Point mutations of c-ras genes in human bladder cancer and kidney cancer.

Point mutations of c-ras genes at codons 12, 13 and 61 were analyzed in 26 cases of bladder cancer and 16 cases of kidney cancer. DNA prepared from either frozen tissues or 10% formalin-fixed, paraffin-embedded tissues were amplified by means of polymerase chain reaction methods, and mutations were analyzed by dot blot hybridization assays with oligonucleotide probes. In three cases of bladder cancer c-ras mutations were found, at codons 13 and 61 of c-Ha-ras and at codon 61 of c-Ki-ras, while no mutation was found in kidney cancer. No mutation was found in normal bladder epithelial tissues from the same patients. Our findings, taken together, may indicate relative scarcity of c-ras mutations in these types of human cancer. The results of dot blot hybridization assays and DNA sequencing showed a G-to-C transition of the first nucleotide at codon 13 c-Ha-ras. This is the first time that such a point mutation has been detected in human cancer tissues.