Abstract 6563: Mechanisms of extracellular vesicle uptake in chemotherapy resistant and sensitive ovarian cancer: insights into tropism and resistance transfer

Background: Ovarian cancer is the most lethal gynecological malignancy, with approximately 19,000 new cases and 12,000 deaths projected in the US for 2024. Despite therapeutic advancements, including platinum-based chemotherapies, the 5-year survival rate remains at 50.8%, largely due to chemotherapy resistance. Extracellular vesicles (EVs), nanosized particles involved in intercellular communication, play critical roles in ovarian cancer progression by promoting tumor aggressiveness and chemoresistance. This study investigates the uptake mechanisms and potential tropism of EVs derived from chemotherapy-sensitive (SensC-EVs) and chemotherapy-resistant (ChemoRC-EVs) ovarian cancer (OC) cell lines. All EVs were tested for uptake in both cisplatin-sensitive and cisplatin-resistant cell lines to characterize their interactions comprehensively. EVs were isolated via size exclusion chromatography from serous (SKOV3 wild type [wt] and SKOV3 cisplatin-resistant [cis]) and endometrioid (A2780 wt and A2780 cis) OC cells. EV characterization was performed using nanoparticle tracking analysis, and EVs were fluorescently labeled with Vybrant DiD for uptake studies. Endocytosis inhibitors were employed to identify dominant uptake pathways. Results: In the serous subtype, ChemoRC-EVs exhibited higher tropism towards SKOV3 cis cells, with significant uptake also observed in SKOV3 wt cells. In SKOV3 wt cells, uptake inhibition by dynasore, nystatin, and NAV2729 revealed the predominant involvement of clathrin-mediated, caveolin-mediated, and receptor-mediated pathways. In SKOV3 cis cells, dynasore and NAV2729 confirmed clathrin- and caveolin-mediated endocytosis as the primary uptake mechanisms, with minimal receptor-mediated involvement. Interestingly, SKOV3 wt cells internalized more ChemoRC-EVs than SensC-EVs, potentially contributing to chemoresistance. In the endometrioid subtype, A2780 wt cells demonstrated higher tropism for SensC-EVs compared to ChemoRC-EVs, while A2780 cis cells exhibited similar uptake levels for both types. Uptake inhibition with dynasore and nystatin highlighted clathrin- and caveolin-mediated mechanisms in A2780 wt cells, whereas nystatin indicated caveolin-mediated uptake as the predominant pathway in A2780 cis cells. These findings suggest that EV uptake mechanisms, and their tropism, vary by OC subtype, resistance status, and EV source. Generally, sensitive cells internalized more ChemoRC-EVs, implicating a potential role in the transfer of resistance traits. Future work will engineer EVs to deliver anticancer agents into OC cells, leveraging their tropism and uptake pathways to overcome chemoresistance. This approach could transform EVs from mediators of resistance into therapeutic vehicles, offering innovative strategies to combat ovarian cancer and improve outcomes. Citation Format: Joana Sousa Esteves, Kadie Edwards, Jetzabel Garcia-Parra, Claire Donnelly, Francesca Taraballi, Deyarina Gonzalez. Mechanisms of extracellular vesicle uptake in chemotherapy resistant and sensitive ovarian cancer: insights into tropism and resistance transfer [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 6563.