TY - JOUR T1 - A New Mechanism of Methotrexate Action Revealed by Target Screening with Affinity Beads JF - Molecular Pharmacology JO - Mol Pharmacol SP - 1832 LP - 1839 DO - 10.1124/mol.106.025866 VL - 70 IS - 5 AU - Hitoshi Uga AU - Chikanori Kuramori AU - Akiko Ohta AU - Yasunori Tsuboi AU - Hiroshi Tanaka AU - Mamoru Hatakeyama AU - Yuki Yamaguchi AU - Takashi Takahashi AU - Masahiro Kizaki AU - Hiroshi Handa Y1 - 2006/11/01 UR - http://molpharm.aspetjournals.org/content/70/5/1832.abstract N2 - Methotrexate (MTX) is the anticancer and antirheumatoid drug that is believed to block nucleotide synthesis and cell cycle by inhibiting dihydrofolate reductase activity. We have developed novel affinity matrices, termed SG beads, that are easy to manipulate and are compatible with surface functionalization. Using the matrices, here we present evidence that deoxycytidine kinase (dCK), an enzyme that acts in the salvage pathway of nucleotide biosynthesis, is another target of MTX. MTX modulates dCK activity differentially depending on substrate concentrations. 1-β-d-Arabinofuranosylcytosine (ara-C), a chemotherapy agent often used in combination with MTX, is a nucleoside analog whose incorporation into chromosome requires prior phosphorylation by dCK. We show that, remarkably, MTX enhances incorporation and cytotoxicity of ara-C through regulation of dCK activity in Burkitt's lymphoma cells. Thus, this study provides new insight into the mechanisms underlying MTX actions and demonstrates the usefulness of the SG beads. The American Society for Pharmacology and Experimental Therapeutics ER -