title: BIBW22 BS, potent multidrug resistance-reversing agent, binds directly to P-glycoprotein and accumulates in drug-resistant cells.
abstract: The expression of P-glycoprotein (P-gp) in tumor cells causes a multidrug resistance (MDR) phenotype. P-gp has been shown to mediate the transport of structurally dissimilar drugs across the cell membrane in an energy-dependent manner. In this report, we show that BIBW22 BS, a phenylpteridine analog, reverses the MDR phenotype of CEM human lymphoma cells in a dose-dependent fashion. Using a photoactive analog of BIBW22 BS {[3H]azido-4-[N-(2-hydroxy-2-methylpropyl)-ethanolamino]-2, 7-bis(cis-2,6-dimethyl-morpholino)-6-phenylpteridine}, we show the photoaffinity labeling of a 170-kDa protein in drug-resistant cells immunoprecipitated with P-gp-specific monoclonal antibodies. The photolabeling of P-gp by [3H]azido-BIBW22 BS was specific and saturable. Furthermore, BIBW22 BS, vinblastine, and verapamil, but not colchicine, inhibited the photolabeling of P-gp by [3H]azido-BIBW22 BS. Drug binding studies showed that membranes from MDR cells bound more BIBW22 BS than parental drug-sensitive cells, and this binding was inhibited with vinblastine and, to a lesser extent, with uridine. However, drug transport studies demonstrated that BIBW22 BS is not a substrate for P-gp efflux pump. Interestingly, BIBW22 BS was shown to accumulate more in resistant cells. Also, BIBW22 BS accumulation in drug-sensitive and -resistant cells was not energy dependent. These results are in contrast with the observed decrease in accumulation or enhanced efflux of [3H]vinblastine seen in the same MDR cells. A comparison of [3H]azido-BIBW22 BS or [3H]azidopine photolabeled P-gp by Cleveland mapping with Staphylococcus aureus V8 protease showed differences in the photolabeled peptides. Taken together, the results of this study show that BIBW22 BS is a potent MDR-reversing agent that binds directly to P-gp but is not effluxed from drug-resistant cells.
authors.affiliation: Institute of Parasitology, McGill University, Quebec, Canada.
authors.forename: Z
authors.initials: Z
authors.lastname: Liu
authors.forename: F
authors.initials: F
authors.lastname: Lheureux
authors.forename: J F
authors.initials: JF
authors.lastname: Pouliot
authors.forename: A
authors.initials: A
authors.lastname: Heckel
authors.forename: U
authors.initials: U
authors.lastname: Bamberger
authors.forename: E
authors.initials: E
authors.lastname: Georges
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000187:drug effects* / Q000378:metabolism*; D000345:Affinity Labels; D000818:Animals; D001386:Azides / Q000378:metabolism* / Q000494:pharmacology*; D001665:Binding Sites; D016466:CHO Cells; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D003078:Colchicine / Q000633:toxicity; D006224:Cricetinae; D004095:Dihydropyridines / Q000378:metabolism; D004317:Doxorubicin / Q000633:toxicity; D018432:Drug Resistance, Multiple; D006801:Humans; D007700:Kinetics; D008223:Lymphoma; D009025:Morpholines / Q000378:metabolism* / Q000494:pharmacology*; D010449:Peptide Mapping; D011485:Protein Binding; D014223:Triamterene / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014700:Verapamil / Q000633:toxicity; D014747:Vinblastine / Q000378:metabolism / Q000633:toxicity
chemical_list: C101514:4-(N-(2-hydroxy-2-methylpropyl)-ethanolamino)-2,7-bis(2,6-dimethylmorpholino)-6-(4-azidophenyl)pteridine; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000345:Affinity Labels; D001386:Azides; D004095:Dihydropyridines; D009025:Morpholines; C080982:BIBW 22; D014747:Vinblastine; C041130:azidopine; D004317:Doxorubicin; D014700:Verapamil; D003078:Colchicine; D014223:Triamterene