Understanding STING Signaling in Glioblastoma (GBM); Identifying a Role for STING in Tumor CellsdissertationsQiu, YanfeicreatorLawler, SeanAdvisorHorrigan, DianaReaderCappillino, GülbenkReaderBrown University. Biology and Medicine: Biotechnologysponsor20260, 50 p.born digitalThesis (Sc. M.)--Brown University, 2026thesesIntroduction: Glioblastoma (GBM) is an aggressive brain tumor with only 5% of patients surviving beyond five years, and it has immunosuppressive tumor microenvironment (TME), which makes it more resistant to immunotherapies and leads to worse treatment responses among patients. STING (Stimulator of Interferon Genes) is essential for secretion of immune activating cytokines in response to some pathogens. Our lab previously showed that ADU-S100, which is a STING agonist, can turn on the pathway and improve survival in mouse GBM models. It is thought that ADU-S100 targets the pathway in the stromal cells of the TME, and as a result, the pathway is disabled in tumor cells, as a potential immunoevasion mechanism. The goal of this study was to understand whether STING signaling can play a role in tumor cells and to better define that role. Methods: We used western blotting, RT-qPCR, RNAseq, MTT cell viability assay, immunofluorescence staining, and ELISA, to examine responses to STING modulation in a panel of patient-derived GBM cell lines. Results: Despite STING phosphorylation, the cytokine analysis indicates pathway failure because of insufficient cytokine secretion. However, CCL5 and CXCL10 are still secreted to some extent, suggesting a potential role in the tumor microenvironment. Furthermore, RNA sequencing after treatment with ADU-S100 revealed very few alterations, suggesting that the defect in STING signaling is at the transcriptional level in GBM cells, which could represent an immune evasion mechanism. Treatment with a STING inhibitor led to a decrease in GBM cell viability, and drug combination results show decreasing cell viability in combination with the MAP kinase pathway inhibitor trametinib, suggesting that STING plays a role in the biology of tumor cells. Conclusions: Treatment with the STING agonists ADU-S100 led to activation of STING signaling as measured by western blotting for phosphorylation of STING and downstream proteins, TBK1 and NF-kB. GBM cells rewire STING signaling likely as an immune evasion mechanism. Our study shows evidence that STING agonists can trigger responses from GBM cell lines, suggesting additional functions of STING signaling which may facilitate tumor growth.Glioblastoma multiforme (GBM)Tumor MicroenvironmentADU-S100STINGEnglishRPB20260516