Abstract
Increased cell proliferation in glioblastoma (GBM) leads to hypoxia in the tumor microenvironment. This is a major concern in GBM patients as it promotes tumor invasion. Glutaminolysis is a hallmark of cancer cells and under hypoxic conditions glutamine metabolism proceeds through reductive carboxylation pathway. Recently, we have shown that oscillating magnetic field (OMF) produces oncolytic effects which can influence cellular metabolism. Here, we have explored the effect of OMF on glutamine metabolism in GBM cells. Patient-derived GBM cells were grown in high glucose (25 mM) DMEM supplemented with 20% fetal bovine serum (FBS), 2.0 mM glutamine and 1.0 mM pyruvate at 37 °C under humidified air and 5% CO2. Cells were divided into 2 groups (Test and Sham; n = 4 each group). When reached confluency (~2.0×106 cells/mL), cells in both groups were treated with 4.0 mM of [U-13C]glutamine in DMEM (supplemented with 20% FBS, and 1.0 mM pyruvate). The “Test” group was subjected to OMF for 3 hours, and the “Sham” group was treated similar to the “Test” group but with non-magnetic rods of the same dimensions as the magnets in the Test group. After 3 h, cells were harvested in 50% methanol analyzed by GC-MS. The 13C-isotopomer analysis showed that glutamine metabolism in GBM cells proceeds through reduction carboxylation, confirmed by the higher levels of M+5 citrate (15.42 ± 1.28 % ) than M+4 citrate (2.05 ± 0.28 %). When GBM cells were treated with OMF, a statistically significant decrease in the citrate M+5 was observed, compared to the “Sham” treated group (15.42 ± 1.28 % vs. 8.89 ± 1.30 %; p = 0.0003). This decrease in M+5 citrate upon OMF treatment clearly indicates that the OMF decreases the reductive carboxylation flux of glutamine in GBM cells which would have therapeutic value in treating GBM patients.
Pathway of Propionate Oxidation by a Syntrophic Culture of Smithella propionica andMethanospirillum hungatei