CXCR4 and neoplasm: Although the role of CXCR4 is better characterized in the tumor interstitium, the CXCR4/CXCL12 axis is also expressed in the tumor vasculature [46, 47] where it is known to promote angiogenesis and vascularization through induction of VEGF [48, 49] and/or recruitment of endothelial progenitor cells [50].