SRA

BACKGROUND AND AIM: Intrahepatic cholangiocarcinoma (ICC) is a liver tumor of increasing incidence and devastating prognosis. A critical barrier to developing an effective regimen for ICC is its intra- and inter-tumoral molecular heterogeneity, which may in part be due to its diverse cellular origin. We investigated clinical relevance and the molecular mechanisms underlying hepatocyte (HC)-driven ICC development. METHODS: Expression of ICC driver genes in human diseased livers at risk for ICC development were examined. Sleeping beauty and hydrodynamic tail vein injection based Akt-NICD/YAP1 ICC model was used to investigate pathogenetic roles of SOX9 and YAP1 in HC-driven ICC. These models and in silico studies led to identification of DNA methyltransferase-1 (DNMT1) as a YAP1 target, which was validated by both loss- and gain-of-function studies. RESULTS: Co-expression of AKT along with NICD/YAP1 in HC yielded ICC which resembled proliferative, Notch-activated, and stem cell-like subclasses of clinical ICC. NICD induced SOX9 and YAP1 in HC-driven ICC and deletion of either significantly delays ICC development. Yap1 deletion or TEAD inhibition, but not Sox9 deletion, impaired HC-to-biliary epithelial cell (BEC) reprogramming. DNMT1 was discovered as a novel downstream effector of YAP1-TEAD complex that directs HC-to-BEC/ICC fate-switch. DNMT1 loss prevented Notch/YAP1-dependent HC-driven cholangiocarcinogenesis, and DNMT1 re-expression restored ICC development following TEAD repression. Co-expression of DNMT1 with AKT was sufficient to induce tumor development including ICC. DNMT1 was detected in subset of HCs and dysplastic BECs in cholestatic human livers prone to ICC development. CONCLUSION: We identify a novel NOTCH-YAP1/TEAD-DNMT1 axis essential for of HC-to-BEC/ICC conversion, may be relevant in cholestasis-to-ICC pathogenesis in the clinic. Overall design: mRNA profiles of two conditions: WT healthy control liver (3 repeats) and human AKT+NICD ICC liver (5 repeats)