Promoter hypermethylation of p14 (ARF) , RB, and INK4 gene family in hepatocellular carcinoma with hepatitis B virus infection

Abstract

Both hepatitis B virus (HBV) and gene methylation play important roles in hepatocarcinogenesis. However, their association between HBV infection and gene methylation is not fully understood. Cell cycle control involving RB1 gene-related cell inhibitors is one of the main regulatory pathways were reported to be altered in hepatocellular carcinoma (HCC). The purpose of this research is to assess the methylation status of p14 (ARF) and INK4 gene family (p14 (ARF) , p15 (INK4B) , p16 (INK4A) , and p18 (INK4C) ) in HCC with HBV infection and HCC without it, and discuss possible role of HBV-induced hypermethylation in the mechanism of hepatocarcinogenesis. Methylation status of RB, p14 (ARF) , and INK4 gene family in 64 case of HCC with HBV infection and 24 cases without it were detected by methylation-specific polymerase chain reaction, and HBV-DNA of the plasma were detected by quantitative real-time polymerase chain reaction. p14 (ARF) , p15 (INK4B) , p16 (INK4A) , and RB hypermethylation were observed in 30 (34.1%), 50 (56.8%), 62 (70.5%), and 24(27.3%) of 88 hepatocellular carcinomas, respectively. Methylation frequencies of them between HCC with HBV infection and HCC without it were 43.8% versus 8.3 % (p14 (ARF) ), 68.9% versus 25% (p15 (INK4B) ), 90.6% versus 16.7% ( p16 (INK4A) ), and 28.1 % versus 25% (RB), respectively. In HBV-associated HCC, the numbers of methylated genes were also more than HCC without virus infection, more than two methylated genes were seen in 48 of 64 (75 %) cases; more than three methylated genes were found in 32 of 64 (50%); correspondently, no one case has more than two genes methylated. p18 (INK4C) methylation product was not found in cancerous or non-cancerous tissues of 88 HCC. HBV infection is associated with p14 (ARF) , p15 (INK4B) , p16 (INK4A) , and RB gene methylation (P = 0.048, 0.035, 0.02); HBV-DNA replication is associated with p14 (ARF) , p15 (INK4B) , p16 (INK4A) , and RB gene methylation (P = 0.048, 0.035, 0.02); high rate of p14 (ARF) , p15 (INK4B) , and p16 (INK4A) in HCC with HBV infection suggests that HBV-induced hypermethylation may be one of the mechanisms of HBV involved in hepatocellular carcinogenesis.