CD133 Shapes Extracellular Vesicle Cargo and Angiogenic Function in Basal‐Like Triple‐Negative Breast Cancer

Extracellular vesicles (EVs) are central mediators of tumour‐stroma communication, yet the mechanisms governing their biogenesis and functional cargo remain poorly understood. Here, we identify CD133 (Prominin‐1), selectively expressed in basal‐like triple‐negative breast cancer (BL‐TNBC) cells, acts as a key organizer of EV production and cargo composition. CD133 localizes to plasma membrane protrusions and lipid rafts, where it maintains membrane architecture, promotes EV release and directs selective cargo loading, including the pro‐angiogenic factor CD105. Functionally, CD133 + EVs potently induce endothelial tubulogenesis in a CD105‐dependent manner, independently of differences in EV association or endothelial proliferation. In vivo, these EVs preferentially accumulate in the lung and liver, highlighting organ‐specific communication. Mechanistically, CD133 maintains lipid raft integrity, facilitating selective CD105 incorporation into vesicles and establishing a spatially coordinated CD133‐CD105 axis. Together, our findings define a subtype‐specific EV population whose identity and angiogenic activity are dictated by membrane organization. By linking protrusion architecture to vesicle‐mediated signalling, this study highlights CD133‐enriched EVs as potential biomarkers and therapeutic targets in aggressive BL‐TNBC.