RT Journal Article SR Electronic T1 Effect of Multidrug Resistance-Reversing Agents on Transporting Activity of Human Canalicular Multispecific Organic Anion Transporter JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 1219 OP 1228 DO 10.1124/mol.56.6.1219 VO 56 IS 6 A1 Chen, Zhe-Sheng A1 Kawabe, Takeshi A1 Ono, Mayumi A1 Aoki, Shunji A1 Sumizawa, Tomoyuki A1 Furukawa, Tatsuhiko A1 Uchiumi, Takeshi A1 Wada, Morimasa A1 Kuwano, Michihiko A1 Akiyama, Shin-Ichi YR 1999 UL http://molpharm.aspetjournals.org/content/56/6/1219.abstract AB The canalicular multispecific organic anion transporter (cMOAT), also termed MRP2, is a recently identified ATP-binding cassette transporter. We previously established stable human cMOAT cDNA-transfected cells, LLC/cMOAT-1 from LLC-PK1 cells, and LLC/CMV cells that were transfected with an empty vector. We found that LLC/cMOAT-1 cells have increased resistance to vincristine (VCR), 7-ethyl-10-hydroxy-camptothecin, and cisplatin but not to etoposide. The multidrug resistance-reversing agents cyclosporin A (CsA) and 2-[4-(diphenylmethyl)-1-piperazinyl]-5-(trans-4,6-dimethyl-1,3,2-dioxaphosphorinan-2-yl)-2,6-dimethyl-4-(3-nitrophenyl)-3-pyridinecarboxylate P-oxide (PAK-104P) almost completely reversed the resistance to VCR, 7-ethyl-10-hydroxy-camptothecin, and cisplatin of LLC/cMOAT-1 cells; anddl-buthionine-(S,R)-sulfoximine, (3′-oxo-4-butenyl-4-methyl-threonine1, (valine2) cyclosporin (PSC833), and 3-([{3-(2-[7-chloro-2-quinolinyl]ethenyl)phenyl}-{(3-dimethylamino-3-oxopropyl)-thio}-methyl]thio)propanoic acid (MK571) partially reversed the resistance to these drugs. CsA and PAK-104P at 10 μM enhanced the accumulation of VCR in LLC/cMOAT-1 cells almost to the level in LLC/CMV cells without the agents. The efflux of VCR from LLC/cMOAT-1 cells was enhanced compared with LLC/CMV cells and inhibited by CsA and PAK-104P. Transport of leukotriene C4 (LTC4) and S-(2, 4-dinitrophenyl)glutathione also was studied with membrane vesicles prepared from these cells. LTC4 and S-(2, 4-dinitrophenyl)glutathione were actively transported into membrane vesicles prepared from LLC/cMOAT-1 cells. TheK m and V maxvalues for the uptake of LTC4 by the LLC/cMOAT-1 membrane vesicles were 0.26 ± 0.05 μM and 7.48 ± 0.67 pmol/min/mg protein, respectively. LTC4 transport was competitively inhibited by PAK-104P, CsA, MK571, and PSC833, withK i values of 3.7, 4.7, 13.1, and 28.9 μM, respectively. These findings demonstrate that cMOAT confers a novel drug-resistance phenotype. CsA and PAK-104P may be useful for reversing cMOAT-mediated drug resistance in tumors.