Activation of Ki-ras2 gene in human colon and lung carcinomas by two different point mutations.

Kirsten (Ki)-ras cDNA clones were prepared from human lung and colon carcinoma cell lines expressing an activated c-Ki-ras2 gene. DNA sequence analysis and transfection studies indicate that different point mutations at the same codon can activate the gene; that most human c-Ki-ras2 mRNA uses sequences from a fourth coding exon distinct from that of its viral counterpart; and that at least one cell line is functionally homozygous for the activated gene.