CXCL12 and cancer: During cancer development, hMSCs have been shown to release several factors, such as insulin-like growth factor 1 (IGF-1), stromal cell-derived factor 1 (SDF-1), TGF-β and vascular endothelial growth factor (VEGF), which play critical roles in promoting tumor growth, improving tumor angiogenesis, and altering tumor immunosurveillance [18–20,48].