title: Intestinal transport of irinotecan in Caco-2 cells and MDCK II cells overexpressing efflux transporters Pgp, cMOAT, and MRP1.
abstract: Irinotecan (CPT-11) is a water-soluble camptothecin (CPT) derivative that has been recently approved in the United States for patients as a first-line therapy in advanced colorectal cancer. Phase I clinical trials using oral CPT-11 have shown poor and variable oral bioavailability. The present study was designed to investigate the intestinal absorption and efflux mechanisms of CPT-11 using in vitro cell culture models, Caco-2 cells, and engineered Madine-Darby canine kidney (MDCK) II cells overexpressing P-glycoprotein (Pgp), canalicular multispecific organic anion transporter (cMOAT), and multidrug resistance-associated protein (MRP1). The intestinal absorptive and secretory transport of CPT-11 was investigated using Caco-2 cell monolayers. Secretory transport was concentration-dependent and saturable. The secretory efflux permeability (P(eff)) of CPT-11 decreased with decreasing temperature, with an estimated activation energy of 19.6 +/- 2.9 kcal/mol suggesting the involvement of active transporters. The involvement of potential secretory transporters was further characterized in MDCK II cells. The secretory efflux carrier permeability (P(c)) was approximately 4- and approximately 2-fold greater in MDCK II/Pgp and MDCK II/cMOAT cells than that in MDCK II/wild-type cells. Furthermore, the secretory efflux P(eff) of CPT-11 was significantly decreased by Pgp inhibitors, elacridar (GF120918) (IC50 = 0.38 +/- 0.06 microM) and verapamil (IC(50) = 234 +/- 48 microM) in MDCK II/Pgp cells and by cMOAT inhibitor 3-([(3-(2-[7-chloro-2-quinolinyl]ethyl)phenyl]-[(3-dimethylamino-3-oxoprphyl)-thio)-methyl]-thio) propanoic acid (MK571) (IC50) = 469 +/- 60 micro;M) in MDCK II/cMOAT cells. Overall, the current study suggests that Pgp and cMOAT are capable of mediating the efflux of CPT-11 in vitro. Since both Pgp and cMOAT are expressed in the intestine, liver, and kidney, it is likely that these efflux transporters play a significant role limiting the oral absorption and disposition of this important anticancer drug.
authors.affiliation: Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA.
authors.forename: Feng R
authors.initials: FR
authors.lastname: Luo
authors.forename: Pankaj V
authors.initials: PV
authors.lastname: Paranjpe
authors.forename: Ailan
authors.initials: A
authors.lastname: Guo
authors.forename: Eric
authors.initials: E
authors.lastname: Rubin
authors.forename: Patrick
authors.initials: P
authors.lastname: Sinko
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis*; D000818:Animals; D001692:Biological Transport / Q000502:physiology; D018938:Caco-2 Cells; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000493:pharmacokinetics*; D002460:Cell Line; D015194:Diffusion Chambers, Culture; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007408:Intestinal Absorption / Q000502:physiology*; D007413:Intestinal Mucosa / Q000378:metabolism* / Q000502:physiology; D000077146:Irinotecan; D026901:Membrane Transport Proteins; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000096:biosynthesis*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002166:Camptothecin; D000077146:Irinotecan; D026901:Membrane Transport Proteins; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; C421109:multidrug resistance-associated protein 1