CXCR4 and B-cell chronic lymphocytic leukemia: TFPI could enhance the CXCL12-mediated transendothelial migration (TEM) of CLL cells by upregulating the expression of the CXCL12 receptor CXCR7 in the in vitro study, but not CXCR4; they also found that these biological effects could be eliminated by the CXCR7 inhibitor CCX771.