title: The multidrug resistance transporter ABCG2 (breast cancer resistance protein 1) effluxes Hoechst 33342 and is overexpressed in hematopoietic stem cells.
abstract: The human ATP-binding cassette superfamily G (White) member 2 (ABCG2) gene and its murine homologue breast cancer resistance protein 1 (Bcrp1) are recently described ATP-binding cassette transporters associated with drug resistance in tumor cell lines, including the MCF-7 cell line, selected for its resistance to mitoxantrone (MCF-7/MitoR). Infection of MCF-7 cells with the retroviral vector containing ABCG2 cDNA (G1-ABCG2) resulted in cells (MCF-7/ABCG2) that were resistant to mitoxantrone at levels similar to those observed in MCF-7/MitoR cells. Previous studies have shown that pluripotent hematopoietic stem cells overexpress the multidrug-resistant transport (MDR1) gene and efflux rhodamine, a substrate for the MDR1 transporter. Other studies have identified a primitive hematopoietic stem cell population, or side population (SP) cells, which are identified by their efflux of the fluorescent dye, Hoechst 33342. In an attempt to identify the transport genes responsible for this phenotype, we examined the uptake of Hoechst 33342 into MCF-7, MCF-7/MitoR, and MCF-7 cells infected with a retroviral vector expressing the ABCG2 gene (MCF-7/ABCG2). MCF-7/MitoR cells as well as MCF-7/ABCG2 cells demonstrated lower levels of Hoechst 33342 uptake compared with the parental MCF-7 cells. We also examined the level of the mouse Bcrp1 RNA in SP cells and non-SP cells isolated from mouse hematopoietic cells. Mouse SP cells expressed relatively high levels of Bcrp1 mRNA relative to non-SP cells. These results suggest that Hoechst 33342 is a substrate for the ABCG2 transporter and that ABCG2/Bcrp1 expression may serve as a marker for hematopoietic stem cells in hematopoietic cells.
authors.affiliation: Eppley Institute for Cancer Research, University of Nebraska Medical Center, Omaha, Nebraska 68198, USA.
authors.forename: Min
authors.initials: M
authors.lastname: Kim
authors.forename: Heth
authors.initials: H
authors.lastname: Turnquist
authors.forename: John
authors.initials: J
authors.lastname: Jackson
authors.forename: Magda
authors.initials: M
authors.lastname: Sgagias
authors.forename: Ying
authors.initials: Y
authors.lastname: Yan
authors.forename: Maokai
authors.initials: M
authors.lastname: Gong
authors.forename: Michael
authors.initials: M
authors.lastname: Dean
authors.forename: John G
authors.initials: JG
authors.lastname: Sharp
authors.forename: Kenneth
authors.initials: K
authors.lastname: Cowan
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001562:Benzimidazoles / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line / Q000187:drug effects / Q000378:metabolism; D017931:DNA Primers / Q000737:chemistry; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D005456:Fluorescent Dyes / Q000378:metabolism*; D005786:Gene Expression Regulation; D006410:Hematopoiesis / Q000235:genetics; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D051379:Mice; D008856:Microscopy, Fluorescence; D008942:Mitoxantrone / Q000494:pharmacology*; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured / Q000378:metabolism
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D001562:Benzimidazoles; D017931:DNA Primers; D005456:Fluorescent Dyes; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D008942:Mitoxantrone; C017807:bisbenzimide ethoxide trihydrochloride