Abstract 4122: Integrin avb3 and HSPG targeting agents prevent extracellular vesicles uptake and breast cancer metastasis

Abstract INTRODUCTION: Metastasis is the major cause of cancer-related deaths (90%). Intercellular communication between cancer cells and with cells in their environment plays a significant function in tumor progression. In fact, secreted factors like cytokines and extracellular vesicles (EVs) can either halt or stimulate tumorigenesis as well as metastasis. We have previously reported, that the integrin B3 (ITGB3) is required for metastasis of breast cancer cells in vivo (Sese et al. Oncotarget, 2017). We furthermore demonstrated, that EVs mediated colony growth is dependent on ITGB3 and that endocytosis mediated uptake of EVs relies on the interaction of ITGB3 with integrin av (ITGav) and heparan sulphated glycoproteins (HSPGs) (Fuentes et al. Nat. Commun. , 2021). OBJECTIVE: The objective of this work is focused on identifying inhibitors targeting the ITGav/B3/HSPGs complex to prevent extracellular vesicle uptake in cancer cells and to test their ability to prevent metastasis. METHODOLOGY. Inhibitors targeting ITGB3/ITGAV or HSPGs were either commercially available or obtained through collaborations and single chain antibodies (scFv) were produced in house. Inhibition of fluorescent labeled EVs was determined by FACS analysis or Incucyte based measurements and the efficacy of inhibitors was determined in a dose dependent manner. Toxicity of inhibitors was studied by crystal violet-based assay in normal and tumor cell lines. Tail vein injection of luciferase labeled MDA-MB-231 cells into nude mice was used as model to study metastatic diseases under treatment with the identified inhibitors. Metastasis formation was monitored by bioluminescence imaging and lungs were examined pathologically at end point. Overall survival was determined. RESULTS: Among the tested Integrin and HSPGs targeting compounds, we identified an integrin-binding antibody, an integrin binding scFv, an RGD-mimetic compound and an HSPGs-binding peptide as inhibitors of EV uptake. Inhibition was validated in a dose dependent manner and toxicity studies did not show adverse effects. Three of those inhibitors, targeting either ITGB3/ITGAV or HSPGs were tested in mice models in vivo and all inhibitors could significantly reduce the formation of metastasis and strongly increase the overall survival. CONCLUSION: We have identified four drug candidates that target the ITGav/B3/HSPGs complex and are able to prevent EV uptake, demonstrating that EV uptake is a druggable process. Even more, the inhibitors tested in vivo could strongly reduce metastasis formation and increase overall survival. This data supports our hypothesis, that targeting EV mediated intercellular communication is a valuable approach to combat cancer metastasis. Citation Format: Elena Muro-Blanc, Rocío Bayona-Ramón y Cajal, Marta Cano-Galietero, Sara García-Ortega, Chiara Falciani, Luisa Bracci, Alberto J. Schuhmacher, Stefan Hümmer, Santiago Ramón y Cajal. Integrin avb3 and HSPG targeting agents prevent extracellular vesicles uptake and breast cancer metastasis abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 4122.