Based on this result, the level of CXCR4, the SDF-1 receptor, in leukemia cells was further examined, finding that in the co-culture system, up-regulation of IFI6 could significantly increase the leukemia cell level of CXCR4 (Fig. 6B), while down-regulation of IFI6 yielded the opposite results (Fig. 6C, D). The gene discussed is IFI6; the disease is leukemia.