Neoplastic transformation of mouse and hamster cells in vitro with and without polyoma virus.

Several cell lines were examined under different culture conditions in an effort to find one that would not undergo "spontaneous" neoplastic transformation but could be transformed by polyoma virus. With such a cell line, large numbers of neoplastic and non-neoplastic cultures might be obtained for comparative studies. Four cell lines derived from different tissues of 2 strains of mice and all 8 lines of cells from 5 different pools of hamster embryo cells underwent spontaneous neoplastic transformation without polyoma virus. However, certain of these lines might be useful, since neoplastic conversion occurred only after prolonged culture. Fairly reproducible neoplastic transformations could be induced by polyoma virus with high multiplicities of infection and rather drastic treatment of cells, including trypsinization. Although it has been postulated that normal Syrian hamster embryo cells have a finite lifespan in vitro, we found that under our culture conditions, continuously growing, non-neoplastic cell lines could be routinely established.