Cancer-derived extracellular vesicles: the 'soil conditioner' in breast cancer metastasis?

It has been recognized that cancer-associated mortality is more often a result of the disrupted physiological functions in multiple organs following metastatic dissemination of cancer cells, rather than the presence and growth of the primary tumor. Despite advances in our understanding of the events leading to cancer initiation, growth, and acquisition of invasive properties, we are still unable to effectively treat metastatic disease. It is now being accepted that the secretion of extracellular vesicles, such as exosomes from cancer cells, has a profound impact on the initiation and propagation of metastatic breast cancer. These cancer-secreted vesicles differ from other means of cellular communication due to their capability of bulk delivery and organotropism. Here, we provide an overview of the role of extracellular vesicles in breast cancer metastasis and discuss key areas that may facilitate our understanding of metastatic breast cancer to guide our efforts towards providing better therapies.