The RFI of CXCR4 expression on bone marrow leukemia cells was 6.31 ± 6.01 (median ± SD), as assessed using flow cytometry, and the value was significantly higher than control cells (1.19 ± 0.21, P ≤ 0.0001, Fig. 1A), indicating that CXCR4 expression was upregulated. This evidence concerns the gene CXCR4 and leukemia.