title: Transport of 7-ethyl-10-hydroxycamptothecin (SN-38) by breast cancer resistance protein ABCG2 in human lung cancer cells.
abstract: Overexpression of breast cancer resistance protein (BCRP) ABCG2 reportedly confers cancer cell resistance to camptothecin-based anticancer drugs, such as topotecan and 7-ethyl-10-hydroxycamptothecin (SN-38: the active metabolite of irinotecan). We have recently shown that SN-38-selected PC-6/SN2-5H human lung carcinoma cells overexpressed BCRP with the reduced intracellular accumulation of SN-38 and SN-38-glucuronide (S. Kawabata et al., Biochem. Biophys. Res. Commun. 280, 1216-1223, 2001). In the present study, we have examined whether BCRP transports SN-38 and/or SN-38-glucuronide in vitro, by using plasma membrane vesicles from the parental PC-6 and resistant PC-6/SN2-5H cells, where SN-38 and SN-38-glucuronide accumulation in membrane vesicles was measured by HPLC. Both SN-38 and SN-38-glucuronide were ATP-dependently transported into membrane vesicles prepared from PC-6/SN2-5H cells, whereas no transport activity was observed in membrane vesicles from PC-6 cells. The kinetic parameters of the transport observed in PC-6/SN2-5H vesicles were K(m) = 4.0 microM, V(max) = 714 pmol/mg/min for SN-38 and K(m) = 26 microM, V(max) = 833 pmol/mg/min for SN-38-glucuronide. These findings suggest that BCRP expressed in PC-6/SN2-5H cells transports both SN-38 and SN-38-glucuronide with a higher affinity toward SN-38.
authors.affiliation: Second Department of Internal Medicine, Nagasaki University School of Medicine, Nagasaki, 852-8501, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Nakatomi
authors.forename: M
authors.initials: M
authors.lastname: Yoshikawa
authors.forename: M
authors.initials: M
authors.lastname: Oka
authors.forename: Y
authors.initials: Y
authors.lastname: Ikegami
authors.forename: S
authors.initials: S
authors.lastname: Hayasaka
authors.forename: K
authors.initials: K
authors.lastname: Sano
authors.forename: K
authors.initials: K
authors.lastname: Shiozawa
authors.forename: S
authors.initials: S
authors.lastname: Kawabata
authors.forename: H
authors.initials: H
authors.lastname: Soda
authors.forename: T
authors.initials: T
authors.lastname: Ishikawa
authors.forename: S
authors.initials: S
authors.lastname: Tanabe
authors.forename: S
authors.initials: S
authors.lastname: Kohno
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000378:metabolism* / Q000493:pharmacokinetics; D001692:Biological Transport / Q000187:drug effects; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000493:pharmacokinetics; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D019008:Drug Resistance, Neoplasm / Q000502:physiology*; D020719:Glucuronides / Q000378:metabolism; D006801:Humans; D000077146:Irinotecan; D007700:Kinetics; D008175:Lung Neoplasms / Q000378:metabolism*; D009363:Neoplasm Proteins; D022142:Secretory Vesicles / Q000187:drug effects / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: C441475:7-ethyl-10-hydroxycamptothecin glucuronide; C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D000972:Antineoplastic Agents, Phytogenic; D020719:Glucuronides; D009363:Neoplasm Proteins; D000077146:Irinotecan; D000255:Adenosine Triphosphate; D002166:Camptothecin