The thymidylate synthase inhibitor, ICI D1694, overcomes translational detainment of the enzyme

摘要: Abstract We have investigated the mechanism of inactivation thymidylate synthase (TS) by ICI D1694 (a folate-based quinazoline) in normal versus tumor-derived human mammary epithelial cells. is a very potent cytotoxic agent against these cells with IC50 values 1-2 nM. Its growth inhibitory activity was completely reversed addition thymidine, confirming that TS its sole target Remarkably, protein levels rose 10-40-fold following treatment D1694, depending on cell type, while mRNA remained constant. The appears to be release "detainment" translation, since cycloheximide, translational inhibitor, blocked from rising. But coadministration 5,6-dichlorobenzimidazole, transcriptional did not overcome accumulation, nor thymidine which overcomes inhibition D1694. 5,10-Methylenetetrahydrofolate (via folinic acid), however, block effects showing drug has effect upon both detainment and enzyme binding folate substrate site TS. In addition, presence no longer cycle-regulated as evident constitutive expression synchronized This accumulation induced should increase resistance under clinical setting. suggest an ideal inhibitor would allosteric binds mRNA, responsible for specific translation protein, thereby complimenting enzyme.