CXCR4 and central nervous system cancer: Chemokine (C-X-C motif) ligand 12 (CXCL12) and its receptors CXCR4 and CXCR7, which are stored in or attached to the ECM, are extremely important in forming a more invasive and resistant phenotype of glioma (Gatti et al., 2013; Zhao et al., 2018a).