Abstract 1347: The acidic tumor microenvironment drives stemness and chemoresistance in colorectal cancer through DHCR7

Abstract Relapse and chemoresistance are critical determinants of poor prognosis in colorectal cancer (CRC). Cancer stem cells (CSCs) significantly contribute to chemoresistance and relapse in CRC. The acidic tumor microenvironment (TME) not only drives the emergence of CSC phenotypes but also impacts cholesterol metabolism reprogramming. However, whether the acidic TME influences CSC phenotypes and chemoresistance by modulating cholesterol metabolism remains to be elucidated.In this study, we utilized the ARGO and TCGA databases to identify cholesterol metabolism-related genes significantly upregulated under acidic conditions. The gene responsible for the final step in cholesterol biosynthesis, DHCR7(7-dehydrocholesterol reductase), was identified as highly expressed in advanced staging CRC and closely associated with poor prognosis in CRC patients.We confirmed that the acidic TME regulates cholesterol metabolism via DHCR7, thereby modulating cancer stemness and chemoresistance in CRC. Using DHCR7-overexpressing and control cell lines, we conducted subcutaneous tumorigenesis experiments in nude mice. Intratumoral injection of the DHCR7-specific inhibitor AY9944 in combination with oxaliplatin demonstrated that AY9944 enhances the cytotoxic effect of oxaliplatin on CRC by inhibiting DHCR7.To investigate the downstream mechanisms of DHCR7 in regulating the malignant phenotype of CRC, we performed transcriptomic profiling of the overexpressing and knockout cell lines. Differential gene analysis revealed an inverse correlation between DHCR7 and CLCA1 expression. Using CHIP-qPCR and dual-luciferase reporter assays, we confirmed that nuclear DHCR7 binds to the promoter region of CLCA1, suppressing its transcription and activating the Wnt/β-catenin signaling pathway. Additionally, at the cellular and organoid levels, we verified that cytoplasmic DHCR7 enhances cholesterol synthesis, thereby upregulating cancer stemness marker LGR5 expression.The acidic tumor microenvironment promotes DHCR7 expression. DHCR7 functions as a transcription factor in the nucleus to inhibit CLCA1 transcription and activate the Wnt/β-catenin pathway. Concurrently, it enhances cholesterol synthesis in the cytoplasm, leading to increased LGR5 expression. Together, these mechanisms drive the stemness and chemoresistant phenotypes of CRC cells. Our findings suggest that targeting cholesterol metabolism, particularly the key enzyme DHCR7, could inhibit CRC stemness and drug resistance, thereby improving patient prognosis. Citation Format: Yiran Bie, Zhengyu Wei, Dongwen Chen, Yao Shang, Zhengran Zhou, Chong Chen, Chuling Hu, Xinxin Huang, Yufeng Chen, Peishan Hu. The acidic tumor microenvironment drives stemness and chemoresistance in colorectal cancer through DHCR7 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1347.