The dual functions of YAP-1 to promote and inhibit cell growth in human malignancy

Downregulation of long noncoding RNA B4GALT1-AS1 is associated with breast cancer development

The misregulation of long non-coding RNAs (lncRNAs) is related to the progressive evolution of various human cancers, such as Breast cancer (BC). The role of lncRNA B4GALT1-AS1 has been investigated in some human cancers. Therefore, studying B4GALT1-AS1 expression was aimed for the first time in the tumor and marginal tissues of BC in this study. The cancer genome atlas (TCGA) database was utilized to evaluate the relative expression of B4GALT1-AS1 in BC and other cancers. RNA was extracted from twenty-eight paired BC and marginal tissues, and cDNA was synthesized. The quantitative expression level of B4GALT1-AS1 was evaluated using real-time PCR. The bioinformatics analyses were performed to identify co-expression genes and related pathways. B4GALT1-AS1 was significantly downregulated in BC specimens compared to tumor marginal samples. The TCGA data analysis confirmed the downregulation of B4GALT1-AS1 in BC. The bioinformatics analysis discovered the correlation between 700 genes and B4GALT1-AS1 and identified GNAI1 as the high degree gene which was positively correlated with B4GALT1-AS1 expression. It seems B4GALT1-AS1 provides its function, at least partly, in association with one of the hippo pathway components, YAP, in other cancers. This protein has the opposite role in BC and its loss of function can result in poor survival in BC. Further research is needed to investigate the interaction between B4GALT1-AS1 and YAP in various subtypes of BC.

Exploring the promising potential of induced pluripotent stem cells in cancer research and therapy

The advent of iPSCs has brought about a significant transformation in stem cell research, opening up promising avenues for advancing cancer treatment. The formation of cancer is a multifaceted process influenced by genetic, epigenetic, and environmental factors. iPSCs offer a distinctive platform for investigating the origin of cancer, paving the way for novel approaches to cancer treatment, drug testing, and tailored medical interventions. This review article will provide an overview of the science behind iPSCs, the current limitations and challenges in iPSC-based cancer therapy, the ethical and social implications, and the comparative analysis with other stem cell types for cancer treatment. The article will also discuss the applications of iPSCs in tumorigenesis, the future of iPSCs in tumorigenesis research, and highlight successful case studies utilizing iPSCs in tumorigenesis research. The conclusion will summarize the advancements made in iPSC-based tumorigenesis research and the importance of continued investment in iPSC research to unlock the full potential of these cells.

Combination of verteporfin-photodynamic therapy with 5-aza-2'-deoxycytidine enhances the anti-tumour immune response in triple negative breast cancer

Introduction

Triple negative breast cancer (TNBC) is a subtype of breast cancer characterised by its high tumourigenic, invasive, and immunosuppressive nature. Photodynamic therapy (PDT) is a focal therapy that uses light to activate a photosensitizing agent and induce a cytotoxic effect. 5-aza-2'-deoxycytidine (5-ADC) is a clinically approved immunomodulatory chemotherapy agent. The mechanism of the combination therapy using PDT and 5-ADC in evoking an anti-tumour response is not fully understood.

Methods

The present study examined whether a single dose of 5-ADC enhances the cytotoxic and anti-tumour immune effect of low dose PDT with verteporfin as the photosensitiser in a TNBC orthotopic syngeneic murine model, using the triple negative murine mammary tumour cell line 4T1. Histopathology analysis, digital pathology and immunohistochemistry of treated tumours and distant sites were assessed. Flow cytometry of splenic and breast tissue was used to identify T cell populations. Bioinformatics were used to identify tumour immune microenvironments related to TNBC patients.

Results

Functional experiments showed that PDT was most effective when used in combination with 5-ADC to optimize its efficacy. 5-ADC/PDT combination therapy elicited a synergistic effect in vitro and was significantly more cytotoxic than monotherapies on 4T1 tumour cells. For tumour therapy, all types of treatments demonstrated histopathologically defined margins of necrosis, increased T cell expression in the spleen with absence of metastases or distant tissue destruction. Flow cytometry and digital pathology results showed significant increases in CD8 expressing cells with all treatments, whereas only the 5-ADC/PDT combination therapy showed increase in CD4 expression. Bioinformatics analysis of in silico publicly available TNBC data identified BCL3 and BCL2 as well as the following anti-tumour immune response biomarkers as significantly altered in TNBC compared to other breast cancer subtypes: GZMA, PRF1, CXCL1, CCL2, CCL4, and CCL5. Interestingly, molecular biomarker assays showed increase in anti-tumour response genes after treatment. The results showed concomitant increase in BCL3, with decrease in BCL2 expression in TNBC treatment. In addition, the treatments showed decrease in PRF1, CCL2, CCL4, and CCL5 genes with 5-ADC and 5-ADC/PDT treatment in both spleen and breast tissue, with the latter showing the most decrease.

Discussion

To our knowledge, this is the first study that shows which of the innate and adaptive immune biomarkers are activated during PDT related treatment of the TNBC 4T1 mouse models. The results also indicate that some of the immune response biomarkers can be used to monitor the effectiveness of PDT treatment in TNBC murine model warranting further investigation in human subjects.

Molecular Alterations in Malignant Pleural Mesothelioma: A Hope for Effective Treatment by Targeting YAP

Malignant pleural mesothelioma is a rare and aggressive neoplasm, which has primarily been attributed to the exposure to asbestos fibers (83% of cases); yet, despite a ban of using asbestos in many countries, the incidence of malignant pleural mesothelioma failed to decline worldwide. While little progress has been made in malignant pleural mesothelioma diagnosis, bevacizumab at first, then followed by double immunotherapy (nivolumab plus ipilumumab), were all shown to improve survival in large phase III randomized trials. The morphological analysis of the histological subtyping remains the primary indicator for therapeutic decision making at an advanced disease stage, while a platinum-based chemotherapy regimen combined with pemetrexed, either with or without bevacizumab, is still the main treatment option. Consequently, malignant pleural mesothelioma still represents a significant health concern owing to poor median survival (12-18 months). Given this context, both diagnosis and therapy improvements require better knowledge of the molecular mechanisms underlying malignant pleural mesothelioma's carcinogenesis and progression. Hence, the Hippo pathway in malignant pleural mesothelioma initiation and progression has recently received increasing attention, as the aberrant expression of its core components may be closely related to patient prognosis. The purpose of this review was to provide a critical analysis of our current knowledge on these topics, the main focus being on the available evidence concerning the role of each Hippo pathway's member as a promising biomarker, enabling detection of the disease at earlier stages and thus improving prognosis.

An overview of the crosstalk between YAP and cGAS-STING signaling in non-small cell lung cancer: it takes two to tango

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway is recognized as a main mediator bridging innate and adaptive immunity, recent advances have expanded its roles to anti-tumor immunity and carcinogenesis. Loss of cGAS-STING signaling in non-small cell lung cancer (NSCLC) leads to enhanced tumorigenicity and decreased cytotoxic T lymphocyte infiltration. Apart from its anticancer response, persistent overreaction of cGAS-STING signaling promotes progression of certain inflammation-aggravated cancers. Activation of the pro-inflammatory nucleic acid sensing pathway can trigger Hippo pathway, which mediates the inactivation of Yes-associated protein 1 (YAP1) and its paralogue transcriptional co-regulators with PDZ-binding motif (TAZ, also known as WWTR1), and subsequent suppression of tumorigenesis. Active YAP acts as a transcriptional driver in bolstering immunosuppressive cytokines to evade immune surveillance and promote occurrence of preneoplasia. It is reasonable that aggressive tumors co-opt these regulators to generate few immunogenic antigens and drive tumorigenic behaviors via a highly cooperative manner. Given their multifaced roles, we profile the molecular biology characteristic and current status underpinning oncogenic YAP, review its crosstalk roles with cGAS/STING pathway in NSCLC, and summarize the major clinical investigations in NSCLC with TCGA database.

Riluzole-induced apoptosis in osteosarcoma is mediated through Yes-associated protein upon phosphorylation by c-Abl Kinase

Our lab has previously demonstrated Riluzole to be an effective drug in inhibiting proliferation and inducing apoptosis in both human and mouse osteosarcoma. Yes-associated protein is a transcription co-activator, known to be involved in cell proliferation or apoptosis depending on its protein partner. In the present study we investigated the role of YAP in apoptosis in osteosarcoma, we hypothesized that YAP may be activated by Riluzole to induce apoptosis in osteosarcoma. By knocking down the expression of YAP, we have demonstrated that Riluzole failed to induce apoptosis in YAP deficient osteosarcoma cells. Riluzole caused translocation of YAP from the cytoplasm to the nucleus, indicating YAP’s role in apoptosis. Both Riluzole-induced phosphorylation of YAP at tyrosine 357 and Riluzole-induced apoptosis were blocked by inhibitors of c-Abl kinase. In addition, knockdown of c-Abl kinase prevented Riluzole-induced apoptosis in LM7 cells. We further demonstrated that Riluzole promoted interaction between YAP and p73, while c-Abl kinase inhibitors abolished the interaction. Subsequently, we demonstrated that Riluzole enhanced activity of the Bax promoter in a luciferase reporter assay and enhanced YAP/p73 binding on endogenous Bax promoter in a ChIP assay. Our data supports a novel mechanism in which Riluzole activates c-Abl kinase to regulate pro-apoptotic activity of YAP in osteosarcoma.

Mechano-Signaling Aspects of Hepatocellular Carcinoma

HCC is one of the leading causes of cancer related death worldwide and comprises about 90% of the cases of primary liver cancer. It is generally accompanied by chronic liver fibrosis characterised by deposition of collagen fibres, which, in turn, causes enhanced stiffness of the liver tissue. Changes of tissue stiffness give rise to alterations of signalling pathways that are associated to mechanical properties of the cells and the extracellular matrix, and that can be subsumed as "mechano-signaling pathways", like, e.g., the YAP/TAZ pathway, or the SRF pathway. Stiffness of the liver tissue modulates mechanical regulation of many genes involved in HCC progression. However, mechano-signaling is still rather underrepresented in our concepts of cancer in comparison to "classical" biochemical signalling pathways. This review aims to give an overview of various stiffness induced mechano-biological aspects of HCC.

Plasma YAP1 predicts esophageal varices and the risk of variceal bleeding in liver cirrhosis

Aim: To explore the predictive value of plasma YAP1 for esophageal varices (EV) and high-risk EV (HRV) in patients with liver cirrhosis. Materials & methods: A total of 208 patients with liver cirrhosis were enrolled and categorized into four groups. Correlation analysis, logistic regression analysis and receiver operating characteristic curve analysis were performed to evaluate the diagnostic performance of plasma YAP1 for EV and HRV. Results: Plasma YAP1 levels were significantly elevated with the occurrence and progression of EV in cirrhotic patients. The multivariate logistic regression analysis revealed that plasma YAP1 is an independent predictor for EV and HRV. For predicting EV and HRV, the YAP1 cut-off values of 5.43 and 6.98 ng/ml yielded the area under the receiver operating characteristic curves of 0.944 and 0.955, respectively. Conclusion: Plasma YAP1 is a potential novel noninvasive biomarker for predicting EV and HRV in patients with liver cirrhosis.

A miR-375/YAP axis regulates neuroendocrine differentiation and tumorigenesis in lung carcinoid cells

Lung carcinoids are variably aggressive and mechanistically understudied neuroendocrine neoplasms (NENs). Here, we identified and elucidated the function of a miR-375/yes-associated protein (YAP) axis in lung carcinoid (H727) cells. miR-375 and YAP are respectively high and low expressed in wild-type H727 cells. Following lentiviral CRISPR/Cas9-mediated miR-375 depletion, we identified distinct transcriptomic changes including dramatic YAP upregulation. We also observed a significant decrease in neuroendocrine differentiation and substantial reductions in cell proliferation, transformation, and tumor growth in cell culture and xenograft mouse disease models. Similarly, YAP overexpression resulted in distinct and partially overlapping transcriptomic changes, phenocopying the effects of miR-375 depletion in the same models as above. Transient YAP knockdown in miR-375-depleted cells reversed the effects of miR-375 on neuroendocrine differentiation and cell proliferation. Pathways analysis and confirmatory real-time PCR studies of shared dysregulated target genes indicate that this axis controls neuroendocrine related functions such as neural differentiation, exocytosis, and secretion. Taken together, we provide compelling evidence that a miR-375/YAP axis is a critical mediator of neuroendocrine differentiation and tumorigenesis in lung carcinoid cells.

Yes-Associated Protein 1 Is a Novel Calcium Sensing Receptor Target in Human Parathyroid Tumors

The Hippo pathway is involved in human tumorigenesis and tissue repair. Here, we investigated the Hippo coactivator Yes-associated protein 1 (YAP1) and the kinase large tumor suppressor 1/2 (LATS1/2) in tumors of the parathyroid glands, which are almost invariably associated with primary hyperparathyroidism. Compared with normal parathyroid glands, parathyroid adenomas (PAds) and carcinomas show variably but reduced nuclear YAP1 expression. The kinase LATS1/2, which phosphorylates YAP1 thus promoting its degradation, was also variably reduced in PAds. Further, YAP1 silencing reduces the expression of the key parathyroid oncosuppressor multiple endocrine neoplasia type 1(MEN1), while MEN1 silencing increases YAP1 expression. Treatment of patient-derived PAds-primary cell cultures and Human embryonic kidney 293A (HEK293A) cells expressing the calcium-sensing receptor (CASR) with the CASR agonist R568 induces YAP1 nuclear accumulation. This effect was prevented by the incubation of the cells with RhoA/Rho-associated coiled-coil-containing protein kinase (ROCK) inhibitors Y27632 and H1152. Lastly, CASR activation increased the expression of the YAP1 gene targets CYR61, CTGF, and WNT5A, and this effect was blunted by YAP1 silencing. Concluding, here we provide preliminary evidence of the involvement of the Hippo pathway in human tumor parathyroid cells and of the existence of a CASR-ROCK-YAP1 axis. We propose a tumor suppressor role for YAP1 and LATS1/2 in parathyroid tumors.

The head and neck cancer genome in the era of immunotherapy

The recent success of immunotherapy in head and neck squamous cell carcinoma (HNSCC) has necessitated a new perspective on the cancer genome. Here we review recent advances in the carcinogenesis and molecular genetics of HNSCC with an eye on their implications for cancer immunity. Newer sequencing technologies have recently facilitated dissection of the complex interaction between the HPV virus, tumor, host factors, and the tumor microenvironment (TME) that help shed light on how the immune system interacts with head and neck malignancies.

Integrated Genome-Wide Methylation and Expression Analyses Reveal Key Regulators in Osteosarcoma

Osteosarcoma (OS) is one of the most common types of primary bone tumors in early adolescence with unsatisfied prognosis. Aberrant DNA methylation had been demonstrated to be related to tumorigenesis and progression of multiple cancers and could serve as the potential biomarkers for the prognosis of human cancers. In conclusion, this study identified 18 downregulated hypomethylation genes and 52 upregulated hypomethylation genes in OS by integrating the analysis the GSE97529 and GSE42572 datasets. Bioinformatics analysis revealed that OS-specific methylated genes were involved in regulating multiple biological processes, including chemical synaptic transmission, transcription, response to drug, and regulating immune response. KEGG pathway analysis showed that OS-specific methylated genes were associated with the regulation of Hippo, cAMP calcium, MAPK, and Wnt signaling pathways. By analyzing R2 datasets, this study showed that the dysregulation of these OS-specific methylated genes was associated with the metastasis-free survival time in patients with OS, including CBLN4, ANKMY1, BZW1, KRTCAP3, GZMB, KRTDAP, LY9, PFKFB2, PTPN22, and CLDN7. This study provided a better understanding of the molecular mechanisms underlying the progression and OS and novel biomarkers for the prognosis of OS.

The Role of the Hippo Pathway in Breast Cancer Carcinogenesis, Prognosis, and Treatment: A Systematic Review

Background

The Hippo pathway is a developmental pathway recently discovered in Drosophila melanogaster; in mammals it normally controls organ development and wound healing. Hippo signaling is deregulated in breast cancer (BC). MST1/2 and LATS1/2 kinases are the upstream molecular elements of Hippo signaling which phosphorylate and regulate the two effectors of Hippo signaling, YAP1 and TAZ cotranscriptional activators. The two molecular effectors of the Hippo pathway facilitate their activity through TEAD transcription factors. Several molecular pathways with known oncogenic functions cross-talk with the Hippo pathway.

Methods

A systematic review studying the correlation of the Hippo pathway with BC tumorigenesis, prognosis, and treatment was performed.

Results

Recent literature highlights the critical role of Hippo signaling in a wide spectrum of biological mechanisms in BC.

Discussion

The Hippo pathway has a crucial position in BC molecular biology, cellular behavior, and response to treatment. Targeting the Hippo pathway could potentially improve the prognosis and outcome of BC patients.

gga-microRNA-375 negatively regulates the cell cycle and proliferation by targeting Yes-associated protein 1 in DF-1 cells

MicroRNAs (miRNAs/miRs) serve a key role in regulating the cell cycle and inducing tumorigenesis. Subgroup J of the avian leukosis virus (ALV-J) belongs to the family Retroviridae, subfamily Orthoretrovirinae and genus Alpharetrovirus that causes tumors in susceptible chickens. gga-miR-375 is downregulated and Yes-associated protein 1 (YAP1) is upregulated in ALV-J-induced tumors in the livers of chickens, and it has been further identified that YAP1 is the direct target gene of gga-miR-375. In the present study, it was found that ALV-J infection promoted the cell cycle and proliferation in DF-1 cells. As the cell cycle and cell proliferation are closely associated with tumorigenesis, further experiments were performed to determine whether gga-miR-375 and YAP1 were involved in these cellular processes. It was demonstrated that gga-miR-375 significantly inhibited the cell cycle by inhibiting G₁ to S/G₂ stage transition and decreasing cell proliferation, while YAP1 significantly promoted the cell cycle and proliferation. Furthermore, these cellular processes in DF-1 cells were affected by gga-miR-375 through the targeting of YAP1. Collectively, the present results suggested that gga-miR-375, downregulated by ALV-J infection, negatively regulated the cell cycle and proliferation via the targeting of YAP1.

Mechanism of inhibiting proliferation of hepatocellular carcinoma Hepa1-6 cells by embryonic stem cell-conditioned medium

The present study aimed to investigate the antiproliferative effect of embryonic stem cell-conditioned medium (ESC-CM) on the mouse liver cancer Hepa1-6 cells in vitro. Furthermore, in order to elucidate the underlying molecular mechanism, the microRNAs (miRNAs) in ESC-CM associated with the inhibition of Hepa1-6 proliferation were identified. Following the co-culture of ESC-CM and Hepa1-6 in Transwell chambers, the proliferation, cell cycle, apoptosis and associated protein expression were determined in Hepal-6 cells. Moreover, miRNA array analysis was employed to identify differentially expressed miRNAs. Based on the differentially expressed miRNAs, the target genes and potential associated signaling pathways were determined. Finally, RT-qPCR was conducted to confirm the above results. The ESC-CM inhibited Hepal-6 cell proliferation and increased the percentage of cells at G₁ phase and decreased the percentage of cells at the G₂/M phase of the cell cycle. The expression of cyclin D1/cyclin-dependent kinase (CDK)4/CDK6 was decreased following co-culture, with no effect on cell apoptosis. Six significantly regulated miRNAs were identified and 423 putative target genes of these regulated miRNAs were predicted. Gene ontology analysis revealed the putative target genes to be associated with the ‘DNA replication (GO: 0006260)’ GO term, ‘apoptosis’ and ‘signal transduction’. The Kyoto Encyclopedia of Genes and Genomes analysis indicated that deregulated miRNAs were enriched in the Wnt signaling (KEGG entry: Map 04310) and Hippo signaling pathways (KEGG entry: Map 04390), pathways associated with cancer. Overall, the present study demonstrated the inhibition of Hepa1-6 cell line proliferation upon treatment with ESC-CM, by decreasing cell cycle-associated protein cyclin D1/CDK4/CDK6 expression and arresting cells in G₁ phase of the cell cycle, with no effect on cell apoptosis. Furthermore, the inhibition of proliferation by ESC-CM may be mediated by miRNAs that affect cell cycle-associated mRNAs and the Wnt signaling pathway.

The Crosstalk Between Hippo-YAP Pathway and Innate Immunity

Recognition of pathogen-associated molecular patterns (PAMPs) triggers expression of antiviral interferons and proinflammatory cytokines, which functions as the frontier of host defense against microbial pathogen invasion. Hippo-YAP pathway regulates cell proliferation, survival, differentiation and is involved in diverse life processes, including tissue homeostasis and tumor suppression. Emerging discoveries elucidated that the components of Hippo-YAP pathway, such as MST1/2, NDR1/2, and YAP/TAZ played crucial regulatory roles in innate immunity. Meanwhile the innate immune signaling also exhibited regulatory effect on Hippo-YAP pathway. As for the importance of these two pathways, it would be interesting to figure out the deeper biological implications of their interplays. This review focuses on the regulation between Hippo-YAP pathway and innate immune signaling. We also propose the possible contribution of these interplays to tumor development.

XB130 deficiency enhances carcinogen-induced skin tumorigenesis

XB130 is an adaptor protein that functions as a mediator of multiple tyrosine kinases important for regulating cell proliferation, survival, migration and invasion. Formerly predicted as an oncogene, alterations of its expression are documented in various human cancers. However, the exact role of XB130 in tumorigenesis is unknown. To address its function in skin tumorigenesis, a two-stage dimethylbenzanthracene (DMBA)/12-O-tetradecanoylphorbol 13-acetate (TPA) study was performed on XB130 knockout (KO), heterozygous (HZ) and wild-type (WT) littermate mice. DMBA/TPA-treated XB130 KO and HZ males developed a significantly higher number of epidermal tumors that were notably larger in size than did WT mice. Interestingly, DMBA/TPA-treated female mice did not show any difference in tumor multiplicity regardless of the genotypes. The skin tumor lesions of XB130 KO males were more progressed with an increased frequency of keratoacanthoma. Deficiency of XB130 dramatically increased epidermal tumor cell proliferation. The responses to DMBA and TPA stimuli were also individually investigated to elucidate the mechanistic role of XB130 at different stages of tumorigenesis. DMBA-treated male XB130 KO mice showed compensatory p53-mediated stress response. TPA-treated XB130 KO males demonstrated more skin ulceration with more severe edema, enhanced cell proliferation, accumulation of infiltrating neutrophils and increased production of pro-inflammatory cytokine genes compared with WT mice. Enhanced activities of nuclear factor-kappa B pathway, increased protein expression of metalloproteinase-9 and ERK1/2 phosphorylation were found in these KO mice. These findings demonstrate that XB130 acts as a tumor suppressor in carcinogen-induced skin tumorigenesis that may be mediated through inhibiting inflammation.

Prognostic significance of nuclear Yes-associated protein 1 in patients with nonsmall cell lung cancer: A systematic review and meta-analysis

BACKGROUND

Nuclear Yes-associated protein 1 (YAP1) has often been regarded as an adverse prognostic indicator in various tumors. Recent studies have associated YAP1 with unfavorable prognosis in nonsmall cell lung cancer (NSCLC). However, due to small sample sizes, the prognostic value of nuclear YAP1 in NSCLC patients is not well understood. In the present study, we evaluated the prognostic role of nuclear YAP1 in NSCLC patients via a systematic review and meta-analysis.

METHODS

We searched the PubMed, EMBASE, Cochrane, Web of Science, China National Knowledge Infrastructure (CNKI), and Wanfang Databases for papers investigating the prognostic significance of nuclear YAP1 expression in NSCLC patients. Hazard ratios (HRs) and the corresponding 95% confidence intervals (CIs) were calculated with reference to overall survival (OS) and progression-free survival (PFS) of NSCLC patients to provide synthesized estimates of the effects of nuclear YAP1 expression.

RESULTS

Among 414 cases, higher nuclear YAP1 expression presented as a predictive factor of poorer OS (HR = 1.52; 95% CI: 1.11-2.08; P = .01; I = 0.0%) and decreased PFS (HR = 2.11; 95% CI: 1.52-2.93; P < .001; I = 44.2%) in NSCLC patients. Subgroup analysis revealed shortened OS (HR = 1.63; 95% CI: 1.14-2.34; P = .007; I = 0.0%) and worse PFS (HR = 2.25; 95% CI: 1.53-3.30; P < .001; I = 0.0%) in patients from Asia with higher nuclear YAP1 expression. Prognosis was also worse in patients with III-IV stage cancer (PFSHR = 2.09; 95% CI: 1.45-3.01; P < .001; I = 58.1%) and in patients treated with epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) (OS HR = 1.59; 95% CI: 1.00-2.51; P = .048; I = 15.5%, and PFS HR = 2.35, 95% CI: 1.62-3.42; P < .001; I = 0.0%).

CONCLUSION

High expression of nuclear YAP1 was associated with shorter survival outcome in patients with NSCLC.

Differential gene expression induced by Verteporfin in endometrial cancer cells

Endometrial cancer (EMCA) is a clinically heterogeneous disease. Previously, we tested the efficacy of Verteporfin (VP) in EMCA cells and observed cytotoxic and anti-proliferative effects. In this study, we analyzed RNA sequencing data to investigate the comprehensive transcriptomic landscape of VP treated Type 1 EMCA cell lines, including HEC-1-A and HEC-1-B. There were 549 genes with differential expression of two-fold or greater and P < 0.05 after false discovery rate correction for the HEC-1-B cell line. Positive regulation of TGFβ1 production, regulation of lipoprotein metabolic process, cell adhesion, endodermal cell differentiation, formation and development, and integrin mediated signaling pathway were among the significantly associated terms. A functional enrichment analysis of differentially expressed genes after VP treatment revealed extracellular matrix organization Gene Ontology as the most significant. CDC23 and BUB1B, two genes crucially involved in mitotic checkpoint progression, were found to be the pair with the best association from STRING among differentially expressed genes in VP treated HEC-1-B cells. Our in vivo results indicate that subcutaneous tumors in mice were regressed after VP treatment by inhibiting cell cycle pathway proteins. The present study revealed multiple key genes of pathological significance in EMCA, thereby improving our understanding of molecular profiles of EMCA cells.

Aberrant Promoter Methylation of YAP Gene and its Subsequent Downregulation in Indian Breast Cancer Patients

BACKGROUND

YAP, a potent oncogene and major downstream effector of the mammalian Hippo tumor suppressor pathway can act as either oncogene or tumor suppressor gene based on the type of tissue involved. Despite various studies, the role and mechanism through which YAP mediates its tumor suppressor or oncogenic effects are not yet fully understood. Therefore in the present study we aimed to investigate YAP at DNA, mRNA and protein level and also attempted to correlate our molecular findings with various clinicopathological variables of the patients.

METHODS

The study comprised of a total 137 genetically unrelated women with sporadic breast cancer cases and normal adjacent tissues not infiltrated with tumor. Mutation of YAP gene was analyzed by automated DNA sequencing. YAP promoter methylation was studied using MS-PCR. Expression at mRNA and protein level was studied using qPCR and IHC respectively.

RESULTS

In our study YAP mRNA expression was found to be 8.65 ± 6.17 fold downregulated in 67.15% cases. The expression of YAP when analyzed at the protein level by IHC was found to be absent in 78.83% cases. Results from MS-PCR analysis showed that YAP promoter methylation plays an important role in declining the expression of YAP protein. The absence of YAP protein coincided with 86.60% methylated cases thereby showing a very strong correlation (p = 0.001). We also investigated YAP mutation at the major check point sites in the Hippo pathway and observed no mutation. A significant association was observed on correlating mRNA expression with clinical stages (p = 0.038) and protein expression with ER status (p = 0.018) among Indian breast cancer patients.

CONCLUSION

The expression of YAP was found to be downregulated in response to aberrant promoter methylation. The downregulation of YAP are consistent with previous studies suggesting it to have a tumor suppressive role in breast cancer. We did not observe any mutation at the major check point sites in the Hippo pathway.

The role of Hippo signal pathway in breast cancer metastasis

The Hippo pathway is a novel and highly conserved mammalian signaling pathway. Mutations and altered expression of core Hippo pathway components promote the migration, invasion, malignancy, and chemotherapy resistance of breast cancer cells. In cancer metastasis, tumor cells must detach from the primary tumor, invade surrounding tissue, and enter and survive in a foreign microenvironment. The metastatic potential of breast cancer is closely related to individual patient genetic profile. Nevertheless, the exact molecular mechanism that regulates the Hippo pathway in breast cancer metastasis is yet to be fully elucidated. This article discusses the function and regulation of the Hippo pathway, with focus given to its role in the context of breast cancer metastasis.

Targeting high Aurora kinases expression as an innovative therapy for hepatocellular carcinoma

The Aurora kinases A and B control tumorigenesis by inhibiting apoptosis and promoting proliferation and metastasis, however, it remains unknown whether Aurora A and B overexpressed concomitantly and its clinical significance in hepatocellular carcinoma (HCC). Here, we obsearved Aurora A and B tended to overexpress parallelly on protein level (r = 0.8679, P < 0.0001) and their co-overexpression (Aurora A^HB^H), associated with the worst prognosis, was an independent predictor for the survival. Importantly, with the lower IC50 and stronger anti-tumor effect than selective inhibitors, SNS-314, the pan-inhibitor of Aurora kinases, which induced YAP (Yes-associated protein) reduction and resulted in P21 accumulation, significantly promoted the polyploidy (> 4N) formation and apoptosis in HCC. High YAP expression (YAP^H) was associated with Aurora A^HB^H, and appeared to be an independent predictor for survival, but P21 not. Moreover, silencing YAP also induced P21 accumulation, and knockdown P21, which enhanced YAP accumulation and weakened the SNS-314-induced YAP reduction, impaired SNS-314-induced apoptosis. Therefore, P21 enhanced the apoptotic effect of SNS-314 in HCC. Taken together, our findings indicated Aurora kinases/YAP/P21 was an oncogenic signaling axis in HCC, and revealed targeting Aurora A^HB^H induced apoptosis by YAP suppression. Our results also provided a solid evidence for SNS-314 as a potential targeted therapy, and a proof-of-concept evidence for a possible combined therapy of SNS-314 plus Hippo pathway inhibitors on HCC.

Two faces of Hippo: activate or suppress the Hippo pathway in cancer

The Hippo pathway has generated considerable interest in recent years because of its involvement in several key hallmarks of cancer progression and metastasis. Research on the Hippo signaling pathway in cancer has been used to determine the activity of yes-associated protein (YAP) in tumorigenesis and disease progression. Previous studies have shown that the Hippo pathway can be used as a target to inhibit YAP activity and is a viable treatment for cancer. However, more studies are required to further advance our understanding of the Hippo signaling pathway in cancer. It has been shown that knockout of serine/threonine-kinases LATS1/2 in the Hippo pathway suppresses cancer immunity in mice. In addition, suppression of the oncogene YAP could contribute toward cancer immune therapy. Therefore, regulation of Hippo signaling can be an attractive alternative strategy for cancer treatment. This review will provide a summary of currently known compounds that activate or suppress the Hippo pathway.

Nuclear localization of TEF3-1 promotes cell cycle progression and angiogenesis in cancer

TEF3-1 (transcriptional enhancer factor 3 isoform 1), also known as TEAD4 (TEA domain family member 4), was recently revealed as an oncogenic character in cancer development. However, the underlying molecular pathogenic mechanisms remain undefined. In this paper, we investigated nuclear TEF3-1 could promote G1/S transition in HUVECs, and the expression levels of cyclins and CDKs were upregulated. Additionally, if TEF3-1 was knocked down, the expression of cyclins and CDKs was downregulated while the expression of P21, a negative regulator of the cell cycle, was upregulated. A microarray analysis also confirmed that TEF3-1 overexpression upregulates genes that are related to cell cycle progression and the promotion of angiogenesis. Moreover, we observed that nuclear TEF3-1 was highly expressed during the formation of vascular structures in gastric cancer (GC). Finally, tumor xenograft experiments indicated that, when TEF3-1 was knocked down, tumor growth and angiogenesis were also suppressed. Taken together, these results demonstrate for the first time that TEF3-1 localization to the nucleus stimulates the cell cycle progression in HUVECs and specifically contributes to tumor angiogenesis. Nuclear TEF3-1 in HUVECs may serve as an oncogenic biomarker, and the suppression of TEF3-1 may be a potential target in anti-tumor therapy.

Amlexanox, a selective inhibitor of IKBKE, generates anti-tumoral effects by disrupting the Hippo pathway in human glioblastoma cell lines

Glioblastoma multiforme (GBM) is the most prevalent form of malignant brain tumor. Amlexanox, a novel compound, has been shown to have anti-cancer potential. In this study, the anti-tumoral effects and the underlying mechanisms of amlexanox were investigated. Amlexanox significantly suppressed proliferation and invasion and induced apoptosis in glioblastoma cells. Furthermore, we found that amlexanox altered the protein expression of the Hippo pathway by downregulating IKBKE. Our data indicates that IKBKE directly targets LATS1/2 and induces degradation of LATS1/2, thereby inhibiting the activity of the Hippo pathway. In vivo results further confirmed the tumor inhibitory effect of amlexanox via the downregulation of IKBKE, and amlexanox induced no apparent toxicity. Collectively, our studies suggest that amlexanox is a promising therapeutic agent for the treatment of GBM.

Dual roles of yes-associated protein (YAP) in colorectal cancer

Yes-associated protein (YAP) is a downstream effector molecule of a newly emerging tumour suppressor pathway called the Hippo pathway. YAP is a transcriptional co-activator and mis-expressed in various cancers, including colorectal cancer (CRC). Accumulating studies show that the high expression of nuclear YAP is linked with tumour progression and decreased survival. Nuclear YAP can interact with other transcription factors to promote cancer cell proliferation, apoptosis, metastasis and maintenance of stemness. Therefore, YAP has the potential to be a tumour biomarker or therapeutic target for CRC. However, recently, a number of studies have supported a contradictory role for YAP as a tumour suppressor, demonstrating inhibition of the tumorigenesis of CRC, involvement in promoting cell apoptosis, and inhibiting the maintenance of intestinal stem cells and inflammatory activity. In these studies, high expression of YAP was highly correlated with worse survival in CRC. In this review, we will comprehensively summarize and analyse these paradoxical reports, and discuss both the oncogenic and tumour suppressor functions of YAP in the differential status of CRC progression. Further investigation into the mechanisms responsible for the dual function of YAP will be of great value in the prevention, early diagnosis, and therapy of CRC.

Thy-1+ Cancer-associated Fibroblasts Adversely Impact Lung Cancer Prognosis

Cancer-associated fibroblasts (CAFs) regulate diverse intratumoral biological programs and can promote or inhibit tumorigenesis, but those CAF populations that negatively impact the clinical outcome of lung cancer patients have not been fully elucidated. Because Thy-1 (CD90) marks CAFs that promote tumor cell invasion in a murine model of Kras^G12D-driven lung adenocarcinoma (Kras^LA1), here we postulated that human lung adenocarcinomas containing Thy-1⁺ CAFs have a worse prognosis. We first examined the location of Thy-1⁺ CAFs within human lung adenocarcinomas. Cells that co-express Thy-1 and α-smooth muscle actin (αSMA), a CAF marker, were located on the tumor periphery surrounding collectively invading tumor cells and in perivascular regions. To interrogate a human lung cancer database for the presence of Thy-1⁺ CAFs, we isolated Thy-1⁺ CAFs and normal lung fibroblasts (LFs) from the lungs of Kras^LA1 mice and wild-type littermates, respectively, and performed global proteomic analysis on the murine CAFs and LFs, which identified 425 proteins that were differentially expressed. Used as a probe to identify Thy-1⁺ CAF-enriched tumors in a compendium of 1,586 lung adenocarcinomas, the presence of the 425-gene signature predicted a significantly shorter survival. Thus, Thy-1 marks a CAF population that adversely impacts clinical outcome in human lung cancer.

IKBKE promotes glioblastoma progression by establishing the regulatory feedback loop of IKBKE/YAP1/miR-Let-7b/i

Recently, we have demonstrated that IKBKE (inhibitor of nuclear factor kappa-B kinase subunit epsilon) is overexpressed in human glioblastoma and that inhibition of IKBKE remarkably suppresses the proliferative and invasive behaviour of glioblastoma cells. However, the specific pathogenic molecular mechanism remains to be elucidated. In this study, we verified that IKBKE promotes YAP1 expression via posttranslational modification and accelerates YAP1 translocation to the nucleus for the development of glioblastoma. We then determined that YAP1 negatively regulates miR-let-7b/i by overexpressing and silencing YAP1 expression. In addition, miR-let-7b/i feedback decreases the expression of IKBKE and YAP1 and suppresses the transportation of YAP1 located in the nucleus. Therefore, the regulatory feedback circuit of IKBKE↑→YAP1↑→miR-let-7b/i↓→IKBKE↑ dictates glioblastoma progression. Thus, we propose that blocking the circuit may be a new therapeutic strategy for the treatment of glioblastoma.

The Hippo Pathway Kinases LATS1/2 Suppress Cancer Immunity

Poorly immunogenic tumor cells evade host immunity and grow even in the presence of an intact immune system, but the complex mechanisms regulating tumor immunogenicity have not been elucidated. Here, we discovered an unexpected role of the Hippo pathway in suppressing anti-tumor immunity. We demonstrate that, in three different murine syngeneic tumor models (B16, SCC7, and 4T1), loss of the Hippo pathway kinases LATS1/2 (large tumor suppressor 1 and 2) in tumor cells inhibits tumor growth. Tumor regression by LATS1/2 deletion requires adaptive immune responses, and LATS1/2 deficiency enhances tumor vaccine efficacy. Mechanistically, LATS1/2-null tumor cells secrete nucleic-acid-rich extracellular vesicles, which induce a type I interferon response via the Toll-like receptors-MYD88/TRIF pathway. LATS1/2 deletion in tumors thus improves tumor immunogenicity, leading to tumor destruction by enhancing anti-tumor immune responses. Our observations uncover a key role of the Hippo pathway in modulating tumor immunogenicity and demonstrate a proof of concept for targeting LATS1/2 in cancer immunotherapy.

Phase I/Ib study of olaparib and carboplatin in women with triple negative breast cancer

PURPOSE

To investigate the safety, activity, and potential biomarkers of response to olaparib and carboplatin combination in sporadic triple negative breast cancer (TNBC). EXPERIMENTAL DESIGN: Metastatic or recurrent TNBC patients with no germline BRCA mutation or with BRCAPro scores <10% and a negative family history were eligible. A 3+3 dose escalation tested olaparib capsules (400mg bid, days1-7) with carboplatin AUC3-5 on day1 or 2 every 21 days, ≤ 8 cycles, with olaparib 400mg bid maintenance. Peripheral blood mononuclear cells were collected for polymorphisms and PAR levels, and paired tumor biopsies (pre-/post-cycle 1) for proteomics and apoptosis endpoints.

RESULTS

28 women were treated (median 5 prior regimens [0-12]). Dose-limiting toxicity was thrombocytopenia, and symptomatic hyponatremia with carboplatin AUC5. The maximum tolerated dose was olaparib 400mg bid+carboplatin AUC4. Grade 3 and 4 adverse events included neutropenia (36%), thrombocytopenia (11%), and anemia (11%). Responses included 1 complete response (CR; 69⁺months) and 5/27 partial responses (19%; median 4months [4-7]), for a response rate of 22%. Biomarker findings did not correlate with response. The long-term CR patient with prior negative BRCA testing was found to have deletion of BRCA1 exons1-2.

CONCLUSIONS

The olaparib/carboplatin combination is tolerable and has modest activity in sporadic TNBC patients. Further evaluation of predictive biomarkers to identify those with BRCA wild type who had response is warranted.

YAP and the Hippo pathway in pediatric cancer

The Hippo pathway is an important signaling pathway that controls cell proliferation and apoptosis. It is evolutionarily conserved in mammals and is stimulated by cell-cell contact, inhibiting cell proliferation in response to increased cell density. During early embryonic development, the Hippo signaling pathway regulates organ development and size, and its functions result in the coordinated balance between proliferation, apoptosis, and differentiation. Its principal effectors, YAP and TAZ, regulate signaling by the embryonic stem cells and determine cell fate and histogenesis. Dysfunction of this pathway contributes to cancer development in adults and children. Emerging studies have shed light on the upregulation of Hippo pathway members in several pediatric cancers and may offer prognostic information on rhabdomyosarcoma, osteosarcoma, Wilms tumor, neuroblastoma, medulloblastoma, and other brain gliomas. We review the results of such published studies and highlight the potential clinical application of this pathway in pediatric oncologic and pathologic studies. These studies support targeting this pathway as a novel treatment strategy.

Lipopolysaccharide Induces Human Pulmonary Micro-Vascular Endothelial Apoptosis via the YAP Signaling Pathway

Gram-negative bacterial lipopolysaccharide (LPS) induces a pathologic increase in lung vascular leakage under septic conditions. LPS-induced human pulmonary micro-vascular endothelial cell (HPMEC) apoptosis launches and aggravates micro-vascular hyper-permeability and acute lung injury (ALI). Previous studies show that the activation of intrinsic apoptotic pathway is vital for LPS-induced EC apoptosis. Yes-associated protein (YAP) has been reported to positively regulate intrinsic apoptotic pathway in tumor cells apoptosis. However, the potential role of YAP protein in LPS-induced HPMEC apoptosis has not been determined. In this study, we found that LPS-induced activation and nuclear accumulation of YAP accelerated HPMECs apoptosis. LPS-induced YAP translocation from cytoplasm to nucleus by the increased phosphorylation on Y357 resulted in the interaction between YAP and transcription factor P73. Furthermore, inhibition of YAP by small interfering RNA (siRNA) not only suppressed the LPS-induced HPMEC apoptosis but also regulated P73-mediated up-regulation of BAX and down-regulation of BCL-2. Taken together, our results demonstrated that activation of the YAP/P73/(BAX and BCL-2)/caspase-3 signaling pathway played a critical role in LPS-induced HPMEC apoptosis. Inhibition of the YAP might be a potential therapeutic strategy for lung injury under sepsis.

Post-translational deregulation of YAP1 is genetically controlled in rat liver cancer and determines the fate and stem-like behavior of the human disease

Previous studies showed that YAP1 is over-expressed in hepatocellular carcinoma (HCC). Here we observed higher expression of Yap1/Ctgf axis in dysplastic nodules and HCC chemically-induced in F344 rats, genetically susceptible to hepatocarcinogenesis, than in lesions induced in resistant BN rats. In BN rats, highest increase in Yap1-tyr357, p73 phosphorylation and Caspase 3 cleavage occurred. In human HCCs with poorer prognosis (< 3 years survival after partial liver resection, HCCP), levels of YAP1, CTGF, 14-3-3, and TEAD proteins, and YAP1-14-3-3 and YAP1-TEAD complexes were higher than in HCCs with better outcome (> 3 years survival; HCCB). In the latter, higher levels of phosphorylated YAP1-ser127, YAP1-tyr357 and p73, YAP1 ubiquitination, and Caspase 3 cleavage occurred. Expression of stemness markers NANOG, OCT-3/4, and CD133 were highest in HCCP and correlated with YAP1 and YAP1-TEAD levels. In HepG2, Huh7, and Hep3B cells, forced YAP1 over-expression led to stem cell markers expression and increased cell viability, whereas inhibition of YAP1 expression by specific siRNA, or transfection of mutant YAP1 which does not bind to TEAD, induced opposite alterations. These changes were associated, in Huh7 cells transfected with YAP1 or YAP1 siRNA, with stimulation or inhibition of cell migration and invasivity, respectively. Furthermore, transcriptome analysis showed that YAP1 transfection in Huh7 cells induces over-expression of genes involved in tumor stemness. In conclusion, Yap1 post-translational modifications favoring its ubiquitination and apoptosis characterize HCC with better prognosis, whereas conditions favoring the formation of YAP1-TEAD complexes are associated with aggressiveness and acquisition of stemness features by HCC cells.

Transformation by Polyomavirus Middle T Antigen Involves a Unique Bimodal Interaction with the Hippo Effector YAP

Murine polyomavirus has repeatedly provided insights into tumorigenesis, revealing key control mechanisms such as tyrosine phosphorylation and phosphoinositide 3-kinase (PI3K) signaling. We recently demonstrated that polyomavirus small T antigen (ST) binds YAP, a major effector of Hippo signaling, to regulate differentiation. Here we characterize YAP as a target of middle T antigen (MT) important for transformation. Through a surface including residues R103 and D182, wild-type MT binds to the YAP WW domains. Mutation of either R103 or D182 of MT abrogates YAP binding without affecting binding to other signaling molecules or the strength of PI3K or Ras signaling. Either genetic abrogation of YAP binding to MT or silencing of YAP via short hairpin RNA (shRNA) reduced MT transformation, suggesting that YAP makes a positive contribution to the transformed phenotype. MT targets YAP both by activating signaling pathways that affect it and by binding to it. MT signaling, whether from wild-type MT or the YAP-binding MT mutant, promoted YAP phosphorylation at S127 and S381/397 (YAP2/YAP1). Consistent with the known functions of these phosphorylated serines, MT signaling leads to the loss of YAP from the nucleus and degradation. Binding of YAP to MT brings it together with protein phosphatase 2A (PP2A), leading to the dephosphorylation of YAP in the MT complex. It also leads to the enrichment of YAP in membranes. Taken together, these results indicate that YAP promotes MT transformation via mechanisms that may depart from YAP's canonical oncogenic transcriptional activation functions.

IMPORTANCE

The highly conserved Hippo/YAP pathway is important for tissue development and homeostasis. Increasingly, changes in this pathway are being associated with cancer. Middle T antigen (MT) is the primary polyomavirus oncogene responsible for tumor formation. In this study, we show that MT signaling promotes YAP phosphorylation, loss from the nucleus, and increased turnover. Notably, MT genetics demonstrate that YAP binding to MT is important for transformation. Because MT also binds PP2A, YAP bound to MT is dephosphorylated, stabilized, and localized to membranes. Taken together, these results indicate that YAP promotes MT transformation via mechanisms that depart from YAP's canonical oncogenic transcriptional activation functions.

The MST/Hippo Pathway and Cell Death: A Non-Canonical Affair

The MST/Hippo signalling pathway was first described over a decade ago in Drosophila melanogaster and the core of the pathway is evolutionary conserved in mammals. The mammalian MST/Hippo pathway regulates organ size, cell proliferation and cell death. In addition, it has been shown to play a central role in the regulation of cellular homeostasis and it is commonly deregulated in human tumours. The delineation of the canonical pathway resembles the behaviour of the Hippo pathway in the fly where the activation of the core kinases of the pathway prevents the proliferative signal mediated by the key effector of the pathway YAP. Nevertheless, several lines of evidence support the idea that the mammalian MST/Hippo pathway has acquired new features during evolution, including different regulators and effectors, crosstalk with other essential signalling pathways involved in cellular homeostasis and the ability to actively trigger cell death. Here we describe the current knowledge of the mechanisms that mediate MST/Hippo dependent cell death, especially apoptosis. We include evidence for the existence of complex signalling networks where the core proteins of the pathway play a central role in controlling the balance between survival and cell death. Finally, we discuss the possible involvement of these signalling networks in several human diseases such as cancer, diabetes and neurodegenerative disorders.

YAP overexpression promotes the epithelial-mesenchymal transition and chemoresistance in pancreatic cancer cells

The expression of Yes-associated protein (YAP) has been reported to be dysregulated in pancreatic cancer. However, its contributions to tumor formation and progression remain to be elucidated. The present study demonstrated that YAP overexpression promoted the epithelial‑mesenchymal transition (EMT) in a manner associated with pancreatic cancer invasion in vitro. RNA interference‑mediated silencing of YAP attenuated cell invasion in vitro. Mechanistically, the present study demonstrated that YAP overexpression fosters pancreatic cancer progression by inducing the EMT in pancreatic cancer cells by activating the AKT cascade, which can counteract the effect of gemcitabine. These data suggested that the YAP acts synergistically to promote pancreatic cancer progression by hyperactivation of AKT signaling. The present study revealed YAP as a potential therapeutic target for pancreatic cancer and a biomarker for predicting gemcitabine treatment response.

Akt and Hippo Pathways in Ewing's Sarcoma Tumors and Their Prognostic Significance

Background: Ewing's sarcoma tumor is an aggressive malignancy of bone and soft tissue in children and young adults. Despite advances in modern therapy, metastasis occurs and results in high mortality. Intracellular molecules Yap, Akt, mTOR, and Erk are signaling pathway members that regulate the proliferation of tumor cells.

Objective and Methods: We studied the immunohistochemical expression of these proteins in 36 tumor samples from adult and pediatric patients with Ewing's sarcoma tumors. Patients' age, sex, tumor site, tumor size, clinical stage and survival (overall and disease-free survival) were collected. Tissue microarrays slides were stained with antibodies against Yap, Akt, mTOR, and Erk proteins.

Results: Tumors exhibited variable expression of Yap, Akt, mTOR, and Erk (from negative, low to high), with high levels of expression present in 31%, 53%, 77% and 0% respectively. Immunohistochemical expression of Akt was associated with worse overall and disease-free survival (p<0.05). The other biomarkers did not demonstrate any difference in survival between low versus high expression.

Conclusion: Although Yap, Akt, mTOR, and Erk protein are all expressed in Ewing's sarcoma by immunohistochemistry, only Akt expression is associated with worse prognosis. Larger studies are needed to verify these results and plan targeted therapy, particularly against Akt.

Hippo pathway in mammary gland development and breast cancer

Accumulated evidence suggests that the Hippo signaling pathway plays crucial roles in mammary gland development and breast cancer. Key components of the Hippo pathway regulate breast epithelial cell proliferation, migration, invasion, and stemness. Additionally, the Hippo pathway regulates breast tumor growth, metastasis, and drug resistance. It is expected that the Hippo pathway will provide novel therapeutic targets for breast cancer. This review will discuss and summarize the roles of several core components of the Hippo pathway in mammary gland development and breast cancer.

The role of the Hippo pathway in human disease and tumorigenesis

Understanding the molecular nature of human cancer is essential to the development of effective and personalized therapies. Several different molecular signal transduction pathways drive tumorigenesis when deregulated and respond to different types of therapeutic interventions. The Hippo signaling pathway has been demonstrated to play a central role in the regulation of tissue and organ size during development. The deregulation of Hippo signaling leads to a concurrent combination of uncontrolled cellular proliferation and inhibition of apoptosis, two key hallmarks in cancer development. The molecular nature of this pathway was first uncovered in Drosophila melanogaster through genetic screens to identify regulators of cell growth and cell division. The pathway is strongly conserved in humans, rendering Drosophila a suitable and efficient model system to better understand the molecular nature of this pathway. In the present study, we review the current understanding of the molecular mechanism and clinical impact of the Hippo pathway. Current studies have demonstrated that a variety of deregulated molecules can alter Hippo signaling, leading to the constitutive activation of the transcriptional activator YAP or its paralog TAZ. Additionally, the Hippo pathway integrates inputs from a number of growth signaling pathways, positioning the Hippo pathway in a central role in the regulation of tissue size. Importantly, deregulated Hippo signaling is frequently observed in human cancers. YAP is commonly activated in a number of in vitro and in vivo models of tumorigenesis, as well as a number of human cancers. The common activation of YAP in many different tumor types provides an attractive target for potential therapeutic intervention.

Yes-associated protein (YAP) modulates oncogenic features and radiation sensitivity in endometrial cancer

BACKGROUND

Yes-associated protein (YAP) is a transcriptional co-activator and regulates cell proliferation and apoptosis. We investigated the clinical and biological significance of YAP in endometrial cancer (EMCA).

METHODS

YAP expression in 150 primary tumor tissues from patients with EMCA was evaluated by immunohistochemistry and its association with clinicopathological data was assessed. The biological functions of YAP were determined in EMCA cell lines through knockdown/overexpression of YAP. The role of YAP in modulating radiation sensitivity was also investigated in EMCA cells.

RESULTS

Increased nuclear YAP expression was significantly associated with higher grade, stage, lympho-vascular space invasion, postoperative recurrence/metastasis and overall survival in estrogen mediated EMCA, called type 1 cancer (p = 0.019,  = 0.028,  = 0.0008,  = 0.046 and  = 0.015, respectively). In multivariate analysis, nuclear YAP expression was confirmed as an independent prognostic factor for overall survival in type 1 EMCA. YAP knockdown by siRNA resulted in a significant decrease in cell proliferation (p<0.05), anchorage-dependent growth (p = 0.015) and migration/invasion (p<0.05), and a significant increase in the number of cells in G0/G1 phase (p = 0.002). Conversely, YAP overexpression promoted cell proliferation. Clonogenic assay demonstrated enhanced radiosensitivity by approximately 36% in YAP inhibited cells.

CONCLUSIONS

Since YAP functions as a transcriptional co-activator, its differential localization in the nucleus of cancer cells and subsequent impact on cell proliferation could have important consequences with respect to its role as an oncogene in EMCA. Nuclear YAP expression could be useful as a prognostic indicator or therapeutic target and predict radiation sensitivity in patients with EMCA.