Gene Expression of Mesothelioma in Vinylidene Chloride-Exposed F344/N Rats Reveals Immune Dysfunction, Tissue Damage, and Inflammation Pathways

A majority (~80%) of human malignant mesotheliomas are asbestos-related. However, non-asbestos risk factors (radiation, chemicals, genetic factors) account for up to 30% of cases. A recent two-year National Toxicology Program carcinogenicity bioassay showed that male F344/N rats exposed to the industrial toxicant vinylidene chloride (VDC) resulted in a marked increase in malignant mesothelioma. Global gene expression profiles of these tumors were compared to spontaneous mesotheliomas and the F344/N rat mesothelial cell line (Fred-PE) in order to characterize the molecular features and chemical-specific profiles of mesothelioma in VDC-exposed rats. As expected, mesotheliomas from control and vinylidene chloride-exposed rats shared pathways associated with tumorigenesis, including cellular and tissue development, organismal injury, embryonic development, inflammatory response, cell cycle regulation, and cellular growth and proliferation, while mesotheliomas from vinylidene chloride-exposed rats alone showed overrepresentation of pathways associated with pro-inflammatory pathways and immune dysfunction such as the NF-kB signaling pathway, IL-8 and IL-12 signaling, interleukin responses, Fc receptor signaling, and NK and DC signaling, as well as overrepresentation of DNA damage and repair. These data suggest that a chronic, proinflammatory environment associated with VDC exposure may exacerbate disturbances in oncogene, growth factor and cell cycle regulation, resulting in an increased incidence of mesothelioma.