1
|
Högberg J, Järnberg J. Approaches for the setting of occupational exposure limits (OELs) for carcinogens. Crit Rev Toxicol 2023:1-37. [PMID: 37366107 DOI: 10.1080/10408444.2023.2218887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 05/12/2023] [Accepted: 05/22/2023] [Indexed: 06/28/2023]
Abstract
This article addresses issues of importance for occupational exposure limits (OELs) and chemical carcinogens with a focus on non-threshold carcinogens. It comprises scientific as well as regulatory issues. It is an overview, not a comprehensive review. A central topic is mechanistic research and insights, and its implications for cancer risk assessment. Alongside scientific advancements, the approaches of hazard identification and qualitative and quantitative risk assessment have developed over the years. The key steps in a quantitative risk assessment are outlined, with special attention given to the dose-response assessment and the derivation of an OEL using risk calculations or default assessment factors. The work procedures of several bodies performing cancer hazard identifications and quantitative risk assessments, as well as regulatory procedures to derive OELs for non-threshold carcinogens, are presented. Non-threshold carcinogens for which the European Union (EU) introduced binding OELs in 2017-2019 serve as illustrations together with some currently used strategies in the EU and elsewhere. Available knowledge supports the derivation of health-based OELs (Hb-OELs) for non-threshold carcinogens, and the use of a risk-based approach with low-dose linear extrapolation (linear non-threshold, LNT) as the default for non-threshold carcinogens. However, there is a need to develop methods that allow recent years' advances in cancer research to be used for improving risk estimates. It is recommended that defined risk levels (terminology and numerical values) are harmonised, and that both collective and individual risks are considered and clearly communicated. Socioeconomic aspects should be dealt with transparently and separated from the scientific health risk assessment.
Collapse
Affiliation(s)
- Johan Högberg
- Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | | |
Collapse
|
2
|
Veltman CHJ, Pennings JLA, van de Water B, Luijten M. An Adverse Outcome Pathway Network for Chemically Induced Oxidative Stress Leading to (Non)genotoxic Carcinogenesis. Chem Res Toxicol 2023. [PMID: 37156502 DOI: 10.1021/acs.chemrestox.2c00396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Nongenotoxic (NGTX) carcinogens induce cancer via other mechanisms than direct DNA damage. A recognized mode of action for NGTX carcinogens is induction of oxidative stress, a state in which the amount of oxidants in a cell exceeds its antioxidant capacity, leading to regenerative proliferation. Currently, carcinogenicity assessment of environmental chemicals primarily relies on genetic toxicity end points. Since NGTX carcinogens lack genotoxic potential, these chemicals may remain undetected in such evaluations. To enhance the predictivity of test strategies for carcinogenicity assessment, a shift toward mechanism-based approaches is required. Here, we present an adverse outcome pathway (AOP) network for chemically induced oxidative stress leading to (NGTX) carcinogenesis. To develop this AOP network, we first investigated the role of oxidative stress in the various cancer hallmarks. Next, possible mechanisms for chemical induction of oxidative stress and the biological effects of oxidative damage to macromolecules were considered. This resulted in an AOP network, of which associated uncertainties were explored. Ultimately, development of AOP networks relevant for carcinogenesis in humans will aid the transition to a mechanism-based, human relevant carcinogenicity assessment that involves a substantially lower number of laboratory animals.
Collapse
Affiliation(s)
- Christina H J Veltman
- Centre for Health Protection, National Institute for Public Health and the Environment (RIVM), 3720 BA Bilthoven, The Netherlands
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research (LACDR), Leiden University, 2333 CC Leiden, The Netherlands
| | - Jeroen L A Pennings
- Centre for Health Protection, National Institute for Public Health and the Environment (RIVM), 3720 BA Bilthoven, The Netherlands
| | - Bob van de Water
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research (LACDR), Leiden University, 2333 CC Leiden, The Netherlands
| | - Mirjam Luijten
- Centre for Health Protection, National Institute for Public Health and the Environment (RIVM), 3720 BA Bilthoven, The Netherlands
| |
Collapse
|
3
|
Spencer PS, Palmer VS, Kisby GE, Lagrange E, Horowitz BZ, Valdes Angues R, Reis J, Vernoux JP, Raoul C, Camu W. Early-onset, conjugal, twin-discordant, and clusters of sporadic ALS: Pathway to discovery of etiology via lifetime exposome research. Front Neurosci 2023; 17:1005096. [PMID: 36860617 PMCID: PMC9969898 DOI: 10.3389/fnins.2023.1005096] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Accepted: 01/09/2023] [Indexed: 02/17/2023] Open
Abstract
The identity and role of environmental factors in the etiology of sporadic amyotrophic lateral sclerosis (sALS) is poorly understood outside of three former high-incidence foci of Western Pacific ALS and a hotspot of sALS in the French Alps. In both instances, there is a strong association with exposure to DNA-damaging (genotoxic) chemicals years or decades prior to clinical onset of motor neuron disease. In light of this recent understanding, we discuss published geographic clusters of ALS, conjugal cases, single-affected twins, and young-onset cases in relation to their demographic, geographic and environmental associations but also whether, in theory, there was the possibility of exposure to genotoxic chemicals of natural or synthetic origin. Special opportunities to test for such exposures in sALS exist in southeast France, northwest Italy, Finland, the U.S. East North Central States, and in the U.S. Air Force and Space Force. Given the degree and timing of exposure to an environmental trigger of ALS may be related to the age at which the disease is expressed, research should focus on the lifetime exposome (from conception to clinical onset) of young sALS cases. Multidisciplinary research of this type may lead to the identification of ALS causation, mechanism, and primary prevention, as well as to early detection of impending ALS and pre-clinical treatment to slow development of this fatal neurological disease.
Collapse
Affiliation(s)
- Peter S. Spencer
- Department of Neurology, School of Medicine, Oregon Health and Science University, Portland, OR, United States,Oregon Institute of Occupational Health Sciences, Oregon Health and Science University, Portland, OR, United States,*Correspondence: Peter S. Spencer,
| | - Valerie S. Palmer
- Department of Neurology, School of Medicine, Oregon Health and Science University, Portland, OR, United States
| | - Glen E. Kisby
- College of Osteopathic Medicine of the Pacific Northwest, Western University of Health Sciences, Lebanon, OR, United States
| | - Emmeline Lagrange
- Department of Neurology, Reference Center of Neuromuscular Disease and ALS Consultations, Grenoble University Hospital, Grenoble, France
| | - B. Zane Horowitz
- Department of Emergency Medicine, Oregon-Alaska Poison Center, Oregon Health and Science University, Portland, OR, United States
| | - Raquel Valdes Angues
- Department of Neurology, School of Medicine, Oregon Health and Science University, Portland, OR, United States
| | - Jacques Reis
- University of Strasbourg, Faculté de Médecine, Strasbourg, France
| | - Jean-Paul Vernoux
- Normandie Université, UNICAEN, Unité de Recherche Aliments Bioprocédés Toxicologie Environnements, Caen, France
| | - Cédric Raoul
- INM, University of Montpellier, INSERM, Montpellier, France
| | - William Camu
- ALS Reference Center, Montpellier University Hospital and University of Montpellier, INSERM, Montpellier, France
| |
Collapse
|
4
|
Spencer PS, Kisby GE. Role of Hydrazine-Related Chemicals in Cancer and Neurodegenerative Disease. Chem Res Toxicol 2021; 34:1953-1969. [PMID: 34379394 DOI: 10.1021/acs.chemrestox.1c00150] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Hydrazine-related chemicals (HRCs) with carcinogenic and neurotoxic potential are found in certain mushrooms and plants used for food and in products employed in various industries, including aerospace. Their propensity to induce DNA damage (mostly O6-, N7- and 8-oxo-guanine lesions) resulting in multiple downstream effects is linked with both cancer and neurological disease. For cycling cells, unrepaired DNA damage leads to mutation and uncontrolled mitosis. By contrast, postmitotic neurons attempt to re-enter the cell cycle but undergo apoptosis or nonapoptotic cell death. Biomarkers of exposure to HRCs can be used to explore whether these substances are risk factors for sporadic amyotrophic laterals sclerosis and other noninherited neurodegenerative diseases, which is the focus of this paper.
Collapse
Affiliation(s)
- Peter S Spencer
- Oregon Health and Science University, Portland, Oregon 97239, United States
| | - Glen E Kisby
- College of Osteopathic Medicine of the Pacific Northwest, Western University of Health Sciences, Lebanon, Oregon 97355, United States
| |
Collapse
|
5
|
Lai C, Wu F, Wang Y, Wang W, Li Y, Zhang G, Gao J, Zhu Z, Yuan J, Yang J, Zhang W. Specific epigenetic microenvironment and the regulation of tumor-related gene expression by trichloroethylene in human hepatocytes. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2021; 208:111453. [PMID: 33068984 DOI: 10.1016/j.ecoenv.2020.111453] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 09/29/2020] [Accepted: 09/30/2020] [Indexed: 06/11/2023]
Abstract
Trichloroethylene (TCE), an important volatile organic solvent, causes a series of toxic damage to human. Conventional genetic mechanisms cannot fully explain its toxicity and carcinogenicity, indicative of the possible involvement of epigenetic mechanisms. Our study was intended to investigate the epigenetic toxicity and underlying mechanisms of TCE. Data showed that 0.3 mM TCE treatment for 24 h increased the growth of L-02 cells transiently. In contrast, subacute exposure to TCE inhibited cell growth and induced the genomic DNA hypomethylation and histone hyperacetylation. Further studies have revealed the TCE-induced DNA hypomethylation in the promoter regions of tumor-related genes, N-Ras, c-Jun, c-Myc, c-Fos and IGF-II, promoting their protein levels in a time-dependent manner. These results reveal there is a negative relationship existing between DNA hypomethylation and protein expression in tumor-related gene after TCE exposure under specific epigenetic microenvironment, serving as early biomarkers for TCE-associated diseases.
Collapse
Affiliation(s)
- Caiyun Lai
- Department of Public Health and Preventive Medicine, School of Medicine, Jinan University, Guangzhou, Guangdong 510632, PR China
| | - Fan Wu
- Department of Public Health and Preventive Medicine, School of Medicine, Jinan University, Guangzhou, Guangdong 510632, PR China
| | - Yan Wang
- Department of Public Health and Preventive Medicine, School of Medicine, Jinan University, Guangzhou, Guangdong 510632, PR China
| | - Wei Wang
- Department of Occupational Health and Occupational Diseases, College of Public Health, Zhengzhou University, Zhengzhou, Henan 450001, PR China
| | - Yueqi Li
- Department of Public Health and Preventive Medicine, School of Medicine, Jinan University, Guangzhou, Guangdong 510632, PR China
| | - Gaoqiang Zhang
- Department of Public Health and Preventive Medicine, School of Medicine, Jinan University, Guangzhou, Guangdong 510632, PR China
| | - Jianji Gao
- Department of Public Health and Preventive Medicine, School of Medicine, Jinan University, Guangzhou, Guangdong 510632, PR China
| | - Zhiliang Zhu
- Baoan District Center for Disease Control and Prevention, Shenzhen, Guangdong 518101, PR China
| | - Jianhui Yuan
- Nanshan District Center for Disease Control and Prevention, Shenzhen, Guangdong 518054, PR China
| | - Jianping Yang
- Shenzhen Taike Test Co., Ltd, Shenzhen, Guangdong 518053, PR China.
| | - Wenjuan Zhang
- Department of Public Health and Preventive Medicine, School of Medicine, Jinan University, Guangzhou, Guangdong 510632, PR China.
| |
Collapse
|
6
|
Jeremias G, Gonçalves FJM, Pereira JL, Asselman J. Prospects for incorporation of epigenetic biomarkers in human health and environmental risk assessment of chemicals. Biol Rev Camb Philos Soc 2020; 95:822-846. [PMID: 32045110 DOI: 10.1111/brv.12589] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 01/28/2020] [Accepted: 01/30/2020] [Indexed: 12/18/2022]
Abstract
Epigenetic mechanisms have gained relevance in human health and environmental studies, due to their pivotal role in disease, gene × environment interactions and adaptation to environmental change and/or contamination. Epigenetic mechanisms are highly responsive to external stimuli and a wide range of chemicals has been shown to determine specific epigenetic patterns in several organisms. Furthermore, the mitotic/meiotic inheritance of such epigenetic marks as well as the resulting changes in gene expression and cell/organismal phenotypes has now been demonstrated. Therefore, epigenetic signatures are interesting candidates for linking environmental exposures to disease as well as informing on past exposures to stressors. Accordingly, epigenetic biomarkers could be useful tools in both prospective and retrospective risk assessment but epigenetic endpoints are currently not yet incorporated into risk assessments. Achieving a better understanding on this apparent impasse, as well as identifying routes to promote the application of epigenetic biomarkers within environmental risk assessment frameworks are the objectives of this review. We first compile evidence from human health studies supporting the use of epigenetic exposure-associated changes as reliable biomarkers of exposure. Then, specifically focusing on environmental science, we examine the potential and challenges of developing epigenetic biomarkers for environmental fields, and discuss useful organisms and appropriate sequencing techniques to foster their development in this context. Finally, we discuss the practical incorporation of epigenetic biomarkers in the environmental risk assessment of chemicals, highlighting critical data gaps and making key recommendations for future research within a regulatory context.
Collapse
Affiliation(s)
- Guilherme Jeremias
- Department of Biology, University of Aveiro, 3810-193, Aveiro, Portugal.,CESAM - Centre for Environmental and Marine Studies, University of Aveiro, 3810-193, Aveiro, Portugal
| | - Fernando J M Gonçalves
- Department of Biology, University of Aveiro, 3810-193, Aveiro, Portugal.,CESAM - Centre for Environmental and Marine Studies, University of Aveiro, 3810-193, Aveiro, Portugal
| | - Joana L Pereira
- Department of Biology, University of Aveiro, 3810-193, Aveiro, Portugal.,CESAM - Centre for Environmental and Marine Studies, University of Aveiro, 3810-193, Aveiro, Portugal
| | - Jana Asselman
- Laboratory of Environmental Toxicology and Aquatic Ecology, Environmental Toxicology Unit - GhEnToxLab, Ghent University, 9000, Gent, Belgium
| |
Collapse
|
7
|
Krewski D, Andersen ME, Tyshenko MG, Krishnan K, Hartung T, Boekelheide K, Wambaugh JF, Jones D, Whelan M, Thomas R, Yauk C, Barton-Maclaren T, Cote I. Toxicity testing in the 21st century: progress in the past decade and future perspectives. Arch Toxicol 2019; 94:1-58. [DOI: 10.1007/s00204-019-02613-4] [Citation(s) in RCA: 124] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Accepted: 11/05/2019] [Indexed: 12/19/2022]
|
8
|
Tryndyak V, Borowa-Mazgaj B, Beland FA, Pogribny IP. Gene expression and cytosine DNA methylation alterations in induced pluripotent stem-cell-derived human hepatocytes treated with low doses of chemical carcinogens. Arch Toxicol 2019; 93:3335-3344. [PMID: 31555880 DOI: 10.1007/s00204-019-02569-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 09/04/2019] [Indexed: 12/15/2022]
Abstract
The increasing number of man-made chemicals in the environment that may pose a carcinogenic risk emphasizes the need to develop reliable time- and cost-effective approaches for carcinogen detection. To address this issue, we have investigated the utility of human hepatocytes for the in vitro identification of genotoxic and non-genotoxic carcinogens. Induced pluripotent stem-cell (iPSC)-derived human hepatocytes were treated with the genotoxic carcinogens aflatoxin B1 (AFB1) and benzo[a]pyrene (B[a]P), the non-genotoxic liver carcinogen methapyrilene, and the non-carcinogens aflatoxin B2 (AFB2) and benzo[e]pyrene (B[e]P) at non-cytotoxic concentrations for 7 days, and transcriptomic and DNA methylation profiles were examined. 1569, 1693, and 2061 differentially expressed genes (DEGs) were detected in cells treated with AFB1, B[a]P, and methapyrilene, respectively, whereas no DEGs were found in cells treated with AFB2 or B[e]P. In contrast to the profound cellular transcriptomic responses, exposure of iPSC-derived hepatocytes to the test chemicals resulted in minor random alterations in global DNA methylome, most of which were not associated with changes in gene expression. Overall, our results demonstrate that the major non-genotoxic effect of exposure to carcinogens, regardless of their mode of action, is a profound global transcriptomic response rather than global DNA methylome alterations, indicating the significance of transcriptomic alterations as an informative endpoint in short-term in vitro carcinogen testing.
Collapse
Affiliation(s)
- Volodymyr Tryndyak
- Division of Biochemical Toxicology, FDA-National Center for Toxicological Research, Jefferson, AR, USA
| | - Barbara Borowa-Mazgaj
- Division of Biochemical Toxicology, FDA-National Center for Toxicological Research, Jefferson, AR, USA
| | - Frederick A Beland
- Division of Biochemical Toxicology, FDA-National Center for Toxicological Research, Jefferson, AR, USA
| | - Igor P Pogribny
- Division of Biochemical Toxicology, FDA-National Center for Toxicological Research, Jefferson, AR, USA.
| |
Collapse
|
9
|
Schmitz-Spanke S. Toxicogenomics - What added Value Do These Approaches Provide for Carcinogen Risk Assessment? ENVIRONMENTAL RESEARCH 2019; 173:157-164. [PMID: 30909101 DOI: 10.1016/j.envres.2019.03.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 03/08/2019] [Accepted: 03/10/2019] [Indexed: 06/09/2023]
Abstract
It is still a major challenge to protect humans at workplaces and in the environment. To cope with this task, it is a prerequisite to obtain detailed information on the extent of chemical perturbations of biological pathways, in particular, adaptive vs. adverse effects and the dose-response relationships. This knowledge serves as the basis for the classification of non-carcinogens and carcinogens and for further distinguishing carcinogens in genotoxic (DNA damaging) or non-genotoxic compounds. Basing on quantitative dose-response relationships, points of departures can be derived for chemical risk assessment. In recent years, new methods have shown their capability to support the established rodent models of carcinogenicity testing. In vitro high throughput screening assays assess more comprehensively cell response. In addition, omics technologies were applied to study the mode of action of chemicals whereby the term "toxicogenomics" comprises various technologies such as transcriptomics, epigenomics, or metabolomics. This review aims to summarize the current state of toxicogenomic approaches in risk science and to compare them with established ones. For example, measurement of global transcriptional changes generates meaningful information for toxicological risk assessment such as accurate classification of genotoxic/non-genotoxic carcinogens. Alteration in mRNA expression offers previously unknown insights in the mode of action and enables the definition of key events. Based on these, benchmark doses can be calculated for the transition from an adaptive to an adverse state. In short, this review assesses the potential and challenges of transcriptomics and addresses the impact of other omics technologies on risk assessment in terms of hazard identification and dose-response assessment.
Collapse
Affiliation(s)
- Simone Schmitz-Spanke
- Institute and Outpatient Clinic of Occupational, Social and Environmental Medicine, University of Erlangen-Nuremberg, Henkestr. 9-11, 91054, Erlangen, Germany.
| |
Collapse
|
10
|
Cote IL, McCullough SD, Hines RN, Vandenberg JJ. Application of epigenetic data in human health risk assessment. CURRENT OPINION IN TOXICOLOGY 2017; 6:71-78. [PMID: 29333520 DOI: 10.1016/j.cotox.2017.09.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Despite the many recent advances in the field of epigenetics, application of this knowledge in environmental health risk assessment has been limited. In this paper, we identify opportunities for application of epigenetic data to support health risk assessment. We consider current applications and present a vision for the future.
Collapse
Affiliation(s)
- Ila L Cote
- National Center for Environmental Assessment, Office of Research and Development, United States Environmental Protection Agency, Washington DC 22202, USA
| | - Shaun D McCullough
- National Health and Environmental Effects Research Laboratory, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, NC 27711, USA
| | - Ronald N Hines
- National Health and Environmental Effects Research Laboratory, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, NC 27711, USA
| | - John J Vandenberg
- National Center for Environmental Assessment, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, NC 27711, USA
| |
Collapse
|
11
|
Wehmas LC, DeAngelo AB, Hester SD, Chorley BN, Carswell G, Olson GR, George MH, Carter JH, Eldridge SR, Fisher A, Vallanat B, Wood CE. Metabolic Disruption Early in Life is Associated With Latent Carcinogenic Activity of Dichloroacetic Acid in Mice. Toxicol Sci 2017; 159:354-365. [PMID: 28962523 PMCID: PMC6223632 DOI: 10.1093/toxsci/kfx146] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Early-life environmental factors can influence later-life susceptibility to cancer. Recent evidence suggests that metabolic pathways may mediate this type of latency effect. Previously, we reported that short-term exposure to dichloroacetic acid (DCA) increased liver cancer in mice 84 weeks after exposure was stopped. Here, we evaluated time course dynamics for key events related to this effect. This study followed a stop-exposure design in which 28-day-old male B6C3F1 mice were given the following treatments in drinking water for up to 93 weeks: deionized water (dH2O, control); 3.5 g/l DCA continuously; or 3.5 g/l DCA for 4-52 weeks followed by dH2O. Effects were evaluated at eight interim time points. A short-term biomarker study was used to evaluate DCA effects at 6, 15, and 30 days. Liver tumor incidence was higher in all DCA treatment groups, including carcinomas in 82% of mice previously treated with DCA for only 4 weeks. Direct effects of DCA in the short-term study included decreased liver cell proliferation and marked mRNA changes related to mitochondrial dysfunction and altered cell metabolism. However, all observed short-term effects of DCA were ultimately reversible, and prior DCA treatment did not affect liver cell proliferation, apoptosis, necrosis, or DNA sequence variants with age. Key intermediate events resulting from transient DCA exposure do not fit classical cytotoxic, mitogenic, or genotoxic modes of action for carcinogenesis, suggesting a distinct mechanism associated with early-life metabolic disruption.
Collapse
Affiliation(s)
- Leah C. Wehmas
- National Health and Environmental Effects Research
Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC,
USA
| | - Anthony B. DeAngelo
- National Health and Environmental Effects Research
Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC,
USA
| | - Susan D. Hester
- National Health and Environmental Effects Research
Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC,
USA
| | - Brian N. Chorley
- National Health and Environmental Effects Research
Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC,
USA
| | - Gleta Carswell
- National Health and Environmental Effects Research
Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC,
USA
| | - Greg R. Olson
- Toxicologic Pathology Associates, Jefferson, AK,
USA
| | - Michael H. George
- National Health and Environmental Effects Research
Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC,
USA
| | | | | | - Anna Fisher
- National Health and Environmental Effects Research
Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC,
USA
| | - Beena Vallanat
- National Health and Environmental Effects Research
Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC,
USA
| | - Charles E. Wood
- National Health and Environmental Effects Research
Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC,
USA
| |
Collapse
|
12
|
LaRocca J, Johnson KJ, LeBaron MJ, Rasoulpour RJ. The interface of epigenetics and toxicology in product safety assessment. CURRENT OPINION IN TOXICOLOGY 2017. [DOI: 10.1016/j.cotox.2017.11.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
|
13
|
A Tox21 Approach to Altered Epigenetic Landscapes: Assessing Epigenetic Toxicity Pathways Leading to Altered Gene Expression and Oncogenic Transformation In Vitro. Int J Mol Sci 2017; 18:ijms18061179. [PMID: 28587163 PMCID: PMC5486002 DOI: 10.3390/ijms18061179] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 05/19/2017] [Accepted: 05/22/2017] [Indexed: 02/07/2023] Open
Abstract
An emerging vision for toxicity testing in the 21st century foresees in vitro assays assuming the leading role in testing for chemical hazards, including testing for carcinogenicity. Toxicity will be determined by monitoring key steps in functionally validated molecular pathways, using tests designed to reveal chemically-induced perturbations that lead to adverse phenotypic endpoints in cultured human cells. Risk assessments would subsequently be derived from the causal in vitro endpoints and concentration vs. effect data extrapolated to human in vivo concentrations. Much direct experimental evidence now shows that disruption of epigenetic processes by chemicals is a carcinogenic mode of action that leads to altered gene functions playing causal roles in cancer initiation and progression. In assessing chemical safety, it would therefore be advantageous to consider an emerging class of carcinogens, the epigenotoxicants, with the ability to change chromatin and/or DNA marks by direct or indirect effects on the activities of enzymes (writers, erasers/editors, remodelers and readers) that convey the epigenetic information. Evidence is reviewed supporting a strategy for in vitro hazard identification of carcinogens that induce toxicity through disturbance of functional epigenetic pathways in human somatic cells, leading to inactivated tumour suppressor genes and carcinogenesis. In the context of human cell transformation models, these in vitro pathway measurements ensure high biological relevance to the apical endpoint of cancer. Four causal mechanisms participating in pathways to persistent epigenetic gene silencing were considered: covalent histone modification, nucleosome remodeling, non-coding RNA interaction and DNA methylation. Within these four interacting mechanisms, 25 epigenetic toxicity pathway components (SET1, MLL1, KDM5, G9A, SUV39H1, SETDB1, EZH2, JMJD3, CBX7, CBX8, BMI, SUZ12, HP1, MPP8, DNMT1, DNMT3A, DNMT3B, TET1, MeCP2, SETDB2, BAZ2A, UHRF1, CTCF, HOTAIR and ANRIL) were found to have experimental evidence showing that functional perturbations played “driver” roles in human cellular transformation. Measurement of epigenotoxicants presents challenges for short-term carcinogenicity testing, especially in the high-throughput modes emphasized in the Tox21 chemicals testing approach. There is need to develop and validate in vitro tests to detect both, locus-specific, and genome-wide, epigenetic alterations with causal links to oncogenic cellular phenotypes. Some recent examples of cell-based high throughput chemical screening assays are presented that have been applied or have shown potential for application to epigenetic endpoints.
Collapse
|
14
|
Timms JA, Relton CL, Rankin J, Strathdee G, McKay JA. DNA methylation as a potential mediator of environmental risks in the development of childhood acute lymphoblastic leukemia. Epigenomics 2016; 8:519-36. [PMID: 27035209 PMCID: PMC4928498 DOI: 10.2217/epi-2015-0011] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 01/22/2016] [Indexed: 11/21/2022] Open
Abstract
5-year survival rate for childhood acute lymphoblastic leukemia (ALL) has risen to approximately 90%, yet the causal disease pathway is still poorly understood. Evidence suggests multiple 'hits' are required for disease progression; an initial genetic abnormality followed by additional secondary 'hits'. It is plausible that environmental influences may trigger these secondary hits, and with the peak incidence of diagnosis between 2 and 5 years of age, early life exposures are likely to be key. DNA methylation can be modified by many environmental exposures and is dramatically altered in cancers, including childhood ALL. Here we explore the potential that DNA methylation may be involved in the causal pathway toward disease by acting as a mediator between established environmental factors and childhood ALL development.
Collapse
Affiliation(s)
- Jessica A Timms
- Institute of Health & Society, Newcastle University, Newcastle, UK
| | - Caroline L Relton
- MRC Integrative Epidemiology Unit, School of Social & Community Medicine, University of Bristol, UK
| | - Judith Rankin
- Institute of Health & Society, Newcastle University, Newcastle, UK
| | - Gordon Strathdee
- Northern Institute for Cancer Research, Newcastle University, UK
| | - Jill A McKay
- Institute of Health & Society, Newcastle University, Newcastle, UK
| |
Collapse
|
15
|
Schulte PA, Whittaker C, Curran CP. Considerations for Using Genetic and Epigenetic Information in Occupational Health Risk Assessment and Standard Setting. JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE 2015; 12 Suppl 1:S69-S81. [PMID: 26583908 PMCID: PMC4685594 DOI: 10.1080/15459624.2015.1060323#.xhlte1uzbx4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Risk assessment forms the basis for both occupational health decision-making and the development of occupational exposure limits (OELs). Although genetic and epigenetic data have not been widely used in risk assessment and ultimately, standard setting, it is possible to envision such uses. A growing body of literature demonstrates that genetic and epigenetic factors condition biological responses to occupational and environmental hazards or serve as targets of them. This presentation addresses the considerations for using genetic and epigenetic information in risk assessments, provides guidance on using this information within the classic risk assessment paradigm, and describes a framework to organize thinking about such uses. The framework is a 4 × 4 matrix involving the risk assessment functions (hazard identification, dose-response modeling, exposure assessment, and risk characterization) on one axis and inherited and acquired genetic and epigenetic data on the other axis. The cells in the matrix identify how genetic and epigenetic data can be used for each risk assessment function. Generally, genetic and epigenetic data might be used as endpoints in hazard identification, as indicators of exposure, as effect modifiers in exposure assessment and dose-response modeling, as descriptors of mode of action, and to characterize toxicity pathways. Vast amounts of genetic and epigenetic data may be generated by high-throughput technologies. These data can be useful for assessing variability and reducing uncertainty in extrapolations, and they may serve as the foundation upon which identification of biological perturbations would lead to a new paradigm of toxicity pathway-based risk assessments.
Collapse
Affiliation(s)
- P. A. Schulte
- Centers for Disease Control and Prevention (CDC), National Institute for Occupational Safety and Health (NIOSH), Education and Information Division, Cincinnati, Ohio
| | - C. Whittaker
- Centers for Disease Control and Prevention (CDC), National Institute for Occupational Safety and Health (NIOSH), Education and Information Division, Cincinnati, Ohio
| | - C. P. Curran
- Northern Kentucky University, Department of Biological Sciences, Highland Heights, Kentucky
| |
Collapse
|
16
|
Schulte PA, Whittaker C, Curran CP. Considerations for Using Genetic and Epigenetic Information in Occupational Health Risk Assessment and Standard Setting. JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE 2015; 12 Suppl 1:S69-81. [PMID: 26583908 PMCID: PMC4685594 DOI: 10.1080/15459624.2015.1060323] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Risk assessment forms the basis for both occupational health decision-making and the development of occupational exposure limits (OELs). Although genetic and epigenetic data have not been widely used in risk assessment and ultimately, standard setting, it is possible to envision such uses. A growing body of literature demonstrates that genetic and epigenetic factors condition biological responses to occupational and environmental hazards or serve as targets of them. This presentation addresses the considerations for using genetic and epigenetic information in risk assessments, provides guidance on using this information within the classic risk assessment paradigm, and describes a framework to organize thinking about such uses. The framework is a 4 × 4 matrix involving the risk assessment functions (hazard identification, dose-response modeling, exposure assessment, and risk characterization) on one axis and inherited and acquired genetic and epigenetic data on the other axis. The cells in the matrix identify how genetic and epigenetic data can be used for each risk assessment function. Generally, genetic and epigenetic data might be used as endpoints in hazard identification, as indicators of exposure, as effect modifiers in exposure assessment and dose-response modeling, as descriptors of mode of action, and to characterize toxicity pathways. Vast amounts of genetic and epigenetic data may be generated by high-throughput technologies. These data can be useful for assessing variability and reducing uncertainty in extrapolations, and they may serve as the foundation upon which identification of biological perturbations would lead to a new paradigm of toxicity pathway-based risk assessments.
Collapse
Affiliation(s)
- P. A. Schulte
- Centers for Disease Control and Prevention (CDC), National Institute for Occupational Safety and Health (NIOSH), Education and Information Division, Cincinnati, Ohio
- Address correspondence to Paul A. Schulte, Centers for Disease Control and Prevention (CDC), National Institute for Occupational Safety and Health (NIOSH), Education and Information Division, 4676 Columbia Parkway, MS-C14 Cincinnati, OH45226, . E-mail:
| | - C. Whittaker
- Centers for Disease Control and Prevention (CDC), National Institute for Occupational Safety and Health (NIOSH), Education and Information Division, Cincinnati, Ohio
| | - C. P. Curran
- Northern Kentucky University, Department of Biological Sciences, Highland Heights, Kentucky
| |
Collapse
|