The chemokine receptor C-X-C chemokine receptor type 4 (CXCR4) and its ligand stromal-cell-derived factor 1 (SDF-1, also known as CXCL12) mediates the homing and migration process in ALL.8 Sipkinset al. demonstrated that B-ALL cells selectively homed to adhesion molecule E-selectin and SDF-1-expressing vesselsvia a CXCR4-dependent process. This evidence concerns the gene SELE and acute lymphoblastic leukemia.