REGULATION OF ANTICANCER DRUG ACTIVATION

基于一种新的战略，拟议研究的总体目标 就是开发新的、更高效、更有选择性的药物组合 用于治疗癌症。许多抗癌剂是用于 受到反馈抑制的酶和这一调节 机制可以限制这些药物的激活。我们对此采取的方法 问题涉及到使用能够刺激这些药物的化合物 通过对抗反馈抑制来激活反应。我们有 证明5‘-氨基-5’-脱氧胸腺嘧啶核苷(5‘-dThd)可拮抗 胸腺嘧啶核苷三磷酸对胸苷激酶的反馈抑制 (DTTP)，从而强烈刺激胸腺嘧啶核苷或 碘脱氧尿苷(IdUrd)，一种细胞毒性类似物。在各种癌细胞中 5‘-AdThd可显著增加阿司匹林的摄取和细胞毒性 IdUrd然而，重要的是，在某些情况下，这种方法可能 在癌症中产生药物激活的优先刺激，如 与正常细胞相比。最近开发的一种方法 体外扩增正常人尿路上皮细胞促进了 将这些细胞与一系列人类膀胱癌细胞进行比较。这个 5‘-AdThd可显著促进IdUrd的摄取和磷酸化 肿瘤细胞但不在正常细胞中。因为这个不同寻常的 优惠刺激可能为进一步发展提供基础 肿瘤选择性化疗，阐明其生化机制 产生这些不同效果的是这个的主要目的 研究。可以解释这一点的几个替代假设 将进行选择性测试。其中包括：池大小的差异 反馈抑制剂；胸苷激酶活性水平的改变； 胸苷激酶调节特性的变化；以及相互作用 和其他主要是分解代谢的酶。从5‘-AdThd开始 刺激小鼠P388白血病细胞摄取IdUrd，因为 这种化疗方法的体内测试是重要的，最初 这种药物组合在BDF1小鼠身上的研究也将进行。 主要问题是5‘-AdThd能否提高治疗指数 这种动物肿瘤中的IdUrd。

Based on a novel strategy, the overall objective of the proposed research is to develop new, more highly efficacious and selective drug combinations for the treatment of cancer. Numerous anticancer agents are substrates for enzymes that are subject to feedback inhibition and this regulatory mechanism can limit the activation of these drugs. Our approach to this problem involves the use of compounds which can stimulate these drug activation reactions by antagonizing feedback inhibition. We have demonstrated that 5'-amino-5'-deoxythymidine (5'-dThd) can antagonize the feedback inhibition of thymidine kinase exerted by thymidine triphosphate (dTTP) and, thereby, strongly stimulate the phosphorylation of thymidine or iododeoxyuridine (IdUrd), a cytotoxic analog. In a variety of cancer cells 5'-AdThd produces a marked increase in the uptake and cytotoxicity of IdUrd. Importantly, however, in certain circumstances this approach may produce preferential stimulation of drug activation in the cancer as compared to the normal cells. A recently developed methodology for propagating normal human urothelial cells in vitro has facilitated the comparison of these cells with a series of human bladder cancer cells. The uptake and phosphorylation of IdUrd was markedly stimulated by 5'-AdThd in the neoplastic but not in the normal cells. Since this unusual preferential stimulation may provide the basis for developing more selective cancer chemotherapy, elucidation of the biochemical mechanisms which produce these differential effects is the primary aim of this research. Several alternative hypotheses which could account for this selectivity will be tested. These include: differences in the pool sizes of the feedback inhibitors; altered levels of thymidine kinase activity; changes in regulatory properties of the thymidine kinases; and interactions with other, primarily catabolic enzymes. Since 5'-AdThd potently stimulates the uptake of IdUrd into mouse P388 leukemia cells, and because in vivo testing of this chemotherapeutic approach is important, initial studies of this drug combination in BDF1 mice will also be carried out. The primary question is whether 5'-AdThd can increase the therapeutic index of IdUrd in this animal tumor.