Abstract
Morphologic revertants which contain avian or murine sarcoma viruses have previously been isolated at low frequency from clonal lines of transformed mammalian cells. In the present study, these lines have been further characterized. They are indistinguishable from nontransformed parent cell lines with respect to parameters such as saturation density and colony formation in depleted medium or on monolayers of contact-inhibited cells. The rate of glucose uptake had also reverted to normal. The malignant potential of one of the revertant lines was examined and found to be markedly reduced compared to that of the corresponding transformed cells. The differences in the susceptibilities of revertant cells to retransformation by the same or other oncogenic viruses suggest that different cellular genes may be involved in expression of transformation by various tumor viruses.