To investigate the significance of Class I HDACs (HDAC1, HDAC2, HDAC3, and HDAC8), HDAC11, and Klfs (Klf1, KLf3, Klf4, and Klf7) in the pathogenesis of human leukemia, we used real-time RT-PCR to evaluate the expression of HDACs and Klfs in bone marrow samples from human leukemia patients. The gene discussed is KLF4; the disease is leukemia.