Global gene expression profiling of mesotheliomas from vehicle control and VDC-exposed male F344N rats

A recent two-year NTP cancer bioassay showed a marked increase in the incidence of malignant mesothelioma arising from the tunica vaginalis in male Fischer 344/N rats exposed to Vinylidene chloride (VDC). Aged male F344/N rats are prone to developing spontaneous peritoneal mesotheliomas, which also arise predominantly from the tunica vaginalis of the testes. A definitive mechanism for the observed increased incidence in VDC-exposed rats is unknown. Investigation of the molecular alterations that occur in mesotheliomas from vehicle control and VDC-exposed rats may provide insight into their pathogenesis, as well enable a better understanding regarding the mechanisms underlying chemically induced mesothelioma in rodents. Mesothelial cell function represents a complex interplay of pathways related to host defense mechanisms and maintenance of cellular homeostasis. Global gene expression profiles of spontaneous mesotheliomas from vehicle control male F344/N rats from various two-year National Toxicology Program carcinogenicity bioassays were compared to mesotheliomas from VDC-exposed rats to characterize the molecular features that are present in mesotheliomas from VDC-exposed animals, and to elucidate tumor-specific gene expression profiles. The resulting gene expression pattern showed that mesotheliomas from VDC-exposed animals are genomically very different from spontaneous tumors; while both tumor types are characterized by alterations in gene expression associated with carcinogenic pathways (oncogenes, tumor suppressor genes, growth factors, etc.), mesotheliomas from VDC-exposed animals are associated with increased dysreguation of immune pathways and inflammatory mediators. Alterations in these pathways may suggest a pro-inflammatory and immune dysfunction signature as one mechanism in the observed increased incidence of these tumors in VDC-exposed animals.

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Blackshear PE, Pandiri AR, Ton TV, Clayton NP, Shockley KR, Peddada SD, Gerrish KE, Sills RC, Hoenerhoff MJ