IMMU-63. Uncovering alternative innate immunity pathways in glioma viroimmunotherapy

Abstract Recent clinical trials have demonstrated that oncolytic virotherapy using adenoviruses can extend survival in a subset of brain tumor patients by promoting T-cell infiltration into otherwise immunologically “cold” tumors (NCT00805376, NCT03178032, and NCT02798406). However, the early detection and elimination of the virus by the host immune system likely limit the therapeutic efficacy of this approach. To address this challenge, we investigated the molecular pathways and sensors responsible for recognizing adenoviruses during infection, with the ultimate goal of modulating this process to improve viroimunotherapy clinical efficacy. RNA-seq analyses revealed the upregulation of Non-Pou Domain-Containing Octamer-Binding (NONO) in intracranial glioma models treated with the oncolytic adenovirus Delta-24-RGD. We demonstrate that NONO is essential for initiating the cGAS-STING pathway and modulating innate immune responses against adenovirus in normal cells and glioma models. Immunoprecipitation and mass spectrometry studies indicate the formation of complexes between NONO and adenovirus DNA-binding protein (DBP), which facilitate cGAS activation. Given that high-grade brain tumors and corresponding cell models often harbor homozygous deletions of downstream interferon effector genes, we further examined the role of the immunotransmitter 2’3’-cyclic GMP-AMP (cGAMP) in local immune activation. Our results show that tumor-derived cGAMP is sufficient to activate local immune cells and that NONO is required for its production following virotherapy. In vivo experiments reveal that downregulation of NONO enhances viral persistence and significantly prolongs overall survival in athymic mice treated with Delta-24-RGD. Collectively, our results identified NONO as a novel sensor of adenoviral DNA and capsid proteins, which is essential for the secretion of cGAMP and activation of innate immune cells. In addition, this data suggests that targeting the NONO-related pathway may guide the development of the next generation of oncolytic viruses to improve the clinical results obtained using viroimmunotherapy and other immunotherapy modalities.