title: Reversion of Multidrug-Resistance by Proteasome Inhibitor Bortezomib in K562/DNR Cell Line.
abstract: OBJECTIVE
  To observe the reversion of multi-drug resistance by proteasome inhibitor bortezomib in K562/DNR cell line and to analyze the possible mechanism of reversion of multidrug-resistance.
  
  
  METHODS
  MTT method was used to determine the drug resistance of K562/DNR cells and the cellular toxicity of bortezomib. K562/DNR cells were cultured for 12 hours, 24 hours and 36 hours with 100 μg/ml DNR only or plus 4 μg/L bortezomib. The expressions of NF-κB, IκB and P-gp of K562/DNR were detected with Western blot method, the activity of NF-κB was tested by ELISA method and the apoptosis rate was observed in each group respectively.
  
  
  RESULTS
  The IC50 of DNR on cells of K562/S and K562/DNR groups were 1.16 μg/ml and 50.43 μg/mL, respectively. The drug-resistant fold was 43.47. The IC10 of PS-341 on Cell strain K562/DNR was 4 μg/L. Therefore, 4 μg/L was selected as the concentration for PS-341 to reverse drug-resistance in this study. DNR induced down-regulation of IκB expression, up-regulation of NF-κB and P-gp expression. After treatment with PS-341, a proteasome inhibitor, the IκB degradation was inhibited, IκB expression increased, NF-κB and P-gp expression decreased in a time dependent manner. Compared to DNR group, the NF-κB p65 activity of DNR+PS-341 group was decreased. Compared to corresponding DNR group, DNR induced apoptosis rate increases after addition of PS-341 in a time dependent manner.
  
  
  CONCLUSIONS
  Proteasome inhibitor bortezomib can convert the leukemia cell drug resistance. The mechanism may be that bortezomib decreases the degradation of IκB and the expression of NF-κB and P-gp, therefore induces the apoptosis of multi-drug resistant cells.
authors: Department of Hematology, Shengjing Hospital, China Medical University, Shenyang 110004, China.
authors: Hui-Han
authors: HH
authors: Wang
authors: Ying-Chun
authors: YC
authors: Li
authors: Ai-Jun
authors: AJ
authors: Liao
authors: Bei-Bei
authors: BB
authors: Fu
authors: Wei
authors: W
authors: Yang
authors: Zhuo-Gang
authors: ZG
authors: Liu
authors: Xiao-Bin
authors: XB
authors: Wang
keywords: Bortezomib; K562 cells; Multi-drug resistance; NF-κB; P-gp; mdr1 gene