Taken together these results provide further evidence of a direct role of STAT5 in the regulation of human DPF3 gene via binding to its promoter and suggest that the increased DPF3 expression in PBMCs and granulocytes of CLL patients is the result of an increase in STAT5 binding to the promoter of DPF3. Here, DPF3 is linked to B-cell chronic lymphocytic leukemia.