Infrequent point mutations of ras oncogenes in gastric cancers.

Adenocarcinomas of the proximal and distal stomach have significant clinical and biological differences. A study was undertaken to determine if a difference in the incidence of mutated ras oncogenes exists between proximal (gastroesophageal junction or cardia) and distal (body or antrum) gastric tumors, and to assess the overall incidence in gastric cancers from non-Asian patients. Deoxyribonucleic acid from 28 primary gastric adenocarcinomas were analyzed for point mutations in codons 12, 13, and 61 of the Ha-ras, Ki-ras, and N-ras protooncogenes using polymerase-catalyzed chain reaction methodology. Twelve tumors were located at the gastroesophageal junction or cardia, and 16 in the body or antrum. Mutated ras genes were detected in 2 of 28 tumors for an overall incidence of 7%. The mutations occurred in codon 61 of the N-ras gene in a proximal gastric cancer and in codon 12 of the Ki-ras gene in a distal gastric cancer. These data indicate that mutations in ras genes are an uncommon event in primary gastric cancers and that there is no meaningful difference in the incidence of ras mutations in proximal and distal stomach cancers.