Background & aims: Non-alcoholic fatty liver disease (NAFLD), the hepatic correlate of the metabolic syndrome, is a major risk factor for hepatobiliary cancer (HBC). Although chronic inflammation is thought to be the root cause of all these diseases, the mechanism whereby it promotes HBC in NAFLD remains poorly understood. Herein, we aim to evaluate the hypothesis that inflammation-related dysregulation of the ESRP2-NF2-YAP/TAZ axis promotes HB carcinogenesis.
Methods: We use murine NAFLD models, liver biopsies from patients with NAFLD, human liver cancer registry data, and studies in liver cancer cell lines.
Results: Our results confirm the hypothesis that inflammation-related dysregulation of the ESRP2-NF2-YAP/TAZ axis promotes HB carcinogenesis, supporting a model whereby chronic inflammation suppresses hepatocyte expression of ESRP2, an RNA splicing factor that directly targets and activates NF2, a tumor suppressor that is necessary to constrain YAP/TAZ activation. The resultant loss of NF2 function permits sustained YAP/TAZ activity that drives hepatocyte proliferation and de-differentiation.
Conclusion: Herein, we report on a novel mechanism by which chronic inflammation leads to sustained activation of YAP/TAZ activity; this imposes a selection pressure that favors liver cells with mutations enabling survival during chronic oncogenic stress.
Lay summary: Non-alcoholic fatty liver disease (NAFLD) increases the risk of hepatobiliary carcinogenesis. However, the underlying mechanism remains unknown. Our study demonstrates that chronic inflammation suppresses hepatocyte expression of ESRP2, an adult RNA splicing factor that activates NF2. Thus, inactive (fetal) NF2 loses the ability to activate Hippo kinases, leading to the increased activity of downstream YAP/TAZ and promoting hepatobiliary carcinogenesis in chronically injured livers.
Keywords: alternative RNA splicing; epithelial splicing regulatory protein-2 (ESRP2); hepatocellular carcinoma (HCC); hippo kinase; liver cancer; neurofibromatosis-2 (NF2); nonalcoholic fatty liver disease (NAFLD); yes-associated protein (YAP).
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