Failure of human cells transformed by simian virus 40 to form tumors in athymic nude mice.

Four individual lines and one subline of human cells, permanently established in tissue culture after infection with simian virus 40, failed to form tumors when inoculated into athymic nude mice. Under identical conditions, three established human cell lines of neoplastic origin and a spontaneously established human lymphocyte line formed tumors. Nude mice that failed to grow tumors from inocula of simian virus 40-transformed human cells, grew tumors from subsequent injections of authentic human cancer cells. Further efforts to demonstrate an immunologic basis for the growth suppression of human simian virus 40 transformants were also negative. The data suggest that the changes in morphology and in vitro growth behavior induced by the viral information are not sufficient for, or are only coincidentally related to, the neoplastic state.