Surprisingly, although NOTCH1 has been reported to regulate numerous chemokine receptors in T-ALL (CCR5, CCR7, and CCR9; see below) this is not true for CXCR4 (21, 43), suggesting that NOTCH1 activation is not responsible for the increased CXCR4 expression. This evidence concerns the gene CCR5 and acute lymphoblastic leukemia.