Identifying a Csmd3⁺ Microglial Subpopulation that Drives Cold-to-Hot Transition and Immune-Cure in Glioblastoma

Glioblastoma (GBM) is immunologically cold and responds poorly to immune-based therapies owing to its highly heterogeneous and immunosuppressive tumor microenvironment (TME). However, strategies to achieve a cold-to-hot transition remain elusive, and suitable research models are still lacking. Here, TME profiling classifies our refractory G422^TN-GBM model as the TME^Med (heterogeneous immune populations, "cold") subtype of human GBM, which can be shifted toward the TME^High (immune-high, "hot") subtype by inhibiting TGF-β signaling. In the multi-drug regimen, only αTGF-β combining temozolomide chemoradiotherapy and αPD-1 achieves immune-cure (ICu, passing tumor rechallenge, 12.5%). ICu screening reveals a newly identified Csmd3⁺ microglial subset with innate immune memory potential, which likely initiates durable anti-GBM immune memory and closely associates with effective GBM therapy and favorable prognosis. MG^{OE• Csmd3 , BV2} (Csmd3-overexpressed microglial BV2) elicit robust anti-GBM effects and achieve a notably 100% tumor rechallenge success in G422^TN-GBM mice via promoting TME^Med-to-TME^High remodeling. Taken together, our findings identify an immunologically cold TME^Med GBM mouse model and provide a proof-of-concept for microglia-based TME reprogramming and cell therapy in GBM.