Work

2 Preclinical modeling of human glioblastoma immunotherapy resistance using a STING pathway defective mouse model

Year: 2026

Type: conference-abstract

Abstract: Background Glioblastoma (GBM) is an aggressive tumor with low patient survival and limited response to anti-PD-1/L1 immunotherapy. 1 An important mechanism of resistance to anti-PD-1 immunotherapy is a defective cGAS/STING innate immune sensing pathways.2 3 GL261 is a commonly used syngeneic murine tumor model of glioblastoma that is sensitive to anti-PD-1 and has an intact cGAS/STING pathway.4 Thus, its ability to model the immune-refractory state of human GBM is limited. We generated a GL261 resistant cell line that is resistant to anti-PD-1 and found it had a defective cGAS/STING pathway. We evaluated the ability of our novel resistant model as a clinically relevant platform for human GBM study.Methods Our anti-PD-1 resistant cell line was established through ex-vivo isolation and expansion of GL261 tumors that failed to respond to anti-PD-1 (clone RMP1-14) in-vivo. The ability of this cell line to respond to STING agonist was investigated by measuring the induction of CXCL10 and IFN-β. Mechanistic study of genetic alterations associated with cGAS/STING defect and anti-PD-1 resistance were performed.Results Unlike the parental GL261, our resistant cell line was not responsive to anti-PD-1 (clones RMP-14 or 8H3). Mechanistically, epigenetic profiling revealed closed chromatin architecture of innate DNA sensing and type I interferon-response genes in our resistant line relative to the parental GL261 cells which was orthogonally validated by RNA-sequencing. Treatment with a STING agonist failed to induce secretion of the inflammatory cytokines CXCL10 and IFN-β or alter the epigenome in the resistant cell line, showing a defect in the cGAS/STING pathway. Transcriptomic analysis revealed upregulation of the cGAS/STING-associated type I interferon gene program upon STING agonist treatment; however, the magnitude of these changes was markedly attenuated compared to parental GL261 cells. A combination of STING agonist with anti-PD-1 conferred partial restoration of anti-tumor immune activity in this model resulting in improved therapeutic efficacy with anti-PD-1 therapy.Conclusions Our results show that defects in the STING pathway may contribute to anti-PD-1 resistance in GBM. Our resistant cell line can be used as a preclinical model to: 1) recapitulate the attenuated innate immune signaling of human glioblastoma; and 2) investigate anti-PD-1 resistance in GBM. In summary, we propose a new GBM mouse model that better mirrors human GBM and may help identify strategies to improve response to immune checkpoint blockade.References Reardon DA, Gokhale PC, Klein SR, Ligon KL, Rodig SJ, Ramkissoon SH, et al. Glioblastoma eradication following immune checkpoint blockade in an orthotopic, immunocompetent model. Cancer Immunol Res. 2016;4(2):124-35.Qiu L, Meng Y, Han J. STING cg16983159 methylation: a key factor for glioblastoma immunosuppression. Signal Transduct Target Ther. 2022;7(1):228.Berger G, Knelson EH, Jimenez-Macias JL, Nowicki MO, Han S, Panagioti E, et al. STING activation promotes robust immune response and NK cell-mediated tumor regression in glioblastoma models. Proc Natl Acad Sci U S A. 2022;119(28):e2111003119.Iorgulescu JB, Ruthen N, Ahn R, Panagioti E, Gokhale PC, Neagu M, et al. Antigen presentation deficiency, mesenchymal differentiation, and resistance to immunotherapy in the murine syngeneic CT2A tumor model. Front Immunol. 2023;14:1297932.

Source: Journal for ImmunoTherapy of Cancer

DOI: 10.1136/jitc-2026-sitc2026.0002