Therapeutic implication of SOX9 and YAP1 co‐repression in advanced intrahepatic cholangiocarcinoma

Abstract

IntroductionIntrahepatic cholangiocarcinoma (iCCA) is a liver tumor of increasing incidence and devastating prognosis. The most critical barrier for developing a globally effective therapy for iCCA is molecular heterogeneity caused by diverse molecular drivers and cellular origins in the liver. Clinically, over 90% of iCCAs show alterations of YAP1 and/or SOX9. Therefore, we investigated the therapeutic potential of co‐repression of YAP1 and SOX9 as a wide range therapeutic option for advanced iCCA.MethodsBy immunohistochemistry (IHC) using 2 tissue microarrays, we examined the localization of SOX9 and YAP in clinical iCCA. We also assessed clinical relevance of AKT‐NICD (AN) /YAP (AY)‐dependent hepatocyte‐driven iCCA by bioinformatic analysis comparing their transcriptome with large human datasets. Lastly, we comprehensively investigated therapeutic effect of simultaneous deletion of Sox9 and Yap1 in advanced murine iCCA using respective floxed mice.ResultsOver 90% of human CCA samples (n=108) exhibited nuclear SOX9 and YAP1. We also identified significant upregulation of p‐AKT, SOX9 and YAP1 in HCs of patients with primary sclerosing cholangitis and nonalcoholic steatotis hepatitis, well‐known risk factors for iCCA. While co‐expression of AN led to hepatocyte‐derived lethal iCCA, conditional deletion of either Yap1 or Sox9 dramatically reduced AN‐ iCCA development. Yap1 deletion impaired HC‐to‐biliary epithelial cell (BEC) fate conversion and tumor cell proliferation, while Sox9 elimination only repressed proliferation. Interestingly, following single deletion of either Yap1 or Sox9 we observed a few iCCA tumors expressing either SOX9 or YAP1 but not both. This is also identified in a small subset of human iCCA; SOX9+/YAP1‐ (4.6%) or SOX9‐/YAP1+ (3.7%), suggesting that single deletion of YAP1 or SOX9 is not sufficient to abrogate clinical iCCA. We also found that simultaneous deletion of Yap1 and Sox9 completely prevents iCCA development. Remarkably, co‐deletion of Yap1 and Sox9profoundly decreases fully developed lethal iCCA burden while extending survival. However, singular deletion of either shows no survival benefit compared to control group harboring advanced iCCA as a therapeutic manner.ConclusionsWe elucidate the critical, but distinct roles of Yap1and Sox9 in iCCA development and demonstrate the therapeutic potential of simultaneous targeting both for wide range of iCCA irrespective of drivers. Ongoing work will comprehensively delineate the molecular mechanism how YAP1 and SOX9 compensate each other when either is removed in iCCA, and will be relevant for studying adaptive resistance against the singular targeting of SOX9 or YAP1 in iCCA.