Extracellular vesicle-derived CDCP1 promotes chemoresistance and macrophage polarization in breast cancer.

Breast cancer derived extracellular vesicles (EVs) mediate tumor progression through surface protein-dependent intercellular communication; however, their molecular heterogeneity remains poorly characterized. In this study, we employed a proximity-dependent barcoding assay (PBA) together with patient-derived organoid (PDO) models and identified CDCP1 as a key driver of EV-mediated oncogenesis. PBA-based surface proteomics revealed CDCP1 as the most upregulated protein in breast cancer-derived EVs compared with EVs from normal tissues. Clinical validation confirmed elevated CDCP1 expression in tumor tissues and matched EVs. PDOs generated from fresh clinical specimens recapitulated CDCP1 expression levels of the parental tumors and secreted CDCP1-enriched EVs. Functional experiments showed that CDCP1-knockdown EVs suppressed PDO proliferation and sensitized tumors to chemotherapy. Mechanistically, CDCP1-positive EVs promoted macrophage polarization toward an M2 phenotype, accompanied by upregulation of IL-10 and TGF-β and CCL22. Multiplex immunofluorescence confirmed that CDCP1-high tumors exhibited increased co-localization of CD68⁺ and CD163⁺ macrophages. These results establish CDCP1 as a master regulator of EV driven breast cancer progression, linking surface proteome remodeling to chemo-resistance and immunosuppressive microenvironment reprogramming. The integration of single-EV profiling and PDO modeling establishes a translational framework for targeting CDCP1 as a promising therapeutic target and a candidate biomarker for future liquid biopsy development in aggressive breast cancer subtypes.