title: MicroRNA-26a promotes cholangiocarcinoma growth by activating β-catenin.
abstract: OBJECTIVE
  MicroRNAs (miRNAs) have been implicated in the development and progression of human cancers. We investigated the roles and mechanisms of miR-26a in human cholangiocarcinoma.
  
  
  METHODS
  We used in situ hybridization and quantitative reverse transcriptase polymerase chain reaction to measure expression of miR-26a in human cholangiocarcinoma tissues and cell lines (eg, CCLP1, SG231, HuCCT1, TFK1). Human cholangiocarcinoma cell lines were transduced with lentiviruses that expressed miR-26a1 or a scrambled sequence (control); proliferation and colony formation were analyzed. We analyzed growth of human cholangiocarcinoma cells that overexpress miR-26a or its inhibitor in severe combined immune-deficient mice. Immunoblot, immunoprecipitation, DNA pull-down, immunofluorescence, and luciferase reporter assays were used to measure expression and activity of glycogen synthase kinase (GSK)-3β, β-catenin, and related signaling molecules.
  
  
  RESULTS
  Human cholangiocarcinoma tissues and cell lines had increased levels of miR-26a compared with the noncancerous biliary epithelial cells. Overexpression of miR-26a increased proliferation of cholangiocarcinoma cells and colony formation in vitro, whereas miR-26 depletion reduced these parameters. In severe combined immune-deficient mice, overexpression of miR-26a by cholangiocarcinoma cells increased tumor growth and overexpression of the miR-26a inhibitor reduced it. GSK-3β messenger RNA was identified as a direct target of miR-26a by computational analysis and experimental assays. miR-26a-mediated reduction of GSK-3β resulted in activation of β-catenin and induction of several downstream genes including c-Myc, cyclinD1, and peroxisome proliferator-activated receptor δ. Depletion of β-catenin partially prevented miR-26a-induced tumor cell proliferation and colony formation.
  
  
  CONCLUSIONS
  miR-26a promotes cholangiocarcinoma growth by inhibition of GSK-3β and subsequent activation of β-catenin. These signaling molecules might be targets for prevention or treatment of cholangiocarcinoma.
authors.affiliation: Department of Pathology and Laboratory Medicine, Tulane University School of Medicine, New Orleans, Louisiana 70112, USA.
authors.forename: Jinqiang
authors.initials: J
authors.lastname: Zhang
authors.forename: Chang
authors.initials: C
authors.lastname: Han
authors.forename: Tong
authors.initials: T
authors.lastname: Wu
mesh_terms: D000818:Animals; D001650:Bile Duct Neoplasms / Q000378:metabolism*; D001653:Bile Ducts, Intrahepatic; D045744:Cell Line, Tumor; D018281:Cholangiocarcinoma / Q000378:metabolism*; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D051379:Mice; D016513:Mice, SCID; D035683:MicroRNAs / Q000096:biosynthesis*; D023041:Xenograft Model Antitumor Assays; D051176:beta Catenin / Q000378:metabolism*
chemical_list: D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D035683:MicroRNAs; D051176:beta Catenin; C528163:MIRN26 microRNA, human; C000605506:GSK3B protein, human; C000605507:Gsk3b protein, mouse