CXCR4 and breast carcinoma: Several investigations report a role for the chemokine receptor CXCR4 and its ligand CXCL12 in site-specific metastasis [84–87], where neutralization of the CXCL12/CXCR4 interaction significantly impaired metastases formation in lymph nodes, bone, and lung in metastatic breast cancer models [84, 87].