p16INK4A hypermethylation is associated with hepatitis virus infection, age, and gender in hepatocellular carcinoma

Purpose: The tumor suppressor gene p16^INK4A is mainly inactivated by an epigenetic change involving promoter hypermethylation in hepatocarcinogenesis. The possible clinical impact of p16^INK4A methylation and the potential risk factors for this epigenetic alteration have not been thoroughly investigated. Experimental Design: We studied the methylation status and mRNA and protein expression of p16^INK4A in 50 hepatocellular carcinomas and corresponding nonneoplastic liver lesions using methylation-specific PCR, reverse transcription-PCR, and immunohistochemical techniques. Results: p16^INK4A hypermethylation was observed in 58% (29 of 50) of the hepatocellular carcinomas and 16% (6 of 38) of the corresponding chronic hepatitis and cirrhosis tissue samples. p16 ^INK4A methylation was significantly associated with mRNA and protein expression (P <0.001 and P = 0.003, respectively). All of the p16 ^INK4A-methylated tumors were positive for hepatitis B virus or hepatitis C virus markers, but none of the virus-negative tumors exhibited p16^INK4A methylation (P = 0.006). The frequency of p16 ^INK4A hypermethylation tended to be higher in hepatitis C virus-related tumors (23 of 32, 72%) than in hepatitis B virus-related tumors (6 of 13, 46%; P = 0.1). Aberrant methylation of p16^INK4A was also related significantly to increasing age, female gender, and normal levels of serum PIVKA-II (P = 0.02, 0.04, and 0.04, respectively). No statistically significant difference in survival was observed between patients with p16 ^INK4A hypermethylation and those without. Conclusions: Our observations suggest that p16^INK4A hypermethylation may contribute to hepatocarcinogenesis from an early stage and that multiple risk factors, such as viral infections, age, and gender, may be associated with p16^INK4A hypermethylation in hepatocarcinogenesis.