CXCR4 and B-cell chronic lymphocytic leukemia: In line, the few residual CLL cells in no tri12 samples that were able to home to BM under CXCL12-CXCR4 blockage displayed elevated CXCR4 levels, suggesting a selection or rescue mechanism occurring in this CXCR4 high subpopulation (Supplemental Figure 2B).