Hepatitis B virus integration and hepatocarcinogenesis.

Hepatitis B virus (HBV) is the most common cause of hepatocellular carcinoma (HCC), which is the predominant liver cancer type in Southeast Asia. Approximately 350 million individuals suffer from persistent hepatitis B infection worldwide. HBV promotes HCC development through direct and indirect mechanisms. HBV DNA integrates into the host genome during the initial stages of tumorigenesis, causing insertional mutagenesis of cancer-related genes and genomic instability. Extrachromosomal circular DNA (ecDNA) is formed, which is efficiently amplified in large quantities to express viral genes and host oncogenes. Moreover, virus-associated proteins, such as the regulatory HBV X (HBx) protein and/or the modified preS/S envelope protein, alter the expression of genes associated with multiple functions in host cells. In this review, we summarize the role of the HBx and preS/S proteins in promoting tumorigenesis. In addition to summarizing the specific mechanism of HBV-related tumorigenesis, the concerns and perspectives for future study are discussed.