Mutation of ras oncogene in gastric adenocarcinoma: association with histological phenotype.

In order to explore the role of ras oncogene in gastric carcinomas from Korean patients, we examined the frequency of point mutations all three ras oncogenes (Ki-, Ha-, and N-ras). A total of 57 DNA samples were prepared from 3 gastric carcinoma cell lines, 10 malignant ascites, and 44 frozen gastric tumor tissues. Exons 1 and 2 of each ras oncogene were amplified by polymerase chain reaction (PCR), and analyzed by single strand conformation polymorphism (SSCP) and direct sequencing. Mutated ras genes were detected in 6 out of 57 samples (10%). One cell line and 2 tumors showed a mutation at exon 1 of Ki-ras. N-ras mutations were also detected at exon 1 of 3 tumors. Histologically, all the ras mutation cases exhibited a diffuse phenotype. In summary, we performed a comprehensive analysis to investigate the mutation of all three ras oncogenes in gastric carcinoma. The results demonstrate infrequent mutations of Ki- and N-ras which may favor the development of diffuse type gastric carcinomas, implicating a different genetic pathway in diffuse and intestinal type gastric carcinomas.