CXCR4 expression was found to be essential for T-ALL maintenance and progression (22, 23) with loss of CXCL12/CXCR4 signaling leading to reduced Myc expression (a transcription factor directly regulated by NOTCH1) and previously linked to leukemia initiating cell activity in T-ALL. This evidence concerns the gene CXCR4 and acute lymphoblastic leukemia.