Abstract 3268: A novel signaling axis of APE1-redox-sensitive SOX9 activation underlying reflux-condition-associated chemoresistance in esophageal adenocarcinoma

Abstract Chronic gastroesophageal reflux disease (GERD), characterized by the reflux of acidic bile salts (ABS) into the esophagus, stands as the primary risk factor for esophageal adenocarcinoma (EAC). EAC, known for its aggressive nature and limited response to therapy, exhibits a disheartening 5-year survival rate of less than 20%. Overcoming drug resistance remains a pressing challenge in achieving optimal therapeutic outcomes for EAC patients. Previous studies from our team have unveiled that exposure to ABS leads to the overexpression of Apurinic/apyrimidinic endonuclease (APE1), which orchestrates various oncogenic pathways in EAC cells. In this study, we delve into the influence of ABS in driving APE1-redox-mediated activation of the SOX9 pathway, thus contributing to the chemoresistance observed in EAC. To identify the enrichment of the SOX9 pathway and the heightened downstream target genes in EAC, we analyzed RNA sequencing data and public databases. Cell models, patient tissue arrays, pL2-IL1β transgenic mice, and de-identified xenografts derived from EAC patients (PDXs) were employed to investigate the signaling axis of APE1-redox-SOX9 in oxaliplatin resistance of EAC. Our analysis of public databases unveiled a significant enrichment of the SOX9 pathway in EAC patients. RNA sequencing data from EAC cells exposed to ABS, with or without APE1-knockdown, suggested APE1's involvement in the GERD-activated SOX9 signaling pathway. Immunohistochemistry staining of human patient tissue arrays, along with immunofluorescent staining of L2-IL1ß transgenic mice, confirmed the co-overexpression of APE1, SOX9, and ALDH1A1 in EAC. Furthermore, APE1 silencing led to the downregulation of SOX9 and exhibited synergistic effects with oxaliplatin in chemo-resistant EAC cells. Mechanistically, we uncovered that APE1's redox function is crucial for AKT-GSK3ß-mediated SOX9 stability. Treatment with the APE1-redox-specific inhibitor, APX2009, sensitized patient-derived xenograft (PDX) tumors to oxaliplatin by repressing SOX9-regulated chemoresistance genes. This study sheds light on a novel signaling axis involving APE1-redox-AKT-GSK3ß-SOX9 in Barrett’s carcinogenesis. The pharmacological inhibition of APE1-redox function presents itself as a promising therapeutic approach to target the previously intractable SOX9 signals, potentially overcoming chemoresistance in EAC. Citation Format: Heng Lu, Lei Chen, Farah Ballout, Dunfa Peng, Zheng Chen, Jianwen Que, Steven Chen, Oliver Gene McDonald, Alexander Zaika, Wael El-Rifai. A novel signaling axis of APE1-redox-sensitive SOX9 activation underlying reflux-condition-associated chemoresistance in esophageal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3268.