clause was very apparent when recently the US FDA had to revoke the food additive approvals of 6 synthetic flavoring substances because high dose testing in animals demonstrated a carcinogenic response. However, US FDA determined that these 6 synthetic flavoring substances do not pose a risk to public health under the conditions of intended use. The 7th substance, styrene, was de-listed because it is no longer used by industry. The scientific community is committed to improving public health by promoting relevant science in risk assessment and regulatory decision making, and this was discussed in scientific sessions at the American Association for the Advancement of Science (AAAS) 2020 Annual Meeting and the Society of Toxicology (SOT) 2019 Annual Meeting. Expert presentations included advances in cancer research since the 1950s; the role of the Delaney Clause in the current regulatory paradigm with a focus on synthetic food additives; and the impact of the clause on scientific advances and regulatory decision making. The sessions concluded with panel discussions on making the clause more relevant based on 21st-century science.
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16
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Tice RR, Bassan A, Amberg A, Anger LT, Beal MA, Bellion P, Benigni R, Birmingham J, Brigo A, Bringezu F, Ceriani L, Crooks I, Cross K, Elespuru R, Faulkner DM, Fortin MC, Fowler P, Frericks M, Gerets HHJ, Jahnke GD, Jones DR, Kruhlak NL, Lo Piparo E, Lopez-Belmonte J, Luniwal A, Luu A, Madia F, Manganelli S, Manickam B, Mestres J, Mihalchik-Burhans AL, Neilson L, Pandiri A, Pavan M, Rider CV, Rooney JP, Trejo-Martin A, Watanabe-Sailor KH, White AT, Woolley D, Myatt GJ. In Silico Approaches In Carcinogenicity Hazard Assessment: Current Status and Future Needs. COMPUTATIONAL TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2021; 20. [PMID: 35368437 DOI: 10.1016/j.comtox.2021.100191] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Historically, identifying carcinogens has relied primarily on tumor studies in rodents, which require enormous resources in both money and time. In silico models have been developed for predicting rodent carcinogens but have not yet found general regulatory acceptance, in part due to the lack of a generally accepted protocol for performing such an assessment as well as limitations in predictive performance and scope. There remains a need for additional, improved in silico carcinogenicity models, especially ones that are more human-relevant, for use in research and regulatory decision-making. As part of an international effort to develop in silico toxicological protocols, a consortium of toxicologists, computational scientists, and regulatory scientists across several industries and governmental agencies evaluated the extent to which in silico models exist for each of the recently defined 10 key characteristics (KCs) of carcinogens. This position paper summarizes the current status of in silico tools for the assessment of each KC and identifies the data gaps that need to be addressed before a comprehensive in silico carcinogenicity protocol can be developed for regulatory use.
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Affiliation(s)
- Raymond R Tice
- RTice Consulting, Hillsborough, North Carolina, 27278, USA
| | | | - Alexander Amberg
- Sanofi Preclinical Safety, Industriepark Höchst, 65926 Frankfurt, Germany
| | - Lennart T Anger
- Genentech, Inc., South San Francisco, California, 94080, USA
| | - Marc A Beal
- Healthy Environments and Consumer Safety Branch, Health Canada, Government of Canada, Ottawa, Ontario, Canada K1A 0K9
| | | | | | - Jeffrey Birmingham
- GlaxoSmithKline, David Jack Centre for R&D, Ware, Hertfordshire, SG12 0DP, United Kingdom
| | - Alessandro Brigo
- Roche Pharmaceutical Research & Early Development, Pharmaceutical Sciences, Roche Innovation, Center Basel, F. Hoffmann-La Roche Ltd, CH-4070, Basel, Switzerland
| | | | - Lidia Ceriani
- Humane Society International, 1000 Brussels, Belgium
| | - Ian Crooks
- British American Tobacco (Investments) Ltd, GR&D Centre, Southampton, SO15 8TL, United Kingdom
| | | | - Rosalie Elespuru
- Food and Drug Administration, Center for Devices and Radiological Health, Silver Spring, Maryland, 20993, USA
| | - David M Faulkner
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Marie C Fortin
- Department of Pharmacology and Toxicology, Ernest Mario School of Pharmacy, Rutgers University, Piscataway, New Jersey, 08855, USA
| | - Paul Fowler
- FSTox Consulting (Genetic Toxicology), Northamptonshire, United Kingdom
| | | | | | - Gloria D Jahnke
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, 27709, USA
| | | | - Naomi L Kruhlak
- Food and Drug Administration, Center for Drug Evaluation and Research, Silver Spring, Maryland, 20993, USA
| | - Elena Lo Piparo
- Chemical Food Safety Group, Nestlé Research, CH-1000 Lausanne 26, Switzerland
| | - Juan Lopez-Belmonte
- Cuts Ice Ltd Chemical Food Safety Group, Nestlé Research, CH-1000 Lausanne 26, Switzerland
| | - Amarjit Luniwal
- North American Science Associates (NAMSA) Inc., Minneapolis, Minnesota, 55426, USA
| | - Alice Luu
- Healthy Environments and Consumer Safety Branch, Health Canada, Government of Canada, Ottawa, Ontario, Canada K1A 0K9
| | - Federica Madia
- European Commission, Joint Research Centre (JRC), Ispra, Italy
| | - Serena Manganelli
- Chemical Food Safety Group, Nestlé Research, CH-1000 Lausanne 26, Switzerland
| | | | - Jordi Mestres
- IMIM Institut Hospital Del Mar d'Investigacions Mèdiques and Universitat Pompeu Fabra, Doctor Aiguader 88, Parc de Recerca Biomèdica, 08003 Barcelona, Spain; and Chemotargets SL, Baldiri Reixac 4, Parc Científic de Barcelona, 08028, Barcelona, Spain
| | | | - Louise Neilson
- Broughton Nicotine Services, Oak Tree House, Earby, Lancashire, BB18 6JZ United Kingdom
| | - Arun Pandiri
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, 27709, USA
| | | | - Cynthia V Rider
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, 27709, USA
| | - John P Rooney
- Integrated Laboratory Systems, LLC., Morrisville, North Carolina, 27560, USA
| | | | - Karen H Watanabe-Sailor
- School of Mathematical and Natural Sciences, Arizona State University, West Campus, Glendale, Arizona, 85306, USA
| | - Angela T White
- GlaxoSmithKline, David Jack Centre for R&D, Ware, Hertfordshire, SG12 0DP, United Kingdom
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17
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Yamada T, Ohara A, Ozawa N, Maeda K, Kondo M, Okuda Y, Abe J, Cohen SM, Lake BG. Comparison of the Hepatic Effects of Phenobarbital in Chimeric Mice Containing Either Rat or Human Hepatocytes With Humanized Constitutive Androstane Receptor and Pregnane X Receptor Mice. Toxicol Sci 2021; 177:362-376. [PMID: 32735318 DOI: 10.1093/toxsci/kfaa125] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Using a chimeric mouse humanized liver model, we provided evidence that human hepatocytes are refractory to the mitogenic effects of rodent constitutive androstane receptor (CAR) activators. To evaluate the functional reliability of this model, the present study examined mitogenic responses to phenobarbital (PB) in chimeric mice transplanted with rat hepatocytes, because rats are responsive to CAR activators. Treatment with 1000 ppm PB for 7 days significantly increased replicative DNA synthesis (RDS) in rat hepatocytes of the chimeric mice, demonstrating that the transplanted hepatocyte model is functionally reliable for cell proliferation analysis. Treatment of humanized CAR and pregnane X receptor (PXR) mice (hCAR/hPXR mice) with 1000 ppm PB for 7 days significantly increased hepatocyte RDS together with increases in several mitogenic genes. Global gene expression analysis was performed with liver samples from this and from previous studies focusing on PB-induced Wnt/β-catenin signaling and showed that altered genes in hCAR/hPXR mice clustered most closely with liver tumor samples from a diethylnitrosamine/PB initiation/promotion study than with wild-type mice. However, different gene clusters were observed for chimeric mice with human hepatocytes for Wnt/β-catenin signaling when compared with those of hCAR/hPXR mice, wild-type mice, and liver tumor samples. The results of this study demonstrate clear differences in the effects of PB on hepatocyte RDS and global gene expression between human hepatocytes of chimeric mice and hCAR/hPXR mice, suggesting that the chimeric mouse model is relevant to humans for studies on the hepatic effects of rodent CAR activators whereas the hCAR/hPXR mouse is not.
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Affiliation(s)
| | - Ayako Ohara
- Bioscience Research Laboratory, Sumitomo Chemical Company, Ltd, Konohana-ku, Osaka 554-8558, Japan
| | - Naoya Ozawa
- Bioscience Research Laboratory, Sumitomo Chemical Company, Ltd, Konohana-ku, Osaka 554-8558, Japan
| | | | | | - Yu Okuda
- Environmental Health Science Laboratory
| | - Jun Abe
- Environmental Health Science Laboratory
| | - Samuel M Cohen
- Department of Pathology and Microbiology, Havlik-Wall Professor of Oncology, University of Nebraska Medical Center, Omaha, Nebraska 68198-3135
| | - Brian G Lake
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom
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18
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Eguchi A, Fukunaga S, Ogata K, Kushida M, Asano H, Cohen SM, Sukata T. Chimeric Mouse With Humanized Liver Is an Appropriate Animal Model to Investigate Mode of Action for Porphyria-Mediated Hepatocytotoxicity. Toxicol Pathol 2021; 49:1243-1254. [PMID: 34238059 PMCID: PMC8521358 DOI: 10.1177/01926233211027474] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Porphyrinogenic compounds are known to induce porphyria-mediated hepatocellular injury and subsequent regenerative proliferation in rodents, ultimately leading to hepatocellular tumor induction. However, an appropriate in vivo experimental model to evaluate an effect of porphyrinogenic compounds on human liver has not been fully established. Recently, the chimeric mouse with humanized liver (PXB mice) became widely used as a humanized model in which human hepatocytes are transplanted. In the present study, we examined the utility of PXB mice as an in vivo experimental model to evaluate the key events of the porphyria-mediated cytotoxicity mode of action (MOA) in humans. The treatment of PXB mice with 5-aminolevulinic acid, a representative porphyrinogenic compound, for 28 days caused protoporphyrin IX accumulation, followed by hepatocyte necrosis, increased mitosis, and an increase in replicative DNA synthesis in human hepatocytes, indicative of cellular injury and regenerative proliferation, similar to findings in patients with porphyria or experimental porphyria models and corresponding to the key events of the MOA for porphyria-mediated hepatocellular carcinogenesis. We conclude that the PXB mouse is a useful model to evaluate the key events of the porphyria-mediated cytotoxicity MOA in humans and suggest the utility of PXB mice for clarifying the human relevancy of findings in mice.
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Affiliation(s)
- Ayumi Eguchi
- Environmental Health Science Laboratory, Sumitomo Chemical Co, Ltd, Osaka, Japan
| | - Satoki Fukunaga
- Environmental Health Science Laboratory, Sumitomo Chemical Co, Ltd, Osaka, Japan
| | - Keiko Ogata
- Environmental Health Science Laboratory, Sumitomo Chemical Co, Ltd, Osaka, Japan
| | - Masahiko Kushida
- Environmental Health Science Laboratory, Sumitomo Chemical Co, Ltd, Osaka, Japan
| | - Hiroyuki Asano
- Environmental Health Science Laboratory, Sumitomo Chemical Co, Ltd, Osaka, Japan
| | - Samuel M Cohen
- Department of Pathology and Microbiology, Havlik-Wall Professor of Oncology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Tokuo Sukata
- Environmental Health Science Laboratory, Sumitomo Chemical Co, Ltd, Osaka, Japan
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19
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Foreman JE, Koga T, Kosyk O, Kang BH, Zhu X, Cohen SM, Billy LJ, Sharma AK, Amin S, Gonzalez FJ, Rusyn I, Peters JM. Species differences between mouse and human PPARα in modulating the hepatocarcinogenic effects of perinatal exposure to a high-affinity human PPARα agonist in mice. Toxicol Sci 2021; 183:81-92. [PMID: 34081146 DOI: 10.1093/toxsci/kfab068] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Evidence suggests that species differences exist between rodents and humans in their biological responses to ligand activation of PPARα. Moreover, neonatal/postnatal rodents may be more sensitive to the effects of activating PPARα. Thus, the present studies examined the effects of chronic ligand activation of PPARα initiated during early neonatal development and continued into adulthood on hepatocarcinogenesis in mice. Wild-type, Ppara-null, or PPARA-humanized mice were administered a potent, high affinity human PPARα agonist GW7647, and cohorts of mice were examined over time. Activation of PPARα with GW7647 increased expression of known PPARα target genes in liver and was associated with hepatomegaly, increased hepatic cytotoxicity and necrosis, increased expression of hepatic MYC, and a high incidence of hepatocarcinogenesis in wild-type mice. These effects did not occur or were largely diminished in Ppara-null and PPARA-humanized mice, although background levels of hepatocarcinogenesis were also noted in both Ppara-null and PPARA-humanized mice. More fatty change (steatosis) was also observed in both Ppara-null and PPARA-humanized mice independent of GW7647 administration. Results from these studies indicate that the mouse PPARα is required to mediate hepatocarcinogenesis induced by GW7647 in mice and that activation of the human PPARα with GW7647 in PPARA-humanized mice are diminished compared to wild-type mice. Ppara-null and PPARA-humanized mice are valuable tools for examining species differences in the mechanisms of PPARα-induced hepatocarcinogenesis, but background levels of liver cancer observed in aged Ppara-null and PPARA-humanized mice must be considered when interpreting results from studies that use these models. These results also demonstrate that early life exposure to a potent human PPARα agonist does not enhance sensitivity to hepatocarcinogenesis.
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Affiliation(s)
- Jennifer E Foreman
- Department of Veterinary and Biomedical Science and Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, Pennsylvania
| | - Takayuki Koga
- Department of Veterinary and Biomedical Science and Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, Pennsylvania
| | - Oksana Kosyk
- Department of Environmental Sciences and Engineering, University of North Carolina, Chapel Hill, North Carolina
| | - Boo-Hyon Kang
- Non-clinical Research Institute, Yangji, Yongin, 17162, Gu Chemon, Myeon, Cheoin-, Si, Gyeonggi-Do Korea
| | - Xiaoyang Zhu
- Department of Veterinary and Biomedical Science and Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, Pennsylvania
| | - Samuel M Cohen
- Havlik-Wall Professor of Oncology, Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, 68198-3135
| | - Laura J Billy
- Department of Veterinary and Biomedical Science and Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, Pennsylvania
| | - Arun K Sharma
- Department of Pharmacology, The Pennsylvania State University, Hershey, Pennsylvania
| | - Shantu Amin
- Department of Pharmacology, The Pennsylvania State University, Hershey, Pennsylvania
| | - Frank J Gonzalez
- Laboratory of Metabolism, National Cancer Institute, Bethesda, Maryland
| | - Ivan Rusyn
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, Texas
| | - Jeffrey M Peters
- Department of Veterinary and Biomedical Science and Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, Pennsylvania
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20
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Rice PA, Cooper J, Koh-Fallet SE, Kabadi SV. Comparative analysis of the physicochemical, toxicokinetic, and toxicological properties of ether-PFAS. Toxicol Appl Pharmacol 2021; 422:115531. [PMID: 33933458 DOI: 10.1016/j.taap.2021.115531] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 04/06/2021] [Accepted: 04/07/2021] [Indexed: 12/29/2022]
Abstract
Perfluoropolyethers, also known as ether-PFAS, are linear or branched alkyl ether polymers, where the substituent hydrogens on the carbon atoms in the chain have been fully replaced by fluorine atoms. Some of these molecules may have a carboxylate functional group attached to one of the terminal carbon atoms to form an ether-PFAS carboxylate. Perfluoropolyethers are used as processing aids in the manufacture of various types of perfluorinated polymeric materials which are used in a variety of consumer applications. Although the physicochemical and toxicological properties of certain perfluoropolyether compounds have been extensively studied, data are relatively sparse for some members of this class of compounds. Moreover, the physicochemical, toxicokinetic, and toxicological properties of ether-PFAS as a class have not been elucidated in previous comprehensive review articles. This article reviews the nomenclature and uses of ether-PFAS and compares the physicochemical properties, toxicokinetic characteristics, apical effects in toxicological studies, and dose-response profiles across four specific ether-PFAS compounds. This comparison, including a description of identified data gaps should help to inform the design of studies to further elucidate the characteristics of ether-PFAS and to propose potential read-across assessment strategies for members of this class.
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Affiliation(s)
- Penelope A Rice
- FDA/CFSAN/OFAS/DFCS, 5001 Campus Drive, HFS 275, College Park, MD 20740, United States of America.
| | - Jessica Cooper
- FDA/CFSAN/OFAS/DFCS, 5001 Campus Drive, HFS 275, College Park, MD 20740, United States of America
| | - Sharon E Koh-Fallet
- FDA/CFSAN/OFAS/DFCS, 5001 Campus Drive, HFS 275, College Park, MD 20740, United States of America
| | - Shruti V Kabadi
- FDA/CFSAN/OFAS/DFCS, 5001 Campus Drive, HFS 275, College Park, MD 20740, United States of America
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21
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Heusinkveld H, Braakhuis H, Gommans R, Botham P, Corvaro M, van der Laan JW, Lewis D, Madia F, Manou I, Schorsch F, Wolterink G, Woutersen R, Corvi R, Mehta J, Luijten M. Towards a mechanism-based approach for the prediction of nongenotoxic carcinogenic potential of agrochemicals. Crit Rev Toxicol 2020; 50:725-739. [DOI: 10.1080/10408444.2020.1841732] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Harm Heusinkveld
- Centre for Health Protection, National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands
| | - Hedwig Braakhuis
- Centre for Health Protection, National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands
| | - Robin Gommans
- Centre for Health Protection, National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands
| | | | | | | | | | - Federica Madia
- European Commission, Joint Research Centre (JRC), Ispra, Italy
| | - Irene Manou
- European Partnership for Alternative Approaches to Animal Testing (EPAA), Brussels, Belgium
| | | | - Gerrit Wolterink
- Centre for Nutrition, Prevention and Health Services, National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands
| | - Ruud Woutersen
- TNO Quality of Life, Zeist, and Wageningen University & Research, Wageningen, the Netherlands
| | - Raffaella Corvi
- European Commission, Joint Research Centre (JRC), Ispra, Italy
| | | | - Mirjam Luijten
- Centre for Health Protection, National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands
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22
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Terry C, Yan Z, Corvaro M, Gehen SC. A retrospective study on EU harmonised classifications for carcinogenicity to guide future research. Regul Toxicol Pharmacol 2020; 119:104800. [PMID: 33129916 DOI: 10.1016/j.yrtph.2020.104800] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 08/05/2020] [Accepted: 10/05/2020] [Indexed: 12/26/2022]
Abstract
Under European Regulation (EC) No 1272/2008 on the classification, labelling and packaging of substances and mixtures (CLP), chemicals can be classified as carcinogenic if they are considered to induce tumours, increase tumour incidence and/or malignancy, or shorten the time to tumour occurrence. Cancer classifications are divided into different hazard categories: Carc. 1A (known human carcinogen), Carc. 1B (presumed human carcinogen), Carc. 2 (suspected human carcinogen), and chemicals not classified for carcinogenicity. Selecting which classification is appropriate can be challenging, as judgements need to be made both on the existing hazard data and on its relevance to humans. One aspect to be considered in defining human relevance is a chemical's mode of action (MoA); the series of necessary key events that lead from an exposure to the adverse effect (in this case, tumours). This work aims to identify and discuss some of the features that have led ECHA's Committee for Risk Assessment (RAC) to decide upon harmonised cancer classifications for chemicals, and to prioritise future research on MoA and/or human relevance. RAC bases its decisions on cancer classification on both the weight-of-evidence (WoE) and strength-of-evidence (SoE) of this particular activity. Multiple factors contribute, including the species in which tumours are seen, and the relevance of the MoA to human health.
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Affiliation(s)
- Claire Terry
- Corteva Agriscience, 9330 Zionsville Road, Indianapolis, IN, USA.
| | - Zhongyu Yan
- Corteva Agriscience, 9330 Zionsville Road, Indianapolis, IN, USA.
| | - Marco Corvaro
- Corteva Agriscience, 3B Milton Park Square, OX14 4RN, Abingdon, UK.
| | - Sean C Gehen
- Corteva Agriscience, 9330 Zionsville Road, Indianapolis, IN, USA.
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23
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Lewis RW, Hill T, Corton JC. A set of six Gene expression biomarkers and their thresholds identify rat liver tumorigens in short-term assays. Toxicology 2020; 443:152547. [PMID: 32755643 PMCID: PMC10439517 DOI: 10.1016/j.tox.2020.152547] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 07/23/2020] [Accepted: 07/28/2020] [Indexed: 02/01/2023]
Abstract
Traditional methods for cancer risk assessment are retrospective, resource-intensive, and not feasible for the vast majority of environmental chemicals. In earlier studies, we used a set of six biomarkers to accurately identify liver tumorigens in transcript profiles derived from chemically-treated rats using either a Toxicological Priority Index (ToxPi) approach or using derived biomarker thresholds for cancer. The biomarkers consisting of 7-113 genes are used to predict the most common liver cancer molecular initiating events: genotoxicity, cytotoxicity and activation of the xenobiotic receptors AhR, CAR, ER, and PPARα. In the present study, we apply and evaluate the performance of these methods for cancer prediction in an independent rat liver study of 44 chemicals (6 h-7d exposures) examined by Affymetrix arrays. In the first approach, ToxPi ranking of biomarker scores consistently gave the highest scores to tumorigenic chemical-dose pairs; balanced accuracies for identification of liver tumorigenic chemicals were up to 89 %. The second approach used tumorigenic thresholds derived in the present study or from our earlier study that were set at the maximum value for chemical-dose exposures without detectable liver tumor outcomes. Using these thresholds, balanced accuracies were up to 90 %. Both approaches identified all tumorigenic chemicals. Almost all of the tumorigenic chemicals activated more than one MIE. We also compared biomarker responses between two types of profiling platforms (Affymetrix full-genome array, TempO-Seq 1500+ array containing ∼2600 genes) and found that the lack of the full set of biomarker genes on the 1500+ array resulted in decreased ability to identify chemicals that activate the MIEs. Overall, these results demonstrate that predictive approaches based on the 6 biomarkers could be used in short-term assays to identify chemicals and their doses that induce liver tumors, the most common endpoint in rodent bioassays.
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Affiliation(s)
- Robert W Lewis
- Center for Computational Toxicology and Exposure, U.S. EPA, Research Triangle Park, NC, United States.
| | - Thomas Hill
- Center for Computational Toxicology and Exposure, U.S. EPA, Research Triangle Park, NC, United States; Oak Ridge Institute for Science and Education (ORISE) fellow Office of Research and Development, U.S. Environmental Protection Agency (EPA), Research Triangle Park, NC, United States.
| | - J Christopher Corton
- Center for Computational Toxicology and Exposure, U.S. EPA, Research Triangle Park, NC, United States.
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24
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Smith MT, Guyton KZ, Kleinstreuer N, Borrel A, Cardenas A, Chiu WA, Felsher DW, Gibbons CF, Goodson WH, Houck KA, Kane AB, La Merrill MA, Lebrec H, Lowe L, McHale CM, Minocherhomji S, Rieswijk L, Sandy MS, Sone H, Wang A, Zhang L, Zeise L, Fielden M. The Key Characteristics of Carcinogens: Relationship to the Hallmarks of Cancer, Relevant Biomarkers, and Assays to Measure Them. Cancer Epidemiol Biomarkers Prev 2020; 29:1887-1903. [PMID: 32152214 PMCID: PMC7483401 DOI: 10.1158/1055-9965.epi-19-1346] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 01/15/2020] [Accepted: 03/04/2020] [Indexed: 12/21/2022] Open
Abstract
The key characteristics (KC) of human carcinogens provide a uniform approach to evaluating mechanistic evidence in cancer hazard identification. Refinements to the approach were requested by organizations and individuals applying the KCs. We assembled an expert committee with knowledge of carcinogenesis and experience in applying the KCs in cancer hazard identification. We leveraged this expertise and examined the literature to more clearly describe each KC, identify current and emerging assays and in vivo biomarkers that can be used to measure them, and make recommendations for future assay development. We found that the KCs are clearly distinct from the Hallmarks of Cancer, that interrelationships among the KCs can be leveraged to strengthen the KC approach (and an understanding of environmental carcinogenesis), and that the KC approach is applicable to the systematic evaluation of a broad range of potential cancer hazards in vivo and in vitro We identified gaps in coverage of the KCs by current assays. Future efforts should expand the breadth, specificity, and sensitivity of validated assays and biomarkers that can measure the 10 KCs. Refinement of the KC approach will enhance and accelerate carcinogen identification, a first step in cancer prevention.See all articles in this CEBP Focus section, "Environmental Carcinogenesis: Pathways to Prevention."
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Affiliation(s)
- Martyn T Smith
- Division of Environmental Health Sciences, School of Public Health, University of California Berkeley, Berkeley, California.
| | - Kathryn Z Guyton
- Monographs Programme, International Agency for Research on Cancer, Lyon, France
| | - Nicole Kleinstreuer
- Division of Intramural Research, Biostatistics and Computational Biology Branch, National Institute of Environmental Health Sciences (NIEHS), Research Triangle Park, North Carolina
- National Toxicology Program Interagency Center for the Evaluation of Alternative Toxicological Methods, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina
| | - Alexandre Borrel
- Division of Intramural Research, Biostatistics and Computational Biology Branch, National Institute of Environmental Health Sciences (NIEHS), Research Triangle Park, North Carolina
| | - Andres Cardenas
- Division of Environmental Health Sciences, School of Public Health, University of California Berkeley, Berkeley, California
| | - Weihsueh A Chiu
- Veterinary Integrative Biosciences, Texas A&M University, College Station, Texas
| | - Dean W Felsher
- Division of Oncology, Departments of Medicine and Pathology, Stanford University School of Medicine, Stanford, California
| | - Catherine F Gibbons
- Office of Research and Development, US Environmental Protection Agency, Washington, D.C
| | - William H Goodson
- California Pacific Medical Center Research Institute, San Francisco, California
| | - Keith A Houck
- Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, North Carolina
| | - Agnes B Kane
- Department of Pathology and Laboratory Medicine, Alpert Medical School, Brown University, Providence, Rhode Island
| | - Michele A La Merrill
- Department of Environmental Toxicology, University of California, Davis, California
| | - Herve Lebrec
- Comparative Biology & Safety Sciences, Amgen Research, Amgen Inc., Thousand Oaks, California
| | - Leroy Lowe
- Getting to Know Cancer, Truro, Nova Scotia, Canada
| | - Cliona M McHale
- Division of Environmental Health Sciences, School of Public Health, University of California Berkeley, Berkeley, California
| | - Sheroy Minocherhomji
- Comparative Biology & Safety Sciences, Amgen Research, Amgen Inc., Thousand Oaks, California
| | - Linda Rieswijk
- Division of Environmental Health Sciences, School of Public Health, University of California Berkeley, Berkeley, California
- Institute of Data Science, Maastricht University, Maastricht, the Netherlands
| | - Martha S Sandy
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, California
| | - Hideko Sone
- Yokohama University of Pharmacy and National Institute for Environmental Studies, Tsukuba Ibaraki, Japan
| | - Amy Wang
- Office of the Report on Carcinogens, Division of National Toxicology Program, The National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina
| | - Luoping Zhang
- Division of Environmental Health Sciences, School of Public Health, University of California Berkeley, Berkeley, California
| | - Lauren Zeise
- Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, California
| | - Mark Fielden
- Expansion Therapeutics Inc, San Diego, California
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Corton JC, Hill T, Sutherland JJ, Stevens JL, Rooney J. A Set of Six Gene Expression Biomarkers Identify Rat Liver Tumorigens in Short-term Assays. Toxicol Sci 2020; 177:11-26. [PMID: 32603430 PMCID: PMC8026143 DOI: 10.1093/toxsci/kfaa101] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Chemical-induced liver cancer occurs in rodents through well-characterized adverse outcome pathways. We hypothesized that measurement of the 6 most common molecular initiating events (MIEs) in liver cancer adverse outcome pathways in short-term assays using only gene expression will allow early identification of chemicals and their associated doses that are likely to be tumorigenic in the liver in 2-year bioassays. We tested this hypothesis using transcript data from a rat liver microarray compendium consisting of 2013 comparisons of 146 chemicals administered at doses with previously established effects on rat liver tumor induction. Five MIEs were measured using previously characterized gene expression biomarkers composed of gene sets predictive for genotoxicity and activation of 1 or more xenobiotic receptors (aryl hydrocarbon receptor, constitutive activated receptor, estrogen receptor, and peroxisome proliferator-activated receptor α). Because chronic injury can be important in tumorigenesis, we also developed a biomarker for cytotoxicity that had a 96% balanced accuracy. Characterization of the genes in each biomarker set using the unsupervised TXG-MAP network model demonstrated that the genes were associated with distinct functional coexpression modules. Using the Toxicological Priority Index to rank chemicals based on their ability to activate the MIEs showed that chemicals administered at tumorigenic doses clearly gave the highest ranked scores. Balanced accuracies using thresholds derived from either TG-GATES or DrugMatrix data sets to predict tumorigenicity in independent sets of chemicals were up to 93%. These results show that a MIE-directed approach using only gene expression biomarkers could be used in short-term assays to identify chemicals and their doses that cause tumors.
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Affiliation(s)
- J Christopher Corton
- Center for Computational Toxicology and Exposure, U.S. Environmental Protection Agency (EPA), Research Triangle Park, North Carolina
| | - Thomas Hill
- Center for Computational Toxicology and Exposure, U.S. Environmental Protection Agency (EPA), Research Triangle Park, North Carolina
- Oak Ridge Institute for Science and Education (ORISE)
| | | | - James L Stevens
- Indiana Biosciences Research Institute, Indianapolis, Indiana
- Paradox Found LLC, Apex, North Carolina
| | - John Rooney
- Center for Computational Toxicology and Exposure, U.S. Environmental Protection Agency (EPA), Research Triangle Park, North Carolina
- Oak Ridge Institute for Science and Education (ORISE)
- Integrated Lab Services, Research Triangle Park, NC 27560
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26
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Huang SH, Lin YC, Tung CW. Identification of Time-Invariant Biomarkers for Non-Genotoxic Hepatocarcinogen Assessment. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2020; 17:ijerph17124298. [PMID: 32560183 PMCID: PMC7345770 DOI: 10.3390/ijerph17124298] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 06/12/2020] [Accepted: 06/14/2020] [Indexed: 12/12/2022]
Abstract
Non-genotoxic hepatocarcinogens (NGHCs) can only be confirmed by 2-year rodent studies. Toxicogenomics (TGx) approaches using gene expression profiles from short-term animal studies could enable early assessment of NGHCs. However, high variance in the modulation of the genes had been noted among exposure styles and datasets. Expanding from our previous strategy in identifying consensus biomarkers in multiple experiments, we aimed to identify time-invariant biomarkers for NGHCs in short-term exposure styles and validate their applicability to long-term exposure styles. In this study, nine time-invariant biomarkers, namely A2m, Akr7a3, Aqp7, Ca3, Cdc2a, Cdkn3, Cyp2c11, Ntf3, and Sds, were identified from four large-scale microarray datasets. Machine learning techniques were subsequently employed to assess the prediction performance of the biomarkers. The biomarker set along with the Random Forest models gave the highest median area under the receiver operating characteristic curve (AUC) of 0.824 and a low interquartile range (IQR) variance of 0.036 based on a leave-one-out cross-validation. The application of the models to the external validation datasets achieved high AUC values of greater than or equal to 0.857. Enrichment analysis of the biomarkers inferred the involvement of chronic inflammatory diseases such as liver cirrhosis, fibrosis, and hepatocellular carcinoma in NGHCs. The time-invariant biomarkers provided a robust alternative for NGHC prediction.
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Affiliation(s)
- Shan-Han Huang
- Ph. D. Program in Toxicology, Kaohsiung Medical University, Kaohsiung 80708, Taiwan; (S.-H.H.); (Y.-C.L.)
| | - Ying-Chi Lin
- Ph. D. Program in Toxicology, Kaohsiung Medical University, Kaohsiung 80708, Taiwan; (S.-H.H.); (Y.-C.L.)
- School of Pharmacy, College of Pharmacy, Kaohsiung Medical University, Kaohsiung 80708, Taiwan
- Research Center for Environmental Medicine, Kaohsiung Medical University, Kaohsiung 80708, Taiwan
| | - Chun-Wei Tung
- Graduate Institute of Data Science, College of Management, Taipei Medical University, Taipei 11031, Taiwan
- National Institute of Environmental Health Sciences, National Health Research Institutes, Miaoli County 35053, Taiwan
- Correspondence:
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27
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Felter SP, Llewelyn C, Navarro L, Zhang X. How the 62-year old Delaney Clause continues to thwart science: Case study of the flavor substance β-myrcene. Regul Toxicol Pharmacol 2020; 115:104708. [PMID: 32522581 DOI: 10.1016/j.yrtph.2020.104708] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Revised: 05/27/2020] [Accepted: 06/04/2020] [Indexed: 10/24/2022]
Abstract
The Delaney Clause is a provision of the 1958 Food Additive Amendment to the Food, Drug and Cosmetic Act of 1938 which stipulates that if a substance is found by the Food and Drug Administration to be carcinogenic in any species of animal or in humans, then it cannot be used as a food additive. This paper presents a case study of β-myrcene, one of seven synthetic substances that was challenged under the Delaney Clause, ultimately resulting in revocation of its regulatory approval as a food additive despite a lack of safety concern. While it is listed as a synthetic flavor in 21 CFR 172.515, β-myrcene is also a substance naturally occurring in a number of dietary plants. The exposure level to naturally-occurring β-myrcene is orders of magnitude higher (estimated to be 16,500 times greater) than the exposure via β-myrcene added to food as a flavoring substance. The National Toxicology Program conducted genotoxicity testing (negative), a 13-week range-finding study, and a two-year cancer bioassay in B6C3F1 mice and F344/N rats. An increase in liver tumors was seen in male mice and kidney tumors in male rats, ultimately resulting in β-myrcene being classified by IARC as a Class 2B carcinogen and being listed on California Proposition 65; in contrast, β-myrcene is not classified as a carcinogen by any other regulatory authority. The doses administered in the NTP bioassay were five-six orders of magnitude higher than human exposures, and the FDA concluded after a thorough evaluation that there was no safety concern associated with the use of β-myrcene as a flavor substance at the current use level. The Delaney Clause, however, does not consider the exposure potential or the human health relevance of effects observed in animals. The lack of options available to the US FDA led to the 2018 decision to remove β-myrcene from the list of approved food additives. This revocation has contributed to the ongoing erosion of trust in regulatory agencies (and industry), which has both economic implications for food manufacturers and consumers alike, and implications for consumer perception of safety of the US food supply. It is time for us to reconsider the rationale behind any legislation that relies on classification alone, and whether there is, in fact, a reason to still classify nongenotoxic carcinogens at all.
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Affiliation(s)
- Susan P Felter
- Procter & Gamble, Central Product Safety, Mason, OH, USA.
| | - Craig Llewelyn
- Toxicology Regulatory Services, Charlottesville, VA, USA
| | | | - Xiaoling Zhang
- Procter & Gamble, Central Product Safety, Mason, OH, USA
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Application of a combined aggregate exposure pathway and adverse outcome pathway (AEP-AOP) approach to inform a cumulative risk assessment: A case study with phthalates. Toxicol In Vitro 2020; 66:104855. [PMID: 32278033 DOI: 10.1016/j.tiv.2020.104855] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 03/26/2020] [Accepted: 04/05/2020] [Indexed: 12/20/2022]
Abstract
Advancements in measurement and modeling capabilities are providing unprecedented access to estimates of chemical exposure and bioactivity. With this influx of new data, there is a need for frameworks that help organize and disseminate information on chemical hazard and exposure in a manner that is accessible and transparent. A case study approach was used to demonstrate integration of the Adverse Outcome Pathway (AOP) and Aggregate Exposure Pathway (AEP) frameworks to support cumulative risk assessment of co-exposure to two phthalate esters that are ubiquitous in the environment and that are associated with disruption of male sexual development in the rat: di(2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DnBP). A putative AOP was developed to guide selection of an in vitro assay for derivation of bioactivity values for DEHP and DnBP and their metabolites. AEPs for DEHP and DnBP were used to extract key exposure data as inputs for a physiologically based pharmacokinetic (PBPK) model to predict internal metabolite concentrations. These metabolite concentrations were then combined using in vitro-based relative potency factors for comparison with an internal dose metric, resulting in an estimated margin of safety of ~13,000. This case study provides an adaptable workflow for integrating exposure and toxicity data by coupling AEP and AOP frameworks and using in vitro and in silico methodologies for cumulative risk assessment.
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29
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Rice PA, Aungst J, Cooper J, Bandele O, Kabadi SV. Comparative analysis of the toxicological databases for 6:2 fluorotelomer alcohol (6:2 FTOH) and perfluorohexanoic acid (PFHxA). Food Chem Toxicol 2020; 138:111210. [DOI: 10.1016/j.fct.2020.111210] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 02/14/2020] [Accepted: 02/16/2020] [Indexed: 12/30/2022]
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30
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Chappell GA, Thompson CM, Wolf JC, Cullen JM, Klaunig JE, Haws LC. Assessment of the Mode of Action Underlying the Effects of GenX in Mouse Liver and Implications for Assessing Human Health Risks. Toxicol Pathol 2020; 48:494-508. [PMID: 32138627 PMCID: PMC7153225 DOI: 10.1177/0192623320905803] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
GenX is an alternative to environmentally persistent long-chain perfluoroalkyl and polyfluoroalkyl substances. Mice exposed to GenX exhibit liver hypertrophy, elevated peroxisomal enzyme activity, and other apical endpoints consistent with peroxisome proliferators. To investigate the potential role of peroxisome proliferator-activated receptor alpha (PPARα) activation in mice, and other molecular signals potentially related to observed liver changes, RNA sequencing was conducted on paraffin-embedded liver sections from a 90-day subchronic toxicity study of GenX conducted in mice. Differentially expressed genes were identified for each treatment group, and gene set enrichment analysis was conducted using gene sets that represent biological processes and known canonical pathways. Peroxisome signaling and fatty acid metabolism were among the most significantly enriched gene sets in both sexes at 0.5 and 5 mg/kg GenX; no pathways were enriched at 0.1 mg/kg. Gene sets specific to the PPARα subtype were significantly enriched. These findings were phenotypically anchored to histopathological changes in the same tissue blocks: hypertrophy, mitoses, and apoptosis. In vitro PPARα transactivation assays indicated that GenX activates mouse PPARα. These results indicate that the liver changes observed in GenX-treated mice occur via a mode of action (MOA) involving PPARα, an important finding for human health risk assessment as this MOA has limited relevance to humans.
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Affiliation(s)
| | | | | | - John M. Cullen
- North Carolina State University College of Veterinary Medicine, Raleigh, NC, USA
| | - James E. Klaunig
- Indiana University, School of Public Health, Bloomington, IN, USA
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31
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Felter SP, Boobis AR, Botham PA, Brousse A, Greim H, Hollnagel HM, Sauer UG. Hazard identification, classification, and risk assessment of carcinogens: too much or too little? - Report of an ECETOC workshop. Crit Rev Toxicol 2020; 50:72-95. [PMID: 32133908 DOI: 10.1080/10408444.2020.1727843] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) organized a workshop "Hazard Identification, Classification and Risk Assessment of Carcinogens: Too Much or Too Little?" to explore the scientific limitations of the current binary carcinogenicity classification scheme that classifies substances as either carcinogenic or not. Classification is often based upon the rodent 2-year bioassay, which has scientific limitations and is not necessary to predict whether substances are likely human carcinogens. By contrast, tiered testing strategies founded on new approach methodologies (NAMs) followed by subchronic toxicity testing, as necessary, are useful to determine if a substance is likely carcinogenic, by which mode-of-action effects would occur and, for non-genotoxic carcinogens, the dose levels below which the key events leading to carcinogenicity are not affected. Importantly, the objective is not for NAMs to mimic high-dose effects recorded in vivo, as these are not relevant to human risk assessment. Carcinogenicity testing at the "maximum tolerated dose" does not reflect human exposure conditions, but causes major disturbances of homeostasis, which are very unlikely to occur at relevant human exposure levels. The evaluation of findings should consider biological relevance and not just statistical significance. Using this approach, safe exposures to non-genotoxic substances can be established.
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Affiliation(s)
| | | | | | - Alice Brousse
- European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC), Brussels, Belgium
| | | | | | - Ursula G Sauer
- Scientific Consultancy - Animal Welfare, Neubiberg, Germany
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32
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Schrenk D, Bignami M, Bodin L, Chipman JK, del Mazo J, Grasl‐Kraupp B, Hogstrand C, Hoogenboom L(R, Leblanc J, Nebbia CS, Ntzani E, Petersen A, Sand S, Schwerdtle T, Vleminckx C, Wallace H, Brüschweiler B, Leonards P, Rose M, Binaglia M, Horváth Z, Ramos Bordajandi L, Nielsen E. Risk assessment of chlorinated paraffins in feed and food. EFSA J 2020; 18:e05991. [PMID: 32874241 PMCID: PMC7447893 DOI: 10.2903/j.efsa.2020.5991] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The European Commission asked EFSA for a scientific opinion on the risks for animal and human health related to the presence of chlorinated paraffins in feed and food. The data for experimental animals were reviewed and the CONTAM Panel identified the liver, kidney and thyroid as the target organs for the SCCP and MCCP mixtures tested in repeated dose toxicity studies. Decreased pup survival and subcutaneous haematoma/haemorrhage were also identified as critical effects for an MCCP mixture. For the LCCP mixtures tested, the liver was identified as the target organ. The Panel selected as reference points a BMDL 10 of 2.3 mg/kg bw per day for increased incidence of nephritis in male rats, and of 36 mg/kg bw per day for increased relative kidney weights in male and female rats for SCCPs and MCCPs, respectively. For LCCPs, a reference point relevant for humans could not be identified. Due to the limitations in the toxicokinetic and toxicological database, the Panel concluded that derivation of a health-based guidance value was not appropriate. Only limited data on the occurrence of SCCPs and MCCPs in some fish species were submitted to EFSA. No data were submitted for LCCPs. Thus, a robust exposure assessment and consequently a complete risk characterisation could not be performed. A preliminary risk characterisation based only on the consumption of fish was performed, and the calculated margins of exposure suggested no health concern for this limited scenario. The Panel noted that dietary exposure will be higher due to the contribution of CPs from other foods. The Panel was not able to identify reference points for farm animals, horses and companion animals. No occurrence data for feed were submitted to EFSA. Therefore, no risk characterisation could be performed for any of these animal species.
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33
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Klaunig JE, Melo L, Tilmant K. Mechanisms of hepatic cancer by persistent organic pollutants. CURRENT OPINION IN TOXICOLOGY 2020. [DOI: 10.1016/j.cotox.2020.02.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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34
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Dekant W. Tetrahydrofuran-induced tumors in rodents are not relevant to humans: Quantitative weight of evidence analysis of mode of action information does not support classification of tetrahydrofuran as a possible human carcinogen. Regul Toxicol Pharmacol 2019; 109:104499. [DOI: 10.1016/j.yrtph.2019.104499] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 10/11/2019] [Accepted: 10/12/2019] [Indexed: 02/05/2023]
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35
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The use of evidence from high-throughput screening and transcriptomic data in human health risk assessments. Toxicol Appl Pharmacol 2019; 380:114706. [DOI: 10.1016/j.taap.2019.114706] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 07/31/2019] [Accepted: 08/06/2019] [Indexed: 12/23/2022]
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36
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Plummer S, Beaumont B, Wallace S, Ball G, Wright J, McInnes L, Currie R, Peffer R, Cowie D. Cross-species comparison of CAR-mediated procarcinogenic key events in a 3D liver microtissue model. Toxicol Rep 2019; 6:998-1005. [PMID: 31673501 PMCID: PMC6816142 DOI: 10.1016/j.toxrep.2019.09.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 09/19/2019] [Accepted: 09/23/2019] [Indexed: 12/25/2022] Open
Abstract
Characterisation of the mode of action (MOA) of constitutive androstane receptor (CAR)-mediated rodent liver tumours involves measurement 5 key events including activation of the CAR receptor, altered gene expression, hepatocellular proliferation, clonal expansion and increased hepatocellular adenomas/carcinomas. To test whether or not liver 3D microtissues (LiMTs) recapitulate CAR- mediated procarcinogenic key events in response to the prototypical CAR activator phenobarbital (PB) we performed hepatocyte proliferation (LI%) analysis in rat and human LiMTs using a microTMA technology in conjunction with integrated transcriptomics (microarray) and proteomics analysis. The rationale for this approach was that LiMTs containing parenchymal and non-parenchymal cells (NPCs) are more physiologically representative of liver and thus would generate data more relevant to the in vivo situation. Rat and human LiMTs were treated with PB over a range of concentrations (500 uM - 2000 uM) and times (24 h - 96 h) in a dose-response/time-course analysis. There was a dose-dependent induction of LI% in rat LiMTs, however there was little or no effect of PB on LI% in human LiMTs. ATP levels in the rat and human LiMTs were similar to control in all of the PB treatments. There was also a dose- and time-dependent PB-mediated RNA induction of CAR regulated genes CYP2B6/Cyp2b2, CYP3A7/Cyp3a9 and UGT1A6/Ugt1a6 in human and rat LiMTs, respectively. These CAR regulated genes were also upregulated at the protein level. Ingenuity pathways analysis (IPA) indicated that there was a significant (Z score >2.0;-log p value >) activation of CAR by PB in both human and rat LiMTs. These results indicate that human and rat LiMTs showed the expected responses at the level of PB-induced hepatocyte proliferation and enzyme induction with rat LiMTs showing significant dose-dependent effects while human LiMTs showed no proliferation response but did show dose-dependent enzyme induction at the RNA and protein levels. In conclusion LiMTs serve as a model to provide mechanistic data for 3 of the 5 key events considered necessary to establish a CAR-mediated MOA for liver tumourigenesis and thus can potentially reduce the use of animals when compiling mechanistic data packages.
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Affiliation(s)
| | | | | | - Graeme Ball
- Dundee University Imaging Facility, Dundee, UK
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37
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Yamada T, Asano H, Miyata K, Rhomberg LR, Haseman JK, Greaves P, Greim H, Berry C, Cohen SM. Toxicological evaluation of carcinogenicity of the pyrethroid imiprothrin in rats and mice. Regul Toxicol Pharmacol 2019; 105:1-14. [DOI: 10.1016/j.yrtph.2019.03.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 03/09/2019] [Accepted: 03/17/2019] [Indexed: 01/07/2023]
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38
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Thompson CM, Fitch SE, Ring C, Rish W, Cullen JM, Haws LC. Development of an oral reference dose for the perfluorinated compound GenX. J Appl Toxicol 2019; 39:1267-1282. [PMID: 31215065 PMCID: PMC6771874 DOI: 10.1002/jat.3812] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 03/29/2019] [Accepted: 03/30/2019] [Indexed: 12/12/2022]
Abstract
Ammonium 2,3,3,3‐tetrafluoro‐2‐(heptafluoropropoxy)‐propanoate, also known as GenX, is a processing aid used in the manufacture of fluoropolymers. GenX is one of several chemistries developed as an alternative to long‐chain poly‐fluoroalkyl substances, which tend to have long clearance half‐lives and are environmentally persistent. Unlike poly‐fluoroalkyl substances, GenX has more rapid clearance, but has been detected in US and international water sources. There are currently no federal drinking water standards for GenX in the USA; therefore, we developed a non‐cancer oral reference dose (RfD) for GenX based on available repeated dose studies. The review of the available data indicate that GenX is unlikely to be genotoxic. A combination of traditional frequentist benchmark dose models and Bayesian benchmark dose models were used derive relevant points of departure from mammalian toxicity studies. In addition, deterministic and probabilistic RfD values were developed using available tools and regulatory guidance. The two approaches resulted in a narrow range of RfD values for liver lesions observed in a 2‐year bioassay in rats (0.01–0.02 mg/kg/day). The probabilistic approach resulted in the lower, i.e., more conservative RfD. The probabilistic RfD of 0.01 mg/kg/day results in a maximum contaminant level goal of 70 ppb. It is anticipated that these values, along with the hazard identification and dose‐response modeling described herein, should be informative for risk assessors and regulators interested in setting health‐protective drinking water guideline values for GenX. Ammonium 2,3,3,3‐tetrafluoro‐2‐(heptafluoropropoxy)‐propanoate, also known as GenX, is a processing aid used in the manufacture of fluoropolymers. There are currently no federal drinking water standards for GenX in the USA. Frequentist benchmark dose models and Bayesian benchmark dose models were used to derive points of departure from mammalian toxicity studies. Deterministic and probabilistic reference dose values were developed and resulted in a narrow range of values (0.01‐0.02 mg/kg/day). The lower reference dose results in a maximum contaminant level goal of 70 ppb.
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Affiliation(s)
| | | | | | | | - John M Cullen
- College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina
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39
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Quist EM, Boorman GA, Cullen JM, Maronpot RR, Remick AK, Swenberg JA, Freshwater L, Hardisty JF. Reevaluation of Hepatocellular Neoplasms in CD-1 Mice from a 2-year Oral Carcinogenicity Study with Permethrin. Toxicol Pathol 2018; 47:11-17. [DOI: 10.1177/0192623318809304] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
A 24-month oral carcinogenicity study of permethrin was conducted by feeding male and female CD-1 mice diets containing concentrations of 0, 20, 500, and 2,000 ppm of permethrin (males) or 0, 20, 2,500, and 5,000 ppm of permethrin (females). After approximately two years on study, surviving mice were sacrificed for the evaluation of chronic toxicity and/or carcinogenicity. An expert panel of pathologists was convened as a Pathology Working Group (PWG) to review coded liver histology sections from male and female mice and to classify all liver neoplasms according to current nomenclature and diagnostic criteria guidelines. The PWG results indicate that permethrin induced a significant dose-dependent increase in the incidence of hepatocellular neoplasms in treated female mice ( p < .01) as well as a nonstatistically significant increase in the incidence of hepatocellular tumors in treated male mice. Given the continuum of the diagnoses of adenoma and carcinoma, and the difficulty in distinguishing some of the lesions, it is appropriate to consider only the combined incidences of hepatocellular tumors (adenoma and/or carcinoma) for biological significance and risk assessment.
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Affiliation(s)
- Erin M. Quist
- Experimental Pathology Laboratories, Inc., Research Triangle Park, North Carolina, USA
| | | | - John M. Cullen
- North Carolina State University, Raleigh, North Carolina, USA
| | | | - Amera K. Remick
- Charles River Laboratories, Inc., Durham, North Carolina, USA
| | | | | | - Jerry F. Hardisty
- Experimental Pathology Laboratories, Inc., Research Triangle Park, North Carolina, USA
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40
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Rooney J, Hill T, Qin C, Sistare FD, Corton JC. Adverse outcome pathway-driven identification of rat liver tumorigens in short-term assays. Toxicol Appl Pharmacol 2018; 356:99-113. [DOI: 10.1016/j.taap.2018.07.023] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 07/12/2018] [Accepted: 07/20/2018] [Indexed: 02/07/2023]
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41
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Yamada T. Case examples of an evaluation of the human relevance of the pyrethroids/pyrethrins-induced liver tumours in rodents based on the mode of action. Toxicol Res (Camb) 2018; 7:681-696. [PMID: 30090614 PMCID: PMC6062351 DOI: 10.1039/c7tx00288b] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 01/10/2018] [Indexed: 01/01/2023] Open
Abstract
Rodent carcinogenicity studies are useful for screening for human carcinogens but they are not perfect. Some modes of action (MOAs) lead to cancers in both experimental rodents and humans, but others that lead to cancers in rodents do not do so in humans. Therefore, analysing the MOAs by which chemicals produce tumours in rodents and determining the relevance of such tumour data for human risk are critical. Recently, experimental data were obtained as case examples of an evaluation of the human relevance of pyrethroid (metofluthrin and momfluorothrin)- and pyrethrins-induced liver tumours in rats based on MOA. The MOA analysis, based on the International Programme on Chemical Safety (IPCS) framework, concluded that experimental data strongly support that the postulated MOA for metofluthrin-, momfluorothrin- and pyrethrins-produced rat hepatocellular tumours is mediated by constitutive androstane receptor (CAR) activation. Since metofluthrin and momfluorothrin are close structural analogues, reproducible outcomes for both chemicals provide confidence in the MOA findings. Furthermore, cultured human hepatocyte studies and humanized chimeric mouse liver studies demonstrated species difference between human hepatocytes (refractory to the mitogenic effects of these compounds) and rat hepatocytes (sensitive to their mitogenic effects). These data strongly support the hypothesis that the CAR-mediated MOA for liver tumorigenesis is of low carcinogenic risk for humans. In this research, in addition to cultured human hepatocyte studies, the usefulness of the humanized chimeric liver mouse models was clearly demonstrated. These data substantially influenced decisions in regulatory toxicology. In this review I comprehensively discuss the human relevance of the CAR-mediated MOA for rodent liver tumorigenesis based on published information, including our recent molecular research on CAR-mediated MOA.
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Affiliation(s)
- Tomoya Yamada
- Environmental Health Science Laboratory , Sumitomo Chemical Co. , Ltd , 1-98 , 3-Chome , Kasugade-Naka , Konohana-ku , Osaka 554-8558 , Japan . ; ; Tel: +81-66466-5322
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Strupp C, Bomann WH, Spézia F, Gervais F, Forster R, Richert L, Singh P. A human relevance investigation of PPARα-mediated key events in the hepatocarcinogenic mode of action of propaquizafop in rats. Regul Toxicol Pharmacol 2018; 95:348-361. [DOI: 10.1016/j.yrtph.2018.04.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Revised: 03/12/2018] [Accepted: 04/03/2018] [Indexed: 10/17/2022]
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Hakkola J, Bernasconi C, Coecke S, Richert L, Andersson TB, Pelkonen O. Cytochrome P450 Induction and Xeno-Sensing Receptors Pregnane X Receptor, Constitutive Androstane Receptor, Aryl Hydrocarbon Receptor and Peroxisome Proliferator-Activated Receptor α at the Crossroads of Toxicokinetics and Toxicodynamics. Basic Clin Pharmacol Toxicol 2018. [DOI: 10.1111/bcpt.13004] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Jukka Hakkola
- Research Unit of Biomedicine, Pharmacology and Toxicology; Faculty of Medicine; University of Oulu; Oulu Finland
- Medical Research Center Oulu; University of Oulu; Oulu Finland
| | | | - Sandra Coecke
- European Commission Joint Research Centre; EURL ECVAM; Ispra Italy
| | | | - Tommy B. Andersson
- Drug Metabolism and Pharmacokinetics; Cardiovascular and Metabolic Diseases; IMED Biotech Unit; AstraZeneca; Gothenburg Sweden
- Department of Physiology and Pharmacology; Section of Pharmacogenetics; Karolinska Institutet; Stockholm Sweden
| | - Olavi Pelkonen
- Research Unit of Biomedicine, Pharmacology and Toxicology; Faculty of Medicine; University of Oulu; Oulu Finland
- Medical Research Center Oulu; University of Oulu; Oulu Finland
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Plummer SM, Wright J, Currie RA. Dose-dependent effects on rat liver miRNAs 200a/b and 429: potential early biomarkers of liver carcinogenesis. Toxicol Rep 2018; 5:309-313. [PMID: 29556478 PMCID: PMC5856664 DOI: 10.1016/j.toxrep.2018.02.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Revised: 02/09/2018] [Accepted: 02/14/2018] [Indexed: 11/29/2022] Open
Abstract
An increased incidence of liver tumours in the long term rodent bioassay is not an uncommon finding, invariably as a result of a non-genotoxic mode of action. Non-genotoxic liver carcinogenesis has been found to involve activation of certain nuclear hormone receptors (NHR) including the constitutive androstane receptor (CAR), peroxisome proliferator activated receptor alpha (PPARalpha) and arylhydrocarbon receptor (AHR) and more recently the induction of specific microRNAs (miRs), has also been demonstrated following CAR activation in studies up to 90 days (Koufaris et al., 2012). The stable induction of these tissue specific miRs, namely miR200a, 200b and 429, by liver non-genotoxic carcinogens may serve as early predictors (biomarkers) of heptocarcinogenic potential. To test this hypothesis we used RT-PCR to measure the levels of these miRs in the livers from Wistar rats treated with two rat hepatocarcinogenic and one non hepatocarcinogenic pyrazole carboxamide succinate dehydrogenase inhibitors, Isopyrazam, Sedaxane and Benzovindiflupyr, respectively. The miRs were quantified by RT-PCR in liver RNA samples from three 90 day repeat dose toxicity studies performed at the low, mid and high doses relative to control. In Isopyrazam treated rats a statistically significant (p < 0.01) dose-dependent increase in miR 200a, 220b and 429 in both males and females was observed, whilst for Sedaxane a significant (p < 0.05) increase in miR200b in males and females at the high dose was seen. Benzovindiflupyr treatment did not cause any dose related changes in miR 200a, 200b and 429 relative to control. Our results suggest that assessment of miR 200a/200b/429 levels has potential as a biomarker of the perturbation of pathways involved in hepatocarcinogenesis in Wistar rats. Further work is required to establish the possible relationship between miR200 cluster induction and CAR-mediated hepatocarcinogenesis in a more diverse range of compounds.
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Affiliation(s)
| | - J Wright
- MicroMatrices Associates Ltd, Dundee, UK
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