title: Overlapping substrate and inhibitor specificity of human and murine ABCG2.
abstract: ABCG2 (also known as breast cancer resistance protein) is an ATP-binding cassette (ABC) transporter localized to the plasma membrane where it mediates the efflux of xenobiotics, including potential therapeutics. Studies investigating Abcg2 function at the blood-brain barrier in mouse models are often compared with human ABCG2 function. It is critical to understand the nature of species differences between mouse and human ABCG2, since extrapolations are made from murine data to humans. Two independent drug-selected cell line pairs expressing human or mouse ABCG2 were compared for efflux of fluorescent substrates using flow cytometry. To this end, we developed and characterized a new mouse Abcg2-expressing subline that demonstrated efflux of known fluorescent ABCG2 substrates and increased resistance to mitoxantrone, which is reduced in the presence of the ABCG2 inhibitor Ko143. Our results indicate that the substrate specificity of human and mouse ABCG2 is very similar. We identified a new human and mouse ABCG2 substrate, a porphyrin analog, purpurin-18 (Pp-18), which is not a substrate for P-glycoprotein or multidrug resistance protein 1. The ability of inhibitors to block efflux activity of ABCG2 was assessed using Pp-18. Inhibitors also demonstrated similar effects on human and mouse ABCG2. Chrysin, benzoflavone, and cyclosporin A inhibited Pp-18 efflux in both human and mouse ABCG2. The similarity of the substrate and inhibitor specificity of human and mouse ABCG2 supports interpretation of mouse models in understanding the clinical, pharmacological, and physiologic roles of ABCG2.
authors.affiliation: Laboratory of Cell Biology (J.B., M.D.H., M.M.G.), Cancer Therapeutics Branch (R.W.R., S.E.B.), Collaborative Protein Technology Resource (M.A.H., J.-Q.C.), Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland.
authors.forename: Joshua
authors.initials: J
authors.lastname: Bakhsheshian
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Hall
authors.forename: Robert W
authors.initials: RW
authors.lastname: Robey
authors.forename: Michelle A
authors.initials: MA
authors.lastname: Herrmann
authors.forename: Jin-Qiu
authors.initials: JQ
authors.lastname: Chen
authors.forename: Susan E
authors.initials: SE
authors.lastname: Bates
authors.forename: Michael M
authors.initials: MM
authors.lastname: Gottesman
mesh_terms: D016475:3T3 Cells; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D018432:Drug Resistance, Multiple / Q000502:physiology; D019008:Drug Resistance, Neoplasm / Q000502:physiology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D061986:MCF-7 Cells; D051379:Mice; D008942:Mitoxantrone / Q000494:pharmacology; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011166:Porphyrins / Q000494:pharmacology; D013379:Substrate Specificity / Q000502:physiology*
chemical_list: C116614:ABCG2 protein, human; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; C501412:Abcg2 protein, mouse; D009363:Neoplasm Proteins; D011166:Porphyrins; C059051:purpurin 18; D008942:Mitoxantrone