RESUMO
Mutation of ras gene family was studied in 206 cases of gastric cancer and precancerous lesions by PCR/RFLP, PCR/SSCP and DNA suquencmg. The results showed: the mutation rates of H-ras 12 codon in metaplasia, atypical dysplasia, early cancer and advanced cancer were 16.7%(6/36), 31.2%(15/48), 50.0% (5/10), 32.2% (20/60), respectively. In the groups of superficial gastritis and normal controls, no mutations were found. Mutations of H-ras 61 codon and N-ras 12 codon in various groups were the same as that of normal controls. Only 2 cases of K-ras 12 codon mutation were detected in gastric cancer group by PCR-SSCP, but it was not identified by DNA sequencing. It might be due to polymorphism. All H-ras 12 codon mutations were of G→T mutation. There were significant differences between groups of metaplasia, dysplasia, gastric carcinoma and normal controls. (P