title: Susceptibility of nanoparticle-encapsulated paclitaxel to P-glycoprotein-mediated drug efflux.
abstract: Overexpression of P-glycoprotein (P-gp) is a key factor contributing to the development of multidrug resistance (MDR) in cancer cells. The objective of the study is to investigate whether a P-gp substrate, paclitaxel, delivered to MDR tumor cells in poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles is susceptible to P-gp - mediated drug efflux. Paclitaxel-loaded nanoparticles were formulated by emulsion-solvent evaporation technique. Nanoparticles had a mean hydrodynamic diameter of about 195nm, and demonstrated sustained release of paclitaxel. In vitro cell culture studies indicated that paclitaxel nanoparticles result in sustained, dose-dependent and significant cytotoxicity in drug-sensitive MCF-7 tumor cells but not in drug-resistant NCI-ADR/RES cells. Resistance to nanoparticle-encapsulated paclitaxel was reversed by verapamil, a P-gp inhibitor. Further, sustained inhibition of P-gp was necessary for sustaining the cytotoxicity of nanoparticle-encapsulated paclitaxel in drug-resistant cells. Inhibition of P-gp by verapamil did not significantly affect the uptake or retention of nanoparticles in drug-resistant cells. In conclusion, our studies suggest that P-gp substrates, such as paclitaxel, delivered to MDR cells by PLGA nanoparticles, are susceptible to efflux by P-gp. Inhibition of P-gp restores sensitivity to paclitaxel; however, sustained inhibition of P-gp is required for sustained therapeutic efficacy of nanoparticle-encapsulated drug.
authors.affiliation: Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI 48201, USA.
authors.forename: Mahesh D
authors.initials: MD
authors.lastname: Chavanpatil
authors.forename: Yogesh
authors.initials: Y
authors.lastname: Patil
authors.forename: Jayanth
authors.initials: J
authors.lastname: Panyam
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000972:Antineoplastic Agents, Phytogenic / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004337:Drug Carriers; D004339:Drug Compounding; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics; D006801:Humans; D019344:Lactic Acid / Q000737:chemistry*; D053758:Nanoparticles; D017239:Paclitaxel / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D010316:Particle Size; D011100:Polyglycolic Acid / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000737:chemistry*; D012995:Solubility; D013997:Time Factors; D014700:Verapamil / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000972:Antineoplastic Agents, Phytogenic; D004337:Drug Carriers; D011108:Polymers; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D014700:Verapamil; D017239:Paclitaxel