Abstract: Objective:To investigate growth inhibition of depsipeptide combined with cytorabine or doxorubicin on human leukemia K562 and HL-60 cells,and analyze synergistic or antagonistic effect of combined agents.Methods:The MTT assay was used to test growth inhibition after 48h of exposure to depsipeptide,cytorabine,doxorubicin alone or two agents.The drugs interaction were analyzed by using the median-effect method of Chou and Talalay.Results:①The growth inhibition of K562 or HL-60 was dose-dependent after exposure to depsipeptide,cytorabine,doxorubicin alone or two agents.②The interaction of depsipeptide with cytorabine or doxorubicin were antagonistic at lower concentration,and synergistic at higher concentration.③ The ratio of drug concentration could influence the combination index（CI）.Conclusion:As a new antitumor agent,the histone deacetylase inhibitor depsipeptide could inhibit the proliferation of human leukemia K562 and HL-60 cells effectively.Depsipeptide combined with the chemotherapeutic drugs cytorabine or doxorubicin could display synergistic activity.The ratio of drug concentration is a significant factor that influence on the growth inhibition.