Abstract 878: IGFBP2 is required to activate EGFR-DNA-PKcs pathway to protect esophageal adenocarcinoma cells from acidic bile salts-induced DNA damage

Abstract

Abstract The incidence of esophageal adenocarcinoma (EAC) is rising rapidly in the US and Western countries. The development of Barrett’s esophagus (BE) and its progression to EAC have been linked to gastroesophageal reflux disease (GERD). Exposure of BE and EAC cells to acidic bile salts (ABS) in GERD conditions induces high levels of DNA damage. In this study, we investigated the role of insulin-like growth factor binding protein 2 (IGFBP2) in regulating ABS-induced DNA double-strand breaks (DSBs). Immunohistochemistry analysis demonstrated frequent overexpression of IGFBP2 in EACs (31/57). Treatment of EAC cells with ABS, to mimic GERD conditions, induced high levels of IGFBP2 expression. Knocking down endogenous IGFBP2 in FLO1 cells (with constitutive high levels of IGFBP2) led to a significant increase in DNA DSBs and apoptosis, following transient exposure (20 min) to ABS. On the other hand, overexpression of exogenous IGFBP2 in OE33 cells (with low endogenous levels of IGFBP2) had a protective effect against DSBs and apoptosis. Using western blotting and immunofluorescence assays, we found that IGFBP2 is required for ABS-induced nuclear accumulation and phosphorylation of EGFR and DNA-PKcs, which are required for DNA damage repair activity. Using co-immunoprecipitation assay, we detected IGFBP2 forms complex with EGFR and DNA-PKcs and co-localizes with EGFR and DNA-PKcs in nucleus, following acidic bile salts treatment. We also demonstrated, using cycloheximide (CHX) chase assay, that IGFBP2 promotes EGFR protein stability in response to ABS exposure. In summary, our data indicate that IGFBP2 protects EAC cells against ABS-induced DNA damage and apoptosis through stabilization and activation of EGFR - DNA-PKcs signaling axis. Citation Format: Zhangjian Zhou, Heng Lu, Shoumin Zhu, Ahmed Gomaa, Zheng Chen, Jin Yan, Wael El-Rifai, Chengxue Dang, Dunfa Peng. IGFBP2 is required to activate EGFR-DNA-PKcs pathway to protect esophageal adenocarcinoma cells from acidic bile salts-induced DNA damage [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 878.