Experimental Study On The Impact Of Leukemia Cells, The Proteasome Inhibitor

PartⅠEffects of proteasome inhibitor bortezomib on NF-κB activation and ICAM-1 mRNA expression of K562 cellsObjective To investigate the effects of proteasome inhibitor bortezomib (Valcade,PS-341)on the activation of NF-κB and the expression of intercellular adhesion molecule-1(ICAM-1)in K562 cells.Methods The K562 cells were incubated in the culture of RPMI1640 with 10%calf serum in 12-well plate and exposed to 0,10,20,30,50,100nM bortezomib for 6 hours.The activation of NF-κB were analyzed by SP immunohistochemistry,meanwhile RT-PCR was performed to measure expressions of ICAM-1.Results1.The activation of NF-κB was analyzed by SP immunohistochemistry:The positive rate and positive value of NF-κB in control group were 95.00±2.00%and 290.33±20.50.And the positive rates of the treatment groups were 84.67±3.51%,77.33±2.52%,66.67±4.16%,58.33±7.64%, 48.67±3.21%.They were decreased significantly compared to the control group(P＜0.05).2.Analysis of ICAM-1 expression by RT-PCR:The expression in translational level of ICAM-1 in control group was 0.7198±0.0562.And the levels of the treatment groups were 0.5795±0.0282,0.4305±0.0608,0.3570±0.0342,0.3120±0.0501,0.3190±0.0333. The expressions of ICAM-1 were decreased significantly after bortezomib treatment(P＜0.01).3.The inhibitory effect on ICAM-1 was positively related with that of the activation of NF-κB.Conclusions It is concluded that proteasome inhibitor bortezomib downregulates the expression of K562 cells ICAM-1 by inhibiting the activation of NF-κB,which provides a new way for the treatment in the acute leukemia.PartⅡEffects of Bortezomib and arabinoside on cell line K562 in vitroObjective To investigate the effect of bortezomib alone and in combination with arabinoside(Ara-C)on inhibitory effects and apoptosis of acute myeloblastic leukemia(K562)cell line.Methods K562 cells were treated with 20nM bortezomib and 0.2ug/ml arabinoside in different groups for 48h.MTT was used to study the inhibitory effects on K562 cells growth and the apoptosis rate was analysed by flow cytometry.Treated respectively with 20nM bortezomib and 0.2ug/ml arabinoside for 6 hours,the activity of NF-κB was analyzed by SP immunohistochemistry,meanwhile the change of cell cycle by flow cytrmetry.Results The inhibition ratio and apoptosis to K562 cells in combination groups were higher than those in the two single groups(P＜0.05).Those especial in group C which combined treatment of Ara-C with Bor 6h later were highest(81.54±3.95%and 29.17±3.1%,respectively)in the three combination groups(P＜0.05).Treated with 20nM bortezomib for 6 hours, the activity of NF-κB was decreased significantly,and the cells were apparently arrested in G2/M phase.Treated with 0.2ug/ml arabinoside for 6 hours,the activity of NF-κB was increased significantly,and the cells were apparently arrested in G1 phase.Conclusions Bortezomib could effectively inhibit K562 cell proliferation, and induced its apoptosis.These effects were enhanced significantly when in combination with arabinoside,especially pretreated with Ara-C.These effects were probably related to the changes of NF-κB activity and cell cycle.