CXCL12 and neoplasm: Under hypoxia and starvation status, MSCs maintain their self-survival via autophagy, meanwhile, they release a lot of anti-apoptotic or pro-survival factors, such as VEGF, bFGF, PDGF, SDF-1α, insulin-like growth factor 1, 2 (IGF-1,2), transforming growth factor-β (TGF-β) and insulin-like factor binding protein-2 (IGFBP-2) [144-146] to prevent tumor cells from apoptosis and support their proliferation, while normal MSCs do not take this properties.