CXCR4 and glioblastoma: Among several chemokines and their receptors, CXC chemokine ligand 12 (CXCL12) and its two GPCR receptors, CXC type 4 (CXCR4) and type 7 (CXCR7), are mainly involved in the migration and the spreading of GBM cells into distant tissues.