title: In vitro transport of gimatecan (7-t-butoxyiminomethylcamptothecin) by breast cancer resistance protein, P-glycoprotein, and multidrug resistance protein 2.
abstract: Lipophilic camptothecin derivatives are considered to have negligible affinity for breast cancer resistance protein (BCRP; ABCG2). Gimatecan, a new orally available 7-t-butoxyiminomethyl-substituted lipophilic camptothecin derivative, has been previously reported to be not a substrate for BCRP. Using a panel of in vitro models, we tested whether gimatecan is a substrate for BCRP as well as for P-glycoprotein (MDR1) or multidrug resistance protein 2 (MRP2; ABCC2), ATP-binding cassette drug efflux transporters involved in anticancer drug resistance, and able to affect the pharmacokinetics of substrate drugs. Cell survival, drug transport, accumulation, and efflux were studied in IGROV1 and (human BCRP overexpressing) T8 cells, Madin-Darby canine kidney II (MDCKII-WT, MDCKII-Bcrp1, MDCKII-MDR1, and MDCKII-MRP2), and LLCPK (LLCPK-WT and LLCPK-MDR1) cells. Competition with methotrexate uptake was studied in Sf9-BCRP membrane vesicles. In vitro, expression of BCRP resulted in 8- to 10-fold resistance to gimatecan. In Transwell experiments, gimatecan was transported by Bcrp1 and transport was inhibited by the BCRP/P-glycoprotein inhibitors elacridar and pantoprazole. Efflux of gimatecan from MDCKII-Bcrp1 cells was faster than in WT cells. In Sf9-BCRP membrane vesicles, gimatecan significantly inhibited BCRP-mediated transport of methotrexate. In contrast, gimatecan was not transported by MDR1 or MRP2. Gimatecan is transported by BCRP/Bcrp1 in vitro, although to a lesser extent than the camptothecin analogue topotecan. Implications of BCRP expression in the gut for the oral development of gimatecan and the interaction between gimatecan and other BCRP substrate drugs and/or inhibitors warrant further clinical investigation.
authors: Department of Experimental Therapy and Medical Oncology, The Netherlands Cancer Institute, Amsterdam, the Netherlands.
authors: Serena
authors: S
authors: Marchetti
authors: Roos L
authors: RL
authors: Oostendorp
authors: Dick
authors: D
authors: Pluim
authors: Monique
authors: M
authors: van Eijndhoven
authors: Olaf
authors: O
authors: van Tellingen
authors: Alfred H
authors: AH
authors: Schinkel
authors: Richard
authors: R
authors: Versace
authors: Jos H
authors: JH
authors: Beijnen
authors: Roberto
authors: R
authors: Mazzanti
authors: Jan H
authors: JH
authors: Schellens
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000378:metabolism*; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000378:metabolism; D001692:Biological Transport; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D004285:Dogs; D004347:Drug Interactions; D006801:Humans; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008727:Methotrexate / Q000378:metabolism; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism*
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D000964:Antimetabolites, Antineoplastic; D002166:Camptothecin; D026901:Membrane Transport Proteins; D008727:Methotrexate; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins; C000715087:ABCC2 protein, human; C116614:ABCG2 protein, human; C433984:ST 1481