CCNA2 and hepatocellular carcinoma: Genes BUB1B, CCNB1, CDK1, CDC25C and CCNA2 play important roles in cell cycle regulation; HCV, EBV and HPV can stimulate cell proliferation through CDK1 or CCNA2. These genes were not found in HBV carcinogenesis pathways, but our results implied that there should be an unknown regulation of cell cycle in HBV-related HCC.