title: Quantitation of doxorubicin uptake, efflux, and modulation of multidrug resistance (MDR) in MDR human cancer cells.
abstract: P-glycoprotein (Pgp), a membrane transporter encoded by the MDR1 gene in human cells, mediates drug efflux from cells, and it plays a major role in causing multidrug resistance (MDR). Confocal microscopy was used to study in vitro and in vivo drug accumulation, net uptake and efflux, and MDR modulation by P-glycoprotein inhibitors in MDR1-transduced human MDA-MB-435mdr (MDR) cancer cells. The MDR cells were approximately 9-fold more resistant to the anticancer drug doxorubicin than their parental wild-type MDA-MB-435wt (WT) cells. Doxorubicin accumulation in the MDR cells was only 19% of that in the WT cells. The net uptake of doxorubicin in the nuclei of the MDR cells was 2-fold lower than that in the nuclei of the WT cells. Pgp inhibitors verapamil, cyclosporine A, or PSC833 increased doxorubicin accumulation in the MDR cells up to 79%, and it reversed drug resistance in these cells. In living animals, doxorubicin accumulation in MDA-MB-435mdr xenograft tumors was 68% of that in the wild-type tumors. Administration of verapamil, cyclosporine A, or PSC833 before doxorubicin treatment of the animals increased doxorubicin accumulation in the MDR tumors up to 94%. These studies have added direct in vitro and in vivo information on the capacity of the transporter protein Pgp to efflux doxorubicin and on the reversal of MDR by Pgp inhibitors in resistant cancer cells.
authors.affiliation: Indiana Cancer Center, Cancer Research Institute, R4-Room 168, 1044 West Walnut St., Indianapolis, IN 46202, USA.
authors.forename: Fei
authors.initials: F
authors.lastname: Shen
authors.forename: Shaoyou
authors.initials: S
authors.lastname: Chu
authors.forename: Aimee K
authors.initials: AK
authors.lastname: Bence
authors.forename: Barbara
authors.initials: B
authors.lastname: Bailey
authors.forename: Xinjian
authors.initials: X
authors.lastname: Xue
authors.forename: Priscilla A
authors.initials: PA
authors.lastname: Erickson
authors.forename: Marshall H
authors.initials: MH
authors.lastname: Montrose
authors.forename: William T
authors.initials: WT
authors.lastname: Beck
authors.forename: Leonard C
authors.initials: LC
authors.lastname: Erickson
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000378:metabolism* / Q000493:pharmacokinetics / Q000633:toxicity; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D016572:Cyclosporine / Q000494:pharmacology; D003524:Cyclosporins / Q000494:pharmacology; D004317:Doxorubicin / Q000378:metabolism* / Q000493:pharmacokinetics / Q000633:toxicity; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D005260:Female; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000378:metabolism; D014700:Verapamil / Q000494:pharmacology
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000903:Antibiotics, Antineoplastic; D003524:Cyclosporins; D004317:Doxorubicin; D016572:Cyclosporine; D014700:Verapamil; C070272:valspodar