2-acetylaminofluorene up-regulates rat mdr1b expression through generating reactive oxygen species that activate NF-kappa B pathway.
Overexpression of multidrug resistance genes and their encoded P-glycoproteins is a major mechanism for the development of multidrug resistance in cancer cells. The hepatocarcinogen 2-acetylaminofluorene (2-AAF) efficiently activates rat mdr1b expression. However, the underlying mechanisms are largely unknown. In this study, we demonstrated that a NF-kappa B site on the mdr1b promoter was required for this induction. Overexpression of antisense p65 and I kappa B alpha partially abolished the induction. We then delineated the pathway through which 2-AAF activates NF-kappa B. 2-AAF treatment led to the increase of intracellular reactive oxygen species (ROS) which causes activation of IKK kinases, degradation of I kappa B beta (but not I kappa B alpha), and increase in NF-kappa B DNA binding activity. Consistent with the idea that ROS may participate in mdr1b regulation, antioxidant N-acetylcysteine inhibited the induction of mdr1b by 2-AAF. Overproduction of a physiological antioxidant glutathione (GSH) blocked the activation of IKK kinase complex and NF-kappa B DNA binding. Based on these results, we conclude that 2-AAF up-regulates mdr1b through the generation of ROS, activation of IKK kinase, degradation of I kappa B beta, and subsequent activation of NF-kappa B. This is the first report that reveals the specific cis-elements and signaling pathway responsible for the induction of mdr1b by the chemical carcinogen 2-AAF.
Deng
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Department of Molecular Pathology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Lin-Lee
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YC
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Kuo
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D015073:2-Acetylaminofluorene / Q000494:pharmacology*; D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics* / Q000378:metabolism; D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D002273:Carcinogens / Q000494:pharmacology*; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005434:Flow Cytometry; D005786:Gene Expression Regulation / Q000187:drug effects*; D017930:Genes, Reporter; D006861:Hydrogen Peroxide / Q000494:pharmacology; D051550:I-kappa B Kinase; D020672:I-kappa B Proteins; D016328:NF-kappa B / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects; D011401:Promoter Regions, Genetic / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection; D014407:Tumor Cells, Cultured; D015854:Up-Regulation / Q000187:drug effects; D000097202:ATP-Binding Cassette Sub-Family B Member 4
D015073:2-Acetylaminofluorene; D018435:ATP Binding Cassette Transporter, Subfamily B; D000111:Acetylcysteine; D002273:Carcinogens; D004247:DNA; D004268:DNA-Binding Proteins; D006861:Hydrogen Peroxide; D051550:I-kappa B Kinase; D020672:I-kappa B Proteins; D016328:NF-kappa B; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D000097202:ATP-Binding Cassette Sub-Family B Member 4; C083487:I kappa B beta protein