title: Reversal of a novel multidrug resistance mechanism in human colon carcinoma cells by fumitremorgin C.
abstract: We selected a human colon carcinoma cell line in increasing concentrations of mitoxantrone to obtain a resistant subline, S1-M1-3.2, with the following characteristics: profound resistance to mitoxantrone; significant cross-resistance to doxorubicin, bisantrene, and topotecan; and very low levels of resistance to Taxol, vinblastine, colchicine, and camptothecin. This multidrug resistance (MDR) phenotype, which was not reversed by verapamil or another potent P-glycoprotein (Pgp) inhibitor, CL 329,753, was dependent, in part, upon an energy-dependent drug efflux mechanism. Pgp and the multidrug resistance protein (MRP) were not elevated in the resistant cells relative to the drug-sensitive parent, suggesting that resistance was mediated by a novel pathway of drug transport. A cell-based screen with S1-M1-3.2 cells was used to identify agents capable of circumventing this non-Pgp, non-MRP MDR. One of the active agents identified was a mycotoxin, fumitremorgin C. This molecule was extremely effective in reversing resistance to mitoxantrone, doxorubicin, and topotecan in multidrug-selected cell lines showing this novel phenotype. Reversal of resistance was associated with an increase in drug accumulation. The compound did not reverse drug resistance in cells with elevated expression of Pgp or MRP. We suggest that fumitremorgin C is a highly selective chemosensitizing agent for the resistance pathway we have identified and can be used as a specific pharmacological probe to distinguish between the diverse resistance mechanisms that occur in the MDR cell.
authors.affiliation: Oncology and Immunology Research, Wyeth-Ayerst Research, Pearl River, New York 10965, USA.
authors.forename: S K
authors.initials: SK
authors.lastname: Rabindran
authors.forename: H
authors.initials: H
authors.lastname: He
authors.forename: M
authors.initials: M
authors.lastname: Singh
authors.forename: E
authors.initials: E
authors.lastname: Brown
authors.forename: K I
authors.initials: KI
authors.lastname: Collins
authors.forename: T
authors.initials: T
authors.lastname: Annable
authors.forename: L M
authors.initials: LM
authors.lastname: Greenberger
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000032:analysis; D018528:ATP-Binding Cassette Transporters / Q000032:analysis; D000970:Antineoplastic Agents / Q000494:pharmacology; D002277:Carcinoma / Q000188:drug therapy*; D003110:Colonic Neoplasms / Q000188:drug therapy*; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D018432:Drug Resistance, Multiple; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D008942:Mitoxantrone / Q000494:pharmacology; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D014407:Tumor Cells, Cultured
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D018528:ATP-Binding Cassette Transporters; D000970:Antineoplastic Agents; D004250:DNA Topoisomerases, Type II; D007211:Indoles; D008942:Mitoxantrone; D027425:ATP-Binding Cassette, Sub-Family C Proteins; C010522:tryptoquivaline