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 of c‐Ha‐ras. This is the first time that such a point mutation has been detected in human cancer tissues.