The role of CXCR4 in CLL has been thoroughly investigated and it has become clear that the CXCR4-CXCL12 axis is essential for CLL cells and their interaction with the microenvironment, especially in response to BTK inhibition with ibrutinib [17, 25]. The gene discussed is CXCR4; the disease is B-cell chronic lymphocytic leukemia.