Abstract 2321: Tumor-derived extracellular vesicles induce macrophages immunosuppressive polarization to promote ovarian cancer progression
Authors: Mittal Sonam , Kadamberi Ishaque Pulikkal , Gupta Prachi , Kumar Sudhir , George Jasmine , Geethadevi Anjali , Chaluvally-Raghavan Pradeep , Pradeep Sunila 
Published: April 2023

Abstract
Background: Communication between cancer cells and surrounding cells in the tumor microenvironment (TME) is critical for tumor metastasis. There has been an increasing focus on how tumor-derived extracellular vesicles (EVs) contribute to the complex intracellular communications within the TME. More recent characterizations in both mice and humans have demonstrated that expression of the immune checkpoint molecule, programmed death ligand-1 (PD-L1) on EVs contributes to systemic immunosuppression, higher overall tumor burdens, and decreased survival of a variety of cancer types. In ovarian carcinoma, macrophages are reprogrammed toward pro-tumorigenic phenotypes, including the release of anti-inflammatory cytokines and expression of immunosuppressive molecules such as arginase-1 and PD-L1. However, a detailed mechanism that explains how tumor-derived EVs induce immunosuppressive phenotype in macrophages is necessary to develop novel immunotherapy strategies for advanced ovarian cancer treatment. The present study aimed to examine the effect of EVs derived from ovarian cancer cells on macrophage functions.
Methods: We isolated murine peritoneal macrophages from naïve C57BL/6 female mice and co-cultured the macrophages with EVs derived from ovarian cancer (ID8-Trp53-/-Brca2-/-) cell lines. The expression of PD-L1, CD206, interleukin-6 (IL-6), and other inflammatory cytokines on EVs treated macrophages was evaluated using flow cytometry and a cytokine array kit. Further, we created Rab27aKO ID8 cell lines to generate ovarian cancer in vivo mouse models for studying the effect of exogenous EVs on the immunosuppressive ability of macrophages and tumor progression.
Results: Our results indicate that EVs uptake efficiency of macrophages is higher than fibroblast, endothelial, and mesothelial cells. We found that tumor-derived EVs can significantly upregulate the expressions of PD-L1, CD206, and IL-6 on macrophages to support tumor growth. Treatment of macrophages with EVs also decreased their phagocytic ability. In addition, our data show that in the Rab27aKO ovarian cancer in vivo mouse model, intravenous injection of tumor-derived EVs increased the tumor burden, metastasis, and ascites accumulation as compared to PBS control. EVs treatment increased the infiltration of tumor-associated macrophages (TAM) in ascites. We also found increased expression of PD-L1 and CD206 on TAM isolated from ascites.
Conclusion: We uncover a tumor-promoting role of ovarian cancer-derived EVs on reprogramming TAM towards pro-tumor phenotype. Our data suggest that tumor-derived EVs contribute to the formation of an immunosuppressive microenvironment to promote ovarian cancer growth.
Citation Format: Sonam Mittal, Ishaque Pulikkal Kadamberi, Prachi Gupta, Sudhir Kumar, Jasmine George, Anjali Geethadevi, Pradeep Chaluvally-Raghavan, Sunila Pradeep. Tumor-derived extracellular vesicles induce macrophages immunosuppressive polarization to promote ovarian cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2321.