Abstract：
NDec is a novel combination of oral decitabine and tetrahydrouridine that is currently under clinical development for the treatment of sickle cell disease (SCD). Here, we investigate the potential for the tetrahydrouridine component of NDec to act as an inhibitor or substrate of key concentrative nucleoside transporters (CNT1-3) and equilibrative nucleoside transporters (ENT1-2). Nucleoside transporter inhibition and tetrahydrouridine accumulation assays were performed using Madin-Darby canine kidney strain II (MDCKII) cells overexpressing human CNT1, CNT2, CNT3, ENT1, and ENT2 transporters. Results showed that tetrahydrouridine did not influence CNT- or ENT-mediated uridine/adenosine accumulation in MDCKII cells at the concentrations tested (25 and 250 µM). Accumulation of tetrahydrouridine in MDCKII cells was initially shown to be mediated by CNT3 and ENT2. However, while time- and concentration-dependence experiments showed active accumulation of tetrahydrouridine in CNT3-expressing cells, allowing for estimation of Km (3,140 µM) and Vmax (1,600 pmol/mg protein/min), accumulation of tetrahydrouridine was not observed in ENT2-expressing cells. Potent CNT3 inhibitors are a class of drugs not generally prescribed to patients with SCD, except in certain specific circumstances. These data suggest that NDec can be administered safely with drugs that act as substrates and inhibitors of the nucleoside transporters included in this study.
摘要：
NDec是口服地西他滨和四氢尿苷的新型组合，目前正在临床开发中用于治疗镰状细胞病（SCD）。这里,我们研究了NDec的四氢尿苷成分作为关键的浓缩型核苷转运蛋白(CNT1-3)和平衡型核苷转运蛋白(ENT1-2)的抑制剂或底物的潜力.使用过表达人CNT1、CNT2、CNT3、ENT1和ENT2转运蛋白的Madin-Darby犬肾菌株II(MDCKII)细胞进行核苷转运蛋白抑制和四氢尿苷积累测定。结果表明，在测试浓度（25和250µM）下，四氢尿苷不影响CNT或ENT介导的尿苷/腺苷在MDCKII细胞中的积累。MDCKII细胞中四氢尿苷的积累最初显示是由CNT3和ENT2介导的。然而,而时间和浓度依赖性实验显示，在CNT3表达细胞中，四氢尿苷活跃积累，允许估计Km（3,140µM）和Vmax（1,600pmol/mg蛋白质/min），在ENT2表达细胞中未观察到四氢尿苷的积累.强效CNT3抑制剂是一类通常不用于SCD患者的药物，除非在某些特定情况下。这些数据表明NDec可以安全地与作为本研究中包括的核苷转运蛋白的底物和抑制剂的药物一起施用。
