Differential activation of the c-Ki-ras-2 proto-oncogene in human colorectal carcinoma.

In colorectal carcinoma, c-Ki-ras-2 mutations predominantly occur in codon 12 and, to a considerably lesser extent, in codon 13. To our knowledge, involvement of codon 61 in c-Ki-ras-2 has been reported only once among the large number of colon cancers investigated altogether. In this study, five human primary colorectal carcinomas were analyzed for the presence of activating c-Ki-ras-2 point mutations in codon 12, 13, and 61. Tumor DNAs were amplified by PCR and subsequently hybridized to a panel of synthetic oligonucleotides representing the complete spectrum of possible mutations. In two of the five tumors, mutations involving codons 13 and 61, respectively, were detected. These data extend previous findings that point mutation of codon 61 may be an improbable yet possible event leading to activation of c-Ki-ras-2 in colorectal carcinoma.