title: Upregulation of mdr1 gene is related to activation of the MAPK/ERK signal transduction pathway and YB-1 nuclear translocation in B-cell lymphoma.
abstract: OBJECTIVE
  Multidrug resistance (MDR) in human B-cell lymphoma constitutes a major obstacle to the effectiveness of chemotherapy. The aim of this study was to investigate the molecular mechanism of MDR in B-cell lymphoma.
  
  
  METHODS
  The B-cell lymphoma MDR sublines were developed by exposing the parental Daudi cells to stepwise increasing concentrations of doxorubicin. Interaction of Y-box binding protein-1 (YB-1) with the Y-box motif of the mdr1 gene promoters was studied by electrophoretic mobility shift assay. The effects of YB-1 on mdr1 promoter activity were examined by luciferase assay. After silencing of YB-1 gene by shRNA, the role of YB-1 nuclear translocation in the formation of induced MDR was examined. Expression of mdr1 and YB-1 was examined further after Daudi cells were pretreated with mitogen-activated protein kinase (MAPK) inhibitor PD98059 for 1 hour.
  
  
  RESULTS
  Doxorubicin-resistant sublines was generated from the Daudi cell line by stepwise selection in doxorubicin. We found that acquisition of MDR is associated with enhanced YB-1 nuclear translocation and MAPK/extracellular signal-regulated kinase (ERK) activity. Electrophoretic mobility shift assay revealed that doxorubicin increased binding of YB-1 to the Y-box of mdr1 promoter. Luciferase reporter assays demonstrated that the Y-box region is essential for YB-1 regulation of mdr1 expression. The introduction of exogenous YB-1 shRNA into Daudi cells resulted in decreased levels of the expression of mdr1 gene and P-glycoprotein induced by doxorubicin. When Daudi cells were pretreated with MAPK inhibitor PD98059, the phosphorylation of ERK was effectively inhibited as well as the nuclear translocation of YB-1 and the expression of mdr1 gene.
  
  
  CONCLUSIONS
  Doxorubicin can increase expression of mdr1/P-glycoprotein through activating MAPK/ERK transduction pathway, then increasing expression of YB-1, inducing YB-1 nuclear translocation, and enhancing DNA-binding activity of YB-1.
authors.affiliation: Key Laboratory of Human Functional Genomics of Jiangsu Province, Nanjing Medical University, 140 Hanzhong Road, Nanjing, PR China.
authors.forename: Huiling
authors.initials: H
authors.lastname: Shen
authors.forename: Wenlin
authors.initials: W
authors.lastname: Xu
authors.forename: Wenjuan
authors.initials: W
authors.lastname: Luo
authors.forename: Leilei
authors.initials: L
authors.lastname: Zhou
authors.forename: Wei
authors.initials: W
authors.lastname: Yong
authors.forename: Fang
authors.initials: F
authors.lastname: Chen
authors.forename: Chaoyang
authors.initials: C
authors.lastname: Wu
authors.forename: Qiaoyun
authors.initials: Q
authors.lastname: Chen
authors.forename: Xiao
authors.initials: X
authors.lastname: Han
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics* / Q000378:metabolism; D002467:Cell Nucleus / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004317:Doxorubicin / Q000494:pharmacology; D006801:Humans; D016393:Lymphoma, B-Cell / Q000235:genetics* / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000235:genetics*; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics*; D014162:Transfection; D014407:Tumor Cells, Cultured; D015854:Up-Regulation / Q000235:genetics*; D051840:Y-Box-Binding Protein 1
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D051840:Y-Box-Binding Protein 1; C070856:YBX1 protein, human; D004317:Doxorubicin