RÉSUMÉ
<p><b>OBJECTIVE</b>To investigate the methylation frequencies of multiple tumor suppressor genes (TSGs) in hepatocellular carcinoma (HCC) and the clinical implication of aberrant DNA methylation in molecular carcinogenesis of HCC.</p><p><b>METHODS</b>Sixty samples of HCC and the paired adjacent liver tissue, 16 samples from post-hepatitis cirrhotic livers, 5 from livers with chronic hepatitis and 5 from normal livers were collected. Eight TSGs frequently silenced by hypermethylation of their promoters in various types of digestive tumors were selected, including APC, RASSF1A, p16, GSTP1, MGMT, DAPK, SOCS-1 and RIZ1. The status of promoter methylation in these 8 genes was investigated using methylation-specific polymerase chain reaction. The clinicopathological data of HCC were also analyzed in order to evaluate the clinical implication of aberrant methylation in HCC.</p><p><b>RESULTS</b>Methylation of the 8 TSGs was quite frequent in HCC, with a methylation rate of 95.0% in RASSF1A, 90.0% in APC, 73.3% in GSTP1, 65.0% in p16, 61.6% in RIZ1 and 60.0% in MGMT. Methylation of the 6 genes was more frequent in HCC than that in adjacent tissues (P < 0.05). The methylation rate of MGMT, GSTP1 and RIZ1 in the adjacent tissues was 41.6%, 40.0% and 25.0%, respectively, significantly higher than that in cirrhotic liver (P < 0.05). p16 methylation was more frequently observed in HCC in elderly patients. The frequency of MGMT methylation was tended to be higher in giant HCC than that in the other types of HCC. Patients with MGMT methylation in the tumor were found to have a shorter disease free survival.</p><p><b>CONCLUSION</b>Different frequency of methylation in hepatocellular carcinomas, adjacent liver tissues and cirrhotic livers implies that epigenetic alteration in the hepatocellular carcinogenesis may be a gradually progressive process. Methylation status of MGMT, GSTP1 and RIZ1 may be promising in risk assessment of hepatocellular carcinoma and in early diagnosis. Furthermore, MGMT methylation might be also used as a potential prognostic biomarker for hepatocellular carcinoma patients.</p>