Gankyrin Drives Malignant Transformation Of Carbon Tetrachloride-mediated Chronic Liver Damage Via Rac1/JNK Pathway

Background and Purpose:Hepatocelluar carcinoma (HCC) is the prototype of inflammation-associated cancer, since most patients with HCC have an established background of unresolved chronic liver injury and cirrhosis. Major HCC risk factors include infection with hepatitis viruses, intake of aflatoxin-contaminated food, obesity, alcoholic liver disease, nonalcoholic steatohepatitis (NASH), chronic hepatic inflammation, and cirrhosis. Chronic liver damage is the primary risk factor for developing HCC, accompanied by long periods of chronic liver disease. To figure out the molecular mechanism of causing transition from chronic liver injury to dysplasia is therefore important.Gankyrin (PSMD10 or p28GANK) was identified as an oncoprotein that frequently overexpressed in human liver cancers, increased in the earlier stage of liver carcinogenesis. It controls phosphorylated Rb and p53 degradation, promotes expansion of tumor-initiating cells, and accelerates HCC progression. Gankyrin has been shown to regulate NF-κB and AKT. We recently found that, in a rat model of carcinogen-induced liver carcinogenesis, endogenous Gankyrin elevated in the stage of liver damage and cirrhosis. However, it is still unknown how Gankyrin regulates chronic liver injury and promotes hepatocarcinogenesis in vivo. This study used hepatocyte-specific Gankyrin-overexpression mice (gankyrinhep mice) to study the role of gankyrin in carbon tetrachloride (CCl4-mediated liver injury and the maligant transformation.Method:Immunoblot for Gankyrin expression in patients with cirrhosis were performed, compared with hemangioma and HCC. A novel model of liver injury transformation into maliganant tumors was developed in hepatocyte-specific Gankyrin overexpression mice injected by CCl4 alone or combination with diethylnitrosamine (DEN). The several pathways about liver injury, inflammation and fibrosis were examined in isolated primary hepatocytes and above liver tissues.Results:Gankyrin increased in patients with cirrhosis. Enhanced hepatic injury, severe inflammation, and persistent dysregulated wound healing, giving rise to strengthened compensatory proliferation of surving hepatocytes, occurred to gankyrinhep mice during CCl4 performance. In addition to more liver fibrosis and tumorigenesis after DEN combination with CCl4 treatment, gankyrinhep mice exhibited maligant transformation from liver injury to liver tumors even under long-term single CCl4 administration, while wild-type mice merely experienced fibrosis. This correlated with augmented expressions of cell cycle related genes and abnormal activation of Racl/c-jun N-terminal kinase (JNK). Pharmacological inhibition of Racl/JNK pathway attenuated hepatic fibrosis, and prevented CCl4-induced carcinogenesis in gankyrinhep mice.Conclusion:Gankyrin promotes liver fibrosis/cirrhosis progression into hepatocarcinoma relying on a persistent liver injury and inflammatory microenvironment. Blockade of Racl/JNK activation impeded Gankyrin-mediated hepatocytic malignant transformation, indicating the combined inhibition of Gankyrin and Racl/JNK as a potential prevention for cirrhosis transition.