Chronic IFN-γ Exposure Induces Divergent Adaptive Programs in Glioblastoma Subtypes

Background: Immunotherapy has transformed cancer treatment by enhancing cytotoxic T-cell activity and interferon-γ (IFN-γ)-mediated tumor clearance. However, glioblastoma (GBM) remains largely refractory to these approaches, reflecting a profoundly immunosuppressive and myeloid-dominant tumor microenvironment. IFN-γ is central to antitumor immunity, yet chronic exposure can paradoxically promote adaptive resistance. How GBM cells respond to sustained IFN-γ signaling, and whether these responses differ across tumor states, remains poorly understood. Methods: To address this, we modeled chronic IFN-γ exposure in mesenchymal-like (U87) and proneural-like (U251) GBM cells over 28 days and performed integrated analyses of transcriptional, proteomic, and secretory responses. Results: While IFN-γ initially suppressed growth in both models, their long-term adaptations diverged. U87 cells developed a persistence-prone state characterized by progressive activation of PI3K–AKT signaling, whereas U251 cells exhibited sustained interferon signaling with persistent interferon-related DNA damage resistance signature (IRDS) expression and suppressed AKT activity. These transcriptional and signaling programs were incompletely reversible after cytokine withdrawal, indicating stable interferon conditioning. Analysis of TCGA glioblastoma datasets demonstrated that interferon-associated transcriptional programs are present across human tumors and are positively associated with PI3K–AKT pathway activity across molecular subtypes. Conclusions: Together, these findings reveal that chronic IFN-γ exposure drives distinct, lineage-dependent adaptive states in GBM, linking interferon signaling to divergent survival and immune-modulatory programs. While IFN-γ enhances immune activation, prolonged signaling may also promote tumor persistence. These results support therapeutic strategies that combine IFN-based approaches with interventions targeting adaptive survival pathways and immune reprogramming.