Abstract PO017: HBV alters YAP regulation in liver cancer by remodeling PP2A complexes

Abstract Viral hepatitis promotes hepatocellular carcinoma (HCC) initiation by inducing inflammation, cellular stress and cell death. However, the cell-intrinsic effects of viral infection in advanced HCC remain unclear. We used affinity purification mass spectrometry to develop a complete map of 145 interactions among Hepatitis B Virus (HBV) and host proteins in the HUH7 HCC tumor cell line, identifying known and novel HBV/host protein-protein interactions. We integrated this map with HCC genomes, identifying 61 proteins with preferential mutation in non-HBV HCC, suggesting that their interaction with HBV plays a role in cancer. Focusing on proteins that directly interact with the HBV oncoprotein X (HBx), we found that HBx rewires the effect of the PP2A phosphatase on HCC signaling. HBx binding excluded striatin-family regulatory subunits from the PP2A complex, causing Hippo kinase activation. This effect creates a requirement for integrin signaling to mTOR complex 2 to maintain expression of the YAP oncoprotein, critical for HCC growth. Thus, HBV rewires HCC signaling and may promote targetable dependencies. Citation Format: John Gordan, Adriana Pitea, Rigney E Turnham, Manon Eckhardt, Gwendolyn M Jang, Huat Lim, Alex L Choi, Sourav Bandyopadhyay, Danielle Swaney, Kevan Shokat, Trey Ideker, Nevan Krogan. HBV alters YAP regulation in liver cancer by remodeling PP2A complexes [abstract]. In: Proceedings of the AACR Special Conference: Advances in the Pathogenesis and Molecular Therapies of Liver Cancer; 2022 May 5-8; Boston, MA. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(17_Suppl):Abstract nr PO017.