Inhibition of glycolysis and mitochondrial respiration promotes radiosensitisation of neuroblastoma and glioma cells

Abstract

Background Neuroblastoma accounts for 7% of paediatric malignancies but is responsible for 15% of all childhood cancer deaths. Despite rigorous treatment involving chemotherapy, surgery, radiotherapy and immunotherapy, the 5-year overall survival rate of high-risk disease remains < 40%, highlighting the need for improved therapy. Since neuroblastoma cells exhibit aberrant metabolism, we determined whether their sensitivity to radiotherapy could be enhanced by drugs affecting cancer cell metabolism. Methods Using a panel of neuroblastoma and glioma cells, we determined the radiosensitising effects of inhibitors of glycolysis (2-DG) and mitochondrial function (metformin). Mechanisms underlying radiosensitisation were determined by metabolomic and bioenergetic profiling, flow cytometry and live cell imaging and by evaluating different treatment schedules. Results The radiosensitising effects of 2-DG were greatly enhanced by combination with the antidiabetic biguanide, metformin. Metabolomic analysis and cellular bioenergetic profiling revealed this combination to elicit severe disruption of key glycolytic and mitochondrial metabolites, causing significant reductions in ATP generation and enhancing radiosensitivity. Combination treatment induced G2/M arrest that persisted for at least 24 h post-irradiation, promoting apoptotic cell death in a large proportion of cells. Conclusion Our findings demonstrate that the radiosensitising effect of 2-DG was significantly enhanced by its combination with metformin. This clearly demonstrates that dual metabolic targeting has potential to improve clinical outcomes in children with high-risk neuroblastoma by overcoming radioresistance.

Dual Effect of Combined Metformin and 2-Deoxy-D-Glucose Treatment on Mitochondrial Biogenesis and PD-L1 Expression in Triple-Negative Breast Cancer Cells

“…The increase in mitochondrial mass therefore seems to correlate with suppressed proliferation but not cell death. We and others have shown previously that metformin + 0.6 mM 2DG caused an arrest in the M and G2 phases in cancer cells [ 22 , 30 ], while tunicamycin (which does not substantially increase mitochondrial mass) was shown to induce cell arrest in G0/G1 phase [ 70 ]. We therefore speculate that the observed differences in mitochondrial biogenesis are partially due to different effects on proliferation.…”

“…The effect of metformin on proliferation is strongly dependent on the intrinsic characteristics of cancer cells which are often capable of compensating inhibited oxidative phosphorylation with increased glycolysis. To overcome this adaptation, synergistic action with glycolysis inhibitors, such as 2-deoxy-D-glucose (2DG), was explored [ 2 , 20 , 21 , 22 , 23 ]. 2DG is a competitive inhibitor of hexokinase and phosphoglucose isomerase [ 24 ].…”

“…In addition, 2DG was shown to selectively inhibit protein N-glycosylation, leading to ER stress and unfolded protein response (UPR), which can also contribute to cancer cell apoptosis [ 25 , 26 , 27 , 28 , 29 ]. The combination of metformin and 2DG has been shown to synergistically suppress cancer cell proliferation [ 20 , 22 ] and decrease angiogenesis [ 23 ]. Previously, we have shown that the combination of metformin and in vivo achievable concentration of 2DG induces detachment of MDA-MB-231 triple-negative breast cancer (TNBC) cells and anchorage-independent growth [ 30 ].…”

Radiotherapy of High-Grade Gliomas: First Half of 2021 Update with Special Reference to Radiosensitization Studies

“…Nile et al have studied the radiosensitization of glioma cells by inhibitors of glycolysis (2-DG) and mitochondrial function (metformin) [76]. The radiosensitising effects of 2-DG were greatly enhanced by combination with the antidiabetic biguanide, metformin.…”

“…Metabolomic analysis and cellular bioenergetic profiling revealed this combination to elicit severe disruption of key glycolytic and mitochondrial metabolites, causing significant reductions in ATP generation and enhancing radiosensitivity. Combination treatment induced G2/M arrest that persisted for at least 24 h post-irradiation, promoting apoptotic cell death in a large proportion of cells [76].…”