Amplification of c-Ki-ras gene and aberrant expression of c-myc in WI-38 cells transformed in vitro by gamma-irradiation.

The expression of c-oncogenes was examined with normal human fibroblasts (WI-38) and the cells transformed in vitro by gamma-irradiation (CT-1). The amount of Ki-ras-specific mRNA in CT-1 cells was found to be approximately twice that in WI-38 cells. By Southern blot hybridization, the c-Ki-ras 2 gene of CT-1 cells was found to be amplified about two-fold. CT-1 cells have higher levels of c-myc mRNA than normal cells, although the gene dosage and the restriction nuclease pattern of the c-myc gene was the same. The content of c-myc mRNA in CT-1 cells was found to be constitutively high, whereas that in normal cells was increased by serum addition.