SFRP1 and hepatocellular carcinoma: In six genes (p16, RASSF1A, GSTP1, APC, p15 and SFRP1), there was significant difference in the level of hypermethylation between HBV-positive carcinoma tissues and HBV-negative carcinoma tissues, revealing that HBV infection could induce methylation of these genes in HCC.