We compared 231-control cells to MDA-MB-231 cells stably expressing CXCR4 (231-CXCR4) or CXCR7 (231-CXCR7) (Figure 3A, B) to assess effects of CXCL12 chemokine receptors on cancer cells in mediating adhesion onto the microfluidic endothelium. Here, CXCL12 is linked to cancer.