Chemokines are small molecular weight, soluble secreted proteins that bind and activate their respective G-protein coupled receptor (GPCR), chemokine receptors in order to evoke a cellular response resulting in migration or chemotaxis1.
The chemokine system involves more than 40 chemokines and 18 chemokine receptors. The receptors are designated CXCR1-5, CCR1-11, XCR1 and CX3CR1, based on their specific ligand preference2.
Chemokine receptors are present on many different cell types. They were initially detected on leukocytes, where they were found to play an important role in the migration of these cells to inflammation sites3.
CXCR4 was originally identified as an orphan receptor, and soon gained much attention when it was discovered as a coreceptor for HIV-14. Besides from being involved in HIV-1 infection/progression, CXCR4 is found to be upregulated in many different cancers/tumors and has evolved to become a target for the development of antagonists5. CXCL12 (SDF-1
