A reassessment of methylcholanthrene transformation in the C3H10T1/2 cell culture system.

We previously demonstrated that four tumorigenic methylcholanthrene (MCA) transformed cell lines derived from C3H10T1/2 cells each contain a common G34----T nucleotide alteration in the c-Ki-ras gene. In contrast, a non-tumorigenic MCA transformant does not contain this mutation. We have now examined 75 newly isolated MCA transformants of C3H10T1/2 cells for their degree of morphological transformation, the presence of the c-Ki-ras G34----T mutation, colony formation in soft agar, and tumorigenicity in nude mice. Although many of these new MCA transformants exhibit morphological characteristics indistinguishable from previously isolated tumorigenic MCA transformants, none contain the G34----T mutation in the c-Ki-ras gene. Only one newly isolated MCA transformant can grow in soft agar. Of 14 tested, none of the new MCA C3H10T1/2 transformants are tumorigenic in nude mice.