Mitochondrial Metabolic Reprogramming along with NRF2/KEAP1-Mediated Antioxidant Mechanisms Drive Temozolomide Resistance in Glioblastoma Multiforme

Temozolomide (TMZ) is a frontline chemotherapeutic agent for glioblastoma multiforme (GBM); however, approximately half of patients develop resistance to therapy. This study investigates the role of altered cellular bioenergetics and metabolism in the acquired TMZ resistance. Using untargeted metabolomics, we explored the metabolic rewiring in TMZ-resistant GBM cells and identified key alterations in glycolysis, the tricarboxylic acid (TCA) cycle, fatty acid metabolism, and amino acid metabolism, all might be linked to cellular proliferation. Our findings suggest that while glycolysis remains important, increased TCA cycle activity contributes to the drug resistance, supported by increased levels of mitochondrial mass and mitochondrial membrane potential. We observed significantly elevated glutamine levels, which may enhance mitochondrial activity, thereby supporting increased energy production. Furthermore, resistant cells exhibited enhanced NRF2 level in parallel with higher levels of antioxidants, including glutathione and catalase enzyme, and a concomitant decrease in the level of its negative regulator, KEAP1. These factors collectively may contribute to drug resistance by mitigating oxidative stress. These findings indicate that mitochondrial metabolic reprogramming and NRF2/KEAP1-mediated antioxidant defense mechanisms play a crucial role in TMZ resistance, and targeting these pathways may offer a novel strategy to overcome resistance in GBM therapy.