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.
Footnotes
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The online version of this article (available at http://molpharm.aspetjournals.org) contains supplemental material.
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This work was supported by the Canadian Institute of Health Research [Grant MT13747] and the VA Merit Review.
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Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
doi:10.1124/mol.110.065078.
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ABBREVIATIONS:
- BCRP
- breast cancer resistance protein
- ABC
- ATP-binding cassette
- ABCG2
- ATP-binding cassette G2 protein
- AHR
- aryl hydrocarbon receptor
- ChIP
- chromatin immunoprecipitation
- DBA
- dimethyl-benzo(a)pyrene
- DMF
- 3,4-dimethoxyflavone
- DMSO
- dimethyl sulfoxide
- DRE
- dioxin response element
- EMSA
- electrophoretic mobility shift assay
- ERα
- estrogen receptor-α
- FTC
- fumitremorgin C
- HIF-1α
- hypoxia-inducible factor 1α
- 3MC
- 3-methylcholanthrene
- Nrf2
- nuclear factor (erythroid 2-like) factor 2
- PgR
- progesterone receptor
- PCR
- polymerase chain reaction
- siRNA
- small interfering RNA
- TCDD
- 2,3,7,8-tetrachlorodibenzo-p-dioxin
- bp
- base pair
- RT-PCR
- reverse-transcriptase polymerase chain reaction
- GAPDH
- glyceraldehyde-3-phosphate dehydrogenase
- SV40
- simian virus 40
- ANOVA
- analysis of variance
- ERE
- estrogen response element
- HRE
- hypoxia response element
- ARNT
- aryl hydrocarbon receptor nuclear translocator
- PD98059
- 2′-amino-3′-methoxyflavone
- SN-38
- 7-ethyl-10-hydroxycamptothecin.
- Received March 25, 2010.
- Accepted May 5, 2010.
- U.S. Government work not protected by U.S. copyright
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