YAP/TEAD co-activator regulated pluripotency and chemoresistance in ovarian cancer initiated cells

MicroRNA-186 affects the proliferation of tumor cells via yes-associated protein 1 in the occurrence and development of pancreatic cancer

The present study aimed to determine the expression of microRNA (miRNA or miR)-186 in tumor tissues and peripheral blood of patients with pancreatic cancer (PC), as well as its mechanism of regulation. A total of 65 patients with PC who underwent surgery between June 2013 and October 2015 were included. In addition, 59 healthy subjects were recruited as controls. Reverse transcription-quantitative polymerase chain reaction was used to measure the expression of mRNA and miRNA. Western blotting and enzyme-linked immunosorbent assay were used to determine protein expression. Bioinformatics was employed for the prediction of the target gene of miR-186, whereas dual luciferase reporter assay was performed to identify whether miR-186 directly bound to YAP1 mRNA. Human pulmonary aortic endothelial cells (HPACs) were transfected with ago-miR-186. YAP1 expression in HPACs was silenced by siRNA. MTT assay was used to evaluate the viability of HPACs. YAP1 mRNA and protein expression levels were elevated in PC. In addition, expression levels of miR-186 in PC were downregulated. miR-186 regulated the expression of YAP1 by binding with the 3'-untranslated region of YAP1. Elevated expression of miR-186 inhibited the proliferation of HPACs by downregulating the expression of YAP1. Decreased expression of YAP1 by siRNA reduced the viability of HPACs. The present study demonstrates that YAP1 is upregulated in the tumor tissues and blood of PC patients, and this may be associated with the downregulation of miR-186. In addition, miR-186 may affect the occurrence and development of PC by controlling the proliferation of PC cells via YAP1.

Role of YAP1 as a Marker of Sensitivity to Dual AKT and P70S6K Inhibition in Ovarian and Uterine Malignancies

Background

The PI3K/AKT/P70S6K pathway is an attractive therapeutic target in ovarian and uterine malignancies because of its high rate of deregulation and key roles in tumor growth. Here, we examined the biological effects of MSC2363318A, which is a novel inhibitor of AKT1, AKT3, and P70S6K.

Methods

Orthotopic murine models of ovarian and uterine cancer were utilized to study the effect of MSC2363318A on survival and regression. For each cell line, 10 mice were treated in each of the experimental arms tested. Moreover, in vitro experiments in 21 cell lines (MTT, immunoblot analysis, plasmid transfection, reverse phase protein array [RPPA]) were carried out to characterize underlying mechanisms and potential biomarkers of response. All statistical tests were two-sided.

Results

MSC2363318A decreased tumor growth and metastases in multiple murine orthotopic models of ovarian (SKOV3ip1, HeyA8, and Igrov1) and uterine (Hec1a) cancer by reducing proliferation and angiogenesis and increasing cell death. Statistically significant prolonged overall survival was achieved with combination MSC2363318A and paclitaxel in the SKUT2 (endometrioid) uterine cancer mouse model ( P <  .001). Mice treated with combination MSC2363318A and paclitaxel had the longest overall survival (mean = 104.2 days, 95% confidence interval [CI] = 97.0 to 111.4) compared with those treated with vehicle (mean = 61.9 days, 95% CI = 46.3 to 77.5), MSC2363318A alone (mean = 89.7 days, 95% CI = 83.0 to 96.4), and paclitaxel alone (mean = 73.6 days, 95% CI = 53.4 to 93.8). Regression and stabilization of established tumors in the Ishikawa (endometrioid) uterine cancer model was observed in mice treated with combination MSC2363318A and paclitaxel. Synergy between MSC2363318A and paclitaxel was observed in vitro in cell lines that had an IC50 of 5 µM or greater. RPPA results identified YAP1 as a candidate marker to predict cell lines that were most sensitive to MSC2363318A (R = 0.54, P =  .02). After establishment of a murine ovarian cancer model of adaptive anti-angiogenic resistance (SKOV3ip1-luciferase), we demonstrate that resensitization to bevacizumab occurs with the addition of MSC2363318A, resulting in improved overall survival ( P =  .01) using the Kaplan-Meier method. Mice treated with bevacizumab induction followed by MSC2363318A had the longest overall survival (mean = 66.0 days, 95% CI = 53.9 to 78.1) compared with mice treated with control (mean = 42.0 days, 95% CI = 31.4 to 52.6) and bevacizumab-sensitive mice (mean = 47.2 days; 95% CI = 37.5 to 56.9).

Conclusions

MSC2363318A has therapeutic efficacy in multiple preclinical models of ovarian and uterine cancer. These findings support clinical development of a dual AKT/P70S6K inhibitor.

Ovarian cancer stem cells: still an elusive entity?

The cancer stem cell (CSC) model proposes that tumor development and progression are fueled and sustained by undifferentiated cancer cells, endowed with self-renewal and tumor-initiating capacity. Ovarian carcinoma, based on its biological features and clinical evolution, appears as a prototypical example of CSC-driven disease. Indeed, ovarian cancer stem cells (OCSC) would account not only for the primary tumor growth, the peritoneal spread and the relapse, but also for the development of chemoresistance, thus having profound implication for the treatment of this deadly disease. In the last decade, an increasing body of experimental evidence has supported the existence of OCSC and their pathogenic role in the disease. Nevertheless, the identification of OCSC and the definition of their phenotypical and functional traits have proven quite challenging, mainly because of the heterogeneity of the disease and of the difficulties in establishing reliable biological models. A deeper understanding of OCSC pathobiology will shed light on the mechanisms that underlie the clinical behaviour of OC. In addition, it will favour the design of innovative treatment regimens that, on one hand, would counteract the resistance to conventional chemotherapy, and, on the other, would aim at the eradication of OC through the elimination of its CSC component.

STROBE-compliant integrin through focal adhesion involve in cancer stem cell and multidrug resistance of ovarian cancer

Cancer stem cells (CSCs) are considered to be the root of carcinoma relapse and drug resistance in ovarian cancer. Hunting for the potential CSC genes and explain their functions would be a feasible strategy to meet the challenge of the drug resistance in ovarian cancer. In this study, we performed bioinformatic approaches such as biochip data extraction and pathway enrichment analyses to elucidate the mechanism of the CSC genes in regulation of drug resistance. Potential key genes, integrins, were identified to be related to CSC in addition to their associations with drug resistance and prognosis in ovarian cancer. A total of 36 ovarian CSC genes involved in regulation of drug resistance were summarized, and potential drug resistance-related CSC genes were identified based on 3 independent microarrays retrieved from the Gene Expression Omnibus (GEO) Profiles. Pathway enrichment of CSC genes associated with drug resistance in ovarian cancer indicated that focal adhesion signaling might play important roles in CSC genes-mediated drug resistance. Integrins are members of the adhesion molecules family, and integrin subunit alpha 1, integrin subunit alpha 5, and integrin subunit alpha 6 (ITGA6) were identified as central CSC genes and their expression in side population cells, cisplatin-resistant SKOV3 (SKOV3/DDP2) cells, and cisplatin-resistant A2780 (A2780/DDP) cells were dysregulated as measured by real-time quantitative polymerase chain reaction. The high expression of ITGA6 in 287 ovarian cancer patients of TCGA cohort was significantly associated with poorer progression-free survival. This study provide the basis for further understanding of CSC genes in regulation of drug resistance in ovarian cancer, and integrins could be a potential biomarker for prognosis of ovarian cancer.

The Hippo Pathway: A Master Regulatory Network Important in Development and Dysregulated in Disease

The Hippo Pathway is a master regulatory network that regulates proliferation, cell growth, stemness, differentiation, and cell death. Coordination of these processes by the Hippo Pathway throughout development and in mature organisms in response to diverse external and internal cues plays a role in morphogenesis, in controlling organ size, and in maintaining organ homeostasis. Given the importance of these processes, the Hippo Pathway also plays an important role in organismal health and has been implicated in a variety of diseases including eye disease, cardiovascular disease, neurodegeneration, and cancer. This review will focus on Drosophila reports that identified the core components of the Hippo Pathway revealing specific downstream biological outputs of this complicated network. A brief description of mammalian reports will complement review of the Drosophila studies. This review will also survey upstream regulation of the core components with a focus on feedback mechanisms.

Overexpression of TAZ promotes cell proliferation, migration and epithelial-mesenchymal transition in ovarian cancer

The Hippo pathway is dysregulated in multiple types of human cancer, including ovarian cancer. Nuclear expression of yes-associated protein 1 (YAP1), a downstream transcription coactivator of the Hippo pathway, has been demonstrated to promote tumorigenesis in ovarian cancer and may serve as a poor prognostic indicator. However, transcriptional coactivator with PDZ binding motif (TAZ), a downstream target of the Hippo pathway and paralog of YAP in mammalian cells, has not been fully investigated in ovarian cancer. The present study aimed to investigate the dysregulation and biological function of TAZ in ovarian cancer. Reverse transcription-quantitative polymerase chain reaction and western blotting revealed that TAZ mRNA and protein levels, respectively, were upregulated in ovarian cancer, and a meta-analysis of ovarian cancer microarray datasets identified that increased expression of TAZ mRNA is correlated with poor prognosis in patients with ovarian cancer. In addition, TAZ-knockdown in ovarian cancer cells demonstrated that TAZ regulates the migration, proliferation and epithelial-mesenchymal transition of ovarian cancer cells. Furthermore, pharmacological disruption of the YAP/TAZ/TEA domain protein complex resulted in a decrease in ovarian cancer cell migration, proliferation and vimentin expression. The results of the present study indicate that the overexpression of TAZ is important in the development and progression of ovarian cancer, and may function as a potential drug target for treatment of this disease entity.

Verteporfin, a suppressor of YAP-TEAD complex, presents promising antitumor properties on ovarian cancer

Yes-associated protein (YAP) is a key transcriptional coactivator of Hippo pathway and has been shown to be an oncoprotein in ovarian cancer (OC). Verteporfin (VP), clinically used in photodynamic therapy for neovascular macular degeneration, has been recently proven to be a suppressor of YAP–TEAD complex and has shown potential in anticancer treatment. In this study, we aimed to explore the potential effect of VP in the treatment of OC. Our results showed that VP led to inhibition of proliferation in a time- and dose-dependent manner and to the suppression of migratory and invasive capacities of OC cells. Western blot and real-time polymerase chain reaction demonstrated that VP induced YAP cytoplasmic retention and deregulated inducible YAP and CCNs in OC cells. In vivo, VP exerted a significant effect on tumor growth in OVCAR8 xenograft mice, resulting in tumor nodules with lower average weight and reduced volume of gross ascites. In addition, VP treatment remarkably upregulated cytoplasmic YAP and phosphorylation YAP and downregulated CCN1 and CCN2, but exerted little effect on YAP-upstream components in Hippo pathway. In conclusion, our results suggested that VP may be a promising agent for OC, acting by suppressing YAP–TEAD complex.

Inactivation of hypoxia-induced YAP by statins overcomes hypoxic resistance tosorafenib in hepatocellular carcinoma cells

Sorafenib is a multikinase inhibitor used as a first-line treatment for advanced hepatocellular carcinoma (HCC), but it has shown modest to low response rates. The characteristic tumour hypoxia of advanced HCC maybe a major factor underlying hypoxia-mediated treatment failure. Thus, it is urgent to elucidate the mechanisms of hypoxia-mediated sorafenib resistance in HCC. In this study, we found that hypoxia induced the nuclear translocation of Yes associate-Protein (YAP) and the subsequent transactivation of target genes that promote cell survival and escape apoptosis, thereby leading to sorafenib resistance. Statins, the inhibitors of hydroxymethylglutaryl-CoA reductase, could ameliorate hypoxia-induced nuclear translocation of YAP and suppress mRNA levels of YAP target genes both in vivo and in vitro. Combined treatment of statins with sorafenib greatly rescued the loss of anti-proliferative effects of sorafenib under hypoxia and improved the inhibitory effects on HepG2 xenograft tumour growth, accompanied by enhanced apoptosis as evidenced by the increased sub-G1 population and PARP cleavage. The expression levels of YAP and its target genes were highly correlated with poor prognosis and predicted a high risk of HCC patients. These findings collectively suggest that statins utilization maybe a promising new strategy to counteract hypoxia-mediated resistance to sorafenib in HCC patients.

An evolutionary, structural and functional overview of the mammalian TEAD1 and TEAD2 transcription factors

TEAD proteins constitute a family of highly conserved transcription factors, characterized by a DNA-binding domain called the TEA domain and a protein-binding domain that permits association with transcriptional co-activators. TEAD proteins are unable to induce transcription on their own. They have to interact with transcriptional cofactors to do so. Once TEADs bind their co-activators, the different complexes formed are known to regulate the expression of genes that are crucial for embryonic development, important for organ formation (heart, muscles), and involved in cell death and proliferation. In the first part of this review we describe what is known of the structure of TEAD proteins. We then focus on two members of the family: TEAD1 and TEAD2. First the different transcriptional cofactors are described. These proteins can be classified in three categories: i), cofactors regulating chromatin conformation, ii), cofactors able to bind DNA, and iii), transcriptional cofactors without DNA binding domain. Finally we discuss the recent findings that identified TEAD1 and 2 and its coactivators involved in cancer progression.

Hippo/YAP signaling pathway is involved in osteosarcoma chemoresistance

Background

Osteosarcoma is the most common bone malignancy in children and adolescents, and 20%–30% of the patients suffer from poor prognosis because of individual chemoresistance. The Hippo/yes-associated protein (YAP) signaling pathway has been shown to play a role in tumor chemoresistance, but no previous report has focused on its involvement in osteosarcoma chemoresistance. This study aimed to investigate the role of the Hippo/YAP signaling pathway in osteosarcoma chemoresistance and to determine potential treatment targets.

Methods

Using the Cell Titer-Glo Luminescent cell viability assay and flow cytometry analysis, we determined the proliferation and chemosensitivity of YAP-overexpressing and YAP-knockdown osteosarcoma cells. In addition, using western blotting and the real-time polymerase chain reaction technique, we investigated the alteration of the Hippo/YAP signaling pathway in osteosarcoma cells treated with chemotherapeutic agents.

Results

Mammalian sterile 20-like kinase 1 (MST1) degradation was increased, and large tumor suppressor kinase 1/2 (LATS1/2) total protein levels were decreased by methotrexate and doxorubicin, which increased activation and nuclear translocation of YAP. Moreover, YAP increased the proliferation and chemoresistance of MG63 cells.

Conclusions

The Hippo/YAP signaling pathway plays a role in osteosarcoma chemoresistance, and YAP is a potential target for reducing chemoresistance.

Nuclear translocation and activation of YAP by hypoxia contributes to the chemoresistance of SN38 in hepatocellular carcinoma cells

Although hypoxia is a prominent feature contributing to the therapeutic resistance of hepatocellular carcinoma cells (HCC) against chemotherapeutic agents, including the Topoisomerase I inhibitor SN38, the underlying mechanism is not fully understood and its understanding remains a major clinical challenge. In the present study, we found that hypoxia-induced nuclear translocation and accumulation of YAP acted as a survival input to promote resistance to SN38 in HCC. The induction of YAP by hypoxia was not mediated by HIF-1α because manipulating the abundance of HIF-1α with CoCl2, exogenous expression, and RNA interference had no effect on the phosphorylation or total levels of YAP. The mevalonate-HMG-CoA reductase (HMGCR) pathway may modulate the YAP activation under hypoxia. Combined YAP inhibition using either siRNA or the HMGCR inhibitor statins together with SN38 treatment produced improved anti-cancer effects in HCC cells. The increased anti-cancer effect of the combined treatment with statins and irinotecan (the prodrug of SN-38) was further validated in a human HepG2 xenograft model of HCC in nude mice. Taken together, our findings identify YAP as a novel mediator of hypoxic-resistance to SN38. These results suggest that the administration of SN28 together with the suppression of YAP using statins is a promising strategy for enhancing the treatment response in HCC patients, particularly in advanced stage HCC cases presenting hypoxic resistance.

The TEAD Family and Its Oncogenic Role in Promoting Tumorigenesis

The TEAD family of transcription factors is necessary for developmental processes. The family members contain a TEA domain for the binding with DNA elements and a transactivation domain for the interaction with transcription coactivators. TEAD proteins are required for the participation of coactivators to transmit the signal of pathways for the downstream signaling processes. TEADs also play an important role in tumor initiation and facilitate cancer progression via activating a series of progression-inducing genes, such as CTGF, Cyr61, Myc and Gli2. Recent studies have highlighted that TEADs, together with their coactivators, promote or even act as the crucial parts in the development of various malignancies, such as liver, ovarian, breast and prostate cancers. Furthermore, TEADs are proposed to be useful prognostic biomarkers due to the ideal correlation between high expression and clinicopathological parameters in gastric, breast, ovarian and prostate cancers. In this review, we summarize the functional role of TEAD proteins in tumorigenesis and discuss the key role of TEAD transcription factors in the linking of signal cascade transductions. Improved knowledge of the TEAD proteins will be helpful for deep understanding of the molecular mechanisms of tumorigenesis and identifying ideal predictive or prognostic biomarkers, even providing clinical translation for anticancer therapy in human cancers.

Role of the YAP Oncoprotein in Priming Ras-Driven Rhabdomyosarcoma

Rhabdomyosarcoma (RMS), a cancer characterized by features of skeletal muscle histogenesis, is the most common soft tissue sarcoma of childhood and adolescence. Survival for high-risk groups is less than 30% at 5 years. RMS also occurs during adulthood, with a lower incidence but higher mortality. Recently, mutational profiling has revealed a correlation between activating Ras mutations in the embryonal (eRMS) and pleomorphic (pRMS) histologic variants of RMS, and a poorer outcome for those patients. Independently, the YAP transcriptional coactivator, an oncoprotein kept in check by the Hippo tumor suppressor pathway, is upregulated in eRMS. Here we show that YAP promotes cell proliferation and antagonizes apoptosis and myogenic differentiation of human RMS cells bearing oncogenic Ras mutations in cell culture studies in vitro and in murine xenografts in vivo. Pharmacologic inhibition of YAP by the benzoporphyrin derivative verteporfin decreased cell proliferation and tumor growth in vivo. To interrogate the temporal contribution of YAP in eRMS tumorigenesis, we used a primary human cell-based genetic model of Ras-driven RMS. Constitutively active YAP functioned as an early genetic lesion, permitting bypass of senescence and priming myoblasts to tolerate subsequent expression of hTERT and oncogenic Ras, which were necessary and sufficient to generate murine xenograft tumors mimicking RMS in vivo. This work provides evidence for cooperation between YAP and oncogenic Ras in RMS tumorigenesis, laying the foundation for preclinical co-targeting of these pathways.