Polyoma Virus and Production of Malignancy In Vitro

Abstract

An attempt was made to induce a rapid and reproducible neoplastic conversion in a single-cell clone of mouse cells during the period in vitro before “spontaneous” conversions occur. Such changes were repeatedly produced in a clone derived from the salivary gland of a C3H mouse by infection with polyoma virus. The mechanism of this change, whether by cell selection or by cell change, awaits further study. Cells of the salivary-gland clone were also compared with 2 other long-term strains of C3H mouse cells, one derived from minced whole embryos and the other from adult connective tissue. Cells were compared with respect to viral susceptibility and tumor-producing capacity. Of the 3 cell types, only the adult fibroblasts from connective tissue failed to show any cytopathogenic response to infection with polyoma. It was shown further that all 3 cell types cultured in a serum-supplemented, chemically defined medium will ultimately undergo a malignant conversion in vitro when no virus is purposely added. Tumors produced by the salivary-gland clone were extraordinary because of the amount of collagen they contained and the distortion of the leg they produced when cells were transplanted to the thigh muscles.