title: Overexpression of the BCRP/MXR/ABCP gene in a topotecan-selected ovarian tumor cell line.
abstract: Topotecan- or mitoxantrone-selected cell lines (T8 and MX3, respectively), derived from the human IGROV1 ovarian cancer cell line, were resistant to the topoisomerase I inhibitors topotecan, SN-38 (the active metabolite of irinotecan), and 9-aminocamptothecin, as well as to the topoisomerase II drug mitoxantrone. In both resistant cell lines, decreased accumulation of topotecan and mitoxantrone was observed, caused by enhanced energy-dependent efflux of the drugs involved. In both cell lines, we found that the breast cancer resistance protein/mitoxantrone resistance/placenta-specific ATP binding cassette (BCRP/MXR/ABCP) gene was overexpressed. Furthermore, BCRP/MXR/ABCP expression levels in various partially revertant T8 cells correlated with the levels of resistance to topotecan, SN-38, and mitoxantrone, strongly suggesting BCRP/MXR/ABCP to be the transporter responsible for the enhanced efflux. Pharmacodynamic analysis demonstrated that BCRP/MXR/ABCP is a very efficient transporter of topotecan; in vitro, 70% of the intracellular topotecan pool was transported out of the T8 or MX3 cells within 30 s. In conclusion, we report for the first time that BCRP/MXR/ABCP can also be up-regulated upon exposure of tumor cells to the clinically important drug topotecan, and that BCRP-mediated efflux of topotecan is very efficient. This highly efficient efflux of topotecan by BCRP/MXR/ABCP may have clinical relevance for patients being treated with topotecan.
authors.affiliation: Division of Experimental Therapy, The Netherlands Cancer Institute, Amsterdam. mama@nki.nl
authors.forename: M
authors.initials: M
authors.lastname: Maliepaard
authors.forename: M A
authors.initials: MA
authors.lastname: van Gastelen
authors.forename: L A
authors.initials: LA
authors.lastname: de Jong
authors.forename: D
authors.initials: D
authors.lastname: Pluim
authors.forename: R C
authors.initials: RC
authors.lastname: van Waardenburg
authors.forename: M C
authors.initials: MC
authors.lastname: Ruevekamp-Helmers
authors.forename: B G
authors.initials: BG
authors.lastname: Floot
authors.forename: J H
authors.initials: JH
authors.lastname: Schellens
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D000972:Antineoplastic Agents, Phytogenic / Q000633:toxicity*; D002166:Camptothecin / Q000031:analogs & derivatives / Q000633:toxicity; D018432:Drug Resistance, Multiple; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D000077146:Irinotecan; D007700:Kinetics; D008942:Mitoxantrone / Q000633:toxicity*; D009363:Neoplasm Proteins; D010051:Ovarian Neoplasms; D019772:Topotecan / Q000633:toxicity*; D014407:Tumor Cells, Cultured
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D000972:Antineoplastic Agents, Phytogenic; D009363:Neoplasm Proteins; D000077146:Irinotecan; D019772:Topotecan; D008942:Mitoxantrone; D002166:Camptothecin