Abstract 925: Golgi-derived extracellular vesicles lack conventional tetraspanins and mediate immune evasion in cancer

Immunotherapy has significantly improved the survival of patients with various malignancies. However, immunotherapies have largely remained ineffective in tumors that have reduced infiltration of T cells, also called immune-cold tumors. Despite an extensive understanding of factors that mediate poor T cell infiltration, current therapies that target these factors have shown modest clinical benefit, indicating that other factors contribute to this process. One such factor that has been shown to contribute to immunosuppression are extracellular vesicles (EVs). However, due to significant EV heterogeneity, discovery of specific EV subpopulations that are responsible for these immunosuppressive effects has remained a challenge. Overcoming this challenge, we first established relevant lung cancer models to study EV-mediated T cell suppression and then identified a previously uncharacterized population of lung cancer-derived EVs that strongly inhibit the proliferation and activation of T cells. We further identified that this novel T cell-suppressive EV subpopulation originates from the trans-Golgi network and expresses the classic trans-Golgi marker protein, TGN46. In addition, the TGN46+ EV subpopulation lacks conventional EV markers CD81 and CD63. In the immunosuppressive lung cancer model, while total EVs suppress T cells, specifically removing the TGN46+ EV subpopulation ameliorated this effect. Conversely, overexpressing TGN46 in a lung cancer model that had no EV-mediated effect on T cells was sufficient to increase TGN46+ EV release and the ability of the EVs to suppress T cells, underscoring the physiological significance of the TGN46+ EV subpopulation. Analysis of patient data from The Cancer Genome Atlas (TCGA) indicates that high TGN46 expression (both transcript and protein) correlates with worse progression-free survival in lung cancer and overall survival in other cancer types - glioblastoma, lower grade glioma, testicular cancer, and large B-cell lymphoma. Most importantly, tumor-immune association analysis of TCGA data suggests that high tumor TGN46 expression significantly correlates with an immunologically-cold tumor signature, i.e., low infiltration of CD8+ T cells and activated NK cells, and high infiltration of M2 macrophages, across several cancer types, stressing the clinical relevance of our findings. The data elucidates that TGN46+ EVs are a novel factor that potentially contributes to immune-cold tumor microenvironment. How TGN46+ EVs suppress T cells mechanistically and their role in overall tumor microenvironment modulation are currently under investigation, which may inform strategies to enhance immunotherapy effectiveness in immune-cold tumors. Citation Format: Ikjot Singh Sohal, Sydney N. Shaw, Lauren N. Meeks, Andrea L. Kasinski. Golgi-derived extracellular vesicles lack conventional tetraspanins and mediate immune evasion in cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 925.