Selective Targeting of EV Uptake Pathways in Glioblastoma to Combat Tumor-Induced Immune Suppression 4324

Abstract Description Glioblastoma (GBM), the most common and malignant primary brain tumor, exhibits profound immune suppression, hindering immunotherapy efficacy. GBM-derived extracellular vesicles (EVs) play a major role through the immunosuppressive polarization of myeloid cells. Inhibition of EV-myeloid cell interactions thus represents a novel target to mitigate GBM-mediated immune suppression. However, there are multiple mechanisms of EV-target interaction, and downstream pathways of GBM-EV signaling are poorly understood. We explored two pharmacological agents targeting different mechanisms of EV uptake: Methyl-B-cyclodextrin (MBCD), which disrupts lipid rafts, and cytochalasin D, which inhibits actin polymerization. Our results showed immunosuppressive myeloid cell (CD11b+/ CD15-/ HLA-DRlow/ CD14high) populations increased upon GBM-EV treatment. Following cytochalasin D treatment, fewer immunosuppressive myeloid cells were observed (7.40%±1.01 vs. untreated 9.66%±2.86), with rescuing T cell proliferation. Conversely, MBCD treatment increased immunosuppressive myeloid cell levels (10.42%±2.38 vs. untreated 8.87%±3.97) without impacting T cell proliferation. This study demonstrates the feasibility of pharmacologically targeting EV-myeloid cell interactions to rescue tumor mediated immune suppression by inhibiting actin-dependent endocytosis with cytochalasin D. The converse results using MBCD treatment indicate differential importance of different EV uptake pathways in monocyte regulation. Topic Categories Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)