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.
This is the first report performing a global analysis of gene expression in normal esophageal cells exposed chronically to bile or acid. Our data identify a downregulation of squamous differentiation pathway by bile. This novel observation may open the way toward new treatment strategies and effective prevention for patients with Barrett's esophagus.
*Department of medicine and pathology, NYU Medical Center, New York, NY;
†Department of Surgery, University of Rochester Medical Center, Rochester, NY;
‡Ontario Institute for Cancer Research, Toronto, Ontario, Canada;
§Department of Pathology, University of Rochester Medical Center, Rochester, NY;
∥Department of Biostatistics, Pittsburgh Cancer Institute, University of Pittsburgh, Pittsburgh, PA.
Corresponding Author: (Reprints will not be available from the author), Jeffrey H. Peters, MD, Department of Surgery, University of Rochester, Rochester, NY 14534. E-mail: Jeffrey_peters@urmc.rochester.edu.
Disclosure: The authors declare no conflicts of interest.
Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (www.annalsofsurgery.com).