Abstract 4200: Elevated dNTP pools impair homologous recombination-mediated repair, promoting apoptosis in therapy-resistant glioblastoma

Abstract Glioblastoma (GBM) is a deadly brain tumor that often develops resistance to DSB-inducing therapeutics due to dysregulated DNA repair. Ionizing radiation (IR) targets these cancer cells by causing DNA double-stranded breaks (DSBs). However, GBM often has overactive genes involved in the error-free DSB-repair process known as Homologous Recombination (HR). This results in therapy resistance and poor patient outcomes. Here, we provide an alternative approach to target DSB-resistant GBM by modulating the dNTP pool instead of solely targeting DNA-repair proteins. Through a comet assay, we found that increasing the dNTP pool prior to IR resulted in impaired DSB-repair. Immunofluorescence analysis of key HR proteins revealed significant disruptions in end resection, a necessary phase of HR. Our RNA-seq results show that increasing the dNTP pool prior to IR treatment caused significant changes in gene expression when compared to IR or dN treatment alone. Pathways most affected include apoptosis and cell cycle arrest. Flow cytometry analysis confirmed the significant increase in apoptosis in irradiated cancer cells with elevated dNTP pools. Not only do these data suggest that HR efficiency is reduced due to end resection impairment, but they also show that as a result, cell viability is destabilized due to prolonged DNA damage, resulting in apoptosis. The identification of this impairment may be essential in finding novel therapeutic approaches to sensitize therapy-resistant GBM. Citation Format: Dominique Monroe, Mercy Kehinde-Ige, Apeksha Anand, Arilyn Williams, Edidiong Usoro, Matthew Kededa, Aman Kalsi, Christian Fahmy, Ramsha Khanam, Huidong Shi, Waaqo Daddacha. Elevated dNTP pools impair homologous recombination-mediated repair, promoting apoptosis in therapy-resistant glioblastoma [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 4200.