CCL2 and central nervous system cancer: Tumor cytokines such as endothelial cell growth factor (EGF), platelet-derived growth factor (PDGF), VEGF, tumor growth factor β1 (TGF-β1), interleukin 8 (IL-8), monocyte chemoattractant protein-1 (MCP-1), and stromal cell-derived factor 1 alpha (SDF-1α) as well as stem cells surface proteins such as CD44, CXC chemokine receptor 4 (CXCR-4), integrin α4, and TGF-β receptors have been associated with increased MSC homing in gliomas (Young et al., 2014; Yamazoe et al., 2015).