406 Reprogramming the Glioma Immunosuppressive Tumor Microenvironment with Engineered Myeloid Cells That Release IL-2 to Delay Malignant Progression

Background Each year in the United States, approximately 20,000 new cases of gliomas are diagnosed in children, adolescents, and adults. These disparate brain tumors are heterogeneous and exist on a pathologic continuum. Low-grade gliomas (LGGs) are more prevalent in adolescents and young adults.1 2 While Grade I LGGs are associated with favorable survival rates, Grade II counterparts remain a significant challenge, given their propensity to recur.3–6 The inability of tumor-centric therapies to impair malignant transformation has been attributed to innate mechanisms of resistance within the brain tumor microenvironment (TME), mediated by a robust infiltration of immunosuppressive myeloid-derived suppressor cells (MDSCs) and tumor-associated M2-like macrophages (TAM).7–10 Immunosuppressive myeloid cells promote tumor escape mechanisms, while impairing the trafficking and cytotoxicity of Natural Killer (NK) and CD8+ (T) cells.10–15 To that end, immunotherapies demonstrated limited efficacy in improving outcomes for primary and secondary HGGs. HYPOTHESIS. We hypothesize that engineered myeloid cells16 17 that release IL-2 will reprogram the TME to enhance the trafficking and activation of activated effector T and NK cells in low-grade glioma bearing mice. Methods A single intravenous dose of syngeneic and genetically engineered bone marrow-derived myeloid cells was used to treat immunocompetent LGG AYA animals, and the impact of this cellular therapy on infiltrating immune cells within the tumor microenvironment was investigated by RNA sequencing and gene enrichment analysis, cytokine arrays, and mass cytometry. Results Three days post-treatment, we observed GEMys infiltration in the local brain tumor microenvironment. In addition, gene enrichment analyses demonstrated pro-inflammatory reprogramming of tumor infiltrating immune cells. Activation of innate and adaptive immune response signaling pathways and networks associated with IFNy and TLR4 were observed post-treatment. Conversely, immunosuppressive signaling of IL10RA and CITED2 were significantly downregulated. Furthermore, biological functions associated with inflammatory response, immune cell trafficking, cellular proliferation, and cell-to cell signaling were significantly upregulated. Additional analysis of the TME by cytokine array and mass cytometry confirmed the therapeutic association of this cell mediated immunotherapy on promoting a pro-inflammatory TME, underscored with an increased trafficking of activated cytotoxic T and NK cells. Conclusions The use of GEMys is a novel cell-mediated approach and may serve as a platform for developing innate immunotherapies for patients with gliomas. References Diwanji TP, et al. Epidemiology, diagnosis, and optimal management of glioma in adolescents and young adults. Adolesc Health Med Ther, 2017;8: 99–113. Grier JT and T Batchelor. Low-grade gliomas in adults. Oncologist, 2006; 11(6): 681–93. Upadhyaya SA, et al. Mortality in children with low-grade glioma or glioneuronal tumors: A single-institution study. Pediatr Blood Cancer, 2018; 65(1). Armstrong GT, et al. Survival and long-term health and cognitive outcomes after low-grade glioma. Neuro-Oncology, 2011; 13(2): 223–234. Jaeckle KA, et al. Transformation of low grade glioma and correlation with outcome: an NCCTG database analysis. J Neurooncol, 2011; 104(1): 253–9. Packer RJ, et al. Pediatric low-grade gliomas: implications of the biologic era. Neuro Oncol, 2017; 19(6): 750–761. Chen Z, et al. Cellular and Molecular Identity of Tumor-Associated Macrophages in Glioblastoma. Cancer Res, 2017; 77(9): 2266–2278. Chen Z and D Hambardzumyan. Immune Microenvironment in Glioblastoma Subtypes. Front Immunol, 2018; 9: 1004. Hambardzumyan D, DH Gutmann, and H Kettenmann. The role of microglia and macrophages in glioma maintenance and progression. Nat Neurosci, 2016; 19(1): 20–7. Raychaudhuri B. et al. Myeloid derived suppressor cell infiltration of murine and human gliomas is associated with reduction of tumor infiltrating lymphocytes. J Neurooncol, 2015. 122(2): 293–301. Liu CY, et al. Population alterations of L-arginase- and inducible nitric oxide synthase-expressed CD11b+/CD14−/CD15+/CD33+ myeloid-derived suppressor cells and CD8+ T lymphocytes in patients with advanced-stage non-small cell lung cancer. J Cancer Res Clin Oncol, 2010. 136(1): 35–45. Pombo Antunes AR, et al. Understanding the glioblastoma immune microenvironment as basis for the development of new immunotherapeutic strategies. Elife, 2020; 9. Kmiecik J, et al. Elevated CD3+ and CD8+ tumor-infiltrating immune cells correlate with prolonged survival in glioblastoma patients despite integrated immunosuppressive mechanisms in the tumor microenvironment and at the systemic level. Journal of Neuroimmunology, 2013; 264(1): 71–83. Grabowski MM, et al. Immune suppression in gliomas. J Neurooncol, 2021; 151(1): 3–12. Klement JD. et al. Tumor PD-L1 engages myeloid PD-1 to suppress type I interferon to impair cytotoxic T lymphocyte recruitment. Cancer Cell, 2023; 41(3): 620–36 e9. Canella A, and P Rajappa. Therapeutic utility of engineered myeloid cells in the tumor microenvironment. Cancer Gene Ther, 2023. Kaczanowska, S., et al. Genetically engineered myeloid cells rebalance the core immune suppression program in metastasis. Cell, 2021. 184(8): 2033–2052 e21.