Bile Acid Reflux Contributes to Development of Esophageal Adenocarcinoma via Activation of Phosphatidylinositol-Specific Phospholipase Cy2 and NADPH Oxidase NOX5-S

Gastroesophageal reflux disease complicated by Barrett's esophagus (BE) is a major risk factor for esophageal adenocarcinoma (EA). However, the mechanisms of the progression from BE to EA are not fully understood. Besides acid reflux, bile acid reflux may also play an important role in the progression from BE to EA. In this study, we examined the role of phosphatidylinositol-specific phospholipase C (PI-PLC) and a novel NADPH oxidase NOX5-S in bile acid-induced increase in cell proliferation. We found that taurodeoxycholic acid (TDCA) significantly increased NOX5-S expression, hydrogen peroxide (H2O2) production, and cell proliferation in EA cells. The TDCA-induced increase in cell proliferation was significantly reduced by U73122, an inhibitor of PIPLC. PI-PLC beta 1, PI-PLC beta 3, PI-PLC beta 4, PI-PLC gamma 1, and PI-PLC gamma 2, but not PI-PLC gamma 2 and PI-PLC gamma 1, were detectable in FLO cells by Western blot analysis. Knockdown of PI-PLC gamma 2 or extracellular signal-regulated kinase (ERK)2 mitogen-activated protein (MAP) kinase with small interfering RNAs (siRNA) significantly decreased TDCA-induced NOX5-S expression, H2O2 production, and cell proliferation. In contrast, knockdown of PI-PLC beta 1, PI-PLC beta 3, PI-PLC beta 4, PI-PLC gamma 1, or ERK1 MAP kinase had no significant effect. TDCA significantly increased ERK2 phosphorylation, an increase that was reduced by U73122 or PI-PLC gamma 2 siRNA. We conclude that TDCA-induced increase in NOX5-S expression and cell proliferation may depend on sequential activation of PI-PLC gamma 2 and ERK2 MAP kinase in EA cells. It is possible that bile acid reflux present in patients with BE may increase reactive oxygen species production and cell proliferation via activation of PI-PLC gamma 2, ERK2 MAP kinase, and NADPH oxidase NOX5-S, thereby contributing to the development of EA. Cancer Res; 70(3); 1247-55. (C) 2010 AACR.