DNA Damage by Tumor Cell-Specific N-Oxides

描述（由申请人提供）：3-氨基-1，2，4-苯并三嗪1，4-二氧化物（替拉扎明，TPZ）是一种生物还原活化的DNA损伤剂，可选择性杀死几乎所有实体瘤中发现的缺氧细胞。这种化合物显示出巨大的临床前景，目前正在十多个不同的临床试验中进行检查，包括几项III期研究。重要的是，TPZ通过一种全新的化学反应序列损伤DNA，其中单电子还原药物引发自由基介导的DNA损伤，然后药物或其代谢物将氧原子从其N-氧化物官能团转移到所得的DNA自由基，从而将其转化为链切割位点。虽然TPZ的药用特性已被广泛研究，但其许多生物学相关的化学特性仍然知之甚少。对TPZ日益增长的临床兴趣为表征该药物的相关化学提供了实际激励。此外，表征这种新的化学基序，有效地提供细胞毒性DNA损伤自由基的内部缺氧细胞可能是根本的兴趣，在药物化学和毒理学。本提案中所述的工作分为三个具体目标：1. TPZ如何在DNA上产生根本性损伤？药物是否用于将已知的DNA损伤剂羟基自由基传递到缺氧细胞？肿瘤细胞中发现的低氧和低pH值的条件如何结合联合收割机以促进药物对DNA的损伤？2. TPZ及其代谢物将氧原子从其N-氧化物官能团转移到DNA自由基的化学机制是什么？这种前所未有的反应使药物能够在缺氧条件下有效地损伤DNA，并可能在确定TPZ引起的最终DNA损伤的结构性质方面发挥核心作用。3.我们建议研究TPZ介导的DNA链断裂和碱基损伤的结构性质。这些研究将探索TPZ在不寻常的条件下运作的可能性，沿着药物独特的化学性质，导致独特的DNA损伤谱，使细胞面临对其DNA修复系统的社会挑战。

DESCRIPTION (provided by applicant): 3-Amino-1,2,4-benzotriazine 1,4-dioxide (tirapazamine, TPZ) is a bioreductively-activated DNA-damaging agent that selectively kills the hypoxic cells found in virtually all solid tumors. This compound shows great clinical promise and is currently being examined in more than ten different clinical trials, including several phase III studies. Importantly, TPZ damages DNA via a completely novel sequence of chemical reactions in which the one-electron reduced drug initiates radical-mediated DNA damage and then the drug or its metabolites transfer oxygen atoms from their N-oxide functional groups to the resulting DNA radicals, thus, converting them to strand cleavage sites. While the medicinal properties of TPZ have been extensively investigated, many of its biologically relevant chemical properties remain poorly understood. The growing clinical interest in TPZ provides a practical incentive to characterize the relevant chemistry of this drug. In addition, characterization of this new chemical motif that efficiently delivers cytotoxic DNA-damaging radicals to the interior of hypoxic cells may be of fundamental interest in both medicinal chemistry and toxicology. The work described in this proposal is divided into three Specific Aims: 1. How does TPZ generate radical lesions on DNA? Does the drug serve to deliver the known DNA-damaging agent hydroxyl radical to hypoxic cells? How do the conditions of low oxygen and low pH found in tumor cells combine to facilitate DNA damage by the drug? 2. What is the chemical mechanism by which TPZ and its metabolites transfer oxygen atoms from their N-oxide functional groups to DNA radicals? This unprecedented reaction allows the drug to efficiently damage DNA under hypoxic conditions and may play a central role in defining the structural nature of the final DNA lesions caused by TPZ. 3. We propose studies to characterize the structural nature of the DNA strand breaks and base damage mediated by TPZ. These studies will explore the possibility that the unusual conditions under which TPZ operates, along with the unique chemical properties of the drug, lead to a unique spectrum of DNA lesions that confront cells with social challenges to their DNA-repair systems.