The C-X-C chemokine receptor-4 (CXCR4) is a seven-transmembrane G-protein coupled receptor (GPCR). It is a member of the family I GPCR or rhodopsin-like GPCR family. The chemokine stromal cell-derived factor-1 (SDF-1 or CXCL12) is a CXC chemokine peptide. Meanwhile, it is the natural ligand for CXCR4. Importantly, the CXCR4...