title: Functional expression and characterization in Xenopus laevis oocytes             of the ABCG2 transporter derived from A549 human lung adenocarcinoma cells.
abstract: We cloned the ATP-binding cassette sub-family G member 2 (ABCG2) transporter,             the most recently identified among several major human multidrug-resistance pumps,             from A549 human lung adenocarcinoma cells in order to characterize its function             and substrate specificity. In a previous report, we confirmed that a stem cell-like             side population of A549 cells highly expressed the ABCG2 gene and had a unique             ability to resist the anticancer drug methotrexate (MTX). In this study, ABCG2             cDNA was cloned by RT-PCR and converted into cRNA by an in vitro transcription             system for expression in Xenopus laevis (X. laevis) oocytes. The transcribed cRNA             of the ABCG2 gene was injected into the oocytes under the absence of cofactors             or heterologous partner proteins or some lipids from the media. A high expression             of ABCG2 was observed on the oocyte surface by immunofluorescence and confocal             laser microscopy. We tested the functional effect of ABCG2 expression on drug             efflux by directly injecting MTX into X. laevis oocytes. The drug concentration             within the oocytes was quantified with LC-MS/MS; the analysis showed that the             accumulation of MTX was significantly decreased in the X. laevis oocytes expressing             ABCG2 compared with the control oocytes not expressing ABCG2. These findings show             that the ABCG2 protein has an important role in the efflux of MTX through the             cell membrane of X. laevis oocytes. Therefore, it might be that ABCG2, abundantly             expressed in the stem cell population of A549 cells, can modulate resistance to             MTX in lung cancer therapy.
authors.affiliation: Department of Veterinary Pharmacology and Toxicology, College                     of Veterinary Medicine, Konkuk University, Seoul 143-701, Republic of                     Korea.
authors.forename: Dong-Goo
authors.initials: DG
authors.lastname: Lee
authors.forename: Hee-Jung
authors.initials: HJ
authors.lastname: Cho
authors.forename: Hee
authors.initials: H
authors.lastname: Yi
authors.forename: Soo-Min
authors.initials: SM
authors.lastname: Cho
authors.forename: Kyul
authors.initials: K
authors.lastname: Jo
authors.forename: Jin-A
authors.initials: JA
authors.lastname: Park
authors.forename: Byung-Hwan
authors.initials: BH
authors.lastname: Lee
authors.forename: Sung-Hee
authors.initials: SH
authors.lastname: Hwang
authors.forename: Sang Min
authors.initials: SM
authors.lastname: Jeong
authors.forename: Seung-Yeol
authors.initials: SY
authors.lastname: Nah
authors.forename: Ho-Chul
authors.initials: HC
authors.lastname: Shin
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism*; D000077192:Adenocarcinoma of Lung; D000595:Amino Acid Sequence; D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000378:metabolism; D001483:Base Sequence; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism*; D008727:Methotrexate / Q000378:metabolism; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics; D021381:Protein Transport; D016415:Sequence Alignment; D014158:Transcription, Genetic; D014982:Xenopus laevis
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D000964:Antimetabolites, Antineoplastic; D018076:DNA, Complementary; D009363:Neoplasm Proteins; D008727:Methotrexate