CXCR4 and B-cell chronic lymphocytic leukemia: By using the Eμ-TCL1 model, Chen et al. showed that downregulation of surface CXCR4 expression and inhibition of CXCR4 downstream signaling in CLL cells can be observed upon treatment with the clinically approved Bruton’s tyrosine kinase (BTK) inhibitor ibrutinib [25].