Mo1938 Differential Response of Normal Esophageal Squamous Cells to Acid and Bile Salt-Induced Injury May Predispose to Barrett's Metaplasia

Abstract

Introduction: Normal esophageal squamous (NES) mucosa normally regenerates after injury from acid and bile salts in gastroesophageal reflux disease (GERD). Sometimes, Barrett's epithelium (BE), a columnar metaplasia, may develop after chronic GERD. BE is a precancerous condition leading to esophageal adenocarcinoma, that has the highest rate of increase in the US and western countries. It is critical therefore to understand the pathogenesis of BE in order to prevent it. Acid and bile salts, the main components of reflux, are known to induce DNA damage, activate cell cycle check points, and induce apoptosis in BE and NES cells in-vitro. Response of NES cells derived from GERD patients with and without BE to chronic acid and bile salts exposure may provide clues to molecular pathogenesis of BE. Aim: To compare expression of genes regulating proliferation, apoptosis, andmucosal healing in NES cells derived from GERD patients with and without BE in response to chronic acid and bile salt exposure. Methods: Telomerase-immortalized NES cell lines derived from GERD patients with (NES-B10T) and without (NES-G2T) BE and a Barrett's epithelial cell line (BAR-T) were used. Cells were exposed to 200μM glycocheno-deoxycholic acid at pH4 (B4) once daily for 5 minutes for three weeks similar to our earlier published studies on BAR-T and BEC (IJC2011). Results are the average of three experiments comparing transcript levels of genes involved in apoptosis (p53, Bcl2, Bax, caspase3), proliferation (Ki-67, p16) and mucosal healing (TFF3) using quantitative RT-PCR analyses. Results: In response to 3 weeks of B4 exposure, the NES-B10T and BAR-T cells induced anti apoptotic Bcl-2 but not p53 and caspase 3 mRNA expression (Table). In contrast, the NES-G2T cells induced p53, caspase3 and Bax mRNAexpression (Table). Expression of Ki-67 mRNA was induced in all the cell lines, albeit to differing levels (Table). The mRNA expression of the anti-proliferative p16 gene was induced only in NES-G2T cells. Expression of TFF3mRNAwas induced inNESG2T, undetectable inNES-B10T, andwas suppressed in BAR-T cells (Table). Conclusion: The esophageal squamous cells derived from a GERD patient without BE induce pro-apoptotic, anti-proliferative and mucosal healing genes in response to chronic acid and bile salts exposure. In contrast, esophageal squamous cells derived from a GERD patient with BE have compromised expression of genes related to mucosal healing, and induction of antiapoptotic and pro-proliferative genes. We speculate that the nature of the molecular response of NES cells to GERD may determine which GERD patients develops Barrett's metaplasia. Fold changes in gene expression compared to paired untreated cells