Melatonin Treatment Triggers Metabolic and Intracellular pH Imbalance in Glioblastoma Fernández Gil, Beatriz Irene Escames Rosa, Germaine Intracellular acidity Cancer metabolism Lactate MCT4 ROS LDHA GBM OXPHOS Glycolysis Supplementary Materials The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/cells11213467/s1, Figure S1: Metabolic baseline characterization, treatments with melatonin agonists, and combina-tion treatments of melatonin (aMT) and the standard of care for GBM; Figure S2: Seahorse com-plementary analyses; Figure S3: pH fluctuations; Figure S4: In vivo results after melatonin intra-tumoral treatment. Funding This research was funded by the Distinguished Mayo Clinic Investigator Award (A.Q.-H.) and the William J. and Charles H. Mayo Professor (A.Q.-H.); the Uihlein Neuro-oncology Research Fund (A.Q.-H.) and R01CA200399 (A.Q.-H.). Metabolic rewiring in glioblastoma (GBM) is linked to intra- and extracellular pH regulation. In this study, we sought to characterize the role of melatonin on intracellular pH modulation and metabolic consequences to identify the mechanisms of action underlying melatonin oncostatic effects on GBM tumor initiating cells. GBM tumor initiating cells were treated at different times with melatonin (1.5 and 3.0 mM).We analyzed melatonin’s functional effects on GBM proliferation, cell cycle, viability, stemness, and chemo-radiosensitivity. We then assessed the effects of melatonin on GBM metabolism by analyzing the mitochondrial and glycolytic parameters. We also measured the intracellular and extracellular pH. Finally, we tested the effects of melatonin on a mouse subcutaneous xenograft model. We found that melatonin downregulated LDHA and MCT4, decreasing lactate production and inducing a decrease in intracellular pH that was associated with an increase in ROS and ATP depletion. These changes blocked cell cycle progression and induced cellular death and we observed similar results in vivo. Melatonin’s cytotoxic effects on GBM were due, at least in part, to intracellular pH modulation, which has emerged as a newly identified mechanism, providing new insights into the oncostatic effect of melatonin on GBM. 2022-12-02T09:40:29Z 2022-12-02T09:40:29Z 2022-11-02 info:eu-repo/semantics/article Fernandez-Gil, B.I.; Otamendi-Lopez, A.; Bechtle, A.; Vazquez-Ramos, C.A.; Qosja, N.; Suarez-Meade, P.; Sarabia-Estrada, R.; Jentoft, M.E.; Guerrero-Cázares, H.; Escames, G.; et al. Melatonin Treatment Triggers Metabolic and Intracellular pH Imbalance in Glioblastoma. Cells 2022, 11, 3467. [https://doi.org/10.3390/cells11213467] https://hdl.handle.net/10481/78242 10.3390/cells11213467 eng http://creativecommons.org/licenses/by/4.0/ info:eu-repo/semantics/openAccess Atribución 4.0 Internacional MDPI