Effect Of JNK And Bim In K562 Leukemia Cell Resistance To Imatinib, KR

In recent years,the different classes of drugs and regimens used clinically have provided an improvement in tumor management.However,cellular resistance to anti-neoplastic drugs is the major reason why treatment of malignant tumors may fail. Multidrug resistance(MDR)is a type of resistance to structurally unrelated chemotherapeutic drugs,and is one of the main obstacles in the chemotherapy of cancer.MDR severely limits the effectiveness of themotherapy in a variety of common malignancies and is responsible for the overall poor efficacy of cancer chemotherapy.The mechanisms leading to MDR have not been well identified.The MDR of one class of chemotherapeutic drugs may come from the alteration of the level of the MDR genes and proteins.Furthermore,the MDR of one cancer may contain several mechanisms.Therefore,we should clarify the mechanisms underlying MDR and to develop agents either to inhibit or circumvent MDR mechanisms in order to find out effective and clinically applicable MDR therapies.To establish K562 leukemia cell resistance to Imatinib(KR)in vitro culture make for research on mechanisms of MDR as well as the effect of the cell signaling pathways in it.We established KR line through culturing K562 cells in gradually increased concentrations of Imatinib over a period of eight months,and identified the mechanisms of MDR in it. Obejective:To explore the role of c-Jun N-terminal kinase(JNK),one kinase of mitogen-activated protein kinase(MAPK),in the proliferation and apoptosis of K562 leukemia cell resistance to Imatinib(KR)and its molecular mechanism.Methods:1.To establish K562 leukemia cell resistance to Imatinib(KR)K562 cells were cultured in gradually increased concentrations of Imatinib over a period of eight months to generate their resistance line KR.Flow cytometric analysis were used to detect the cell cycle.2.To detect the change of protein levels of KR and K562The protein levels of Phospho-JNK and Bim in KR and K562 were detected by Western blot.3.To dect the drug susceptibility of KR and K562MTS/PES were used to affirm the effects of SP600125,a specific inhibitor of JNK, and/or Imatinib on KR and K562.Results:1.Establishment and culture of K562 leukemia cell resistance to Imatinib(KR)We found that KR cells could successfully survive in RPMI-1640 which contained 15%calf serum and 2μM Imatinib through in vitro culture.2.The alteration of protein levels of KR and K562In KR cells,the expression of Phospho-JNK protein was increased while the level of Bim was decreased compared with those of K562.The expression of Bim was upregulated in KR after blocking JNK activation by SP600125.3.Result of MTS/PESThe inhibition ratio of KR in medium containing 25nM SP600125 and 2.0μM Imatinib was significantly higher than that of KR in medium containing 2.0μM Imatinib only(P=0.003). Conclusion:1.The cell line of K562 leukemia cell resistance to Imatinib(KR)was successfully established.KR cells could survive in RPMI-1640 which contains 15%calf serum and 2μM Imatinib.Compared with K562,KR cells could grow in the medium containing higher concentration of Imatinib.2.There are activation of JNK signaling pathway and downregulation of proapoptotic protein,Bim,in KR cells.3.SP600125 can increase the expression of Bim and induce apoptosis in KR.It reverse the resistant ability of KR to Imatinib to some extent.