IFN-γ signaling drives multiple immunosuppressive pathways and poor clinical outcome in glioblastoma

Glioblastoma (GBM) is a highly aggressive brain tumor characterized by a profoundly immunosuppressive tumor microenvironment and limited response to immunotherapy. While interferon-γ (IFN-γ) signaling is classically associated with antitumor immunity, sustained activation of this pathway has been linked to immune dysfunction in several cancers. However, its tumor-intrinsic role in shaping immunosuppression in GBM remains poorly understood. We integrated transcriptomic and immunohistochemical analyses with clinical data from GBM patients to assess associations between IFN-γ signaling, patient survival, immune cell infiltration, and immune checkpoint expression. Genetic and pharmacological perturbation of IFN-γ signaling was performed to dissect pathway-specific effects in GBM-derived cellular models. Functional immune responses were evaluated through co-culture assays with human peripheral blood mononuclear cells (PBMCs) or isolated natural killer (NK) cells. IFN-γ signaling was found significantly upregulated in GBM and associated with poor patient survival. While the activation of this pathway reduced tumor cell growth, it simultaneously induced a broad immunoregulatory transcriptional program. In turn, high IFN-γ activity was associated with increased myeloid infiltration, impaired NK and T cell cytotoxicity, and upregulation of multiple inhibitory immune checkpoints. In this context, targeting a single checkpoint, such as PD-1, failed to restore antitumor immunity. By contrast, genetic ablation of STAT1, but not IRF-1, effectively reversed IFN-γ-induced immunosuppression and restored immune effector function, identifying STAT1 as a central mediator of this phenotype. Pharmacological inhibition of JAK1/2 recapitulated STAT1 loss in vitro, suppressing IFN-γ-dependent immune inhibitory programs and restoring cytotoxic activity. These findings demonstrated that tumor IFN-γ signaling drives a STAT1-dependent immunosuppressive state in GBM that functionally impairs antitumor immunity. Our study defines a dominant regulatory axis linking IFN-γ signaling to immune escape mechanisms in GBM and provides a mechanistic framework for future studies exploring therapeutic modulation of this pathway to enhance immunotherapy response.