CXCR4 and breast cancer: While CXCR4 or CXCR7 expression on circulating breast cancer cells increased adhesion to endothelium (Figure 3C), CXCL12-dependent enhancements in adhesion or adhesion selectivity were, surprisingly, statistically the same (Figure 3D) (p = 0.48) and therefore independent of expression of CXCR4 or CXCR7 on cancer cells.