title: Reversal of breast cancer resistance protein (BCRP/ABCG2)-mediated drug resistance by novobiocin, a coumermycin antibiotic.
abstract: Breast cancer resistance protein (BCRP/ABCG2) of an ATP-binding cassette half-transporter confers resistance against mitoxantrone and camptothecin derivatives of topotecan and irinotecan. Novobiocin, a coumermycin antibiotic, is known to enhance anticancer drug sensitivity of cancer cells in vitro and in vivo, the mechanism of which remains undetermined. Here we focused on drug efflux pump and examined whether novobiocin reversed drug resistance in multidrug-resistant cells highly expressing BCRP. To explore the reversal mechanisms, intracellular drug accumulation was measured by flow cytometry, and a topotecan transport study using plasma membrane vesicles was performed. We used PC-6/SN2-5H2 small cell lung cancer and MCF-7/MX breast cancer cells selected with SN-38 of the active irinotecan metabolite and mitoxantrone, respectively, and the BCRP cDNA transfectant MCF-7/clone 8 cells. These cells expressed high levels of BCRP mRNA but not other known transporters. Compared to the parental PC-6 cells, PC-6/SN2-5H2 cells were 141-, 173- and 57.2-fold resistant to topotecan, SN-38 and mitoxantrone, respectively. Novobiocin at 60 microM decreased the degree of the above resistance by approximately 26-fold in PC-6/SN2-5H2 cells, and similarly reversed resistance in MCF-7/MX, MCF-7/clone 8 and un-selected NCI-H460 cells highly expressing BCRP. Furthermore, novobiocin increased the intracellular topotecan accumulation in these cells and inhibited the topotecan transport into the membrane vesicles of PC-6/SN2-5H2 cells. No effects of novobiocin in these assay were observed in the parental PC-6 and MCF-7 cells. The kinetic parameters in the transport study indicated that novobiocin was a inhibitor for BCRP, resulting in competitive inhibition of BCRP-mediated topotecan transport. These findings suggest that novobiocin effectively overcomes BCRP-mediated drug resistance at acceptable concentrations.
authors: Second Department of Internal Medicine, Nagasaki University School of Medicine, Nagasaki, Japan.
authors: Ken
authors: K
authors: Shiozawa
authors: Mikio
authors: M
authors: Oka
authors: Hiroshi
authors: H
authors: Soda
authors: Megumi
authors: M
authors: Yoshikawa
authors: Yoji
authors: Y
authors: Ikegami
authors: Junji
authors: J
authors: Tsurutani
authors: Katsumi
authors: K
authors: Nakatomi
authors: Yoichi
authors: Y
authors: Nakamura
authors: Seiji
authors: S
authors: Doi
authors: Takeshi
authors: T
authors: Kitazaki
authors: Yohei
authors: Y
authors: Mizuta
authors: Kunihiko
authors: K
authors: Murase
authors: Hisahiro
authors: H
authors: Yoshida
authors: Douglas D
authors: DD
authors: Ross
authors: Shigeru
authors: S
authors: Kohno
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors / Q000378:metabolism*; D049933:Aminocoumarins; D001943:Breast Neoplasms / Q000188:drug therapy*; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000494:pharmacology; D003374:Coumarins / Q000494:pharmacology; D018432:Drug Resistance, Multiple / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D006801:Humans; D000077146:Irinotecan; D008175:Lung Neoplasms / Q000188:drug therapy; D008942:Mitoxantrone / Q000494:pharmacology; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009675:Novobiocin / Q000494:pharmacology*; D059004:Topoisomerase I Inhibitors; D019772:Topotecan / Q000378:metabolism / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D049933:Aminocoumarins; D003374:Coumarins; D009363:Neoplasm Proteins; D059004:Topoisomerase I Inhibitors; D009675:Novobiocin; D000077146:Irinotecan; D019772:Topotecan; D008942:Mitoxantrone; C004628:coumermycin; D002166:Camptothecin