Study Of Aberrant Methylation And Clinical Significance Of Suppressor Gene In Hepatocellular Carcinoma

Objective:To investigate the promoter methylation status of GSTP1, P16, RIZ1, RASSF1A inpaired hepatocellular carcinoma(HCC) and adjacent non-cancerous tissues, the comparednormal liver tissues, and to assess their significant role in hepatocarcinogenesis, to selectthe molecular biological indicator for the early clinical diagnosis of HCC.Method:Methylation status of GSTP1, P16, RIZ1and RASSF1A genes promoter weredetected by Methylation Specific PCR(MSP) in35paired HCC and adjacentnon-cancerous tissues,20normal liver tissues as control. The relationship betweenmethylation and clinicopathologic factors(such as sex, age, tumor size, histopathologicaldifferentiation, AFP, cirrhosis, capsular invasion, tumor metastasis) were analyzed.Result:GSTP1promoter methylation ratios were observed in57.1%(20/35),25.7%(9/35),0%(0/20) and P16promoter methylation ratios were observed in54.3%(19/35)，37.1%(13/35)，0%(0/20) in HCC, adjacent non-cancerous tissues and normal controltissues, respectively. While RIZ1promoter methylation ratios were observed in68.6%(24/35)，14.3%(5/35)，0%(0/20) and RASSF1A promoter methylation ratios wereobserved in88.6%(31/35)，74.3%(26/35)，10%(2/20) in HCC, adjacent non-canceroustissues and normal control tissues, respectively. The rate of methylation of GSTP1andRIZ1genes in HCC was significantly higher than in adjacent non-cancerous tissues(P＜0.01) and normal control tissues(P＜0.01).The rate of methylation of P16and RASSF1Agenes in HCC was higher than in adjacent non-cancerous tissues, but showed no significance(P＞0.05). The rate of methylation of P16and RASSF1A genes in HCC wassignificantly higher than in normal control tissues(P＜0.01). When the relationshipbetween methylation and clinicopathologic factors were analyzed, we could see that therate of methylation of GSTP1gene was significantly higher in tumor with capsularinvasion than in tumor without capsular invasion(P＜0.05); the rate of methylation of P16gene was significantly higher in tumor with HbsAg positive than in tumor with HbsAgnegative(P＜0.05); promoter methylation of RIZ1and RASSF1A had no statisticalcorrelation with the clinicopathologic factors（P＞0.05）.Conclusion:1. In the progression of HCC, the promoter methylation of the tumor suppressor genesof GSTP1, P16, RIZ1and RASSF1A, which regarded as common epigenetic modificationmethod, does not only occur in after the appearance of the tumor, but also happens in theearly stage, and it will gradually accumulate in the malignant transformation process ofHCC.2. The methylation status of GSTP1and RIZ1promoter were specific to HCC, theycan make good differentiation between HCC and non-cancerous tissues. Promotermethylation of the tumor suppressor genes of GSTP1and RIZ1might serve as themolecular biology markers for the auxiliary diagnosis and risk evaluation of HCC.3.Chronic HBV infection may be lead to promoter methylation of P16, and thepromoter methylation of GSTP1probably has effect on the invasion of HCC.4.MSP is a simple, sensitive and specific method for determining the methylationstatus of gene promoter CpG island, and it can be used in the auxiliary diagnosis of HCC.