CLDN3 and breast cancer: An investigative literature search of the working list of identified potential biomarkers revealed a subset of proteins with known relevance in cancer and BC that have not yet been studied in the context of EVs: Suppressor of tumorigenicity 14 protein (ST14; MDA-MB-231 and MCF7 sEV-specific), Claudin-3 (CLDN3; MCF7 sEV-specific), Tyrosine-protein kinase receptor UFO (AXL—MDA-MB-231 sEV-specific), and Integrin alpha-7 (ITGA7; MCF10A sEV-specific).