ABSTRACT: Hepatocellular carcinoma (HCC) is caused by hepatitis virus HBV/HCV, non-alcoholic steatohepatitis (NASH), and alcoholic liver disease (ALD), which typically progress from liver fibrosis, to cirrhosis and cancer. Our preliminary data demonstrate that genetic deletion of IL-17 signaling in steatotic hepatocytes significantly attenuates the development of HCC in ALD-injured mice, suggesting that IL-17 signaling is a target for anti- HCC therapy. Our central hypothesis is that IL-17 signaling regulates chemokine production, de novo lipogenesis, and TNFRI expression/turnover in steatotic hepatocytes. IL-17 signaling promotes ALD- and NASH-induced HCC via activation of TNF/TNFRI-SREBP1/2-DHCR7-cholesterol synthesis, and suppression of ARTS-1/NUC2-dependent TNFRI exocytosis. The goal of the study is to characterize the mechanism by which IL-17A/IL-17RA signaling regulates responses in metabolically injured hepatocytes, and to compare the pathways of IL-17 signaling in the experimental models of ALD- and NASH. Strategy: Responses to IL-17 signaling will be compared side-by side in ALD- and NASH-injured WT and hepatocyte-specific IL-17RA knockout mice with HCC. We determine if IL-17 signaling is similarly activated in NASH- and ALD-injured hepatocytes. We determine if blocking of IL-17 signaling in steatotic hepatocytes is sufficient to suppress HCC in the metabolically injured liver. Specifically, the role of IL-17 in the pathogenesis of DEN- or (Mup-uPA)- induced HCC in ALD- and NASH-injury will be studied in WT and hepatocyte-specific IL-17RA knockout mice (IL-17RAΔHep mice). Development of HCC, inflammation, steatosis and liver fibrosis will be across all groups of mice. Mutagenesis of WT and IL-17RA-deficient AFP+YAP+ HCC, and responses of steatotic hepatocytes to IL-17A will be characterized. Specifically, we determine if chemokine secretion, cholesterol synthesis are suppressed in metabolically injured IL-17RA-deficient hepatocytes (AIM1). We will test a novel hypothesis by which IL-17 signaling facilitates TNF/TNFRI-Caspase2-SP1-SREBP1/2-DHCR7-dependent cholesterol synthesis in steatotic hepatocytes via blocking ARTS-1-NUCB2-regulated TNFRI exocytosis (and possibly IL- 6, IL-1RII) thereby prolonging TNF (IL-6, IL-1) signaling and promoting alcohol-induced HCC (AIM2). Our findings will be translated into humans by characterization of IL-17RA-TNFRI-signaling pathways in archived human livers from HCC patients with ALD. We will test if therapeutic blocking of the key IL-17 signaling molecules (IL-17RA, TNFRI, ARTS-1, and DHCR7) specifically in hepatocytes using N-acetylgalactosamine (GalNAc)-conjugated antisense RNA oligonucleotides (ASOs) can effectively suppress steatosis, fibrosis, and HCC in WT mice with NASH and ALD (AIM3). If proven, hepatocyte-specific blocking of IL-17 signaling using GalNAc-ASOs can provide a new strategy for HCC treatment in ALD and NASH patients.