Analysis of metabolic rewiring in MDR1-overexpressing drug-resistant glioblastoma

Glioblastoma (GBM) is a primary brain tumor, and temozolomide is the first-line alkylating agent utilized as a chemotherapeutic treatment. Despite major improvements in diagnosis and therapy, patient's outcomes remain poor, mostly due to acquired temozolomide resistance. ABC transporter-mediated drug efflux is one of the mechanisms that play a crucial role in temozolomide resistance; however, the metabolic mechanisms that sustain MDR1 (ABCB1) activity in GBM remain unknown. Here, we established stable MDR1-overexpressing GBM cells and demonstrated their functional involvement in drug efflux by decreased intracellular doxorubicin accumulation and increased cell viability. Gas chromatography-mass spectrometry-based untargeted metabolomics profiling identified significantly altered metabolites in MDR1-overexpressing cells. Results of multivariate and univariate statistical analysis revealed higher levels of tricarboxylic acid (TCA) cycle intermediates that are associated with enhanced mitochondrial bioenergetics. Pathway enrichment revealed metabolite alterations in the TCA cycle, amino acid, and glutathione metabolism, indicating a coordinated metabolic rewiring potentially linked to increased ATP demand for MDR1 activity. The annexin V staining showed increased apoptotic cell populations upon metformin treatment, supporting the association between mitochondrial metabolism and intracellular drug accumulation. Overall, this study suggests that mitochondrial metabolism is a bioenergetic driver of MDR1 activity, and it could be a potential therapeutic target for overcoming MDR1-mediated drug resistance in GBM.