PROJECT 1: SUMMARY Hepatocellular cancer (HCC) is a rising cause of cancer-related mortality. Nonalcoholic fatty liver disease (NAFLD), especially its aggressive form, nonalcoholic steatohepatitis (NASH), is a leading cause of cirrhosis and HCC. Gene-environmental interactions underlie the development of HCC in NAFLD. The I148M variant of the patatin-like phospholipase A-3 (PNPLA3I148M) gene is one of the best-described genetic determinants of HCC risk across multiple etiologies of chronic liver disease, including NAFLD. The mechanisms by which PNPLA3I148M leads to HCC are poorly understood. This gap in knowledge limits the ability to develop targeted preventive and therapeutic strategies for those with NAFLD carrying this mutation. It is our long-term goal to better understand the pathogenesis of NAFLD and the factors driving progression to cirrhosis and HCC and translate this information into preventive, diagnostic, and treatment strategies. This project is a natural evolution of our collaboration with ELEVATE program investigators and represents one of four interrelated projects targeting aspects of metabolic inflammation as a driver of HCC in NAFLD. Building on our previous publications and preliminary data, this project will test the central hypothesis that the PNPLA3I148M variant promotes HCC development in the setting of NASH via sphingosine-1-phosphate receptor 2 (S1PR2) activation in hepatocytes and macrophages via three specific aims: 1) Define the role of hepatic S1PR2 activation in Myc activation in PNPLA3I148M-associated NASH-HCC; 2) Define the role of S1PR2 activation in monocyte-derived macrophages as a PNPLA3I148M-related driver of inflammation, NASH progression, and HCC; 3) Test the therapeutic effects of a Myc inhibitor and S1PR2 antagonist on PNPLA3I148M-associated HCC. Our studies have shown that dysregulated bile acid homeostasis is closely associated with NASH-HCC disease progression. Bile acids are important signaling molecules and play a critical role in hepatic lipid metabolism by activating different bile acid receptors. We have also previously shown that conjugated primary bile acid-induced activation of S1PR2 plays an important role in regulating hepatic lipid and glucose metabolism. Our preliminary data further showed that bile acid levels and composition were significantly changed in human NASH patients and NASH mice, especially with overexpression of PNPLA3I148M. It has been well-established that Myc is a prototypic oncogene involved in various cancers, including HCC. Our preliminary studies also showed that bile acid-induced activation of S1PR2 in the liver and macrophages contributes to NASH progression. In this project, the newly developed NASH-HCC mouse models with liver-specific overexpression of human PNPLA3WT and PNPLA3I148M variant in our diet-induced animal model of NAFLD (DIAMOND) will be used to test the therapeutic effects by targeting Myc and S1PR2. Completion of our proposed studies will have a major impact by providing novel insights on mechanisms of HCC development in NASH, especially in the context of PNPLA3I148M that will inform future therapeutic strategies.

PROJECT 1: NARRATIVE Nonalcoholic fatty liver disease (NAFLD), especially its aggressive form, nonalcoholic steatohepatitis (NASH), is a leading cause of cirrhosis and hepatocellular cancer (HCC). The I148M variant of the patatin-like phospholipase A-3 (PNPLA3) gene is one of the best-described genetic determinants of HCC risk across multiple etiologies of chronic liver disease, including NAFLD; however, the mechanisms by which PNPLA3I148M leads to HCC are poorly understood. The focus of this application is to examine the role of the PNPLA3I148M variant in promoting HCC development and further identify the underlying mechanisms for developing potential therapies.