title: Down-regulation of Yes Associated Protein 1 expression reduces cell proliferation and clonogenicity of pancreatic cancer cells.
abstract: BACKGROUND
  The 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.
  
  
  METHODS
  Immunohistochemical 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.
  
  
  RESULTS
  Immunohistochemistry 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.
  
  
  CONCLUSIONS
  YAP1 is overexpressed in pancreatic cancer tissues and potentially plays an important role in the clonogenicity and growth of pancreatic cancer cells.
authors.affiliation: Clinical Translational Division, Translational Genomics Research Institute, Scottsdale, Arizona, United States of America.
authors.forename: Caroline H
authors.initials: CH
authors.lastname: Diep
authors.forename: Kelly M
authors.initials: KM
authors.lastname: Zucker
authors.forename: Galen
authors.initials: G
authors.lastname: Hostetter
authors.forename: Aprill
authors.initials: A
authors.lastname: Watanabe
authors.forename: Chengcheng
authors.initials: C
authors.lastname: Hu
authors.forename: Ruben M
authors.initials: RM
authors.lastname: Munoz
authors.forename: Daniel D
authors.initials: DD
authors.lastname: Von Hoff
authors.forename: Haiyong
authors.initials: H
authors.lastname: Han
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000096:biosynthesis*; D017209:Apoptosis; D002448:Cell Adhesion; D002453:Cell Cycle; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D015233:Models, Statistical; D020411:Oligonucleotide Array Sequence Analysis; D009841:Oligonucleotides / Q000737:chemistry; D010190:Pancreatic Neoplasms / Q000378:metabolism*; D010750:Phosphoproteins / Q000096:biosynthesis*; D034741:RNA, Small Interfering / Q000378:metabolism; D014018:Tissue Distribution; D014157:Transcription Factors; D000091102:YAP-Signaling Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D009841:Oligonucleotides; D010750:Phosphoproteins; D034741:RNA, Small Interfering; D014157:Transcription Factors; D000091102:YAP-Signaling Proteins; C088374:YAP1 protein, human