CXCR4 and cancer: We region selectively treated this endothelium with various combinations of CXCL12, TNF-α and AMD3100, a specific inhibitor of CXCL12 binding to CXCR4 but not CXCR7 [30] To eliminate confounding effects from cancer cell signaling we focused on 231-control breast cancer cells, which do not express CXCR4 or CXCR7, bind bioluminescent chemokine, or signal in response to CXCL12 (Figure 3A, B) (Luker et al, manuscript In Press).