Fully Synthetic Prodiginines as Probes of Protein-Protein Interactions Regulating

描述（由申请人提供）：在癌细胞中重建凋亡对于靶向、无毒治疗具有相当大的希望。我们先前通过“smac模拟物”的开发证明了这一点，smac模拟物是一种破坏蛋白质-蛋白质相互作用的小分子，其抑制了适当的半胱天冬酶激活。来自几个组织的Smac模拟物已经进入了人体临床试验。这些实验仍在进行中。在这项提案中，我们概述了新的化学，旨在第二组蛋白质-蛋白质相互作用，阻止癌症细胞凋亡，并有助于耐药性。 Bcl-2家族蛋白门控线粒体外膜通透性，调节细胞质释放正常细胞死亡所必需的因子。抗凋亡Bcl-2蛋白的过表达在化疗和放射抗性癌症中很常见。因此，Bcl-2系统作为药物开发的靶点得到了深入研究。这些努力中最先进的已达到临床阶段。然而，尽管该机制有巨大的前景，但未预料到的脱靶效应，特别是基于Mcl-1的对靶向Bcl-XL的药物的耐药性限制了进展。需要具有上级特征的新化合物。 柄型桥连的前色素是由细菌产生的细胞毒性色素。这些天然产物之一，链脲菌素B，被海岸鉴定为在细胞培养中增强细胞凋亡的分子-据报道通过与Bcl-2蛋白的相互作用。这一观察结果为obatoclax的开发奠定了基础，obatoclax是一种合成的前吉兰碱，目前正在临床试验中用于治疗淋巴细胞白血病。Obatoclax被描述为靶向BH 3螺旋结合表面的泛Bcl-2拮抗剂，包括Mcl-1上的Noxa结合位点。数据是有希望的，但受到选择性的影响。obatoclax中的三吡咯发色团在金属离子存在下产生ROS，并且可以通过跨膜离子转运来中和pH梯度。这两种效应都会损害正常细胞。 我们建议研究新的pyrrollophane变种链脲菌素B，缺乏obatoclax的结构负债。基于我们最近完成的全合成的roseophilin，我们概述了新的方法来合成marineosins A和B -新分离的抗白血病的海洋细菌产生的前体。与麦吉尔大学的Gordon海岸合作，我们发现了在我们的亲玫瑰素合成中的中间体，其在体外阻断t-Bid依赖性Mcl-1功能。我们建议通过沿着沿着几条路线推进我们的合成化学来建立这些结果。基于计算模型，我们相信所讨论的天然产物的柄桥杂环核心可以支撑一类新的β-螺旋肽模拟物。实验来验证这一假设的描述。这些包括选择性靶向Mcl-1/Noxa、Bcl-XL /Bim和p53/mdm 2相互作用的配体的定制合成。最后，作为在细胞培养和体内鉴定非Bcl-2效应的手段，我们建议使用基于亲和力的生物化学方法和最先进的功能基因组筛选来寻找这种结构类别的其他靶标。

DESCRIPTION (provided by applicant): Reestablishing apoptosis in cancer cells holds considerable promise for targeted, non-toxic therapy. We demonstrated this previously with the development of 'smac mimetics', small molecules that disrupt protein- protein interactions that suppress proper caspase activation. Smac mimetics from several organizations have since advanced to human clinical trials. These experiments remain ongoing. In this proposal we outline new chemistry aimed at a second set of protein-protein interactions that block apoptosis in cancer and contribute to drug resistance. Bcl-2 family proteins gate mitochondrial outer membrane permeability and regulate cytoplasmic release of factors essential for normal cell death. Over-expression of anti-apoptotic Bcl-2 proteins is common in chemotherapy and radiation resistant cancers. As a result, the Bcl-2 system has been intensely studied as a target for drug development. The most advanced of these efforts have reached clinic stages. However, despite tremendous promise for the mechanism, unanticipated off-target effects and, notably, Mcl-1 based resistance to agents targeting Bcl-XL are limiting progress. New compounds with superior profiles are needed. Ansa-bridged prodiginines are cytotoxic pigments produced by bacteria. One of these natural products, streptorubin B, was identified by Shore as a molecule that potentiates apoptosis in cell culture - reportedly through interactions with Bcl-2 proteins. This observation seeded development of obatoclax, a synthetic prodiginine now in clinical trials as therapy for lymphocytic leukemia. Obatoclax is described as a pan Bcl-2 antagonist that targets BH3 helix-binding surfaces, including the Noxa binding site on Mcl-1. Data is promising but tempered by selectivity. The tri-pyrrolic chromophore in obatoclax generates ROS in the presence of metal ions and can neutralize pH gradients via transmembrane ion transport. Both effects damage normal cells. We propose to study new pyrrolophane variants of streptorubin B that lack the structural liabilities of obatoclax. Based on our recently completed total synthesis f roseophilin, we outline new methods to synthesize marineosins A and B - newly isolated anti-leukemic prodiginines produced by marine bacteria. In collaboration with Gordon Shore at McGill University, we have discovered intermediates in our roseophilin synthesis that block t-Bid dependent Mcl-1 functions in vitro. We propose to build on these results by advancing our synthetic chemistry along several lines. Based on computational models, we believe the ansa- bridged heterocyclic cores of the natural products in question can scaffold a new class of �-helix peptidomimetics. Experiments to test this hypothesis are described. These include custom syntheses of ligands targeting the Mcl-1/Noxa, Bcl-XL /Bim and p53/mdm2 interactions selectively. Lastly, as means to identify non Bcl-2 based effects in cell culture and in vivo, we propose to search for additional targets of this structural class using affinity based biochemical methods and state-of-the-art functional genomic screens.