Reprogramming of Glioblastoma-Immune Crosstalk to Overcome Immunotherapy Failure 2258791

Abstract Introduction Glioblastoma multiforme (GBM) is a lethal brain cancer with a median survival of less than a year. Immunotherapies, such as immune checkpoint blockade (ICB), represent promising treatment options but still face challenges due to tumor resilience. Understanding how the brain and tumor environment shape immune responses is critical to overcoming therapy failure. GBM tumors are heterogeneous, with four subtypes: mesenchymal-like (MES), astrocyte-like (AC), oligodendrocyte-progenitor-like (OPC), and neural-progenitor-like (NPC), but their interactions with immune cells remain unclear. Here, this study aims to identify targetable GBM subtype-immune interactions that undermine ICB efficacy. Methods We applied Xenium spatial single-cell transcriptomics in an orthotopic GBM mouse model to achieve high-resolution mapping of spatial relationships between tumor and immune cell populations. We further employed small-molecule inhibitors to suppress mesenchymal (MES) subtypes and evaluate their synergistic efficacy with anti—PD-1 immunotherapy in vivo. Results Spatial transcriptomic profiling demonstrated that tumoricidal T cells and immunosuppressive tumor-associated macrophages (TAMs) were concentrated within mesenchymal-like (MES) GBM regions. Ligand—receptor mapping revealed that MES-like tumor cells and TAMs overexpress extracellular matrix proteins such as fibronectin (Fn1), which may hinder T-cell function. As the bromodomain-containing protein 2 (BRD2) complex drives the MES-like phenotype, its inhibition decreased Fn1 expression in GBM cells and, when combined with anti—PD-1 therapy, markedly prolonged survival in mice compared to anti—PD-1 treatment alone. Conclusion This study identifies a targetable molecular axis linking the BRD2 complex to fibronectin-driven immune suppression in mesenchymal-like GBM niches. By disrupting this pathway, BRD2 inhibition enhances the efficacy of immune checkpoint blockade, offering a promising combinatorial therapeutic strategy. Funding Source National Institute of Health Topic Categories Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)