title: Microplate screening of the differential effects of test agents on Hoechst 33342, rhodamine 123, and rhodamine 6G accumulation in breast cancer cells that overexpress P-glycoprotein.
abstract: A microplate screening method has been developed to evaluate the effects of test agents on the accumulation of the fluorescent P-glycoprotein (Pgp) substrates Hoechst 33342, rhodamine 123, and rhodamine 6G in multidrug-resistant (MDR) breast cancer cells that overexpress Pgp. All three substrates exhibit substantially higher accumulation in MCF7 non-MDR cells versus NCI/ADR-RES MDR cells, while incubation with 50 microM reserpine significantly reduces or eliminates these differences. Rhodamine 123 shows the lowest substrate accumulation efficiency in non-MDR cells relative to the substrate incubation level. The effects of several chemosensitizing agents and a series of paclitaxel analogs on the accumulation of each fluorescent substrate suggest that there are distinct differences in the substrate interaction profiles exhibited by these different agents. The described methods may be useful in Pgp-related research in the areas of cancer MDR, oral drug absorption, the blood-brain barrier, renal/hepatic transport processes, and drug-drug interactions.
authors.affiliation: Center for Drug Design and Development, The University of Toledo College of Pharmacy, Toledo, OH 43606, USA. jsarver@utnet.utoledo.edu
authors.forename: Jeffrey G
authors.initials: JG
authors.lastname: Sarver
authors.forename: Wieslaw A
authors.initials: WA
authors.lastname: Klis
authors.forename: James P
authors.initials: JP
authors.lastname: Byers
authors.forename: Paul W
authors.initials: PW
authors.lastname: Erhardt
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001562:Benzimidazoles / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000378:metabolism*; D004347:Drug Interactions; D019008:Drug Resistance, Neoplasm; D005260:Female; D005456:Fluorescent Dyes / Q000494:pharmacology*; D006801:Humans; D011485:Protein Binding; D020112:Rhodamine 123 / Q000494:pharmacology*; D012235:Rhodamines / Q000494:pharmacology*; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D001562:Benzimidazoles; D005456:Fluorescent Dyes; D012235:Rhodamines; C026188:rhodamine 6G; D020112:Rhodamine 123; D000255:Adenosine Triphosphate; C017807:bisbenzimide ethoxide trihydrochloride