CXCR4 and neoplasm: For example, transforming growth factor β (TGF-β), stroma-derived factor (SDF1), and osteoprotegerin (OPG) (activates the SDF-1/CXCR4 axis) [355], activated plasminogen, the progelatinases MMP-1/9, MIF, and IL-6 induce migration of MSC to OS cells and promote tumor growth and metastasis through neovascularization [352].