title: The solvents cremophor EL and Tween 80 modulate daunorubicin resistance in the multidrug resistant Ehrlich ascites tumor.
abstract: Cremophor EL (polyoxyethylene castor oil) and Tween 80, used as solvents for cyclosporin A and VP-16, respectively, were found to reverse the multidrug resistant (MDR) phenotype. In daunorubicin (DNR) resistant Ehrlich ascites tumor cells (EHR2/DNR+), both solvents at percentages of 0.01% (v/v) enhanced DNR accumulation to sensitive levels. Cremophor EL and Tween 80 did not influence DNR accumulation in drug-sensitive cells (EHR2). The concentration of cyclosporin A alone that enhanced DNR accumulation in EHR2/DNR+ cells to sensitive levels was 5 micrograms/mL whereas 0.2 micrograms/mL of cyclosporin A dissolved in 0.001% (v/v) Cremophor EL enhanced DNR accumulation to sensitive levels, thus indicating synergy between Cremophor EL and cyclosporin A. Cyclosporin A had a negligible effect on DNR accumulation in the drug-sensitive cells. In clonogenic assays, the LD10 of DNR was 1 microM in EHR2/DNR+ cells. Combining 1 microM DNR with non-toxic amounts of Cremophor EL (0.001% and 0.002%, v/v) potentiated the cytotoxicity of DNR and resulted in a cell kill of 77% and 86%, respectively, in the resistant cells. In non-toxic amounts, CrEL and Tween 80 acted synergistically with reduced concentrations of verapamil, resulting in DNR accumulation approaching close to the sensitive level. Azidopine photoaffinity labeling of P-glycoprotein in plasma membrane vesicles from EHR2/DNR+ cells was inhibited 100% and 80%, by 0.003% (v/v) Cremophor EL or Tween 80, respectively. These data permit the conclusion that non-toxic amounts of CrEL and Tween 80 modulated DNR resistance by raising intracellular DNR levels, due to their abilities to bind to the plasma membrane P-glycoprotein.
authors.affiliation: Department of Medicine, Finsen Institute-Rigshospitalet, Copenhagen, Denmark.
authors.forename: E
authors.initials: E
authors.lastname: Friche
authors.forename: P B
authors.initials: PB
authors.lastname: Jensen
authors.forename: M
authors.initials: M
authors.lastname: Sehested
authors.forename: E J
authors.initials: EJ
authors.lastname: Demant
authors.forename: N N
authors.initials: NN
authors.lastname: Nissen
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000818:Animals; D001386:Azides; D002286:Carcinoma, Ehrlich Tumor / Q000188:drug therapy* / Q000378:metabolism; D003524:Cyclosporins / Q000494:pharmacology; D003630:Daunorubicin / Q000493:pharmacokinetics / Q000494:pharmacology*; D004095:Dihydropyridines; D004351:Drug Resistance / Q000502:physiology; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D005990:Glycerol / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D011136:Polysorbates / Q000494:pharmacology*; D014316:Tritium; D014407:Tumor Cells, Cultured; D014700:Verapamil / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D001386:Azides; D003524:Cyclosporins; D004095:Dihydropyridines; D008562:Membrane Glycoproteins; D011136:Polysorbates; D014316:Tritium; C041130:azidopine; C000515:cremophor EL; D014700:Verapamil; D005990:Glycerol; D003630:Daunorubicin