Development of PARP-Isoform Selective Inhibitory Chemical Probes

项目总结/摘要 高异构体选择性聚（ADP-核糖）聚合酶（PARP）生物化学探针的开发将填补 我们对PARP酶的生物学功能的理解中存在的关键知识差距。PARP是一个 催化底物蛋白的聚（ADP-核糖基）化（PAR化）的核酶家族，例如 组蛋白PAR化促进DNA修复蛋白的募集。因此，PARP抑制剂（PARPi）是 作为一类新型抗癌药物开发，作为单一药物用于治疗BRCA缺陷型肿瘤 以及作为与DNA损伤剂的联合治疗。PARP超家族由17个成员组成。 临床PARPi通常与PARP-1和PARP-2的混杂抑制有关，其中一些PARP-1和PARP-2的混杂抑制与PARP-1和PARP-2的混杂抑制有关， 甚至抑制其他PARP。这成为其脱靶血液学毒性的潜在原因。由于非- 目前已知的PARPi对多种PARP亚型的特异性靶向作用， 药理学/临床特征已经变得高度复杂。此外，还表明单独抑制PARP-1 足以抑制MDA-MB-436肿瘤异种移植物的生长。PARP-1和PARP-2的耗尽导致 胚胎致死性和侵袭性T细胞淋巴瘤阻碍评估PARP的挑战之一- 细胞环境中同种型特异性分子相互作用景观是缺乏有效和高度PARP同种型 选择性化学探针因此，迫切需要开发具有高度异构体选择性的PARP抑制性探针 needed.我们计划通过开发异构体选择性和潜在无毒的新型PARP抑制剂来解决这个问题。 化学探针，将允许询问个体PARP的下游信号传导事件的变化， 分子水平。本文产生的探针还将用作下一代临床前检测的模板。 剂.我们将应用一组高效且新型的UTT先导化合物来开发精致的PARP亚型 选择性的化学探针，这将有助于我们了解在这两个PARP的生物学功能， 正常和病变细胞。作为概念验证，我们已经合成并表征了几种PARPi， 针对PARP-1和PARP-2的纳摩尔效力，对PARP-2的偏好性高约30倍。基于 在这个科学前提和初步数据的基础上，我们提出了以下具体目标：（A）确定PARP-1 和PARP-2选择性生物化学探针;（B）进行体外PARP酶测定和同种型选择性 筛选，和（C）评估CAPAN-1中同种型选择性最佳PARPi的细胞毒性（BRCA 2-/-和 BRCA 2cor）和SUM 149（BRCA 1-/-和BRCA 1cor）细胞。这些研究有望扩大我们的知识 通过开发的PARP化学探针抑制特定PARP同种型的影响。在补助金结束时 项目期间，我们将准备评估高价值的细胞活性和高PARP选择性化学探针 细胞实验随后，我们计划研究PARP亚型特异性下游信号传导， 事件、新PAR化底物蛋白的鉴定、靶向接合和表型变化，以及 以验证其他PARP是否是可行的药理学靶点。

Project Summary/Abstract The development of highly isoform-selective poly(ADP-ribose) polymerase (PARP) biochemical probes will fill crucial knowledge gaps that exist in our understanding of biological functions of PARP enzymes. PARPs are a family of nuclear enzymes that catalyze poly(ADP-ribosyl)ation (PARylation) of substrate proteins such as histones. PARylation facilitates recruitment of DNA repair proteins. Consequently, PARP inhibitors (PARPi) are developed as a novel class of anticancer drugs that are used as single agents to treat BRCA-deficient tumors and as combination therapy with DNA damaging agents. The PARP superfamily is comprised of 17 members. Clinical PARPi are often associated with promiscuous inhibition of both PARP-1 and PARP-2 and some of them even inhibit other PARPs. This becomes a potential cause for their off-target hematologic toxicity. Due to non- specific targeting of multiple PARP-isoforms by currently known PARPi, a thorough interpretation of their pharmacological/clinical profiles has become highly complex. Further it was shown that PARP-1 inhibition alone is sufficient to repress the growth of MDA-MB-436 tumor xenograft. Depletion of both PARP-1 and PARP-2 led to embryonic lethality and aggressive T-cell lymphomas. One of the challenges impeding evaluation of PARP- isoform specific molecular interaction landscape in cellular context is the lack of potent and highly PARP-isoform selective chemical probes. Therefore, development of highly isoform selective PARP inhibitory probes is urgently needed. Weplan to address this by developing isoform-selective and potentially non-toxic novel PARP inhibitory chemical probes that will allow interrogation of changes in downstream signaling events of individual PARPs at a molecular level. The probes generated herein will also serve as template for the next generation preclinical agents. We will apply highly potent and novel set of UTT-lead compounds to develop exquisitely PARP-isoform selective chemical probes that will facilitate our understanding of biological functions of individual PARPs in both normal and diseased cells. As a proof-of-concept, we have synthesized and characterized several PARPi with nanomolar potency against both PARP-1 and PARP-2, with ~30-fold higher preference toward PARP-2. Based on this scientific premise and preliminary data, we propose the following specific aims: (A) to identify PARP-1 and PARP-2 selective biochemical probes; (B) to conduct in vitro PARP enzyme assays and isoform selectivity screening, and (C) to evaluate cytotoxicity of an isoform selective best PARPi in CAPAN-1 (BRCA2-/- and BRCA2cor) and SUM149 (BRCA1-/- and BRCA1cor) cells. These studies are expected to expand our knowledge on the impact of inhibiting a specific PARP-isoform by developed PARP chemical probes. By the end of the grant project period, we will be poised to evaluate cell-active and highly PARP-selective chemical probes in high value cell-based experiments. Subsequently, we plan to investigate PARP-isoform specific downstream signaling events, identification of new PARylated substrate proteins, on-target engagement and phenotypic change, and to validate if other PARPs are viable pharmacological targets.