MODULATION OF NUCLEOSIDE TRANSPORT IN CHEMOTHERAPY

描述（改编自申请人的摘要）：核苷的摄取 由哺乳动物细胞是复杂的，由多种转运蛋白介导 它们的底物特异性和对抑制剂的敏感性不同。 有两大类核苷转运蛋白。 第一，均衡 (e)也称为易化扩散机制，第二， （c）. 均衡又分为两部分。 这是基于 对NBMPR敏感，所以es敏感，ei不敏感。 所有 集中型转运蛋白对NBMPR（1微摩尔）不敏感（ci） 根据底物特异性分为3种，因此CIF接受 福霉素B、cit、胸苷和ciB接受广泛的核苷。 这个项目的基本假设是选择性化疗 与抗代谢药联合使用核苷转运抑制剂 可以基于肿瘤的核苷转运特性来开发 和剂量限制的正常组织。 上一次供资期间的研究 已经确定了肿瘤细胞系的核苷转运特性， 骨髓和肠的关键正常细胞，并已确定 这些差异可以通过联合核苷抑制剂来利用， 用从头胸苷酸合成抑制剂转运。 申请人的 小组和其他人也发现了核苷转运的变化， 骨髓性白血病细胞在分化过程中可能被利用， 增加嘌呤核苷类似物对抗这种白血病的活性。 因此，这个项目的继续将测试扩展的假设 在核苷转运方面， 正常组织和一些肿瘤（目标3），以及可以诱导的差异 在一些肿瘤中，通过分化剂，可以被利用， 治疗目的。 这一假设将通过体外和 调节胸苷酸合成酶抑制剂的体内研究 横纹肌肉瘤中的核苷转运抑制剂（目的1和2）;以及 嘌呤核苷类似物调节的体外研究（具体地， 2-氯脱氧腺苷，2-CdA）在髓系分化剂中的毒性 白血病细胞（Aim 4）。 最近克隆的一些核苷 转运蛋白将允许这些研究进行到分子水平， 以及开发所需的分子试剂和测定方法（目标5）， 确定正常组织和肿瘤的核苷转运蛋白表型 从小样本。 预期体外和动物研究， 分子试剂的开发将为 将这些治疗方法从实验室转化为 诊所

DESCRIPTION (Adapted from Applicant's Abstract): The uptake of nucleosides by mammalian cells is complex and mediated by multiple transport proteins that differ in their substrate specificity and sensitivity to inhibitors. There are two major groups of nucleoside transporters. First, equilibrative (e) also known as facilitated diffusion mechanism and second, concentrative (c). Equilibrative is further divided into two. This is based on the sensitivity to NBMPR, so es is sensitive and ei is insensitive. All concentrative type transporters are insensitive (ci) to NBMPR (1 micromolar) and depending on substrate specificity are divided into 3, hence cif accepts formycin B, cit, thymidine, and cib, accepts broad range of nucleosides. The basic hypothesis of this project has been that selective chemotherapy using nucleoside transport inhibitors in combination with antimetabolites can be developed based on the nucleoside transport properties of the tumor and the dose-limiting normal tissues. Studies during the previous funding period have defined nucleoside transport properties of tumor cell lines and critical normal cells of the bone marrow and intestine, and have identified differences that might be exploited by combining inhibitors of nucleoside transport with inhibitors of de novo thymidylate synthesis. The applicant's group and others have also identified changes in nucleoside transport in myeloid leukemia cells during differentiation that might be exploited to increase the activity of purine nucleoside analogs against this leukemia. Thus, the continuation of this project will test the expanded hypothesis that there are both intrinsic differences in nucleoside transport between normal tissues and some tumors (Aim 3), and differences that can be induced in some tumors by differentiating agents, that can be exploited for therapeutic purposes. This hypothesis will be tested through in vitro and in vivo studies of the modulation of thymidylate synthase inhibitors by nucleoside transport inhibitors in rhabdomyosarcoma (Aims 1 and 2); and in vitro studies of the modulation of purine nucleoside analog (specifically, 2-chlorodeoxyadenosine, 2-CdA) toxicity by differentiating agents in myeloid leukemia cells (Aim 4). The recent cloning of some of the nucleoside transporters will permit these studies to be carried to the molecular level, and the development of molecular reagents and assays (Aim 5) needed to determine the nucleoside transporter phenotype of normal tissues and tumors from small samples. It is anticipated that the in vitro and animal studies, and the development of the molecular reagents will provide a sound basis for the translation of these therapeutic approaches from the laboratory to the clinic.