Abnormal change of p53 gene in gastric and precancerous lesions and APC gene deletion in gastric carcinoma and near tissues.

p53 gene mutation (exon4, 5, 6, 7, 8 and intron6) in gastric cancer and precancerous lesions and p53 gene (exon4 and ontron6), APC gene deletion in gastric carcinomas were studied by PCR/SSCP and PCR/RFLP. Results showed mutation rate of p53 in metaplasia, dysplasia and gastric carcinoma was 37.5% (3/8), 42.17% (8/19), 53.33 (16/30) respectively. There was significant difference among groups of metaplasia, dysplasia, cancer and normal controls. No exon8 mutation was found in metaplasia and dysplasia, but 4 cases were found to have exon8 mutation in cancer group. It is suggested that exon8 mutation occurs at the late stage of gastric cancer, but exon 5, 6, 7 mutation occur in the course of precancerous lesion to cancer. Loss of heterozygosity (LOH) of exon4, intron6, APC was 47, 37% (9/19), 8.73% (2/23), 16.67% (3/18) respectively. LOH of exon4 had something to do with poor differentiation, lymph node metastasis, depth of invasion. LOH of exon4 may be of prognostic marker of gastric cancer. We are led to conclude that p53 gene mutation is an early event and perhaps work together with ras oncogene in gastric carcinogenesis.