Gene expression profiling to recognize specific features of non-genotoxic carcinogens
Ontology highlight
ABSTRACT: The current test strategy for carcinogenicity is generally based on in vitro and in vivo genotoxicity assays. Non-genotoxic carcinogens (NGTXC) are negative for genotoxicity and go undetected. Therefore, alternative tests to detect these chemicals are urgently needed. NGTXC act through different modes of action, which complicates the development of such assays. We have demonstrated recently in primary mouse hepatocytes that some, but certainly not all, NGTXC can be categorized according to their mode of action based on feature detection at a gene expression level (Schaap et al. 2012 (PMID 22710402)). Identification of a wider range of chemicals probably requires multiple in vitro systems. In the current study, we describe the added value of using mouse embryonic stem cells. In this study, the focus is on NGTXC, but we also included genotoxic carcinogens and non-carcinogens. This approach enables us to assess the robustness of this method and to evaluate the system for recognizing features of chemicals in general, which is important for application in future risk assessment.
Project description:The current test strategy for carcinogenicity is generally based on in vitro and in vivo genotoxicity assays. Non-genotoxic carcinogens (NGTXC) are negative for genotoxicity and go undetected. Therefore, alternative tests to detect these chemicals are urgently needed. NGTXC act through different modes of action, which complicates the development of such assays. We have demonstrated recently in primary mouse hepatocytes that some, but certainly not all, NGTXC can be categorized according to their mode of action based on feature detection at a gene expression level (Schaap et al. 2012 (PMID 22710402)). Identification of a wider range of chemicals probably requires multiple in vitro systems. In the current study, we describe the added value of using mouse embryonic stem cells. In this study, the focus is on NGTXC, but we also included genotoxic carcinogens and non-carcinogens. This approach enables us to assess the robustness of this method and to evaluate the system for recognizing features of chemicals in general, which is important for application in future risk assessment. Primary mouse hepatocytes and mouse embryonic stem cells were exposed to 26 chemicals (non-genotoxic carcinogens and non-carcinogens) representing diverse modes of action. Upon profiling, an unsupervised comparison approach was applied to recognize similar features at the transcriptomic level. This Series consists of the gene expression data of the primary mouse hepatocytes. The expression data of the mouse embryonic stem cells is submitted separately under another accession number. In this study we tested 26 chemicals of which 16 non-genotoxic carcinogens, 4 genotoxic carcinogens, 2 genotoxic non-carcinogens and 4 non-carcinogens. Specification of the chemicals can be found in the readme file.
Project description:The current test strategy for carcinogenicity is generally based on in vitro and in vivo genotoxicity assays. Non-genotoxic carcinogens (NGTXC) are negative for genotoxicity and go undetected. Therefore, alternative tests to detect these chemicals are urgently needed. NGTXC act through different modes of action, which complicates the development of such assays. We have demonstrated recently in primary mouse hepatocytes that some, but certainly not all, NGTXC can be categorized according to their mode of action based on feature detection at a gene expression level (Schaap et al. 2012, PMID22710402). Identification of a wider range of chemicals probably requires multiple in vitro systems. In the current study we describe the added value of using mouse embryonic stem cells. In this study the focus is on NGTXC, but we also included genotoxic carcinogens and non-carcinogens. This approach enables us to assess the robustness of this method and to evaluate the system for recognizing features of chemicals in general, which is important for application in future risk assessment. This serie consists of the gene expression data of the mouse embryonic stem cells. The expression data of the primary mouse hepatocytes cells is submitted separately under accession number GSE44088.
Project description:Under REACH, the European Community Regulation on chemicals, the testing strategy for carcinogenicity is generally based on in vitro and in vivo genotoxicity assays. Given that non-genotoxic carcinogens are negative for genotoxicity, this class of carcinogens will not be detected. Therefore, alternative test are urgently needed. Non-genotoxic carcinogens, however, act through different modes of action, which complicates the development of such an assay. The aim of this study was to investigate whether gene expression profiling in primary mouse hepatocytes can be used to distinguish different modes of action of non-genotoxic carcinogens.
Project description:Under REACH, the European Community Regulation on chemicals, the testing strategy for carcinogenicity is generally based on in vitro and in vivo genotoxicity assays. Given that non-genotoxic carcinogens are negative for genotoxicity, this class of carcinogens will not be detected. Therefore, alternative test are urgently needed. Non-genotoxic carcinogens, however, act through different modes of action, which complicates the development of such an assay. The aim of this study was to investigate whether gene expression profiling in primary mouse hepatocytes can be used to distinguish different modes of action of non-genotoxic carcinogens. Primary mouse hepatocytes were exposed to 16 non-genotoxic carcinogens with diverse modes of action. Upon profiling, pathway analysis was performed to obtain insight into the biological relevance of the observed changes in gene expression. To recognize similarities in mode of action at the transcriptomic level, both a supervised and an unsupervised comparison approach was applied.
Project description:The current test strategy for carcinogenicity consists initially of in vivo and in vitro genotoxicity tests. Non-genotoxic carcinogens do not directly induce DNA damage and, as such, go undetected under this test strategy. In a previous study we setup a comparison approach to categorize chemicals having similar modes of action, according to similarity in gene expression. In the current study we will investigate whether this comparison approach can be improved by omptimizing the concentration selection procedure and by testing a concentration range per chemical.
Project description:The increasing number of man-made chemicals in the environment that may pose a carcinogenic risk emphasizes the need for the development of 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) and with the non-genotoxic liver carcinogen methapyrilene at non-cytotoxic concentrations for 7 days, and transcriptomic profile was examined. 1569 (892 protein-coding and 677 non-coding), 1693 (922 protein-coding and 771 non-coding), and 2061 (1462 protein-coding and 599 non-coding) differentially expressed genes were detected in cells treated with AFB1, B[a]P, and methapyrilene, respectively. Additionally, we examined the toxicogenomics response to AFB1, B[a]P, and methapyrilene exposure in human HepaRG cells and demonstrated that carcinogens had a less prominent effect on the cellular transcriptome as compared to that in human iPSC-derived hepatocytes. Overall, the results demonstrate that the prime non-genotoxic effect of exposure to carcinogens, regardless of their mode of action, in short-term in vitro testing is a profound global transcriptome response, indicating a greater value of toxicogenomics for rapid carcinogen screening in vitro.
Project description:The carcinogenic potential of chemicals is currently evaluated with rodent life-time bioassays, which are time consuming, and expensive with respect to cost, number of animals and amount of compound required. Since the results of these 2-year bioassays are not known until quite late during development of new chemical entities, and since the short-term test battery to test for genotoxicity, a characteristic of genotoxic carcinogens, is hampered by low specificity, the identification of early biomarkers for carcinogenicity would be a big step forward. Using gene expression profiles from the livers of rats treated up to 14 days with genotoxic and non-genotoxic carcinogens we previously identified characteristic gene expression profiles for these two groups of carcinogens. We have now added expression profiles from further hepatocarcinogens and from non-carcinogens the latter serving as control profiles. We used these profiles to extract biomarkers discriminating genotoxic from non-genotoxic carcinogens and to calculate classifiers based on the support vector machine (SVM) algorithm. These classifiers then predicted a set of independent validation compound profiles with up to 88% accuracy, depending on the marker gene set. We would like to present this study as proof of the concept that a classification of carcinogens based on short-term studies may be feasible.
Project description:Conventional notion regards the action of non-genotoxic carcinogens (NGC) an autonomous process largely confined to parenchymal cells. Here we aim to elucidate the role of the hepatic mesenchyme for the action of two prototypical NGC, phenobarbital (PB), an anti-epileptic drug, and cyproterone acetate (CPA) a gestagen used in contraceptive pills.
Project description:The prediction of possible carcinogenicity of chemicals for humans represents an ongoing challenge. Chronic rodent bioassays predict human cancer risk at only limited reliability while simultaneously being expensive and long-lasting. In order to seek for alternatives, in the present study, the ability of a transcriptomics-based primary mouse hepatocyte model to classify carcinogens by their modes of action was evaluated. As it is obvious that exposure will induce a cascade of gene expression modifications, in particular, the influence of exposure time in vitro on discriminating genotoxic (GTX) carcinogens from non-genotoxic (NGTX) carcinogens class prediction was investigated. Primary mouse hepatocytes from male C57Bl6 mice were treated for 12, 24, 36 and 48 h with two GTX and two NGTX carcinogens. For the purpose of validation, two additional GTX compounds were studied after incubation periods of 24 and 48 h. Immunostaining of ?H2AX foci was applied to phenotypically verify DNA damage. Whole genome gene expression modifications were analyzed by means of Affymetrix mouse genome 430 2.0 microarrays. Datasets were normalized using RMA and differentially expressed genes were selected for assessing class prediction. The ?H2AX assay confirmed significant induction of DNA damage after treatment with GTX compounds, whereas NGTX compounds showed no activity beyond background levels. Discrimination of GTX and NGTX carcinogens by Prediction Analysis of Microarray (PAM) was validated and resulted in a perfect classification. The present study shows that gene expression profiling in primary mouse hepatocytes is promising for discriminating between GTX and NGTX compounds and that this classification improves with increasing treatment period.
Project description:Many innovative techniques and scientific improvements are available to tackle societal concerns, like public health safety and confining the risk of cancerous exposure to chemicals, but have not been thoroughly tested and implicated yet. We investigated if microRNA and mRNA transcription profiles can be implemented in a short-term carcinogen classifier assay. Our study is additionally focusing on the drawbacks of present-day carcinogen screening strategies and also aims to contribute to a more ethical approach towards animal use and welfare within risk assessment. Since current in vitro and in silico assays are still not able to mimic the in vivo situation accurately we set out to develop an alternative short-term in vivo assay. Five genotoxic, seven non-genotoxic and five non-carcinogen exposure studies were used to investigate if murine hepatic microRNA and mNA profiles after 7-day exposure are suitable tools to classify carcinogens. Classification analyses showed that a small transcript set, consisting of both microRNA and mRNA, is able to classify the genotoxic, non-genotoxic and non-carcinogens tested with 100% accuracy. The results indicate that microRNAs have the potential to be used as transcriptional classifiers and that a short-term transcriptional classifier assay in mice can be a powerful tool in carcinogenicity risk assessment. Since current in vitro and in silico assays are still not able to mimic the in vivo situation accurately we set out to develop an alternative short-term in vivo assay. Five genotoxic, seven non-genotoxic and five non-carcinogen exposure studies were used to investigate if murine hepatic microRNA and mNA profiles after 7-day exposure are suitable tools to classify carcinogens. Classification analyses showed that a small transcript set, consisting of both microRNA and mRNA, is able to classify the genotoxic, non-genotoxic and non-carcinogens tested with 100% accuracy. The results indicate that microRNAs have the potential to be used as transcriptional classifiers and that a short-term transcriptional classifier assay in mice can be a powerful tool in carcinogenicity risk assessment. [mRNA profling] 96 hepatic samples in total, 8 control untreated samples, replicates per treated group n=4-6