TMIC-85. Microenvironment-derived acetylated amino acids promote glioblastoma DNA repair by rerouting glucose fates and enhancing histone acetylation

Abstract Genotoxic therapy resistance in glioblastoma (GBM) is mediated by rapid DNA repair. We hypothesized that non-malignant cells in the heterogenous GBM microenvironment assist rapid DNA repair in neoplastic cells. Supporting this hypothesis, intracranial GBM tumors (orthotopic GBM PDXs and syngeneic murine GBMs) in mice had rapid DNA repair and poorer survival after radiation compared to flank GBM tumors of identical genotype. Gamma-H2AX immunofluorescence analysis of irradiated intracranial tumors revealed spatial heterogeneity in resolution of DNA damage. Coupling these analyses with spatial transcriptomics in irradiated intracranial syngeneic murine GBM tissues suggested that regions with fast repair were rich in microglia. Coculture of patient derived GBM cells with human primary microglia ex vivo enhanced DNA repair post irradiation in GBM cells. This phenotype was independent of cell contact, suggesting a microglia-derived soluble factor. Indeed, mass spectrometry analysis revealed that microglia secrete acetylated amino acids that are then consumed by neoplastic cells. Supplementation of acetylated amino acids hastened the repair of radiation-induced DNA damage and promoted an invasive phenotype. Metabolomic analysis of GBM cells supplemented with acetylated amino acids showed that glioma cells re-route glucose utilization towards nucleotide synthesis. Spatial transcriptomic analysis of human GBM tissue explant treated with radiation and lung cancer metastasis to the brain resected after irradiation, showed higher expression of genes essential for synthesis of the acetylated amino acids in myeloid cells. Furthermore, supplementation of acetylated amino acids increased acetylation of H2AX post radiation in GBM cells. Hence, we show that microglia in the GBM microenvironment secrete acetylated amino acids which are consumed by GBM cells and used to repair radiation induced DNA damage by repurposing glucose for nucleotide synthesis and increase H2AX acetylation, thereby conferring treatment resistance to the GBM cells.