CCL2 and neoplasm: The bone system expresses several growth factors, such as insulin-like growth factor type 1 (IGF-1), fibroblast growth factor (FGF), platelet-derived growth factor (PDGF), transforming growth factor beta (TGF-β), vascular endothelial growth factor (VEGF), hypoxia-inducible factor (HIF), and some cytokines, like interleukin 11 (IL-11), as well as chemokines, including monocyte chemotactic protein 1 (MCP-1), which are associated with the development of a microenvironment that supports tumor cell proliferation [2,4,5].