CXCR4 and B-cell chronic lymphocytic leukemia: Thus, besides decreasing CXCR4 expression and altering CLL cell trafficking, ibrutinib, and SEL24-B489 also inhibited CXCL12/CXCR4-mediated CLL cell-tumor microenvironment cross-talk signaling, such as induction of cell survival and CD20 upregulation (131, 144).