Abstract 7183: METTL1-mediated m7G modification promotes 5-FU resistance in colorectal carcinoma

Abstract Background: Colorectal cancer (CRC) ranks among the most common malignancies worldwide. Despite 5-fluorouracil (5-FU) being a cornerstone of CRC therapy, resistance to this chemotherapeutic agent occurs in approximately 50-60% of patients, significantly contributing to poor prognosis. Emerging studies have highlighted the role of METTL1, a methyltransferase mediating N7-methylguanosine (m7G) modifications, in promoting tumor progression and drug resistance. However, the specific regulatory mechanisms by which METTL1 contributes to 5-FU resistance in CRC remain poorly understood. Methods: METTL1 expression was analyzed in paired tumor and adjacent normal (AN) tissue specimens in publicly available datasets. Validation of METTL1 dysregulation in CRC tissues and cell lines was performed using qRT-PCR and western blotting (WB), while m7G levels were assessed by northwestern blot. Functional assays, including cell viability, colony formation, apoptosis, and invasion assays, were conducted to evaluate the role of METTL1 in CRC. RNA sequencing (RNA-seq) and m7G Methylated RNA Immunoprecipitation sequencing (MeRIP-seq) were used to identify downstream targets of METTL1 associated with chemoresistance. Results: METTL1 was significantly overexpressed in CRC tissues compared to AN tissues (p<0.001), with high METTL1 levels correlating with unfavorable clinical outcomes in both public datasets and our clinical cohort (p<0.05). Biologically, genetic depletion of METTL1 via CRISPR-Cas9 markedly led to reduced cell proliferation and enhanced apoptosis after 48 hours of 5-FU treatment in HCT116 and SW480 5-FU resistant cell lines. In vivo, METTL1 knockdown significantly enhanced the efficacy of 5-FU in a xenograft mouse model, leading to decreased tumor growth. Mechanistically, METTL1-mediated m7G methylation influenced the translation of mRNAs, including those involved in the TNF and NOTCH1 signaling pathways, both of which are critical in driving 5-FU resistance. Conclusion: This study identifies METTL1-mediated m7G modifications as a pivotal mechanism underlying 5-FU resistance in CRC. By regulating the translation of components in the NOTCH1 signaling pathway, METTL1 drives chemoresistance, presenting a potential therapeutic target to enhance the effectiveness of 5-FU-based treatment regimens in CRC patients. Citation Format: Silei Sui, Yuan Li, Rui Su, Man Li, Ajay Goel. METTL1-mediated m7G modification promotes 5-FU resistance in colorectal carcinoma [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 7183.