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). This evidence concerns the gene CXCL12 and cancer.