Mitochondrial Antioxidant Mitoq Induces Fatal Alterations in Brain Cancer Cell metabolism

Introduction: Diffuse intrinsic pontine glioma (DIPG) is a malignant pediatric brain tumor, while Glioblastoma (GBM) is the most malignant primary brain tumor in adults. Surgery is not an option for DIPG and chemo/radiation therapy are ineffective. The median survival in DIPG patients is 8-12 months whereas overall survival in GBM is < 16 months despite surgical treatment and chemo/radiation therapy. The lack of effective treatment conveys need for new therapies. In this study, we have tested the effect of MitoQ (a mitochondria targeting antioxidant) on the metabolism of DIPG and GBM cells using [U-13C]glucose as a metabolic tracer.

Methods: DIPG cells harboring H3.3K27M mutation and patient-derived GBM cells were grown in DMEM media (11.0 mM D-glucose), supplemented with 10% FBS and 2.0 mM L-glutamine, under humidified air with 5% CO2 at 37 °C (n=3). When cells reached ~80% confluency, they were treated with 11.0 mM [U-13C]glucose in the presence and the absence of MitoQ. Normal human astrocytes (NHAs) grown in ABMTM astrocyte media were also treated similarly for comparison. After overnight incubation, cells were harvested and the perchloric acid extracts of cells were analyzed by 1H13C NMR spectroscopy for 13C-metabolic flux analysis.

Results: 13C-NMR spectroscopic analysis showed that C4-glutamate (marker of mitochondrial metabolism) derived from the metabolism of [U-13C]glucose was absent in MitoQ treated cells in all the cell lines (DIPG, GBM, and NHAs), while lactate synthesis was decreased only in DIPG and GBM cells. Metabolic flux analysis revealed that MitoQ completely inhibited mitochondrial metabolism in both DIPG and GBM cells and the alanine/lactate ratio was elevated, suggesting inhibition of glycolysis only in DIPG and GBM cells. Although MitoQ inhibited the mitochondrial metabolism in NHAs, glycolytic flux was unaffected.

Conclusion : MitoQ can be used for targeting energy metabolism in DIPG and GBM tumors and has great potential for the treatment of malignant brain tumors.