Down-Regulation of Yes Associated Protein 1 Expression Reduces Cell Proliferation and Clonogenicity of Pancreatic Cancer Cells

Abstract

BackgroundThe Hippo pathway regulates organ size by inhibiting cell proliferation and promoting cell apoptosis upon its activation. The Yes Associated Protein 1 (YAP1) is a nuclear effector of the Hippo pathway that promotes cell growth as a transcription co-activator. In human cancer, the YAP1 gene was reported as amplified and over-expressed in several tumor types.MethodsImmunohistochemical staining of YAP1 protein was used to assess the expression of YAP1 in pancreatic tumor tissues. siRNA oligonucleotides were used to knockdown the expression of YAP1 and their effects on pancreatic cancer cells were investigated using cell proliferation, apoptosis, and anchorage-independent growth assays. The Wilcoxon signed-rank, Pearson correlation coefficient, Kendall's Tau, Spearman's Rho, and an independent two-sample t (two-tailed) test were used to determine the statistical significance of the data.ResultsImmunohistochemistry studies in pancreatic tumor tissues revealed YAP1 staining intensities were moderate to strong in the nucleus and cytoplasm of the tumor cells, whereas the adjacent normal epithelial showed negative to weak staining. In cultured cells, YAP1 expression and localization was modulated by cell density. YAP1 total protein expression increased in the nuclear fractions in BxPC-3 and PANC-1, while it declined in HPDE6 as cell density increased. Additionally, treatment of pancreatic cancer cell lines, BxPC-3 and PANC-1, with YAP1-targeting siRNA oligonucleotides significantly reduced their proliferation in vitro. Furthermore, treatment with YAP1 siRNA oligonucleotides diminished the anchorage-independent growth on soft agar of pancreatic cancer cells, suggesting a role of YAP1 in pancreatic cancer tumorigenesis.ConclusionsYAP1 is overexpressed in pancreatic cancer tissues and potentially plays an important role in the clonogenicity and growth of pancreatic cancer cells.

TAZ Protein Accumulation Is Negatively Regulated by YAP Abundance in Mammalian Cells

“…Consistent with reports in other cell lines (10,41), ablation of YAP in LPCs decreased cellular proliferation (Fig. 1A) in cells with undetectable YAP expression as determined by Western blot (Fig.…”

PTPN14 is required for the density-dependent control of YAP1

“…Overexpression of YAP1 leads to loss of contact inhibition and increases the organ size (Huang et al 2005;Camargo et al 2007). Dysregulation of YAP1 has been identified in various types of cancer (Yuan et al 2008;Liu et al 2010;Wu et al 2010;Orr et al 2011;Zhang et al 2011;Diep et al 2012). Because of its crucial function in tissue growth and tumor development, YAP1 and its regulation have been studied extensively.…”

Cytoplasmatic and Nuclear YAP1 and pYAP1 Staining in Urothelial Bladder Cancer

“…In pancreatic cancer cells, for instance, YAP1 expression was higher in the cytoplasm than in the nucleus [3]. However, most studies observed an increase of YAP1 in the nucleus [4,9,24].…”

“…It plays an important role during carcinogenesis in many human malignancies. The components of the Hippo signaling pathway (MST1/2, WW45, LATS1/2 and MOB1) form a protein kinase complex that leads to phosphorylation of YAP1 (YES-associated protein 1), the downstream nuclear effector of the Hippo pathway [3,4,5]. YAP1 acts as an oncogene and is overexpressed in many human tumors including colon, liver, lung, ovarian, breast and prostate cancer [4,6,7,8,9].…”