VEGFA and neoplasm: In addition to exosomes, primary tumor cells release nonencapsulated growth factors (e.g., VEGF or transforming growth factor β1), cytokines (e.g., tumor necrosis factor α) or chemokines (e.g., CXCL12) which recruit to the target metastatic site(s)’ highly mobile, poorly differentiated cells which are normally involved in tissue repair, such as mesenchymal stem cells and bone marrow-derived myeloid cell precursors [105].