Exosomes in Breast Cancer - Mechanisms of Action and Clinical Potential

Extracellular vesicles (EV) are a heterogeneous group of cell-derived membrane vesicles comprising apoptotic bodies, microvesicles, and small EVs also called as exosomes. Exosomes when initially identified were considered as a waste product but the advancement in research techniques have provided insight into the important roles of exosomes in cell-cell communication, various biological processes and diseases, including cancer. As an important component of EVs, exosomes contain various biomolecules such as miRNAs, lipids, and proteins that largely reflect the characteristics of their parent cells. Notably, cancer cells generate and secrete many more exosomes than normal cells. A growing body of evidence suggests that exosomes, as mediators of intercellular cross-talk, play a role in tumorigenesis, cancer cell invasion, angiogenesis, tumor microenvironment (TME) formation, and cancer metastasis. As we gain more insights into the association between exosomes and cancer, the potential of exosomes for clinical use is becoming more intriguing. This review is focused on the role of exosomes in breast cancer, in terms of breast cancer biology, mechanism of action, potential as biomarkers, and therapeutic opportunities.