title: Aryl hydrocarbon receptor is a transcriptional activator of the human breast cancer resistance protein (BCRP/ABCG2).
abstract: Breast cancer resistance protein (BCRP/ABCG2) is a membrane-bound efflux transporter important in cellular detoxification and multidrug resistance. Some aryl hydrocarbon receptor (AHR) agonists were reported to induce BCRP expression in human colon carcinoma cells. However, a direct involvement of AHR transcriptional regulation remains unexplored. In this study, we show that BCRP induction by AHR ligands occurs in human intestinal, liver, and mammary carcinoma cells and in primary colonocytes and hepatocytes. Increased BCRP transporter activity consistent with gene induction was also evident in the Caco2 subclone C2bbe1 cells. Using RNA interference and ectopic expression techniques to manipulate cellular AHR status, we confirmed AHR dependence of ABCG2 gene regulation. By gene promoter analysis, chromatin immunoprecipitation, and electrophoretic mobility shift assays, an active, proximal dioxin-response element at -194/-190 base pairs upstream of the transcription start site of the human ABCG2 gene was identified. Despite a common observation in human-derived cells, our in vitro and in vivo studies supported by phylogenetic footprinting analysis did not find that mouse Abcg2 is subject to AHR regulation. We conclude that AHR is a direct transcriptional regulator of human BCRP and provide an unprecedented role of AHR in cellular adaptive response and cytoprotection by up-regulating an important ATP-binding cassette efflux transporter.
authors.affiliation: Physiology and Experimental Medicine Program, University of Toronto, Ontario, Canada.
authors.forename: Kah Poh
authors.initials: KP
authors.lastname: Tan
authors.forename: Bernice
authors.initials: B
authors.lastname: Wang
authors.forename: Mingdong
authors.initials: M
authors.lastname: Yang
authors.forename: Paul C
authors.initials: PC
authors.lastname: Boutros
authors.forename: Jane
authors.initials: J
authors.lastname: Macaulay
authors.forename: Haibo
authors.initials: H
authors.lastname: Xu
authors.forename: Andrew I
authors.initials: AI
authors.lastname: Chuang
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kosuge
authors.forename: Mika
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Takahashi
authors.forename: Alex M L
authors.initials: AM
authors.lastname: Wu
authors.forename: Douglas D
authors.initials: DD
authors.lastname: Ross
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Harper
authors.forename: Shinya
authors.initials: S
authors.lastname: Ito
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D045744:Cell Line, Tumor; D017931:DNA Primers; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D009363:Neoplasm Proteins / Q000235:genetics*; D010802:Phylogeny; D011247:Pregnancy; D018336:Receptors, Aryl Hydrocarbon / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000502:physiology*
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D017931:DNA Primers; D009363:Neoplasm Proteins; D018336:Receptors, Aryl Hydrocarbon; D015534:Trans-Activators