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Hepatocellular carcinoma (HCC) generally occurs in the presence of chronic liver injury, often as a sequela of liver fibrosis. Hepatic progenitor cells (HPCs) are known to be capable of forming both hepatocytes and cholangiocytes in chronic liver injury, which are also considered a source of myofibroblasts and tumor-initiating cells, under carcinogenic circumstances. However, the underlying mechanisms that activate HPCs to give rise to HCC are still unclear. In current study, the correlation between HPCs activation and liver fibrosis and carcinogenesis was investigated in rats and human specimens. We analyzed the role of HPCs in tumorigenesis, by transplanting exogenous HPCs in a diethylnitrosamine-induced rat HCC model. Our data indicated that HPC activation correlated with hepatic fibrosis and hepatocarcinogenesis. We further found that exogenous HPC infusion promoted liver fibrosis and hepatocarcinogenesis, while lipopolysaccharides (LPS) played an important role in this process. However, results of our study indicated that LPS did not induce HPCs to form tumor in nude mice directly. Rather, LPS induced myofibroblast-like morphology in HPCs, which enhanced the tumorigenic potential of HPCs. Further experiments showed that LPS/Toll-like receptor 4 (TLR4) signaling mediated the differentiation of HPCs into myofibroblasts and enhanced the production of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), which led to the aberrant expression of Ras and p53 signaling pathways in HPCs, and finally, promoted the proliferation and malignant transformation of HPCs, by long non-coding RNA regulation. Besides, examination of HCC clinical samples demonstrated that IL-6 and TNF-α production correlated with HPC activation, hepatic fibrosis, and HCC recurrence. Our study indicates that both myofibroblasts and tumor cells are derived from HPCs. HPC-derived myofibroblasts create tumor microenvironment and contribute to the proliferation and malignant transformation of HPCs. Furthermore, LPS present in the chronic liver inflammation microenvironment might play an important role in hepatocarcinogenesis, by regulating the plastic potential of HPCs.

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., (Copyright © 2017. Published by Elsevier Inc.)

Normally, hepatic progenitor cells (HPCs) are activated and differentiate into hepatocytes or bile ductular cells to repair liver damage during liver injury. However, it remains controversial whether the abnormal differentiation of HPCs occurs under abnormal conditions. Lipopolysaccharide (LPS), a component of the microenvironment, promotes liver fibrosis. In the present study, HPCs promoted liver fibrosis in rats following carbon tetrachloride (CCl 4 ) treatment. Meanwhile, the LPS level in the portal vein was elevated and played a primary role in the fate of HPCs. In vitro, LPS inhibited the hepatobiliary differentiation of HPCs. Concurrently, HPCs co-cultured with LPS for 2 weeks showed a tendency to differentiate into myofibroblasts (MFs). Thus, we conclude that LPS promotes the aberrant differentiation of HPCs into MFs as a third type of descendant. This study provides insight into a novel differentiation fate of HPCs in their microenvironment, and could thus lead to the development of HPCs for treatment methods in liver fibrosis.

Hepatic progenitor cells (HPCs) are bipotential stem cells that can differentiate into mature hepatocytes or biliary epithelial cells (BECs). They are thought to be involved in repair of liver injury and the incidence of hepatic carcinoma. Their physiology is closely associated with the microenvironment where they reside. Lipopolysaccharide (LPS), an important component of the hepatic pathological microenvironment, is stored in the liver and affects many types of cells in various hepatosis. HPCs may also be influenced by LPS. In this paper, mouse ED13.5 E-cadherin + foetal liver cells were isolated as mouse hepatic progenitor cells (mHPCs). Proliferation of mHPCs was promoted under LPS conditions both in vivo and in vitro. Moreover, LPS enhanced colony formation ability of mHPCs, and blocked them differentiation into mature hepatocytes and formation of a bile duct-liked structure. More importantly, long-term treatment with LPS promoted tumorigenesis of mHPCs in nude mice. Thus, we conclude that LPS may promote aberrant proliferation of mHPCs and restrict their normal differentiation. Long-term exposure of mHPCs to LPS increased the risk of tumour formation. These data provide insight into the links between LPS, HPCs fate, and tumorigenesis, and present novel insight into the relationship between HPCs and their microenvironment., (Copyright © 2016 The Author(s). Published by Elsevier Ireland Ltd.. All rights reserved.)