Leveraging the cGAS-STING pathway to modulate the tumor microenvironment and enhance immunotherapies in glioblastoma

Abstract

BACKGROUND
Glioblastoma (GBM) is the most lethal primary brain tumor, characterized by rapid progression, treatment resistance, and an immunosuppressive tumor microenvironment (TME). The cGAS-STING pathway is a key sensor of cytosolic DNA that plays a critical role in innate immunity by inducing type I interferons and pro-inflammatory cytokines. In GBM, STING expression is frequently downregulated in GBM, resulting in impaired immune activation and facilitating tumor immune escape. Restoring STING activity is a promising immunotherapeutic strategy to stimulate innate immune recruitment and reprogram the TME.

METHODS
We evaluated cGAS-STING signaling in a panel of murine GBM stem cell lines (005, NF53, C3, RIG) that closely recapitulate patient GBM heterogeneity while allowing immunocompetent in vivo experimentation. STING was activated using synthetic agonists (e.g., ADU-S100), alone or in combination with autophagy inhibitors or G47Δ oncolytic herpes simplex virus (oHSV) therapy.

RESULTS
RNA sequencing and western blot analyses revealed diverse basal expression profiles of cGAS-STING components across mGSCs: C3 and RIG expressed higher levels of cGAS, while 005 and NF53 showed greater STING expression. Despite this variability, all lines responded robustly to STING agonists, with transient IRF3 phosphorylation and significant upregulation of type I interferons (e.g., IFN-β) and inflammatory chemokines (e.g., CXCL10, CCL5). Notably, STING activation reduced oHSV replication, while viral exposure dampened STING-induced signaling, suggesting viral interference with host immunity. Conversely, pharmacological inhibition of autophagy enhanced STING-driven cytokine responses, revealing a synergistic avenue for immune activation.

CONCLUSION
Our data highlight the therapeutic promise of cGAS-STING modulation in GBM. While oHSV therapy may antagonize STING signaling, combining STING activation with autophagy inhibition can potentiate innate immune responses. Ongoing in vivo studies aim to define how these therapies reshape the TME and improve treatment efficacy. Targeting the cGAS-STING axis represents a promising strategy to overcome immune suppression in GBM and enhance immunotherapy outcomes.