CXCL12 and neoplasm: Potential mechanisms by which tumour macrophages can stimulate blood vessel growth include the secretion of pro-angiogenic factors (such as Vegfa, Egf, Fgf2, Cxcl8 and Cxcl12) to promote the proliferation and migration of endothelial cells through the graft and also the secretion of enzymes that stimulate the breakdown of the extracellular matrix (ECM) (such as uPA or Mmp2 and 9) (Albini et al., 2018).