TMIC-59. IL-2 SECRETING ENGINEERED MYELOID CELLS POTENTIATE CYTOTOXIC EFFECTOR CELL ACTIVATION TO DELAY MALIGNANT PROGRESSION IN A PRECLINICAL MODEL OF GLIOMA

Abstract

Abstract INTRODUCTION Gliomas are the most prevalent brain tumor in the adolescent and young adult population (AYA) and one of the leading causes of cancer-related death. In fact, two-thirds of glioma AYA patients are affected by low-grade gliomas (LGGs). Moreover, there are no therapies to prevent glioma LGG malignant progression. Malignant progression is associated with a significant reduction of tumor infiltrating cytotoxic effector immune cells, primarily due to the immunosuppressive tumor microenvironment (TME) mediated by regulatory T lymphocytes, tumor associated macrophages (TAMs), and myeloid-derived suppressor cells (MDSCs). To that end, immunotherapies have had limited efficacy in improving outcomes for primary and secondary HGGs. HYPOTHESIS We hypothesize that engineered myeloid cells that release IL-2 will enhance the trafficking of activated effector T cells and potentiate a pro-inflammatory cascade in the low-grade glioma TME, delaying malignant progression. METHODS Immunocompetent RCAS n/tv-a LGG bearing animals were retro-orbitally treated at day 21 with a single dose of bone-marrow derived myeloid cells, engineered for the release of Interlekin-2 (GEMys-IL2). The inflammatory status of the TME along with the composition and functional status of tumor infiltrating immune cells were investigated in vivo by cytokine array, mass cytometry, and bulk RNA sequencing. RESULTS Our complementary dataset demonstrated that GEMys-IL2 infiltrated the glioma microenvironment and triggered a pro-inflammatory cascade involving the upregulation and release of IL2, IFNy, CXCL9, Tim1, CD26 and other pro-inflammatory cytokines associated with the activation and recruitment of innate and adaptive immune cells within the TME. In addition, we observed a downregulation of immunosuppressive signaling pathways such as IL10, PPAR, LXR/RXR, CTLA4 and PD-1. Also, a single dose of GEMys-IL2 systemically injected in RCAS/t-va immunocompetent LGG bearing mice potentiated pro-inflammatory remodeling of the TME and significantly improved overall survival. CONCLUSIONS These preclinical studies highlight a novel approach in developing next-generation innate immunotherapies.