Proteomics Study of Breast Cancer-Derived Small Extracellular Vesicles: Unveiling Potential Cancer Biomarkers.

Small extracellular vesicles (sEVs) are lipid-bilayer-enclosed vesicles secreted by cells into the extracellular environment, carrying a variety of biomolecules, including proteins that reflect the molecular profile of their cell of origin. In particular, cancer-derived sEVs hold significant potential for cancer diagnosis due to their unique biomolecular content. In this study, we utilized mass spectrometry to profile the protein expression in plasma-derived sEVs from both healthy controls (HCs) and breast cancer (BC) patients with the aim of discovering new protein biomarkers for potential BC diagnosis. Through the cross-validation of differentially expressed proteins between the two independent cohorts, we identified nine proteins that were significantly upregulated in BC-derived sEVs. Further validation using online gene expression data sets, Western blot, and ELISA revealed that OIT3 was upregulated in BC tissue compared to HC tissue, suggesting its potential as a novel BC biomarker. These findings contribute to advancing the knowledge of proteins within sEVs, as well as offering promising avenues for the use of sEVs as biomarkers in future cancer diagnostic applications.