The Study On The Mechanism Of Apoptosis By Bortezomib And Imatinib In K562 Cells

BackgroundLeukemia is a group of heterogeneous malignancy of hematopoietic system in which the hematopoietic stem cells and progenitor cells have a malignant change,and the cells blocked in different stages of haematogenesis lose the ability of further differentiation and maturation.Although the effectivity treatment has been increased in recent years,there are still a considerable numbers of refractory cases of leukemia due to relapse or drug resistance,it is particularly important for us to seek new methods of treatment in the current.Bortezomib,which is the first proteasome inhibitor to enter clinical trials,has been widely used for patients with refractory and relapsed hematological malignancy.In vitro studies,bortezomib had shown a good effect on a variety of malignant tumors cells including K562 cell,but the mechanism is not clear,and there is no correlative literature about the combination of bortezomib and imatinib was reported.In this experiment,we choose bortezomib in combination with imatinib,to observe the depressant effect on human K562 cells,to study if proteasome inhibitor can increase K562 cells'sensibility to imatinib and co-induct the cells'apoptosis and to explore the mechanism, and this will provide a theoretical basis for the treatment of leukemia.MethodsThe object was divided into eight group as the density of bortezomib and imatinib.The time was divided into three phases: 12h,48h,72h.To detect the change of correlated index:(1)The cell proliferating activity was assessed with MTT assay;(2)Cell apoptotic rate was examined by floe cytometry(FCM);(3)The expression of Livin mRNA was detected by semi-quantitate reservese transcripition polymers chain reaction(RT-PCR).Result(1)MTT assay displayed that:At the same time,compared with contral group,both single drug group and combination group can decrease the K562 cells'survival rate which in a dose-dependent manner.The suvival rate of each group at the same consistency drug group is lowest after treating for 48h.The suppressant effect of combination group obviously outweigh the single group.The survival rate is lowest as 37.67 % when treated for 48h with bortezomib(10nmol/L) in combined with imatinib. (2)FCM analysis showed that the effect of each group is the most marked when treated for 48h,and cells'apoptotic rate appeared dose-dependent manner in each group at the same time point.Bortezomib can stengthen the apoptotic effect of imatinib.The apoptosis rate rised from 10.15%(imatinib alone for 48h) to 56.42% when combination treatment(10nmol/L bortezomib) is given.(3)RT-PCR disclosed that the expression of Livin mRNA was decresed by bortezomib or imatinib alone to some extent ,which in a dose-dependent manner and up to the ceiling effect when treated for 48h.It was downregulated significantly when combined treatment was given,in which the expression of Livin mRNA is the lowest when treated with imatinib in combined with bortezomib(10nmol/L) for 48h.ConclusionBortezomib alone and in combination with imatinib can induce K562 cells apoptosis ,in which decrease of the expression of Livin mRNA is the possible mechanism.