title: Aberrant regulation of the MRP3 gene in non-small cell lung carcinoma.
abstract: BACKGROUND
  Multidrug-resistant protein-3 (MRP3), a membrane-bound transporter, facilitates efflux of toxic compounds, including certain chemotherapies, out of cells. Aberrant MRP3 expression has been linked to drug resistance in non-small cell lung carcinoma (NSCLC). We sought to determine if tumor MRP3 expression patterns correlate with the mutational status of upstream regulators, including nuclear factor erythroid-2-related factor 2 (Nrf2) and its functional repressor Keap1 in NSCLC cell lines and patient samples.
  
  
  METHODS
  To identify putative Nrf2-binding sites in the MRP3 promoter and to evaluate Keap1, Nrf2, and p53 mutation status in four cell lines and 33 NSCLC surgically resected tumor specimens with regard to their impact on MRP3 levels.
  
  
  RESULTS
  Chromatin immunoprecipitation analysis of the MRP3 promoter revealed an almost threefold increase in Nrf2 binding to the third putative Nrf2-binding sequence distal to the start site, demonstrating direct regulation of MRP3 by Nrf2. In NSCLC cell lines, elevated Nrf2 protein was observed in cell lines with increased MRP3 RNA expression. In patient tumor specimens, the presence of mutations in Keap1/Nrf2 correlated with MRP3 RNA levels (p < 0.05). p53 mutations were observed in 33% of cases, and all Keap1 mutant-positive tumors possessed a p53 mutation (n = 5; p = 0.0019).
  
  
  CONCLUSIONS
  We demonstrate direct involvement between the transcription factor Nrf2 and the MRP3 promoter, which leads to the up-regulation of the MRP3 gene. In addition, we found a statistically significant correlation between the presence of Keap1/Nrf2 mutations and increased MRP3 messenger RNA levels in our NSCLC patient samples.
authors.affiliation: School of Natural Sciences, University of California, Merced, California, USA. christopher.mahaffey@ucdmc.ucdavis.edu
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Mahaffey
authors.forename: Nichole C
authors.initials: NC
authors.lastname: Mahaffey
authors.forename: William
authors.initials: W
authors.lastname: Holland
authors.forename: Hongqiao
authors.initials: H
authors.lastname: Zhang
authors.forename: David R
authors.initials: DR
authors.lastname: Gandara
authors.forename: Philip C
authors.initials: PC
authors.lastname: Mack
authors.forename: Henry Jay
authors.initials: HJ
authors.lastname: Forman
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic; D016158:Genes, p53 / Q000235:genetics; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics; D000072019:Kelch-Like ECH-Associated Protein 1; D008175:Lung Neoplasms / Q000235:genetics* / Q000378:metabolism; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D000072019:Kelch-Like ECH-Associated Protein 1; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D051267:NF-E2-Related Factor 2; D012333:RNA, Messenger; C431364:KEAP1 protein, human; C114462:multidrug resistance-associated protein 3
references.citation: J Pharmacol Exp Ther. 2002 Aug;302(2):407-15
references.pmid: 12130697
references.citation: Proc Natl Acad Sci U S A. 1999 Jun 8;96(12):6914-9
references.pmid: 10359813
references.citation: Mol Cancer Ther. 2003 Jul;2(7):685-98
references.pmid: 12883042
references.citation: Mol Cancer Ther. 2010 Feb;9(2):336-46
references.pmid: 20124447
references.citation: Redox Rep. 2007;12(1):101-6
references.pmid: 17263920
references.citation: Proc Natl Acad Sci U S A. 2008 Sep 9;105(36):13568-73
references.pmid: 18757741
references.citation: Cancer Res. 2008 Mar 15;68(6):1777-85
references.pmid: 18339858
references.citation: Toxicol Sci. 2005 Feb;83(2):313-28
references.pmid: 15525690
references.citation: Clin Cancer Res. 2009 May 15;15(10):3423-32
references.pmid: 19417020
references.citation: Free Radic Biol Med. 2009 Jun 15;46(12):1650-7
references.pmid: 19345732
references.citation: Mutat Res. 2002 Mar;511(1):45-62
references.pmid: 11906841
references.citation: J Clin Invest. 2000 May;105(9):1261-7
references.pmid: 10792001
references.citation: Mol Pharmacol. 2002 Nov;62(5):1001-10
references.pmid: 12391262
references.citation: Gastroenterology. 2008 Oct;135(4):1358-1368, 1368.e1-4
references.pmid: 18692501
references.citation: Cancer Res. 2008 Mar 1;68(5):1303-9
references.pmid: 18316592
references.citation: Clin Cancer Res. 1999 Mar;5(3):673-80
references.pmid: 10100721
references.citation: Clin Lung Cancer. 2007 Nov;8(9):548-53
references.pmid: 18186959
references.citation: PLoS Med. 2006 Oct;3(10):e420
references.pmid: 17020408
references.citation: Clin Cancer Res. 1998 Jun;4(6):1393-403
references.pmid: 9626455
references.citation: Toxicol Lett. 2002 Jun 7;132(1):27-36
references.pmid: 12084617