Tumorigenic methylcholanthrene transformants of C3H/10T1/2 cells have a common nucleotide alteration in the c-Ki-ras gene.

The polymerase chain reaction was used to amplify DNA surrounding the codon 12 region of the c-Ki-ras gene from C3H/10T1/2 cells and from a number of 3-methylcholanthrene (MCA)-transformed derivatives of these cells. Sequence analysis demonstrated that tumorigenic MCAC116/39 cells, known by DNA-mediated transfection to contain an activated c-Ki-ras oncogene, had a G----T transversion in the first position of codon 12 of this gene, resulting in a Gly12----Cys mutation. A combination of polymerase chain-reaction amplification and oligonucleotide hybridization demonstrated that three additional tumorigenic MCA transformants of C3H/10T1/2 cells had an identical mutation in the c-Ki-ras gene. In contrast, this mutation was not present in an MCA-induced C3H/10T 1/2 transformant that was not tumorigenic. The molecular specificity of this MCA-induced mutation resulting in C3H/10T1/2 tumorigenic transformants should provide an excellent system in which to study the roles of transcription, replication, repair, and exogenous factors in the establishment and expression of transformation and tumorigenicity.