"Spontaneous " Neoplastic Transformation In Vitro: Influence of Endogenous Murine Leukemia Virus and Serum Fractions '

SUMMARY—Cell lines From 3 pools of normal C3HF mouse-embryo cells were examined during long-term culture, For both "spontaneous " neoplastic transformation and presence of murine leukemia virus group-specific anti-gens. A correlation between presence of antigen and onset of neoplastic transformation would strengthen the hypothesis of a direct causal relation-ship between virus and transformation. Tests for neoplastic transformation were made by implantation of cells into syngeneic hosts and examination For sarcomas at the injection site. Cells were also examined cytologically For evidence of neoplastic transformation. No correlation between presence of antigen and neoplastic transformation could be established among the 48 cell lines studied. Tumors were produced by cells either positive or negative For group-specific antigens. Also, cells that did not undergo neoplastic transformation were either antigen positive or negative. Differences in sus-ceptibility to neoplastic transformation between embryo cell pools were observed. In addition, the effects of various fractions of Fetal bovine seru