title: Estrogen receptor-dependent regulation of CYP2B6 in human breast cancer cells.
abstract: Estrogen receptor alpha (ERalpha) mediates the biological actions of estrogens and also contributes to the development and progression of breast cancer. To gain a more comprehensive understanding of ERalpha-mediated transcription, we used chromatin immunoprecipitation and promoter focused microarrays (ChIP-chip) to identify ERalpha binding sites in T-47D human breast cancer cells. Transcription factor binding site analysis revealed that the estrogen response element (ERE) was significantly over-represented and was found in 50% of the 243 ERalpha-bound regions identified. Interestingly, multiple ERalpha-bound regions were detected in the upstream regulatory sequences of the CYP2B gene cluster. Because ERalpha has been reported to regulate the expression of other cytochrome P450 enzymes and CYP2B6 is highly expressed in ERalpha-positive breast tumors, we focused on characterizing the ERalpha-dependent regulation of CYP2B6. Reporter gene assays revealed that ERalpha and ERbeta increased CYP2B6-regulated gene expression through a functional ERE located at -1669 to -1657 in the upstream regulatory region of CYP2B6. E2 increased ERalpha and nuclear receptor coactivator 3 (NCoA3) recruitment to the 5'-flanking region of CYP2B6, and increased CYP2B6 mRNA levels in T-47D but not in MCF-7 human breast cancer cells. RNAi-mediated knockdown of ERalpha in the T-47D cells resulted in a significant decrease in CYP2B6 mRNA levels. Taken together, our study provides evidence for cell-type specific transcriptional regulation of the CYP2B6 gene by ERs.
authors.affiliation: Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Raymond
authors.initials: R
authors.lastname: Lo
authors.forename: Lyle
authors.initials: L
authors.lastname: Burgoon
authors.forename: Laura
authors.initials: L
authors.lastname: Macpherson
authors.forename: Shaimaa
authors.initials: S
authors.lastname: Ahmed
authors.forename: Jason
authors.initials: J
authors.lastname: Matthews
mesh_terms: D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics*; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism*; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D065702:Cytochrome P-450 CYP2B6; D017931:DNA Primers / Q000235:genetics; D004273:DNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D004958:Estradiol / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D047629:Estrogen Receptor beta / Q000378:metabolism*; D005260:Female; D000077267:Fulvestrant; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D017930:Genes, Reporter; D006801:Humans; D008969:Molecular Sequence Data; D056921:Nuclear Receptor Coactivator 3 / Q000378:metabolism; D010089:Oxidoreductases, N-Demethylating / Q000235:genetics*; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D014162:Transfection; D000071163:Trefoil Factor-1; D025521:Tumor Suppressor Proteins / Q000378:metabolism
chemical_list: D017931:DNA Primers; D004273:DNA, Neoplasm; D004965:Estrogen Antagonists; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D034741:RNA, Small Interfering; C051838:TFF1 protein, human; D000071163:Trefoil Factor-1; D025521:Tumor Suppressor Proteins; D000077267:Fulvestrant; D004958:Estradiol; D001189:Aryl Hydrocarbon Hydroxylases; C585599:CYP2B6 protein, human; D065702:Cytochrome P-450 CYP2B6; D010089:Oxidoreductases, N-Demethylating; C538866:NCOA3 protein, human; D056921:Nuclear Receptor Coactivator 3