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ABSTRACT: The monkey is an important experimental model in the pharmacological evaluation of new drugs. We isolated monkey multidrug resistance-associated protein 2 (MRP2) cDNA to examine expression profiles among various tissues and measured ATPase activity to assess substrate specificity. The amino acid sequence encoded by monkey MRP2 cDNA was very similar (96% identity) to the reported human MRP2 cDNA (GenBank accession no. NM_000392). The tissue distribution of MRP2 in monkeys was partially different from that in humans. We found relatively high expression of MRP2 in the monkey kidney and small intestine using Northern blotting. Substrate specificity was compared between human and monkey MRP2. The affinity of 17beta-estradiol 17-(beta-d-glucuronide), methotrexate, vinblastine, and probenecid to monkey MRP2 was higher than that to human MRP2. Functional and expression differences between human and monkey MRP2 should be incorporated into the evaluation of candidate drugs.
European Journal of Pharmaceutical Sciences 09/2008; 35(4):326-34. · 3.21 Impact Factor
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ABSTRACT: Gefitinib (Iressa) is a selective epidermal growth factor receptor tyrosine kinase inhibitor and is used for the treatment of lung cancer. Recently, we discovered that it inhibits the breast cancer resistance protein, which is an ATP-binding cassette transporter. P-glycoprotein (Pgp) also pumps multiple types of drugs out of the cell using energy generated from ATP, and confers multidrug resistance on cancer cells. This study was designed to examine whether gefitinib inhibits the function of Pgp. We used multidrug resistant PC-6/PTX lung cancer and MCF-7/Adr breast cancer cells which overexpress Pgp and measured their drug sensitivity and drug-efflux function by tetrazolium assay and flowcytometry, respectively. In addition, the drug-stimulated ATPase activity of Pgp was measured using insect membranes that express human Pgp. Epidermal growth factor receptor was expressed in MCF-7/Adr, but not in PC-6/PTX cells, and the overexpression of Pgp did not confer resistance to gefitinib to both cell types. However, clinically achievable levels of gefitinib moderately reversed the Pgp-mediated resistance to paclitaxel and docetaxel in Pgp overexpressing cells. In addition, gefitinib increased the intracellular accumulation of the Pgp substrate rhodamine-123 in resistant cells, and activated ATPase in a preparation of pure Pgp-expressing membrane. These findings suggest that gefitinib directly interacts with Pgp and inhibits its function. Gefitinib may clinically inhibit the excretion of Pgp substrate drugs including anticancer agents, and its drug-interaction should therefore be considered.
Lung Cancer 10/2005; 49(3):337-43. · 3.43 Impact Factor
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ABSTRACT: We have developed a practical synthetic route to construct C-aromatic taxane derivatives as three-dimension templates by way of intramolecular alkylation. The usefulness of synthesized compounds as the core template was evaluated by using a newly developed screening system for P-glycoprotein.
Bioorganic & Medicinal Chemistry Letters 06/2005; 15(10):2601-5. · 2.55 Impact Factor
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ABSTRACT: Accumulating evidence suggests that several ATP-binding cassette (ABC) transporters mediate the elimination of anticancer drugs from cancer cells and thereby confer drug resistance. SN-38-selected PC-6/SN2-5H human lung carcinoma cells were shown to overexpress ABCG2 with the reduced intracellular accumulation of SN-38, the active metabolite of irinotecan. We have recently demonstrated that plasma membrane vesicles prepared from those cells transported SN-38 in an ATP-dependent manner, and it was suggested that ABCG2 is involved in the active extrusion of SN-38 from cancer cells. In the present study, we have cloned the cDNA of ABCG2 from PC-6/SN2-5H human lung carcinoma cells, expressed ABCG2 in Sf9 insect cells, and characterized its function. Sequence analysis has revealed that the cloned ABCG2 has an arginine at the amino acid position 482, as does the wild type. Expression of the cloned ABCG2 in Sf9 cell membranes was detected by immunoblotting with the BXP-21 antibody. Contrary to our expectation, however, ATPase activity in the cell membranes expressing ABCG2 was stimulated by neither SN-38 nor rhodamine 123. It is suggested that there is a partner protein of ABCG2 required for heterodimer formation to exhibit transport activity toward SN-38.
Drug Metabolism and Pharmacokinetics 02/2002; 17(2):130-5. · 2.32 Impact Factor
