Combination metabolic therapy for diffuse midline glioma - PROJECT SUMMARY Diffuse midline gliomas (DMGs) are devastating primary brain tumors in children. Patient prognosis is abysmal with median survival of ~9 months after initial diagnosis. DMGs are driven by recurrent lysine to methionine mutations in histone H3 (H3K27M) that lead to widespread epigenetic dysregulation and oncogenic gene expression. Pinpointing vulnerabilities induced by the H3K27M mutation has the potential to lead to precision therapies for DMG patients. Tumors reprogram metabolism to generate biosynthetic precursors for uncontrolled proliferation and to maintain defense mechanisms. Glucose-6-phosphate dehydrogenase (G6PD) generates ribose-5-phosphate, which is a precursor for nucleotide biosynthesis. It also generates NADPH, which maintains glutathione (GSH) in the reduced state. GSH, in turn, is essential for glyoxalase 1 (GLO1) to detoxify methylglyoxal (MGO), a waste product of glycolysis. Our studies with isogenic and patient-derived models indicate that the H3K27M mutation transcriptionally upregulates G6PD and GLO1 expression in DMGs. Combined inhibition of G6PD and GLO1 using doxycycline-inducible shRNA or novel brain penetrant inhibitors is synergistically lethal in vitro and causes tumor regression in vivo. Mechanistically, G6PD and GLO1 inhibition depletes nucleotides and causes accumulation of MGO, leading to macromolecular glycation and apoptosis in DMGs. Deuterium metabolic imaging is a novel, clinically translatable method of visualizing glucose metabolism in vivo. Our studies indicate that MGO downregulates glycolysis by glycating phosphoglycerate kinase 1 (PGK1). Importantly, lactate production from [6,6’-2H]-glucose is altered at early timepoints following G6PD and GLO1 inhibition when changes cannot be observed on anatomical imaging in DMG-bearing mice. Based on these results, we will determine whether combined inhibition of G6PD and GLO1 abrogates DMG proliferation (Aim 1) and [6,6’-2H]-glucose provides an early readout of response to therapy at 3T (Aim 2). Our application is innovative because we identify, to the best of our knowledge for the first time, G6PD and GLO1 as oncogene-induced metabolic vulnerabilities in DMGs. Our proposal is significant because we have identified G6PD and GLO1 inhibitors that are synthetically lethal and have the potential for clinical translation. Furthermore, we will validate [6,6’-2H]-glucose as an agent that can provide a biologically meaningful readout of treatment response in vivo. We anticipate that our studies will provide the preclinical foundation needed to initiate imaging-driven clinical trials of our G6PD and GLO1 inhibitors in DMG patients. In summary, our proposal will develop metabolic therapy and imaging that can improve outcomes and quality of life for DMG patients.
