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（替拉帕嗪，TPZ）是一种生物还原激活的dna损伤剂，可以选择性地杀死几乎所有实体肿瘤中的缺氧细胞。该化合物显示出巨大的临床前景，目前正在进行十多项不同的临床试验，包括几项III期研究。重要的是，TPZ通过一系列全新的化学反应破坏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产生的DNA自由基上，从而将它们转化为链切割位点。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提供了一个实际的激励来表征该药物的相关化学。此外，表征这种新的化学基序，有效地将细胞毒性dna损伤自由基传递到缺氧细胞内部，可能是药物化学和毒理学的基本兴趣。本提案所描述的工作分为三个具体目标：1。TPZ是如何在DNA上产生根治性损伤的？这种药物是否可以将已知的dna损伤剂羟基自由基传递到缺氧细胞中？肿瘤细胞中的低氧和低pH值是如何结合起来促进药物对DNA的损伤的？2. TPZ及其代谢物将氧原子从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破坏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. 我们建议研究表征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在不寻常条件下运作的可能性，以及该药物独特的化学性质，导致独特的DNA损伤光谱，使细胞面临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.