Abstract 237: Selective Cytotoxicity of Base Excision Repair Inhibitor, TRC102, in DNA Damage Response Hyperactivated Glioblastoma.

Abstract Background Glioblastoma is the most aggressive and lethal type of brain tumor. Tumor heterogeneity and DNA repair pathways contribute strongly to poor outcomes, highlighting the need for more personalized approaches. TRC102 (methoxyamine hydrochloride) is a small-molecule inhibitor of base excision repair that acts by covalently binding to abasic sites and preventing downstream repair enzymes from repairing the lesion. Clinical studies utilizing TRC102 in glioblastoma have identified hyperactivated DNA damage response (DDR) gene signature among exceptional responders, suggesting DDR-hyperactivity as a potential clinical biomarker. Here, we evaluated whether glioblastoma cells reliant on DDR signaling are particularly vulnerable to TRC102 treatment. Methods We performed gene set enrichment analysis using RNA-seq data across 24 glioblastoma cell lines within the NCI, Neuro Oncology Branch database and identified three patient-derived cell lines (L0, L1, GSC627) with hyperactivated DDR signature. Treatment efficacy was evaluated using cell viability, colony formation, DNA damage, repair and immunofluorescence assays. Results TRC102 treatment alone induced significant DNA damage and cell death in DDR-hyperactivated glioblastoma cell lines, whereas DDR-hypoactivated cells showed minimal sensitivity. In L0 and L1 cell lines, TRC102 treatment significantly inhibited colony formation and cell proliferation over 72-hour treatment. Mechanistic studies through western blotting revealed that TRC102 led to significant suppression of CHK2 activity, a key kinase involved in the DDR that controls cell cycle progression. Abrogation of cell cycle checkpoint blockades through CHK2 depletion may allow glioblastoma cells to initiate mitosis without fully resolving DNA damage, leading to mitotic catastrophe and cell death. Interestingly, TRC102 also suppressed HIF protein expression in hypoxic conditions, leading to eventual cell death. Conclusions The antitumor effect of TRC102 appears to be mediated through targeting of the newly identified ATM-CHK2-HIF axis, allowing for selective cytotoxicity in DDR-hyperactivated glioblastoma. These results suggest a specific vulnerability to TRC102 in DDR-hyperactivated glioblastoma that are typically resistant to conventional chemotherapy and radiation therapy, supporting biomarker-driven patient selection in future clinical studies. Citation Format: Shaunak Sathe, Qi Li, Jinkyu Jung, Peng Lu, Zach Sergi, Herui Wang, Jing Wu. Selective Cytotoxicity of Base Excision Repair Inhibitor, TRC102, in DNA Damage Response Hyperactivated Glioblastoma 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 237.