CCL2 and neoplasm: Similarly, the tumor environment consists of a large number of immune cells, which alongside tumor cells, secrete soluble factors such as VEGF, PDGF, IL-8, IL-6, basic fibroblast growth factor (bFGF or FGF2), stromal cell-derived factor 1 (SDF-1), granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony stimulating factor (GM-CSF), monocyte chemoattractant protein 1 (MCP1), hepatocyte growth factor (HGF), TGF-β and urokinase-type plasminogen activator receptor (UPAR), attracting MSCs (Ponte et al., 2007).