The Study Of The Apoptotic Mechanism Of Multidrug Resistant Cell Line K562/A02 Induced By Tunicamycin

OBJECTIVE:The multidrug resistance (MDR) of leukemia played an important causative role in the treatment failure of patients with leukemia. Therefore, understanding the mechanism of MDR is very important for extending the survival of leukemia patients. Tunicamycin is an inhibitor of dolichol and can induce apoptosis through endoplasmic reticulum stress (ER stress). So, we investigated the effect of tunicamycin on the multidrug resistance (MDR) of human leukemic K562/A02 cells.METHODS:The MTT assay was used to test the toxicity of tunicamycin and the chemosensitivity to chemotherapeutics in tunicamycin-treated K562/A02 cells (IC50). The concentrations of the adriamycin(ADM) and Rhodamine 123 as well as the expression of Annexin V, Pgp and Caspase-3,8,9,12 were assayed by flow cytometry.RESULTS:The accumulation of ADM and Rhodamine was less in K562/A02 cells, which produced Pgp and showed drug resistance, than normal K562 cells. The inhibitory rates of K.562 and K562/A02 cells caused by tunicamycin were lower than 30% in the dose of 5ug/ml, and the IC50 were30.30ug/ml and 23.18ug/ml, respectively. K562/A02 cells seem to be more susceptible to tunicamycin than normal K562 cells. The tunicamycin (5ug/ml) partly reversed the MDR of K562/A02 cells. After exposure to 5ug/ml tunicamycin, the concentration of ADR and Rhodamine 123 were significantly increased while Pgp expression was not increased. The expression of Caspase-12 and 9 was also increased significantly after the treatment of tunicamycin. The combination of ADM and tunicamycin resulted in cell death in multidrug resistance cell line more significantly.CONCLUSION Tunicamycin can induce apoptosis of the multidrug resistance leukemic cells lines-K562/A02. The mechanism is related to the inhibition of Pgp function, but not the expression of P-gp. In addition to,the ER stress is also involved in the apoptotic effects of tunicamycin on K562/A02.