Spatially resolved single-cell analysis uncovers protein kinase C-& expressing microglia with anti-tumor activity in glioblastoma

Glioblastoma (GBM) is a brain tumor that continues to pose a formidable challenge to cure with limited treatment options. The tumor microenvironment (TME) in GBM is highly complex, marked by immunosuppression and cellular heterogeneity. Understanding the cellular interactions and their spatial organization within the TME is crucial for developing effective therapeutic strategies. In this study, we integrated single-cell RNA sequencing and spatial transcriptomics in a GBM mouse model to unravel the spatial landscape of the brain TME. We identified a previously unrecognized microglia subset expressing protein kinase C& (PRKCD) associated with potent anti-tumor functions. The presence of PRKCD-expressing microglia is affirmed in resected human GBM specimens. Elevating tumoral PRKCD using niacin or adeno-associated virus in mice enhanced the phagocytosis of GBM cells by microglia in culture and increased the lifespan of mice with intracranial GBM. These findings were corroborated in analyses of TCGA GBM datasets where high PRKCD samples showed positive enrichment for apoptosis, phagocytosis, and immune signaling pathways. Our study underscores the importance of integrating spatial context to unravel the TME, resulting in the identification of previously unrecognized subsets of immune cells with anti-tumor functions. These findings provide valuable insights for advancing innovative immunotherapeutic strategies in GBM. ### Competing Interest Statement The authors have declared no competing interest.