Abstract A12: Bladder cancer-derived extracellular vesicles and immune activation
Authors: Tham Sin Mun , Esuvaranathan Kesavan , Mahendran Ratha 
Published: August 2020

Background: Bladder tumors occur on the luminal surface of the bladder, and cancer cells and cellular components are shed in urine, which permits the isolation of an enriched population of bladder cancer-specific extracellular vesicles (EVs). EVs contain proteins, miRNA, mRNA, and cellular metabolites, which may serve as stimulators of immune cells. The objective of this study was to evaluate the immune potential of tumor-derived EVs (TEVs) produced on exposure to BCG using a murine bladder cancer cell line and immune cells.

Methods: TEVs were isolated by differential high-speed centrifugation of cell culture supernatants. They were confirmed to be extracellular vesicles by electron microscopy and size measurement using nanoparticle tracking analysis. Unstimulated murine bladder cancer cells (MB49) were used to prepare TEV1. The cells were then exposed to BCG Tokyo (MOI 4) and TEVs were isolated after 2 hours (TEV2). BCG was then washed off and the cells were allowed to grow in complete media for 2 days before isolation of the third sample, TEV3. EVs from BCG (BEV) were collected to serve as a control. Bone marrow-derived cells were obtained from C57BL/6J mice to generate dendritic cells (DC) and neutrophils. These cells were untreated or treated with 1ug of TEVs or BEV or BCG (MOI 5) for 24 hours. The supernatants were analyzed for cytokine production and the DCs and neutrophils were analyzed for activation markers by flow cytometry. The institutional animal care and use committee approved the use of mice.

Results: DCs treated with TEV2 had significantly higher expression of CD86 (at similar levels when DCs were treated with BCG) and MHC2, both of which enhanced the DC's capacity to present antigens to T cells, when compared to TEV1 or TEV3. While neutrophils induced by BCG expressed significantly higher levels of costimulatory molecules CD80, CD83, CD86, and MHC2, TEV2 induced significant expression of CD80 and CD86. BCG caused a massive release of proinflammatory cytokines (IL6, TNFa, and IL12p70) and the anti-inflammatory cytokine IL10. Cytokine production induced by TEV2 was not as high as that induced by direct BCG stimulation, but it was significantly higher than that produced by untreated cells or TEV1 and TEV3. Unlike BCG, TEV2 did not significantly stimulate IL10 production.

Conclusion: Our results demonstrate that tumor cells treated with BCG for 2 hours produce EVs that are able to cause significant modulation of DCs and neutrophils. TEVs generated during BCG immunotherapy have immunostimulatory potential. Therefore, TEVs represent a promising source of material to increase immune activation and efficacy of BCG therapy. This could reduce the number of instillations and adverse effects associated with BCG therapy.

Citation Format: Sin Mun Tham, Kesavan Esuvaranathan, Ratha Mahendran. Bladder cancer-derived extracellular vesicles and immune activation [abstract]. In: Proceedings of the AACR Special Conference on Bladder Cancer: Transforming the Field; 2019 May 18-21; Denver, CO. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(15_Suppl):Abstract nr A12.