Chemerin Is Induced in Non-Alcoholic Fatty Liver Disease and Hepatitis B-Related Hepatocellular Carcinoma

SIMPLE SUMMARY: Hepatocellular carcinoma (HCC) is a frequent liver cancer and high expression of bioactive chemerin in hepatocytes was protective in experimental HCC models. The main risk factors for HCC are non-alcoholic fatty liver disease (NAFLD), hepatitis B and C infections. The current analysis showed that chemerin protein was induced in HCC tissues of NAFLD and hepatitis B infected patients. This upregulation was modest in patients with unknown disease etiology and not detected in hepatitis C infected patients. Protein levels of the chemerin receptor CMKLR1 strongly declined in the tumors of NAFLD patients and patients with unclear disease etiology but not in patients with viral infections. Our results demonstrate that the expression of chemerin in HCC is related to disease etiology and this could also apply to the role of chemerin in human HCC. In contrast to the present findings, chemerin was shown to be low in the HCC tissues of Asian patients with mostly viral disease etiology and this indicates ancestry-specific regulation of chemerin in HCC. ABSTRACT: Chemerin is protective in experimental models of hepatocellular carcinoma (HCC). Noteworthy, chemerin mRNA and protein were reduced in HCC tissues of Asian patients with mostly hepatitis B disease etiology. The current study nevertheless showed that chemerin protein was induced in tumor tissues of European HCC patients with non-alcoholic fatty liver disease (NAFLD) and patients with unclear disease etiology. A similar regulation was observed in hepatitis B virus (HBV), but not in hepatitis C virus (HCV), related HCC. The apparent discrepancy between the regulation of chemerin in HBV-HCC obtained from our study and recent reports led us to use the chemerin antibodies applied in the previous assays. These antibodies could not equally detect different chemerin isoforms, which were overexpressed in HepG2 cells. Higher chemerin protein in HCC was nevertheless confirmed by the use of all antibodies. Chemerin protein was low in Huh7 and PLC/PRF/5 cells whereas HepG2 and Hep3B cells had chemerin protein similar as primary human hepatocytes. Besides, the anti-tumor effects of retinoids in hepatocyte cell lines did not enclose upregulation of chemerin, which was initially discovered as a tazarotene induced protein in the skin. Finally, protein levels of the chemerin receptor, chemokine-like receptor 1 (CMKLR1), declined in non-viral, and tended to be lower in HBV-HCC tissues suggesting reduced chemerin activity in the tumors. To sum up, our work showed an opposite regulation of chemerin and CMKLR1 in NAFLD and HBV associated HCC. In HCV-HCC neither chemerin nor its receptor were changed in the tumor tissues. Current findings do not support a critical role of total chemerin protein levels in HCC of non-viral and viral etiology. Accordingly, tumor-localized chemerin protein was not associated with tumor-node-metastasis classification.