Ruth Broering

Background and Aims Hepatitis B virus (HBV) infection is a major cause of hepatocellular carcinoma (HCC) development and progression. The aim of this study was to mechanistically investigate the involvement of Hippo signalling in HBV surface antigen (HBsAg)‐dependent neoplastic transformation. Methods Liver tissue and hepatocytes from HBsAg‐transgenic mice were examined for the Hippo cascade and proliferative events. Functional experiments in mouse hepatoma cells included knockdown, overexpression, luciferase reporter assays and chromatin immunoprecipitation. Results were validated in HBV‐related HCC biopsies. Results Hepatic expression signatures in HBsAg‐transgenic mice correlated with YAP responses, cell cycle control, DNA damage and spindle events. Polyploidy and aneuploidy occurred in HBsAg‐transgenic hepatocytes. Suppression and inactivation of MST1/2 led to the loss of YAP phosphorylation and the induction of BMI1 expression in vivo and in vitro. Increased BMI1 directly mediated cell proliferation associated with decreased level of p16 INK4a , p19 ARF , p53 and Caspase 3 as well as increased Cyclin D1 and γ‐H2AX expression. Chromatin immunoprecipitation and the analysis of mutated binding sites in dual‐luciferase reporter assays confirmed that the YAP/TEAD4 transcription factor complex bound and activated the Bmi1 promoter. In chronic hepatitis B patients, paired liver biopsies of non‐tumour and tumour tissue indicated a correlation between YAP expression and the abundance of BMI1. In a proof‐of‐concept, treatment of HBsAg‐transgenic mice with YAP inhibitor verteporfin directly suppressed the BMI1‐related cell cycle. Conclusion HBV‐associated proliferative HCC might be related to the HBsAg‐YAP‐BMI1 axis and offer a potential target for the development of new therapeutic approaches.

Background and Aims: Being the most common cause of acute viral hepatitis with >20 million cases per year and 70,000 deaths annually, HEV presents a long-neglected and underinvestigated health burden. Although the entry process of viral particles is an attractive target for pharmacological intervention, druggable host factors to restrict HEV entry have not been identified so far. Approach and Results: Here we identify the EGF receptor (EGFR) as a novel host factor for HEV and reveal the significance of EGFR for the HEV entry process. By utilizing RNAi, chemical modulation with Food and Drug Administration–approved drugs, and ectopic expression of EGFR, we revealed that EGFR is critical for HEV infection without affecting HEV RNA replication or assembly of progeny virus. We further unveiled that EGFR itself and its ligand-binding domain, rather than its signaling function, is responsible for the proviral effect. Modulation of EGF expression in HepaRG cells and primary human hepatocytes affected HEV infection. Conclusions: Taken together, our study provides novel insights into the life cycle of HEV and identified EGFR as a possible target for future antiviral strategies against HEV.