The lack of approved targeted
therapies highlights the need for new treatments for
triple-negative breast cancer (TNBC) patients.
Interleukin-3 (IL-3) acts as an autocrine factor for
tumor-endothelial cells (TEC), and exerts pro-angiogenic paracrine action via extracellular vesicles (EVs). IL-3Rα blockade on TEC changes TEC-EV (anti-IL-3R-EV)
microRNA (miR) content and promotes the regression of established vessels. As TEC is the doorway for "drug" entry into
tumors, we aimed to assess whether IL-3R blockade on TEC impacts
tumor progression via its unique EV cargo. First, the expression of IL-3Rα was evaluated in 27 human TNBC samples. It was noticed that, besides TEC and inflammatory cells,
tumor cells from 55.5% of the human TNBC samples expressed IL-3Rα. Using human TNBC cell lines for in vitro studies, we found that, unlike native TEC-EVs (nEVs), anti-IL-3R-EVs increase apoptosis and reduced cell viability and migration. In vivo, anti-IL-3R-EV treatment induced vessel regression in established
tumors formed of MDA-MB-231 cells, decreased
Vimentin, β-
catenin, and TWIST1 expression, almost abolished liver and lung
metastases from primary
tumors, and reduced lung
metastasis generated via the
intravenous injection of MDA-MB-231 cells. nEVs depleted of miR-24-3p (antago-miR-24-3p-EVs) were effective as anti-IL-3R-EVs in downregulating TWIST1 and reducing metastatic lesions in vivo. Consistent with network analyses of miR-24-3p gene targeting, anti-IL-3R-EVs and antago-miR-24-3p-EVs upregulate SPRY2 in MDA-MB-231 cells. Finally, SPRY2 silencing prevented anti-IL-3R-EV and antago-miR-24-3p-EV-mediated apoptotic cues.Overall, these data provide the first evidence that IL-3Rα is highly expressed in TNBC cells, TEC, and inflammatory cells, and that IL-3Rα blockade on TEC impacts
tumor progression.