RBIO-15. Diverse redox states underpin glioblastoma heterogeneity in preclinical models and patient samples

Glioblastoma (GBM) remains the most lethal and aggressive primary brain cancer with limited treatment options. A hallmark of GBM is its pronounced intra- and inter-tumoral heterogeneity at cellular, molecular, genetic, epigenetic and metabolic levels. Here, we demonstrate that GBM also exhibits significant intertumoral heterogeneity in its basal redox environment. Owing to their high metabolic demand and mutational burden, GBM tumors are typically in a pro-oxidative state, characterized by elevated levels of reactive oxygen species (ROS) compared to normal brain tissue. However, the extent of redox imbalance varies widely across tumors. To characterize this variability, we profiled biomarkers of basal redox status, including low-molecular weight and total reduced thiols, lipid peroxidation, protein oxidation/nitration, DNA oxidation, activities of antioxidant enzymes across five patient-derived xenograft (PDX)-derived cell lines with distinct genetic backgrounds. We then evaluated their sensitivity to oxidative stress through direct ROS exposure (hydrogen peroxide) and indirect induction (ionizing radiation). Basal redox biomarkers were also assessed in corresponding intracranial xenograft models in immunocompromised mice and in GBM patient samples obtained intraoperatively from both gadolinium-enhancing and non-enhancing tumor regions. Redox biomarkers were quantified using LC-MS/MS, UV-vis, and immunohistochemistry. We observed marked heterogeneity in oxidative stress biomarkers across the five PDX cell lines and their intracranial tumors, all of which exhibited elevated oxidative stress relative to normal brain. Furthermore, the sensitivity to ROS varied by up to 100-fold across GBM models. Similarly, inter-patient tumor regions differed by up to 200-fold in redox biomarkers levels. These findings underscore the extensive heterogeneity across GBM tumors and highlight the need to consider redox variability when designing and implementing redox-targeted therapeutics.