Mitoq Drives Diffuse Intrinsic Pontine Glioma into a Stressed State of Reductive Disequilibrium

Introduction: Diffuse intrinsic pontine glioma (DIPG) is fast growing malignant pediatric brain tumor with < 12 months of median survival. Radiotherapy adds just 3-4 months to life expectancy. There is no chemotherapy for DIPG, and new therapies are needed for the treatment of DIPG. MitoQ is an FDA-approved mitochondrial targeted antioxidant used as a diet supplement. We postulated that MitoQ may be capable of inducing mitochondrial redox stress in DIPG and may have anti-cancer effects.

Methods: DIPG cells with H3.3K27M mutation (SF8628) were used for this study. In scratch assays, wells with DIPG cells were scratched and imaged prior to the addition of MitoQ/vehicle. In clonogenic assays, ~140 cells/well were plated and 24-hours later they were treated with MitoQ/vehicle, incubated for 10-days, and the colonies were fixed and stained. For oxygen consumption studies, cells were seeded at low density and the oxygen consumption rates were measured over 4-days. Vehicle, disulfiram or MitoQ additions were made 48-hours after seeding, and subsequent additions were made 24 hours later.

Results: In scratch assay, MitoQ decreased wound healing in DIPG cells, with statistical significance (p < 0.05) at ≥1.5 µM MitoQ. The 10-day clonogenic assay showed that colony formation collapsed at >0.8 µM MitoQ compared to the vehicle treated group. In oxygen consumption studies, exposure of DIPG cells to MitoQ at 1.0 and 2.5 µM decreased oxygen consumption rates over the course of hours, however there is recovery of the consumption rate at 1.0 µM after a number of hours. Preincubation of DIPG cells with disulfiram, which inhibits the generation of mitochondrial NADPH, negated the effects of MitoQ on DIPG oxygen consumption.

Conclusion : MitoQ inhibits mitochondrial oxygen consumption in DIPG cells and decreases colony formation at concentration range 0.8–1.6 µM. MitoQ has pleiotropic properties and may be used as an antineoplastic agent in the treatment of DIPG.