Project description:Transcriptomic profiling classifies pancreatic ductal adenocarcinoma (PDAC) into several molecular subtypes with distinctive histological and clinical characteristics. However, little is known about the molecular mechanisms that define each subtype and how this correlates with clinical outcome. Mutant KRAS is the most prominent driver in PDAC, present in over 90% of tumors, but the dependence of tumors on oncogenic KRAS signaling varies between subtypes. In particular, squamous subtype PDACs are relatively independent of oncogenic KRAS signaling and typically display much more aggressive clinical behavior versus progenitor subtype PDACs. Here, we identified that YAP1 activation is enriched in the squamous subtype and associated with poor prognosis. Activation of YAP1 in progenitor subtype cancer cells profoundly enhanced malignant phenotypes and transformed progenitor subtype cells into squamous subtype. Conversely, depletion of YAP1 specifically suppressed tumorigenicity of squamous subtype PDAC tumors. Mechanistically, we uncovered a significant positive correlation between WNT5A expression and the YAP activation signature, and we demonstrated that WNT5A overexpression led to YAP activation and recapitulated YAP1-dependent but but Kras-independent phenotype of tumor progression and maintenance. Thus, our study identifies YAP1 oncogene as a major driver of squamous subtype PDAC and uncovers the role of WNT5A to drive PDAC malignancy via activation of the YAP pathway.
Project description:Transcriptomic profiling classifies pancreatic ductal adenocarcinoma (PDAC) into several molecular subtypes with distinctive histological and clinical characteristics. However, little is known about the molecular mechanisms that define each subtype and their correlation with clinical outcome. Mutant KRAS is the most prominent driver in PDAC, present in over 90% of tumors, but the dependence of tumors on oncogenic KRAS signaling varies between subtypes. In particular, the squamous subtype is relatively independent of oncogenic KRAS signaling and typically displays much more aggressive clinical behavior versus the progenitor subtype. Here, we identified that yes-associated protein 1 (YAP1) activation is enriched in the squamous subtype and associated with poor prognosis. Activation of YAP1 in progenitor subtype cancer cells profoundly enhanced malignant phenotypes and transformed progenitor subtype cells into squamous subtype. Conversely, depletion of YAP1 specifically suppressed tumorigenicity of squamous subtype PDAC cells. Mechanistically, we uncovered a significant positive correlation between WNT5A expression and YAP1 activity in human PDAC and demonstrated that WNT5A overexpression led to YAP1 activation and recapitulated a YAP1-dependent but Kras-independent phenotype of tumor progression and maintenance. Thus, our study identifies YAP1 oncogene as a major driver of squamous subtype PDAC and uncovers the role of WNT5A in driving PDAC malignancy through activation of the YAP pathway.
Project description:The transcriptional co-activator YAP1 oncogene is the downstream effector of the Hippo pathway, which regulates tissue homeostasis, organ size, regeneration and tumorigenesis. Multiple cancers are dependent on sustained expression of YAP1 for cell proliferation, survival and tumorigenesis, but the molecular basis of this oncogene dependency is not well understood. To identify genes that can functionally substitute for YAP1, we performed a genome-scale genetic rescue screen in YAP1-dependent colon cancer cells expressing an inducible YAP1-specific shRNA. We found that the transcription factor PRDM14 rescued cell proliferation and tumorigenesis upon YAP1 suppression in YAP1-dependent cells, xenografts, and colon cancer organoids. YAP1 and PRDM14 individually activated the transcription of calmodulin 2 (CALM2) and a glucose transporter SLC2A1 upon YAP1 suppression; and CALM2 or SLC2A1 expression was required for the rescue of YAP1 suppression. Together, these findings implicate PRDM14-mediated transcriptional upregulation of CALM2 and SLC2A1 as key components of oncogenic YAP1 signaling and dependency.
Project description:Tumors acquire somatic DNA copy number aberrations, leading to activation of oncogenes and inactivation of tumor suppressors. Many studies have focused on the analysis of single copy number aberrations and associated driver genes, but few studies have performed combinatorial analyses. We propose a genome-wide scoring framework to find mutually exclusive gains and losses. Mutually exclusive copy number aberrations can identify genes whose oncogenic function is redundant, either by functioning in the same pathway or in a parallel pathway. As one gene is aberrated the selective pressure for its partner is alleviated which leads to a mutually exclusive perturbation pattern. In a dataset of mouse models for invasive lobular carcinoma we found three mutually exclusive DNA amplifications, containing several well-known oncogenes: the Met proto-oncogene on chromosome 6, the cluster of Birc2, Birc3 and Yap1 genes on chromosome 9, and Nras on chromosome 3. Furthermore, gene expression or protein expression of these genes correlates very well with copy number data indicating that they are the target of the amplification. Although homologous amplifications in human tumors are rare, the mutual exclusivity of MET, BIRC/YAP1 and NRAS is maintained in a variety of cancer types. This suggests a novel function for YAP1 in the mitogen-activated signaling pathway by association with MET and NRAS, known players in this pathway. This function is independent to the propensity of YAP1 to cause Epithelial-to-Mesenchymal transition. aCGH data of 67 mouse mammary tumors from K14-Cre and WAP-Cre driven P53-F/F;Cdh1-F/F animals - tumor DNA hybridized against same-animal splenic DNA
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:The Hippo pathway effector YAP1 controls stem cell fate in epithelial tissues, but its role in stem cells of non-epithelial tissues, such as skeletal muscle, is poorly documented. Here we show that sustained YAP1 activity in mouse activated satellite cells in vivo induces rhabdomyosarcoma (RMS) resembling human embryonal RMS (ERMS) with high penetrance and short latency. The transcriptional program of YAP1 in ERMS drives pro-proliferative pathways whilst decreasing MyoD1 and MEF2 pro-differentiation activity to globally maintain the myoblastic phenotype of ERMS. Normalization of YAP1 expression reduced tumor burden and allowed myogenic differentiation of YAP1-driven and RD ERMS xenografts in situ, thereby identifying YAP1 as a potent RMS-causing oncogene and potential target for differentiation therapy. A total of four samples were analyzed. Two ChIP-Seq datasets from RD human cells, containing reads connected to TEAD binding and IgG binding as control/background; two ChIP-Seq datasets from YAP-ERMS mouse cells, containing reads connected to TEAD binding and Input reads as control/background
Project description:YAP1 is a major effector of the Hippo pathway and a well-established oncogene. Elevated YAP1 activity due to mutations in Hippo pathway components or YAP1 amplification is observed in several types of human cancers. Here we investigated its genomic binding landscape in YAP1-activated cancer cells, as well as in non-transformed cells. We demonstrate that TEAD transcription factors mediate YAP1 chromatin-binding genome-wide, further explaining their dominant role as primary mediators of YAP1-transcriptional activity. Moreover, we show that YAP1 largely exerts its transcriptional control via distal enhancers that are marked by H3K27 acetylation and that YAP1 is necessary for this chromatin mark at bound enhancers and the activity of the associated genes. This work establishes YAP1-mediated transcriptional regulation at distal enhancers and provides an expanded set of target genes resulting in a fundamental source to study YAP1 function in a normal and cancer setting.
Project description:The effect of overexpression HpHAP4-A, HpHAP4-B and ScYAP1 in Sc delta yap1 genetic background in native (no stress) and H2O2 oxidative stress conditions.
Project description:The Hippo/YAP1 signaling pathway regulates normal development by controlling contact inhibition of growth. In cancer, YAP1 activation is often dysregulated, leading to excessive tumor growth and metastasis. We demonstrate that the RNA-binding protein IGF2BP1 impedes the repression of YAP1 by Hippo signaling in carcinomas. IGF2BP1 stabilizes YAP1 mRNA and enhances YAP1 protein synthesis through an m6A-dependent interaction with the 3’UTR of the YAP1 mRNA. This results in increased nuclear YAP1 accumulation in IGF2BP1-expressing ovarian cancer, boosting transcriptional activity and bypassing contact inhibition. Inhibiting IGF2BP1-mRNA binding using the small molecule BTYNB reduces YAP1 levels and transcriptional activity, leading to significant growth inhibition in carcinoma cells and ovarian cancer organoids. Conversely, SRC inhibition via Saracatinib only impacts epithelial-like tumor cells, suggesting that the impact of SRC is limited by the stalling of YAP1 at adherens junction. This is particularly significant in de-differentiated, rather mesenchymal carcinoma-derived cells, which exhibit high IGF2BP1 and YAP1 expression, rendering them less reliant on SRC -directed growth stimulation. In such invasive carcinoma models, the combined inhibition of SRC and IGF2BP1 or YAP1/TAZ by Verteporfin proved superior over monotherapies. These findings highlight the therapeutic potential of targeting IGF2BP1, a key regulator of oncogenic transcription networks.