Integrated transcriptomics, proteomics, and functional analysis to characterize the tissue‐specific small extracellular vesicle network of breast cancer

Small extracellular vesicles (sEVs) are essential mediators of intercellular communication within the tumor microenvironment (TME). Although the biological features of sEVs have been characterized based on in vitro culture models, recent evidence indicates significant differences between sEVs derived from tissue and those derived from in vitro models in terms of both content and biological function. However, comprehensive comparisons and functional analyses are still limited. Here, we collected sEVs from breast cancer tissues (T‐sEVs), paired normal tissues (N‐sEVs), corresponding plasma (B‐sEVs), and tumor organoids (O‐sEVs) to characterize their transcriptomic and proteomic profiles. We identified the actual cancer‐specific sEV signatures characterized by enriched cell adhesion and immunomodulatory molecules. Furthermore, we revealed the significant contribution of cancer‐associated fibroblasts in the sEV network within the TME. In vitro model‐derived sEVs did not entirely inherit the extracellular matrix‐ and immunity regulation‐related features of T‐sEVs. Also, we demonstrated the greater immunostimulatory ability of T‐sEVs on macrophages and CD8+ T cells compared to O‐sEVs. Moreover, certain sEV biomarkers derived from noncancer cells in the circulation exhibited promising diagnostic potential. This study provides valuable insights into the functional characteristics of tumor tissue‐derived sEVs, highlighting their potential as diagnostic markers and therapeutic agents for breast cancer.