Having also established VLA-4 as the chief orchestrator of BM homing of CLL cells [4, 15], we here dissected its interplay with the CXCL12-CXCR4 axis, an important component of the BM homing machinery of lymphocytes and progenitor cells [27] in tri12 CLL. Here, CXCR4 is linked to B-cell chronic lymphocytic leukemia.