Document Detail

Increased AP-1 activity in drug resistant human breast cancer MCF-7 cells.
MedLine Citation:
PMID:  10369069     Owner:  NLM     Status:  MEDLINE    
The expression, DNA binding, and transactivating activity of activator protein 1 (AP-1) was examined in a series of multidrug resistant (MDR) MCF-7 human breast cancer cells that have increasing levels of MDR1 gene expression. We observed an increase in the amount of both c-jun and c-fos mRNA in cells with 12-, 65-, or 200-fold higher resistance to adriamycin when compared to drug-sensitive MCF-7 wild type (WT) cells. Electrophoretic mobility shift assays (EMSA) demonstrated an increase in the DNA binding activity of an AP-1 complex in nuclear extracts from MDR MCF-7 cells when compared to extracts from WT cells. We observed a proportional increase in luciferase expression from a reporter vector containing consensus AP-1 binding sites in transiently transfected MDR cells when compared to WT cells, indicating that AP-1 mediated gene expression is increased in drug-resistant MCF-7 cells. Since the MDR1 promoter contains a putative AP-1 binding site, we used EMSA to examine AP-1 binding activity to an oligonucleotide probe that contained the relevant MDR1 promoter sequences (-123 to -108). Nuclear extracts from resistant MCF-7 cells displayed an increased level of DNA binding of Jun/Jun dimers to the probe, indicating that AP-1 was capable of binding to this promoter site. A luciferase reporter construct containing triplicate copies of the MDR1 promoter sequence was expressed at higher levels in transiently transfected MDR cells when compared to expression in WT cells. Co-transfection of WT cells with a c-jun expression vector and either of the AP-1 luciferase constructs demonstrated that c-jun could activate gene expression from both the consensus and the MDR1 AP-1 sites in a dose dependent manner. In addition, RT-PCR and western blot analysis showed that levels of MDR1 mRNA and Pgp were increased in c-jun transfected WT cells. Taken together, these data indicate that increased AP-1 activity may be an important mediator of MDR by regulating the expression of MDR1.
P J Daschner; H P Ciolino; C A Plouzek; G C Yeh
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Breast cancer research and treatment     Volume:  53     ISSN:  0167-6806     ISO Abbreviation:  Breast Cancer Res. Treat.     Publication Date:  1999 Feb 
Date Detail:
Created Date:  1999-09-10     Completed Date:  1999-09-10     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  8111104     Medline TA:  Breast Cancer Res Treat     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  229-40     Citation Subset:  IM    
Intramural Research Support Program, SAIC, NCI-FCRDC, Frederick, MD 21702, USA.
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MeSH Terms
Blotting, Western
Breast Neoplasms / metabolism*
Cell Nucleus / metabolism
DNA / metabolism
Doxorubicin / pharmacology
Drug Resistance, Neoplasm
Electrophoresis, Polyacrylamide Gel
Gene Expression / drug effects
P-Glycoprotein / genetics,  metabolism
Paclitaxel / pharmacology
Promoter Regions, Genetic / drug effects
Proto-Oncogene Proteins c-fos / biosynthesis
Proto-Oncogene Proteins c-jun / biosynthesis
RNA, Messenger / metabolism
Reverse Transcriptase Polymerase Chain Reaction
Transcription Factor AP-1 / metabolism*
Tumor Cells, Cultured
Up-Regulation / drug effects
Vinblastine / pharmacology
Grant Support
Reg. No./Substance:
0/P-Glycoprotein; 0/Proto-Oncogene Proteins c-fos; 0/Proto-Oncogene Proteins c-jun; 0/RNA, Messenger; 0/Transcription Factor AP-1; 23214-92-8/Doxorubicin; 33069-62-4/Paclitaxel; 865-21-4/Vinblastine; 9007-49-2/DNA

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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