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. Overall design: Using immunocompetent de novo mouse models of pediatric high grade glioma (pHGG), we generated tumors in both the cortical hemisphere and midline to represent each major subtype of pHGG including H3WT, H3.1K27M, or H3.3K27M pHGGs. Each tumor subtype contains the relevant driver mutations found in their human counterparts. Further experiments utilizing H3.1K27M DMGs in Ccl8/12 total knockout mice were performed, using H3.1K27M samples as wild type controls.Brain tumor cells were isolated at the humane endpoint of these mice, and sc-RNA seq was conducted to compare their functional differences.