title: Effects of α-adrenoceptor antagonists on ABCG2/BCRP-mediated resistance and transport.
abstract: Acquired resistance of cancer cells to various chemotherapeutic agents is known as multidrug resistance, and remains a critical factor in the success of cancer treatment. It is necessary to develop the inhibitors for multidrug resistance. The aim of this study was to examine the effects of eight α-adrenoceptor antagonists on ABCG2/BCRP-mediated resistance and transport. Previously established HeLa/SN100 cells, which overexpress ABCG2/BCRP but not ABCB1/MDR1, were used. The effects of the antagonists on sensitivity to mitoxantrone and the transport activity of Hoehst33342, both substrates for ABCG2/BCRP, were evaluated using the WST-1 assay and cellular kinetics, respectively. ABCG2/BCRP mRNA expression and the cell cycle were also examined by real-time RT-PCR and flow cytometry, respectively. Sensitivity to mitoxantrone was reversed by the α-adrenoceptor antagonists in a concentration-dependent manner, although such effects were also found in the parental HeLa cells. Levels of ABCG2/BCRP mRNA expression were not influenced by the antagonists. The transport activity of Hoechst33342 was decreased by doxazosin and prazosin, but unaffected by the other antagonists. In addition, doxazosin and prazosin increased the proportion of S phase cells in the cultures treated with mitoxantrone, whereas the other α-adrenoceptor antagonists increased the percentage of cells in G(2)/M phase. These findings suggested that doxazosin and prazosin reversed resistance mainly by inhibiting ABCG2/BCRP-mediated transport, but the others affected sensitivity to mitoxantrone via a different mechanism.
authors.affiliation: Department of Clinical Pharmaceutics, Faculty of Pharmaceutical Sciences, Himeji Dokkyo University, Himeji, Japan. takara@gm.himeji-du.ac.jp
authors.forename: Kohji
authors.initials: K
authors.lastname: Takara
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Mika
authors.initials: M
authors.lastname: Matsubara
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Minegaki
authors.forename: Minoru
authors.initials: M
authors.lastname: Takahashi
authors.forename: Teruyoshi
authors.initials: T
authors.lastname: Yokoyama
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Okumura
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D058668:Adrenergic alpha-1 Receptor Antagonists / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects*; D015153:Blotting, Western; D018432:Drug Resistance, Multiple / Q000187:drug effects*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D005434:Flow Cytometry; D006367:HeLa Cells; D006801:Humans; D008942:Mitoxantrone / Q000494:pharmacology*; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D009369:Neoplasms / Q000188:drug therapy / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D018340:Receptors, Adrenergic, alpha-1 / Q000737:chemistry
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D058668:Adrenergic alpha-1 Receptor Antagonists; D000970:Antineoplastic Agents; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D018340:Receptors, Adrenergic, alpha-1; D008942:Mitoxantrone