title: PSC833, cyclosporine analogue, downregulates MDR1 expression by activating JNK/c-Jun/AP-1 and suppressing NF-kappaB.
abstract: OBJECTIVE
  Multidrug resistance (MDR) is one of the major causes of clinical cancer chemotherapy failure. PSC833 is well known as a non-immunosuppressant cyclosporine analogue that functionally inhibits P-glycoprotein (Pgp), a product of the MDR1 gene. We investigated whether PSC833 could also alter MDR1 expression and, if so, which mitogen-activated protein kinases (MAPKs) and nuclear factor-kappaB (NF-kappaB) pathways were involved in this event.
  
  
  METHODS
  MTT assay and flow cytometry were used for the analysis of cytotoxicity and intracellular drug accumulation, respectively. RT-PCR and Western blot assays for analysis of gene expression and electrophoretic mobility shift assays for determination of DNA-binding activity of transcription factors were used.
  
  
  RESULTS
  The doxorubicin-resistant lung cancer cell subline (SK-MES-1/DX1000), selected from SK-MES-1/WT cells, upregulated MDR1 expression, thereby showing MDR phenotypes. PSC833 sensitized SK-MES-1/DX1000 cells to doxorubicin. PSC833 (5 microM) also decreased the intracellular accumulation of fluorescent Pgp substrates such as rhodamine 123 and daunorubicin in SK-MES-1/DX1000 cells. PSC833 downregulated MDR1 mRNA and Pgp expression in a time- and concentration-dependent manner. PSC833 activated c-Jun NH2-terminal kinase (JNK)/c-Jun and enhanced AP-1 DNA-binding activity, but suppressed nuclear translocation of NF-kappaB, all of which were prevented by pretreatment with a JNK inhibitor SP600125.
  
  
  CONCLUSIONS
  These results indicate that PSC833 not only sensitizes SK-MES-1/DX1000 cells to doxorubicin by enhancing drug accumulation, but also downregulates MDR1 expression by activating JNK/c-Jun/AP-1 and suppressing NF-kappaB.
authors.affiliation: Department of Pharmacology, Research Center for Resistant Cells, Chosun University Medical School, 375 Seosuk-dong Dong-gu, Gwangju, 501-759, Korea.
authors.forename: H
authors.initials: H
authors.lastname: Bark
authors.forename: Cheol-Hee
authors.initials: CH
authors.lastname: Choi
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics* / Q000378:metabolism; D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D003524:Cyclosporins / Q000494:pharmacology*; D015536:Down-Regulation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D009841:Oligonucleotides / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D051996:Transcription Factor RelA / Q000378:metabolism
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D003524:Cyclosporins; D016328:NF-kappa B; D009841:Oligonucleotides; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D051996:Transcription Factor RelA; D051550:I-kappa B Kinase; D048031:JNK Mitogen-Activated Protein Kinases; C070272:valspodar