Nuclear Yes-associated Protein 1 Research Articles

Prognostic Value of Yes-Associated Protein 1 (YAP1) in Various Cancers: A Meta-Analysis.

BackgroundYes-associated protein 1 (YAP1) is an effector of Hippo pathway, which is critical for regulating organ size, cell proliferation and tumor growth in mammals. Many previous studies have explored the relationship between YAP1 and various types of cancer. However, these studies were limited by the small samples size and the findings were inconsistent among them. Therefore, a meta-analysis was conducted to assess the association between YAP1 and malignancies.MethodsA systematic literature search was conducted for eligible studies in the PubMed, Corchane Library, Web of Knowledge, EMBASE and CBM disc databases from inception to August 1st 2014. After heterogeneity analysis, pooled harzad ratio (HR) with 95% confidence interval (95%CI) using both fixed and random effect models were estimated in STATA 10.0. Meta regression analysis, subgroup analysis and sensitivity analysis were performed to explore the potential sources of heterogeneity and to evaluate the robustness of the result. Publication bias was assessed by Egger’s test and funnel plot.ResultsA total of 21 unique articles from 2009 to 2014, comprising 2983 patients, were analyzed in the meta-analysis. The association of YAP1 expression and overall survival time (OS) was evaluated in 20 studies including 2067 patients. Positive YAP1 showed poorer OS (HR = 1.826; 95% CI = 1.465–2.275; p <0.002). For evaluating disease-free survival time (DFS), 10 studies with 1139 patients were analyzed. Positive YAP1 indicated worse DFS (HR = 2.114; 95%CI = 1.406–3.179; p <0.001). Subgroup analysis showed that both positive nuclear YAP1 (HR = 1.390, 95% CI: 0.810–2.400, p = 0.729) and up-regulation overall YAP1 (HR = 2.237, 95% CI: 1.548–3.232, p <0.001) had poorer OS for patients with malignancies. Similarly, both positive nuclear YAP1 (HR = 3.733, 95% CI: 1.469–9.483, p = 0.001) and up-regulation overall YAP1 (HR = 1.481, 95% CI: 1.163–1.886, p = 0.554) showed worse DFS. The patients with urogenital system cancer had the poorest OS (HR = 2.133, 95% CI: 1.549–2.937, p = 0.020). The patients with alimentary system cancer had the most significant impact on DFS (HR = 1.879, 95% CI: 1.537–2.297, p <0.001).ConclusionBoth overall and nuclear YAP1 overexpression are intimately associated with adverse OS and DFS in numerous cancers, suggesting that YAP1 may act as a potential therapeutic targets of these malignancies in the future.

Yes-associated protein 1 (YAP1) promotes human gallbladder tumor growth via activation of the AXL/MAPK pathway

The transcriptional coactivator Yes-associated protein 1 (YAP1), a key regulator of cell proliferation and organ size in vertebrates, has been implicated in various malignancies. However, little is known about the expression and biological function of YAP1 in human gallbladder cancer (GBC). In this study we examined the clinical significance and biological functions of YAP1 in GBC and found that nuclear YAP1 and its target gene AXL were overexpressed in GBC tissues. We also observed a significant correlation between high YAP1 and AXL expression levels and worse prognosis. The depletion of YAP1 using lentivirus shRNAs significantly inhibited cell proliferation by inducing cell cycle arrest in S phase in concordance with the decrease of CDK2, CDC25A, and cyclin A, and resulted in increased cell apoptosis and invasive repression in GBC cell lines in vitro. Furthermore, knockdown of YAP1 also inhibited tumor growth in vivo. Additionally, we demonstrated that the activation of the AXL/MAPK pathway was involved in the oncogenic functions of YAP1 in GBC. These results demonstrated that YAP1 is a putative oncogene and represents a prognostic marker and potentially a novel therapeutic target for GBC.

Aberrant activation, nuclear localization, and phosphorylation of yes-associated protein-1 in the embryonic kidney and Wilms tumor

The Yes-associated-protein-1 (YAP1) is a novel, direct regulator of stem cell genes both in development and cancer. FAT4 is an upstream regulator that induces YAP1 cytosolic sequestering by phosphorylation (p-Ser 127) and therefore inhibits YAP1-dependent cellular proliferation. We hypothesized that loss of FAT4 signaling would result in expansion of the nephron progenitor population in kidney development and that YAP1 subcellular localization would be dysregulated in Wilms tumor (WT), an embryonal malignancy that retains gene expression profiles and histologic features reminiscent of the embryonic kidney. Fetal kidneys from Fat4(-/-) mice were harvested at e18.5 and markers of nephron progenitors were investigated using immunohistochemical analysis. To examine YAP1 subcellular localization in WT, a primary WT cell line (VUWT30) was analyzed by immunofluorescence. Forty WT specimens evenly distributed between favorable and unfavorable histology (n = 20 each), and treatment failure or success (n = 20 each) was analyzed for total and phosphorylated YAP1 using immunohistochemistry and Western blot. Fat4(-/-) mouse fetal kidneys exhibit nuclear YAP1 with increased proliferation and expansion of nephron progenitor cells. In contrast to kidney development, subcellular localization of YAP1 is dysregulated in WT, with a preponderance of nuclear p-YAP1. By Western blot, median p-YAP1 quantity was 5.2-fold greater in unfavorable histology WT (P = 0.05). Fetal kidneys in Fat4(-/-) mice exhibit a phenotype reminiscent of nephrogenic rests, a WT precursor lesion. In WT, YAP1 subcellular localization is dysregulated and p-YAP1 accumulation is a novel biomarker of unfavorable histology.

RAF kinase inhibitor-independent constitutive activation of Yes-associated protein 1 promotes tumor progression in thyroid cancer

The transcription coactivator Yes-associated protein 1 (YAP1) is regulated by the Hippo tumor suppressor pathway. However, the role of YAP1 in thyroid cancer, which is frequently associated with the BRAFV600E mutation, remains unknown. This study aimed to investigate the role of YAP1 in thyroid cancer. YAP1 was overexpressed in papillary (PTC) and anaplastic thyroid cancer, and nuclear YAP1 was more frequently detected in BRAFV600E (+) PTC. In the thyroid cancer cell lines TPC-1 and HTH7, which do not have the BRAFV600E mutation, YAP1 was cytosolic and inactive at high cell densities. In contrast, YAP1 was retained in the nucleus and its target genes were expressed in the thyroid cancer cells 8505C and K1, which harbor the BRAFV600E mutation, regardless of cell density. Furthermore, the nuclear activation of YAP1 in 8505C was not inhibited by RAF or MEK inhibitor. In vitro experiments, YAP1 silencing or overexpression affected migratory capacities of 8505C and TPC-1 cells. YAP1 knockdown resulted in marked decrease of tumor volume, invasion and distant metastasis in orthotopic tumor xenograft mouse models using the 8505C thyroid cancer cell line. Taken together, YAP1 is involved in the tumor progression of thyroid cancer and YAP1-mediated effects might not be affected by the currently used RAF kinase inhibitors.

Yes-Associated Protein 1 Is Widely Expressed in Human Brain Tumors and Promotes Glioblastoma Growth

The hippo pathway and its downstream mediator yes-associated protein 1 (YAP1) regulate mammalian organ size in part through modulating progenitor cell numbers. YAP1 has also been implicated as an oncogene in multiple human cancers. Currently, little is known about the expression of YAP1 either in normal human brain tissue or in central nervous system neoplasms. We used immunohistochemistry to evaluate nuclear YAP1 expression in the fetal and normal adult human brains and in 264 brain tumors. YAP1 was expressed in fetal and adult brain regions known to harbor neural progenitor cells, but there was little YAP1 immunoreactivity in the adult cerebral cortex. YAP1 protein was also readily detected in the nuclei of human brain tumors. In medulloblastoma, the expression varied between histologic subtypes and was most prominent in nodular/desmoplastic tumors. In gliomas, it was frequently expressed in infiltrating astrocytomas and oligodendrogliomas but rarely in pilocytic astrocytomas. Using a loss-of-function approach, we show that YAP1 promoted growth of glioblastoma cell lines in vitro. High levels of YAP1 messenger RNA expression were associated with aggressive molecular subsets of glioblastoma and with a nonsignificant trend toward reduced mean survival in human astrocytoma patients. These findings suggest that YAP1 may play an important role in normal human brain development and that it could represent a new target in human brain tumors.