Modulation of Klf4 levels by altering shRNA or using an ectopic expression vector can mimic the effects of HDAC1 on cell proliferation, cell cycle, and the expression level of p21 and p27 in human leukemia cell lines K562, HL-60, and U937 (Figures 3b and f). The gene discussed is CDKN1B; the disease is leukemia.