In vitro acid exposure has a differential effect on apoptotic and proliferative pathways in a Barrett's adenocarcinoma cell line

INTRODUCTION: Acid, a principal component of refluxate, may contribute to the neoplastic progression of Barrett's esophagus. Brief acid exposure in vivo and in vitro has been shown to increase cell proliferation. The mechanisms underlying the hyperproliferative response are not well elucidated but may include alterations in Na+-H+ exchanger activity and MAPK signaling pathways. OBJECTIVE: To ascertain the effects of pulsatile acid exposure on gene expression in a Barrett's adenocarcinoma cell line (SEG-1). METHODS: SEG-1 cells were exposed to either acidified DMEM at pH 3.5 (0.1 M hydrochloric acid) or pH 7.4 (control) for 20 min followed by neutralization of the medium. Total RNA was extracted before acid exposure and over a 10-h time course (0.5, 2, 4, 6, 8, and :10 hours) and hybridized to Affymetrix human U133A oligonucleotide arrays. Data were analyzed using the Affymetrix statistical expression algorithms. Only alterations in gene expression that were greater than or equal to2 and less than or equal to-2 fold were studied further and a subset was further investigated by reverse transcription polymerase chain reaction (RT-PCR) and densitometry. Apoptosis was assayed in SEG-1 cells by western blot for cleaved caspase 3 and an apoptosis ELISA assay. RESULTS: Changes in expression were identified for 138 genes. Analysis of gene function identified immediate downregulation of genes associated with apoptosis and early upregulation of genes associated with proliferation. The gene expression profiles suggest that MAPK pathways may be involved and suppression of apoptosis may occur via p53-dependent mechanisms. CONCLUSION: Microarray analysis of gene expression changes in a Barrett's adenocarcinoma cell line has identified cellular pathways that may be disrupted following acid exposure.