IMMU-17. SINGLE-CELL RNA-SEQ REVEALS HIGH-GRADE GLIOMA ASSOCIATED MICROGLIA WITH PROINFLAMMATORY AND STEM-LIKE FEATURES SUPPORT TUMOR PROGRESSION
Abstract Poor response of human glioblastoma to current therapies are influenced by tumor microenvironment. Although glioblastoma is recognized by large enrichment of microglia, characterization of diverse cell subsets and their functions remain challenging because of high heterogenicity. Here, we analyzed single-cell transcriptomics to comprehensively map the cell populations and determine the roles of microglia in IDH1/2 wild-type (IDH-wt) glioblastoma progression. Besides finding microglia were significantly enriched in IDH-wt glioblastoma compared to IDH1/2 mutant (IDH-mut) gliomas, we identified a unique high-grade glioma microglia (HGAM) subtype characterized by proinflammatory and stem-like features. In particular, HGAM’s pro-tumoral IL1β secretion is mediated via ApoE-induced activation of NLRP1 inflammasome. HGAM phagocytosed OPC-like malignant cells forming the neoplastic microglia, which presented the stem-like potential giving rise to activated microglia. Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation. Additionally, an intricated evaluation of glioma patients revealed that SETD2 mutation/low-expression correlated with adverse prognosis. Further analysis showed that SETD2 -dificient tumor cells presented hypersensitivity to HGAM-derived IL1β via epigenetic dysregulation of PHF6. Also, SETD2 -deficient tumor cells produced TGF-β1 contributing to microglia activation. Finally, targeting the TGF-β1/TβRI signaling impaired HGAM activation and tumor growth. Our studies identify a unique neoplastic microglia subpopulation and establish cellular basis of interactions with tumor cells important for disease progression.