Simian virus 40 infection down-regulates the expression of nitric oxide synthase in human mesothelial cells.

The cytotoxic effects of asbestos are partly mediated by the production of free radicals, including nitric oxide (NO). SV40 has been suggested to synergize with asbestos in the pathogenesis of malignant mesothelioma. Crocidolite asbestos fibers induced in human mesothelial and malignant mesothelioma cells a significant increase of NO synthase activity and expression, which was absent in SV40-infected cells. Furthermore, SV40 infection prevented the NF kappa B activation elicited by crocidolite in both mesothelial and mesothelioma cells. These data suggest that SV40, by inhibiting the synthesis of NO, could favor the survival of transformed, potentially neoplastic cells.