TMET-32. Cell-intrinsic pyrimidine synthesis pathway choice in human brain and glioma

Abstract Metabolic rewiring supports glioma progression. Previous studies have produced deep understanding of carbon metabolism, yet comparatively little is known about how brain tumors utilize nitrogen. We therefore developed and validated a platform to simultaneously evaluate the fates of 30 nitrogenous substrates in models of human brain and glioma. Applying this platform to glioma stem-like cells (GSCs) and immortalized astrocytes revealed divergent routes of pyrimidine synthesis. Pyrimidine nucleotides can be synthesized via de novo or salvage routes. GSCs used both routes, while immortalized astrocytes relied exclusively on salvage. We then performed stable isotope tracing with amide-15N-glutamine, a substrate of the de novo pathway, and 15N2-uridine, the salvage substrate, in a panel of GSCs of varying genetic backgrounds, neural stem cells, and differentiated nonmalignant cells. These studies revealed that de novo pyrimidine synthesis was strongly enriched in progenitor-like populations. Induced pluripotent stem cell-derived neural progenitors exhibited greater de novo pathway activity than the primary human fibroblasts from which they originated. We then sought to test this association in vivo, performing stable isotope infusions in wild-type mice and mice bearing orthotopic glioma xenografts. Nonmalignant brain tissue from adult mice exclusively incorporated 15N2-uridine in pyrimidines. In contrast, xenografted glioma tissue and fetal mouse brain incorporated both amide-15N-glutamine and 15N2-uridine, indicating selective de novo pathway engagement in primitive cells. We then obtained 5 glioma tissue explants and 2 metastasis-adjacent nonmalignant brain tissue explants from patients who underwent surgical resection as well as 3 nonmalignant brain explants. Stable isotope tracing patterns in these human samples mirrored those in mice, with all tissues exhibiting robust uridine salvage but only glioma tissue using de novo pyrimidine synthesis. These data identify de novo pyrimidine synthesis as a hallmark of primitive neural cells, including those involved in glioma progression, offering rationale for therapeutic index in targeting this pathway.