In addition, methylation of p16, RASSF1A, APC, p15 and SFRP1 genes in HBV-positive carcinoma tissues was significantly higher than HBV-negative carcinoma tissues but not adjacent tissues, revealing that methylation of these five genes may play a significant role in the middle-late stage of the hepatocarcinogenesis process. The gene discussed is APC; the disease is carcinoma.