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In order to study the status of DNA methylation of specific oncogenes and the relationship between them and the pathological changes in gastric carcinoma, we analysed the methylated status of c-myc, c-Ha-ras oncogenes by Southern blot hybridization. Genomic DNA from cancerous, paracancerous and non-cancerous areas of surgically resected specimens were examined in 22 cases of advanced human gastric carcinoma. Specimens were digested by the restriction endonucleases MspI/HpaII, which are able to cleave between methylated and non-methylated cytosine at their nucleotide recognition site the DNA 5'-CCGG sequence, and were hybridized with c-myc, c-Ha-ras oncogene probes. Moreover, the corresponding pathological changes in gastric carcinoma were observed. The results showed that c-myc, c-Ha-ras oncogenes from cancerous (10/22, 5/10) and paracancerous areas (13/22, 4/10) were hypomethylated and that there was no significant relationship between them and the histopathological changes.
Fang et al. (1996) studied this question.