RT Journal Article SR Electronic T1 High-Affinity Interaction of Tyrosine Kinase Inhibitors with the ABCG2 Multidrug Transporter JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 1485 OP 1495 DO 10.1124/mol.65.6.1485 VO 65 IS 6 A1 Csilla Özvegy-Laczka A1 Tamás Hegedűs A1 György Várady A1 Olga Ujhelly A1 John D. Schuetz A1 András Váradi A1 György Kéri A1 László Őrfi A1 Katalin Német A1 Balázs Sarkadi YR 2004 UL http://molpharm.aspetjournals.org/content/65/6/1485.abstract AB Tyrosine kinase inhibitors (TKIs) are promising new agents for specific inhibition of malignant cell growth and metastasis formation. Because most of the TKIs have to reach an intracellular target, specific membrane transporters may significantly modulate their effectiveness. In addition, the hydrophobic TKIs may interact with so-called multidrug transporters and thus alter the cellular distribution of unrelated pharmacological agents. In the present work, we show that certain TKIs, already in the clinical phase of drug development, directly interact with the ABCG2 multidrug transporter protein with a high affinity. We found that in several in vitro assay systems, STI-571 (Gleevec; imatinib mesylate), ZD1839 (Iressa; gefitinib), and N-[4-[(3-bromophenyl)amino]-6-quinazolinyl]-2-butynamide (EKI-785) interacted with ABCG2 at submicromolar concentrations, whereas other multidrug transporters, human multidrug resistance protein (P-glycoprotein, ABCB1) and human multidrug resistance protein 1 (ABCC1), showed much lower reactivity toward these agents. Low concentrations of the TKIs examined selectively modulated ABCG2-ATPase activity, inhibited ABCG2-dependent active drug extrusion, and significantly affected drug resistance patterns in cells expressing ABCG2. Our results indicate that multidrug resistance protein modulation by TKIs may be an important factor in the clinical treatment of cancer patients. These data also raise the possibility that an extrusion of TKIs by multidrug transporters, e.g., ABCG2, may be involved in tumor cell TKI resistance.