title: Bile exposure inhibits expression of squamous differentiation genes in human esophageal epithelial cells.
abstract: OBJECTIVE
  This study aimed to identify pathways and cellular processes that are modulated by exposure of normal esophageal cells to bile and acid.
  
  
  BACKGROUND
  Barrett's esophagus most likely develops as a response of esophageal stem cells to the abnormal reflux environment. Although insights into the underlying molecular mechanisms are slowly emerging, much of the metaplastic process remains unknown.
  
  
  METHODS
  We performed a global analysis of gene expression in normal squamous esophageal cells in response to bile or acid exposure. Differentially expressed genes were classified into major biological functions using pathway analysis and interaction network software. Array data were verified by quantitative PCR and western blot both in vitro and in human esophageal biopsies.
  
  
  RESULTS
  Bile modulated expression of 202 genes, and acid modulated expression of 103 genes. Genes involved in squamous differentiation formed the largest functional group (n = 45) all of which were downregulated by bile exposure. This included genes such as involucrin (IVL), keratinocyte differentiation-associated protein (KRTDAP), grainyhead-like 1 (GRHL1), and desmoglein1 (DSG1) the downregulation of which was confirmed by quantitative PCR and western blot. Bile also caused expression changes in genes involved in cell adhesion, DNA repair, oxidative stress, cell cycle, Wnt signaling, and lipid metabolism. Analysis of human esophageal biopsies demonstrated greatly reduced expression of IVL, KRTDAP, DSG1, and GRHL1 in metaplastic compared to squamous epithelia.
  
  
  CONCLUSIONS
  We report for the first time that bile inhibits the squamous differentiation program of esophageal epithelial cells. This, coordinated with induction of genes driving intestinal differentiation, may be required for the development of Barrett's esophagus.
authors.affiliation: Department of medicine and pathology, NYU Medical Center, New York, NY, USA.
authors.forename: Marie
authors.initials: M
authors.lastname: Reveiller
authors.forename: Sayak
authors.initials: S
authors.lastname: Ghatak
authors.forename: Liana
authors.initials: L
authors.lastname: Toia
authors.forename: Irina
authors.initials: I
authors.lastname: Kalatskaya
authors.forename: Lincoln
authors.initials: L
authors.lastname: Stein
authors.forename: Mary
authors.initials: M
authors.lastname: D'Souza
authors.forename: Zhongren
authors.initials: Z
authors.lastname: Zhou
authors.forename: Santhoshi
authors.initials: S
authors.lastname: Bandla
authors.forename: William E
authors.initials: WE
authors.lastname: Gooding
authors.forename: Tony E
authors.initials: TE
authors.lastname: Godfrey
authors.forename: Jeffrey H
authors.initials: JH
authors.lastname: Peters
mesh_terms: D001646:Bile / Q000502:physiology*; D001706:Biopsy; D002454:Cell Differentiation / Q000235:genetics*; D002460:Cell Line; D004847:Epithelial Cells / Q000166:cytology* / Q000502:physiology; D004947:Esophagus / Q000166:cytology / Q000473:pathology* / Q000503:physiopathology*; D005744:Gastric Acid / Q000502:physiology*; D015870:Gene Expression; D020869:Gene Expression Profiling; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis