Immune response involved in liver damage and the activation of hepatic progenitor cells during liver tumorigenesis

Hepatocellular carcinoma (HCC) is a typical inflammation-related cancer. Hepatitis B virus (HBV) and hepatitis C virus (HCV) infection are well-known leading causes of HCC. However, the mechanism of the induction of HCC by these virus is still being debated. This review will focus on the current knowledge of the pathogenesis of HBV- and HCV-induced inflammation and the role of such immune activation in the tumorigenesis of HCC. It is well established that the recruitment of certain number and type of immune cells to liver is essential for the resolution of HBV and HCV infection and the prevention of subsequent chronic persistent infection. However, in case that the immune response do not completely clear virus, persistent chronic infection occurs, and the perpetual immune response may contribute to chronic damages of the liver. Such chronic inflammatory damages further harm hepatocytes, but not hepatic progenitor cells (HPCs). Thus, following chronic damages, HPCs are activated and their dysregulated proliferation ensures survival in the hostile environment, contributing to the tumorigenesis of HCC. Furthermore, accumulating evidence also provides a strong link between HPCs and human hepatocellular carcinoma. Collectively, these findings support a notion that immune response is involved in liver damage during hepatitis virus infection, and the activation and dysregulated differentiation of hepatic progenitor cells promote the tumorigenesis of human hepatocellular carcinoma.