Project description: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.
Project description: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.
Project description:Background & aimsIntrahepatic cholangiocarcinoma (ICC) is a devastating liver cancer with extremely high intra- and inter-tumoral molecular heterogeneity, partly due to its diverse cellular origins. We investigated clinical relevance and the molecular mechanisms underlying hepatocyte (HC)-driven ICC development.MethodsExpression of ICC driver genes in human diseased livers at risk for ICC development were examined. The sleeping beauty and hydrodynamic tail vein injection based Akt-NICD/YAP1 ICC model was used to investigate pathogenetic roles of SRY-box transcription factor 9 (SOX9) and yes-associated protein 1 (YAP1) in HC-driven ICC. We identified DNA methyltransferase 1 (DNMT1) as a YAP1 target, which was validated by loss- and gain-of-function studies, and its mechanism addressed by chromatin immunoprecipitation sequencing.ResultsCo-expression of AKT and Notch intracellular domain (NICD)/YAP1 in HC yielded ICC that represents 13% to 29% of clinical ICC. NICD independently regulates SOX9 and YAP1 and deletion of either, significantly delays ICC development. Yap1 or TEAD inhibition, but not Sox9 deletion, impairs 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 through the repression of HC-specific genes regulated by master regulators for HC differentiation, including hepatocyte nuclear factor 4 alpha, hepatocyte nuclear factor 1 alpha, and CCAAT/enhancer-binding protein alpha/beta. 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 a subset of HCs and dysplastic BECs in cholestatic human livers prone to ICC development.ConclusionWe identified a novel NOTCH-YAP1/TEAD-DNMT1 axis essential for HC-to-BEC/ICC conversion, which may be relevant in cholestasis-to-ICC pathogenesis in the clinic.
Project description:We investigate the dependence of human malignant pleural mesothelioma on a functional YAP1-TEAD transcription factor complex to maintain fully established tumors in vivo. We show that, in a dysfunctional Hippo genetic background, downregulation of YAP1 by shRNA results in modulation of YAP1/TEAD-dependent gene expression and regression of established tumor xenografts. Our data demonstrate that, in the context of a mutated Hippo pathway, YAP1 activity is essential to maintain the growth of mesothelioma cells in vivo, thus validating the concept of inhibiting the activated YAP1/TEAD complex for the treatment of malignant pleural mesothelioma patients.
Project description:YAP is the principle effector of the Hippo signaling pathway; a key regulator of tissue homeostasis whose dysregulation is linked to cancer development. YAP regulation of gene expression is thought to involve the TEAD transcription factor family. Here we show that YAP and TEAD1 binding always co-occurs and is mediated by single as well as double TEAD1 motifs with a particular 3bp spacer (CATTCCNNNCATTCC). This suggests that YAP activity appears exclusively mediated by TEAD1. Despite being characterized as a promoter-binding factor YAP/TEAD actually binds predominantly to enhancers. Moreover we show that YAP is necessary for activity of the linked gene and proper chromatin state of regulated enhancers. These results establish mode of binding and activation of YAP mediated nuclear response of the Hippo pathway by TEAD1 and provide a comprehensive list and a novel class of direct target genes that are regulated distally and could be exploited for cancer therapeutics. Sequencing of ChIP and input samples for YAP1 and TEAD1 transcription factors and H3K27ac histone modification in SF268 glioblastoma cells and for YAP1 transcription factor in NCI-H2052 mesothelioma cells.