CXCR4 is a member of the chemokine receptor family and its endogenous ligand CXCL12 has been implicated in tumor development, including gliomas, facilitating angiogenesis, infiltration and metastasis through modulation of VEGF signaling, PAI-1 (plasminogen activator inhibitor-1) production and membrane type-2 matrix metalloproteinase expression (reviewed in [85], [86]). This evidence concerns the gene MMP15 and central nervous system cancer.