Tumor Associated Macrophages And Microglia Drive Tumor Progression And Are Transcriptionally Shaped By Histone Mutations In Pediatric Diffuse Midline Glioma

Pediatric high-grade gliomas, including diffuse midline gliomas (DMG), harbor mutually exclusive tumor location specific histone mutations. Using immunocompetent genetically engineered mouse models, we demonstrate the predominant non-neoplastic cell population are infiltrating myeloid cells, including peripheral monocytes and brain resident microglia. Single cell RNA sequencing, flow cytometry, and immunohistochemistry demonstrate the presence of unique myeloid cell populations distinctly shaped by the specific histone mutation. Disease associated myeloid cell phenotypes are identified, resembling those found in other neurodegenerative diseases, and demonstrate immune permissive characteristics. H3.3K27M DMGs, the most aggressive DMG subtype, demonstrate enrichment of disease associated myeloid cells as well as proliferating myeloid and tumor cells.