SV40 INDUCES MESOTHELIOMAS IN HAMSTERS

In the course of studies to elucidate the relative contribution of sim ian virus 40 (SV40) large T and small t proteins during oncogenesis, w e observed the appearance of pericardial and pleural tumors in 100% of Syrian hamsters injected in the pleural space with wild type SV40. Wh en SV40 was injected via the intracardiac or intraperitoneal routes, m ore than 50% of hamsters developed mesothelial tumors. Macroscopic, mi croscopic, ultramicroscopic, and bistochemical characteristics identif y these neoplasms and derived cell lines as mesotheliomas and mesothel ioma-derived cell lines. The SV40 genome was integrated and expressed in the mesotheliomas and derived cell lines. The absence of mesothelio mas in hamsters injected with SV40 small t deletion mutants indicates that the small t protein plays an important role in the development of SV40-induced mesotheliomas. To the best of our knowledge, this is the first definitive report of virus-induced mesotheliomas in mammals.