Project description:Malignant mesothelioma (MM) is an incurable malignancy that is caused by exposure to asbestos and is accompanied by severe fibrosis. Because MM is usually diagnosed at an advanced stage and clinical identification of early lesions is difficult, its molecular pathogenesis has not been completely elucidated. Nearly 75% of MM cases have inactivating mutations in the NF2 (neurofibromatosis type 2; Merlin) gene or in downstream signaling molecules of the Hippo signaling cascade, which negatively regulates the transcription factor Yes-associated protein (YAP). In this study, we demonstrate a functional interaction between the Hippo and TGF-? pathways in regulating connective tissue growth factor (CTGF). Expression of CTGF in MM cells was induced by the formation of a YAP-TEAD4-Smad3-p300 complex on the CTGF promoter. Knocking down CTGF expression in MM cells prolonged the survival of xenografted mice, and a significant association was seen between CTGF expression and extracellular matrix deposition in MM xenografts and in patient tissue specimens. We further suggest that CTGF may influence the malignancy of mesothelioma because of the different histological expression patterns observed in human MM tissues. These data suggest that CTGF is an important modulator of MM growth and pathology and represents a novel therapeutic target for this disease.
Project description:Many genes responsible for Malignant mesothelioma (MM) have been identified as tumor suppressor genes and it is difficult to target these genes directly at a molecular level. We searched for the gene which showed synthetic lethal phenotype with LATS2, one of the MM causative genes and one of the kinases in the Hippo pathway. Here we showed that knockdown of SMG6 results in synthetic lethality in LATS2-inactivated cells. We found that this synthetic lethality required the nuclear translocation of YAP1 and TAZ. Both are downstream factors of the Hippo pathway. We also demonstrated that this synthetic lethality did not require SMG6 in nonsense-mediated mRNA decay (NMD) but in regulating telomerase reverse transcriptase (TERT) activity. In addition, the RNA-dependent DNA polymerase (RdDP) activity of TERT was required for this synthetic lethal phenotype. We confirmed the inhibitory effects of LATS2 and SMG6 on cell proliferation in vivo. The result suggests an interaction between the Hippo and TERT signaling pathways. We also propose that SMG6 and TERT are novel molecular target candidates for LATS2-inactivated cancers such as MM.
Project description:Endometrial cancer, one of the most prevalent malignant cancers tumors of the female reproductive tract, has been increasing in incidence and mortality rates around the world. The Hippo pathway, one of the eight traditional human cancer signaling pathways, is an intricate signaling network that regulates cell proliferation, differentiation, and migration as well as restricting organ size in response to a range of intracellular and extracellular signals. Inhibiting the Hippo pathway results in aberrant activation of its downstream core component YAP/TAZ, which can enhance cancer cells' metabolism and maintain their stemness. Additionally, the Hippo pathway can modulate the tumor microenvironment and induce drug resistance, where tumorigenesis and tumor progression occur. However, the Hippo pathway has been little researched in endometrial cancer. Here, we aim to review how the Hippo pathway contributes to the onset, development and the potential treatment of endometrial cancer with the aim of providing new therapeutic targets.
Project description:The DRE/DREF transcriptional regulatory system has been demonstrated to activate a wide variety of genes with various functions. In Drosophila, the Hippo pathway is known to suppress cell proliferation by inducing apoptosis and cell cycle arrest through inactivation of Yorkie, a transcription co-activator. In the present study, we found that half dose reduction of the hippo (hpo) gene induces ectopic DNA synthesis in eye discs that is suppressed by overexpression of DREF. Half reduction of the hpo gene dose reduced apoptosis in DREF-overexpressing flies. Consistent with these observations, overexpression of DREF increased the levels of hpo and phosphorylated Yorkie in eye discs. Interestingly, the diap1-lacZ reporter was seen to be significantly decreased by overexpression of DREF. Luciferase reporter assays in cultured S2 cells revealed that one of two DREs identified in the hpo gene promoter region was responsible for promoter activity in S2 cells. Furthermore, endogenous hpo mRNA was reduced in DREF knockdown S2 cells, and chromatin immnunoprecipitation assays with anti-DREF antibodies proved that DREF binds specifically to the hpo gene promoter region containing DREs in vivo. Together, these results indicate that the DRE/DREF pathway is required for transcriptional activation of the hpo gene to positively control Hippo pathways.
Project description:The hippo signaling pathway is a central tumor suppressor cascade frequently inactivated in selected human cancers, leading to the aberrant activation of TEAD transcription factors. Whereas several TEAD auto-palmitoylation inhibitors are currently in development, a comprehensive assessment of this novel drug-modality is missing. Here, we report a comparative analysis among six TEADi(s) using cell-based and biochemical assays in Hippo pathway deficient mesothelioma. Our analysis revealed varying potency and selectivity across TEADi, also highlighting their limited efficacy. To overcome this limitation, we performed an unbiased, quantitative high-throughput drug screening by combining the TEADi VT-103 with a library of approximately 3000 oncology-focused drugs. By exploiting this library's mechanistic redundancy, we identified several drug-classes robustly synergized with TEADi. These included glucocorticoid-receptor (GR) agonists, Mek1/2 inhibitors, mTOR inhibitors, and PI3K inhibitors, among others. Altogether, we report a coherent single-agent dataset informing on potency and selectivity of TEAD-palmitoylation inhibitors as single-agents. We also describe a rational pipeline enabling the systematic identification of TEAD druggable co-dependencies. This data should support the pre-clinical development of drug combination strategies for the treatment of Hippo-deficient mesothelioma, and more broadly, for other cancers dependent on the oncogenic activity of YAP/TEAD.
Project description:Osteosarcoma and Ewing sarcoma are the most prevalent bone pediatric tumors. Despite intensive basic and medical research studies to discover new therapeutics and to improve current treatments, almost 40% of osteosarcoma and Ewing sarcoma patients succumb to the disease. Patients with poor prognosis are related to either the presence of metastases at diagnosis or resistance to chemotherapy. Over the past ten years, considerable interest for the Hippo/YAP signaling pathway has taken place within the cancer research community. This signaling pathway operates at different steps of tumor progression: Primary tumor growth, angiogenesis, epithelial to mesenchymal transition, and metastatic dissemination. This review discusses the current knowledge about the involvement of the Hippo signaling pathway in cancer and specifically in paediatric bone sarcoma progression.
Project description:The transcriptional coactivator Yes-associated protein (YAP) is a major regulator of organ size and proliferation in vertebrates. As such, YAP can act as an oncogene in several tissue types if its activity is increased aberrantly. Although no activating mutations in the yap1 gene have been identified in human cancer, yap1 is located on the 11q22 amplicon, which is amplified in several human tumors. In addition, mutations or epigenetic silencing of members of the Hippo pathway, which represses YAP function, have been identified in human cancers. Here we demonstrate that, in addition to increasing tumor growth, increased YAP activity is potently prometastatic in breast cancer and melanoma cells. Using a Luminex-based approach to multiplex in vivo assays, we determined that the domain of YAP that interacts with the TEAD/TEF family of transcription factors but not the WW domains or PDZ-binding motif, is essential for YAP-mediated tumor growth and metastasis. We further demonstrate that, through its TEAD-interaction domain, YAP enhances multiple processes known to be important for tumor progression and metastasis, including cellular proliferation, transformation, migration, and invasion. Finally, we found that the metastatic potential of breast cancer and melanoma cells is strongly correlated with increased TEAD transcriptional activity. Together, our results suggest that increased YAP/TEAD activity plays a causal role in cancer progression and metastasis.
Project description:The Hippo signaling pathway regulates tissue growth and organ development in many animals, including humans. Pathway activity leads to inactivation of Yorkie (Yki), a transcriptional coactivator that drives expression of growth-promoting genes. In addition, Yki has been shown to recruit chromatin modifiers that enhance chromatin accessibility and thereby enhance Yki function. Here, we asked whether changes in chromatin accessibility that occur during DNA replication could also affect Yki function. We found that depletion of the chromatin assembly complex-1 (CAF-1) complex, a histone chaperone that is required for nucleosome assembly after DNA replication, in the wing imaginal epithelium leads to increased Hippo pathway target gene expression but does not affect expression of other genes. Yki shows greater association with target sites when CAF-1 is depleted and misregulation of target gene expression is Yki-dependent, suggesting that nucleosome assembly competes with Yki for pathway targets post-DNA replication. Consistent with this idea, increased target gene expression is DNA replication dependent and newly replicated chromatin at target sites shows marked nucleosome depletion when CAF-1 function is reduced. These observations suggest a connection between cell cycle progression and Hippo pathway target expression, providing insights into functions of the Hippo pathway in normal and abnormal tissue growth.
Project description:The critical role of the Hippo pathway has been recently investigated in various cancers, but little is known about its role in glioblastoma (GBM). In order to evaluate the clinical relevance of the Hippo pathway in GBM, we generated a core gene expression signature from four different previously-established silence of Hippo pathway (SOH) signatures. Based on a newly generated core SOH signature, a SOH and active Hippo pathway (AH) was predicted in GBM samples from The Cancer Genome Atlas (TCGA) and validated in a separate cohort. A comparative analysis was performed on multi-panel genomic datasets from TCGA and the possible association of SOH with immune activity and epithelial mesenchymal transition was also evaluated. The SOH signature was associated with poor prognosis in GBM in both cohorts. Expression levels of CTGF and CYR61, the most reliable and well-known downstream targets of YAP1, were markedly increased in the SOH subgroup of GBM patients. SOH signature was strongly associated with a high immune signature score and mesenchymal features. Genes differentially expressed between SOH and AH groups revealed many markers for inhibitory immune checkpoints and M2-polarized macrophages were upregulated in the SOH subgroup, suggesting that SOH may induce the resistance of cancer cells to host immune response in GBM. In summary, SOH is significantly associated with the poor prognosis of GBM patients and is possibly mediated by pro-tumoral immunosuppression.
Project description:Drug resistance is always a great obstacle in any endocrine therapy of breast cancer. Although the combination of endocrine therapy and targeted therapy has been shown to significantly improve prognosis, refractory endocrine resistance is still common. Dysregulation of the Hippo pathway is often related to the occurrence and the development of many tumors. Targeted therapies of this pathway have played important roles in the study of triple negative breast cancer (TNBC). Targeting the Hippo pathway in combination with chemotherapy or other targeted therapies has been shown to significantly improve specific antitumor effects and reduce cancer antidrug resistance. Further exploration has shown that the Hippo pathway is closely related to endocrine resistance, and it plays a "co-correlation point" role in numerous pathways involving endocrine resistance, including related pathways in breast cancer stem cells (BCSCs). Agents and miRNAs targeting the components of the Hippo pathway are expected to significantly enhance the sensitivity of breast cancer cells to endocrine therapy. This review initially explains the possible mechanism of the Hippo pathway in combating endocrine resistance, and it concludes by recommending endocrine therapy in combination with therapies targeting the Hippo pathway in the study of endocrine-resistant breast cancers.