Using the Eμ-TCL1 murine model of CLL (132), as well as human CLL cells, Chen et al. (130) showed that BTK inhibition by ibrutinib decreased CXCR4 membrane expression along with a rapid release of CLL cells from spleen and LNs to the circulation. The gene discussed is CXCR4; the disease is B-cell chronic lymphocytic leukemia.