Abstract 6018: Reactive oxygen species (ROS)-sensitive SOX4 signaling mediates ferroptosis in esophageal adenocarcinoma

Abstract Introduction: Esophageal adenocarcinoma (EAC), a malignancy largely driven by gastroesophageal reflux disease (GERD), remains highly resistant to chemotherapy, resulting in poor clinical outcomes. Ferroptosis is an iron-dependent, non-apoptotic form of regulated cell death characterized by lipid peroxidation and oxidative membrane injury. SOX4, a critical transcription factor, has been broadly implicated in tumorigenesis and the maintenance of cancer stemness. This study investigates SOX4-mediated anti-ferroptosis as a mechanism of chemoresistance in EAC, focusing on the reactive oxygen species (ROS)-sensitive APE1-redox-STAT3-SOX4 signaling axis, with the goal of identifying novel therapeutic strategies. Methods: Public datasets and multiple experimental models were employed, including 3D organotypic cultures, patient-derived organoids, and tumor spheres. In vivo validation was performed using a patient-derived xenograft (PDX) model. Results: Analysis of EAC public datasets revealed significant enrichment of the SOX4 transcriptional signature in tumor tissues. SOX4 activation was induced by elevated ROS and APE1 protein under reflux-mimicking conditions (acidic bile salt exposure, ABS), while treatment with a ROS scavenger, N-acetyl-l-cysteine (NAC), blocked ABS-induced SOX4 upregulation. Chromatin immunoprecipitation (ChIP) assay identified a STAT3 binding site within the SOX4 promoter, indicating that STAT3, an APE1 redox-sensitive transcription factor, directly regulates SOX4 expression. Silencing of APE1 or pharmacological inhibition of STAT3 suppressed SOX4 expression under both reflux conditions and oxaliplatin treatment. Single-sample gene set enrichment analysis (ssGSEA) demonstrated a strong correlation between ferroptosis-related signaling and the SOX4 signature in the TCGA EAC cohort. Notably, SOX4 knockdown reduced GPX4 expression and sensitized both intrinsically resistant SK-GT-4 cells and acquired oxaliplatin-resistant FLO-1 cells to oxaliplatin. These findings were validated in PDX tumors treated with the APE1 redox-specific inhibitor APX2009 in combination with oxaliplatin. Conclusion: ROS/APE1-dependent activation of SOX4 plays a crucial role in anti-ferroptosis and chemoresistance in EAC. Targeting the redox function of APE1 represents a promising therapeutic approach to overcome SOX4-mediated ferroptosis resistance and enhance chemotherapy efficacy in EAC. Citation Format: Heng Lu, Farah Ballout, Dunfa Peng, Lei Chen, Zheng Chen, Wael El-Rifai. Reactive oxygen species (ROS)-sensitive SOX4 signaling mediates ferroptosis in esophageal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 6018.