CXCL12 binds CXCR4 on CLL cells, is a dominant factor in the homing of CLL cells to bone marrow, and activates different intracellular signaling cascades associated with chemotaxis and leukemia cell survival, including STAT3 (6, 9, 23, 44). This evidence concerns the gene CXCL12 and B-cell chronic lymphocytic leukemia.