Methylation of tumor associated genes in tissue and plasma samples from liver disease patients

To investigate whether aberrant hypermethylation in plasma DNA could be used as diagnosis makers for hepatocellular carcinoma (HCC), we performed methylation-specific PCR (MSP) to check the methylation status of five tumor associated genes in 36 cases of tissue and 42 cases of plasma samples from HCC and liver cirrhosis patients, respectively. The hypermethylation frequency of GSTP1 and RASSF1A showed significant difference between HCCs and liver cirrhosis with or without HBV infection (P<0.05), but differences of the hypermethylation status of APC, E-cadherin, and P16 were not statistically significant. There were no significant differences in the hypermethylation status of five genes between the groups of cirrhosis with and without HBV infection. The significant differences of E-cadherin, GSTP1, P16, and RASSF1A in methylation between HCCs and liver cirrhosis were not observed in the plasma samples. Furthermore, the inconsistent results of MSP and real-time quantitative PCR for the paired samples of tissue and plasma suggested that plasma DNA could not fully stand for tissue DNA. In conclusion, hypermethylation of some specific, but not all, tumor associated genes may be involved in hepatocarcinogenesis; examination of the methylation status of E-cadherin, GSTP1, P16, and RASSF1A in the plasma samples might have limited usage for HCC diagnosis.