MDB-31. The eEF2 kinase supports MYC-driven medulloblastoma metabolic adaptation to nutrient deprivation

Group 3 affiliation and MYC genetic amplification determine poor prognosis and high morbidity in children with medulloblastoma (MB). MYC-driven transformation increases metabolic demand, making MYC-overexpressing MB cells more susceptible to death during nutrient deprivation (ND). Previously, we found that eukaryotic Elongation Factor Kinase 2 (eEF2K), a regulator of mRNA translation elongation, is overexpressed in MYC-driven MB and aids tumor survival under acute ND. Proteomic analysis of eEF2K knockout (KO) MB cells revealed alterations in oxidative phosphorylation (OXPHOS) and fatty acid oxidation (FAO) pathways. We hypothesized that eEF2K supports acute stress adaptation in MB by promoting OXPHOS through enhanced FAO in MB. We used MYC-amplified MB cell line D425 to generate the following series: eEF2K wildtype (WT), knockout (KO), WT eEF2K rescue and K170M (kinase dead) rescue. The effects of eEF2K inactivation on oxygen consumption, metabolic fluxes, and nutrient energy dependency were studied utilizing Seahorse and other technologies. Cell viability was assessed by Incucyte following ND of multiple nutrients and treatments with FAO pathway inhibitors (e.g. Etomoxir). NADPH/NADP+ ratios were assessed by colorimetric assays. MB cells with active eEF2K displayed increased stability of mitochondrial membrane potential, and have a higher capacity to undergo glycolysis. NADPH/NADP+ ratios were significantly decreased upon eEF2K KO, indicating that eEF2K supports NADPH oxidation homeostasis. Additionally, eEF2K expressing cells were resistant to glutamine and aspartate deprivation but sensitive to FAO inhibition, the latter of which resulted in reduced oxygen consumption and impaired proliferation. We conclude that the mRNA translation elongation regulator eEF2K is essential for effective mitochondrial respiration through FAO in MYC-overexpressing MB, potentially serving as an adaptive mechanism for cells to manage acute metabolic stress. As eEF2K activity appears critical under metabolic stress conditions, the combination of eEF2K inhibition with specific metabolic inhibitors may represent a potential therapeutic approach for MYC-driven MB.