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.

缺乏批准的靶向疗法凸显了三阴性乳腺癌（TNBC）患者对新疗法的需求。白介素 3 (IL-3) 作为肿瘤内皮细胞 (TEC) 的自分泌因子，并通过细胞外囊泡 (EV) 发挥促血管生成旁分泌作用。IL-3Rα 对 TEC 的阻断会改变 TEC-EV（抗 IL-3R-EV）microRNA (miR) 含量并促进已建立血管的消退。由于 TEC 是“药物”进入肿瘤的门户，我们旨在评估 TEC 上的 IL-3R 阻断是否通过其独特的 EV 货物影响肿瘤进展。首先，评估了 27 份人类 TNBC 样本中 IL-3Rα 的表达。人们注意到，除了TEC和炎症细胞外，55.5%的人类TNBC样本中的肿瘤细胞表达IL-3Rα。使用人类 TNBC 细胞系进行体外研究，我们发现，与天然 TEC-EV (nEV) 不同，抗 IL-3R-EV 会增加细胞凋亡并降低细胞活力和迁移。在体内，抗 IL-3R-EV 治疗诱导由 MDA-MB-231 细胞形成的已建立肿瘤中的血管消退，降低波形蛋白、β-连环蛋白和 TWIST1 表达，几乎消除原发肿瘤的肝和肺转移，并减少肺转移通过静脉注射 MDA-MB-231 细胞产生转移。耗尽 miR-24-3p 的 nEV（antago-miR-24-3p-EV）可作为抗 IL-3R-EV 有效下调 TWIST1 并减少体内转移性病变。与 miR-24-3p 基因靶向的网络分析一致，抗 IL-3R-EV 和 antago-miR-24-3p-EV 上调 MDA-MB-231 细胞中的 SPRY2。最后，SPRY2 沉默阻止了抗 IL-3R-EV 和 antago-miR-24-3p-EV 介导的细胞凋亡信号。

总体而言，这些数据提供了第一个证据，证明 IL-3Rα 在 TNBC 细胞、TEC 和炎症细胞中高表达，并且 IL-3Rα 对 TEC 的阻断会影响肿瘤进展。