They showed that in the tumor microenvironment (TME) there is a chemotactic gradient consisting of different chemokines, cytokines, and growth factors including CCL2, CCL5, CXCL12, CXCL13, CXCL16, NT-3, GM-CSF, G-CSF, VEGF, MCP1, MIP-1α, TGF-β, SCF-c-Kit, HGF/c- Met, SDF-1, TNF-α, IL-8, IL-1β, IL-6, IL-3, and UPAR, which are able to recruit MSCs. The gene discussed is CCL2; the disease is neoplasm.