title: Wnt/β-catenin signaling enhances cyclooxygenase-2 (COX2) transcriptional activity in gastric cancer cells.
abstract: BACKGROUND
  Increased expression of the cyclooxygenase-2 enzyme (COX2) is one of the main characteristics of gastric cancer (GC), which is a leading cause of death in the world, particularly in Asia and South America. Although the Wnt/β-catenin signaling pathway has been involved in the transcriptional activation of the COX2 gene, the precise mechanism modulating this response is still unknown.
  
  
  RESULTS
  Here we studied the transcriptional regulation of the COX2 gene in GC cell lines and assessed whether this phenomenon is modulated by Wnt/β-catenin signaling. We first examined the expression of COX2 mRNA in GC cells and found that there is a differential expression pattern consistent with high levels of nuclear-localized β-catenin. Pharmacological treatment with either lithium or valproic acid and molecular induction with purified canonical Wnt3a significantly enhanced COX2 mRNA expression in a dose- and time-dependent manner. Serial deletion of a 1.6 Kbp COX2 promoter fragment and gain- or loss-of-function experiments allowed us to identify a minimal Wnt/β-catenin responsive region consisting of 0.8 Kbp of the COX2 promoter (pCOX2-0.8), which showed maximal response in gene-reporter assays. The activity of this pCOX2-0.8 promoter region was further confirmed by site-directed mutagenesis and DNA-protein binding assays.
  
  
  CONCLUSIONS
  We conclude that the pCOX2-0.8 minimal promoter contains a novel functional T-cell factor/lymphoid enhancer factor (TCF/LEF)-response element (TBE Site II; -689/-684) that responds directly to enhanced Wnt/β-catenin signaling and which may be important for the onset/progression of GC.
authors.affiliation: Centro de Tecnología e Innovación para el Cáncer, Department of Biochemistry and Molecular Biology, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile.
authors.forename: Felipe
authors.initials: F
authors.lastname: Nuñez
authors.forename: Soraya
authors.initials: S
authors.lastname: Bravo
authors.forename: Fernando
authors.initials: F
authors.lastname: Cruzat
authors.forename: Martín
authors.initials: M
authors.lastname: Montecino
authors.forename: Giancarlo V
authors.initials: GV
authors.lastname: De Ferrari
mesh_terms: D001665:Binding Sites; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000235:genetics* / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D021381:Protein Transport; D015398:Signal Transduction / Q000235:genetics*; D013274:Stomach Neoplasms / Q000201:enzymology* / Q000235:genetics* / Q000473:pathology; D014158:Transcription, Genetic; D015854:Up-Regulation / Q000235:genetics; D051153:Wnt Proteins / Q000378:metabolism*; D051176:beta Catenin / Q000378:metabolism*
chemical_list: D051153:Wnt Proteins; D051176:beta Catenin; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human