Dataset Information

Whole exome sequencing of an asbestos-induced wild-type murine model of malignant mesothelioma.

ABSTRACT: Malignant mesothelioma (MM) is an aggressive cancer of the pleural and peritoneal cavities caused by exposure to asbestos. Asbestos-induced mesotheliomas in wild-type mice have been used extensively as a preclinical model because they are phenotypically identical to their human counterpart. However, it is not known if the genetic lesions in these mice tumours are similar to in the human disease, a prerequisite for any new preclinical studies that target genetic abnormalities.We performed whole exome sequencing of fifteen asbestos-induced murine MM tumour cell lines from BALB/c, CBA and C57BL/6 mouse strains and compared the somatic mutations and copy number variations with those recurrently reported in human MM. We then catalogued and characterised the mutational landscape of the wild-type murine MM tumours. Quantitative RT-PCR was used to interrogate the expression of key MM genes of interest in the mRNA.Consistent with human MM tumours, we identified homozygous loss of the tumour suppressor Cdkn2a in 14/15 tumours. One tumour retained the first exon of both of the p16INK4a and p19ARF isoforms though this tumour also contained genetic amplification of Myc resulting in increased expression of the c-Myc proto-oncogene in the mRNA. There were no chromosomal losses in either the Bap1 or Nf2 regions. One tumour harbored homozygous loss of Trp53 in the DNA. Mutation rates were similar in tumours generated in the CBA and C57BL/6 strains when compared to human MM. Interestingly, all BALB/c tumour lines displayed high mutational loads, consistent with the known mutator phenotype of the host strain. The Wnt, MAPK and Jak-STAT signaling pathways were found to be the most commonly affected biological pathways. Mutations and copy number deletions also occurred in the Hedgehog and Hippo pathways.These data suggest that in the wild-type murine model asbestos causes mesotheliomas in a similar way to in human MM. This further supports the notion that the murine model of MM represents a genuine homologue of the human disease, something uncommon in cancer, and is thus a valuable tool to provide insight into MM tumour development and to aide the search for novel therapeutic strategies.

SUBMITTER: Sneddon S

PROVIDER: S-EPMC5455120 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Whole exome sequencing of an asbestos-induced wild-type murine model of malignant mesothelioma.

Sneddon Sophie S Patch Ann-Marie AM Dick Ian M IM Kazakoff Stephen S Pearson John V JV Waddell Nicola N Allcock Richard J N RJN Holt Robert A RA Robinson Bruce W S BWS Creaney Jenette J

BMC cancer 20170602 1

<h4>Background</h4>Malignant mesothelioma (MM) is an aggressive cancer of the pleural and peritoneal cavities caused by exposure to asbestos. Asbestos-induced mesotheliomas in wild-type mice have been used extensively as a preclinical model because they are phenotypically identical to their human counterpart. However, it is not known if the genetic lesions in these mice tumours are similar to in the human disease, a prerequisite for any new preclinical studies that target genetic abnormalities.< ...[more]

PMID: 28577549

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Project description:BackgroundThe MexTAg transgenic mouse model of mesothelioma replicates many aspects of human mesothelioma, including induction by asbestos, pathogenicity and response to cytotoxic chemotherapy, despite high levels of the SV40 large T Antigen (TAg) in the mesothelial compartment. This model enables analysis of the molecular events associated with asbestos induced mesothelioma and is utilised here to investigate the molecular dynamics of tumours induced in these mice, using gene expression patterns as a read out.MethodsGene expression of MexTAg mesothelioma cell lines bearing a high or low number of copies of the TAg transgene were compared to wild type mouse mesotheliomas and normal mouse mesothelial cells using Affymetrix microarray. These data were then compared to a similar published human microarray study using the same platform.ResultsThe main expression differences between transgenic mouse and wild type mouse mesotheliomas occurred for genes involved in cell cycle regulation and DNA replication, as would be expected from overexpression of the TAg oncogene. Quantitative PCR confirmed that E2F and E2F regulated genes were significantly more upregulated in MexTAg mesotheliomas and MexTAg mesothelial cells compared to wild type mesotheliomas. Like human mesothelioma, both MexTAg and wild type mesotheliomas had more genes underexpressed than overexpressed compared to normal mouse mesothelial cells. Most notably, the cdkn2 locus was deleted in the wild type mouse mesotheliomas, consistent with 80 % human mesotheliomas, however, this region was not deleted in MexTAg mesotheliomas. Regardless of the presence of TAg, all mouse mesotheliomas had a highly concordant set of deregulated genes compared to normal mesothelial cells that overlapped with the deregulated genes between human mesotheliomas and mesothelial cells.ConclusionsThis investigation demonstrates that the MexTAg mesotheliomas are comparable with wild type mouse mesotheliomas in their representation of human mesothelioma at the molecular level, with some key gene expression differences that are attributable to the TAg transgene expression. Of particular note, MexTAg mesothelioma development was not dependent on cdkn2 deletion.

Project description:Background: The causal association between mesothelioma and asbestos exposure is conclusive, and many studies have proved that the trend in asbestos use is a strong predictor of the pattern in mesothelioma cases with an adequate latency time (generally around 30–40 years or more). Recently, a novel approach for predicting malignant pleural mesothelioma, based on asbestos consumption trend and using distributed non-linear models, has been applied. Objectives: The purpose of this study is to analyse trends in asbestos consumption and malignant mesothelioma mortality in the major asbestos-user countries. Furthermore, we applied distributed non-linear models to estimate and compare epidemiological relationships between asbestos consumption and mesothelioma mortality across these countries. Methods: The study involves major asbestos-user countries in which historical asbestos consumption and mesothelioma mortality data are available. Data on asbestos consumption were derived from worldwide asbestos supply and mesothelioma mortality data from World Health Organization (WHO) mortality archives. A quasi-Poisson generalized linear model was used to model past asbestos exposure and male mesothelioma mortality rates in each country. Exposure-response associations have been modelled using distributed lag non-linear models. Findings and conclusions: According to the criteria defined above, we selected 18 countries with raw asbestos cumulative consumptions higher than two million tons in the period 1933–2012. Overall, a clear linear relationship can be observed between total consumption and total deaths for mesothelioma. Country-specific exposure, lag and age-response relationships were identified and common functions extracted by a meta-analysis procedure. Non-linear models appear suitable and flexible tools for investigating the association between mesothelioma mortality and asbestos consumption. There is a need to improve the global epidemiological surveillance of asbestos-related diseases, particularly mesothelioma mortality, and the absence of reliable data for some major asbestos-user countries is a real concern. A reliable assessment of mesothelioma mortality is a fundamental step towards increasing the awareness of related risks and the need of an international ban on asbestos.

Dataset Information

Whole exome sequencing of an asbestos-induced wild-type murine model of malignant mesothelioma.

Publications

Whole exome sequencing of an asbestos-induced wild-type murine model of malignant mesothelioma.

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