title: Effect of combination of suboptimal concentrations of P-glycoprotein blockers on the proliferation of MDR1 gene expressing cells.
abstract: Pharmacologically active in vivo doses of P-glycoprotein (Pgp) blockers, specifically verapamil, Cremophor EL and PSC833 cause toxicity in addition to that from the concomitantly used cancer chemotherapeutic drugs. It was shown before that these blockers cause different types of toxicities in vivo. We found that these 3 chemically distinct Pgp blockers exert different biophysical effects on the membranes of L1210 MDR cells. They also affect the general metabolism of these cells differently, but all block affinity labeling of Pgp. We could also show that the combination of suboptimal doses of these blockers can restore the uptake of the Pgp substrate rhodamine 123 into L1210MDR, 3T3MDR and KB-VI cells and can reduce the survival rate of these cells when treated in combination with daunorubicin. Our results suggest that the combination of suboptimal doses of these Pgp blockers may be advantageous in clinical practice.
authors.affiliation: Center for Drug Evaluation and Research, Food and Drug Administration, Washington, DC 20204, USA.
authors.forename: M
authors.initials: M
authors.lastname: Hwang
authors.forename: C H
authors.initials: CH
authors.lastname: Ahn
authors.forename: P S
authors.initials: PS
authors.lastname: Pine
authors.forename: J J
authors.initials: JJ
authors.lastname: Yin
authors.forename: C A
authors.initials: CA
authors.lastname: Hrycyna
authors.forename: T
authors.initials: T
authors.lastname: Licht
authors.forename: A
authors.initials: A
authors.lastname: Aszalos
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors* / Q000235:genetics*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D003524:Cyclosporins / Q000494:pharmacology*; D005990:Glycerol / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D007938:Leukemia; D014162:Transfection; D014407:Tumor Cells, Cultured; D014700:Verapamil / Q000494:pharmacology*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002121:Calcium Channel Blockers; D003524:Cyclosporins; C000515:cremophor EL; D014700:Verapamil; D005990:Glycerol; C070272:valspodar