Inhibition of Wnt/B-Catenin Signaling in Colorectal Cancer Therapy

描述(申请人提供)：Wnt信号转导通路，以调节与细胞增殖、迁移、自我更新和生存有关的基因而闻名，在许多类型的癌症中调节失调，尤其是结直肠癌(CRC)，超过80%的散发性结直肠癌会发生这一通路的激活突变。因此，抑制该途径的药物作为新一代创新治疗剂的基础备受追捧。不幸的是，在用小的类药物分子靶向该途径的能力方面存在缺口，这一缺口是发现靶向该途径缺陷的药物的障碍。作为我们床到床工作的一部分，我们最近报道了FDA批准的药物氯硝柳胺通过一种新的机制抑制Wnt/ç-catenin信号转导，该机制涉及Frizzled型受体的内部化和杂乱和ç-catenin的下调。随后的研究表明，氯硝柳胺有望治疗结直肠癌。具体地说，我们证明了氯硝柳胺选择性地抑制结直肠癌细胞系和新切除的人结直肠肿瘤中的肿瘤细胞增殖，包括含有APC和？-catenin突变的细胞。重要的是，氯硝柳胺在小鼠异种移植模型中也抑制了Wnt/ç-catenin信号转导和结直肠癌的生长，而没有明显的毒性迹象。基于我们的发现，拟议的临床试验正在开发中，其中将在结肠镜检查前的磨合阶段后用组织化学方法评估氯硝柳胺在息肉中的WNT抑制活性。考虑到在可用于药物发现的生化目标方面的长期努力和差距，FDA批准的药物氯硝柳胺抑制该途径的发现具有非常重要的意义，并为开发创新的临床药物提供了机会。然而，改变氯硝柳胺的用途来治疗转移性结直肠癌可能受到驱虫作用机制和不理想的全身生物利用度的限制。具有更好效力、选择性和药代动力学特性的生化靶点和抑制剂的鉴定为改进结直肠癌的治疗提供了潜在的可能性。我们的工作导致了这样的假设，即氯硝柳胺和优化的衍生物调节Wnt信号对治疗CRC有用，并且抑制是通过结合可用于药物发现的特定蛋白质靶点而发生的。该建议的目的是确定氯硝柳胺介导的Wnt信号抑制的靶点并确定其机制，以便为氯硝柳胺的临床试验设计提供信息，并为未来的临床研究开发更有效和选择性最好的、具有适当PK特性的Wnt信号抑制剂。该提案的具体目的是：(1)界定结构-活动 目的：(1)研究氯硝柳胺对Wnt信号通路的抑制作用；(2)阐明氯硝柳胺抑制Wnt信号转导的分子机制，确定氯硝柳胺的分子靶点；(3)确定新型氯硝柳胺衍生物的体内肿瘤抑制作用。这项提案的资金将使我们能够确定生物靶点和确定抑制物，以便在临床研究中取得进展，以克服发现Wnt/ü-catenin抑制剂的障碍。从而加速氯硝柳胺及其衍生物的翻译应用，以提高患者的存活率。

DESCRIPTION (provided by applicant): The Wnt signal transduction pathway, known for regulating genes involved in cell proliferation, migration, self- renewal, and survival, is dysregulated in many types of cancers, particularly colorectal cancer (CRC) where activating mutations in this pathway occur in over 80% of sporadic colorectal cancers. As a result, drugs that inhibit the pathway are highly sought-after as the basis of a new generation of innovative therapeutic agents. Unfortunately, a gap exists in the ability to target the pathway with small, drug-like molecules, a gap that is the barrier to discovering drugs targeting defects in this pathway. As part of our bed-to-bedside effort, we recently reported the FDA-approved drug niclosamide inhibits Wnt/ß-catenin signaling via a novel mechanism involving internalization of Frizzled receptors and downregulation of Dishevelled and ß-catenin. Subsequent studies showed that niclosamide holds promise to treat colorectal cancer. Specifically, we demonstrated that niclosamide selectively inhibited tumor cell proliferation in colorectal cancer cell lines and freshly resected human colorectal tumors, including cells harboring mutations in APC and ß-catenin. Importantly, niclosamide also inhibited Wnt/ß-catenin signaling and colorectal tumor growth in vivo without obvious signs of toxicity in mouse xenograft models. Based on our discovery, proposed clinical trials are being developed, in which the Wnt inhibitory activity of niclosamide in polyps will be evaluated histochemically after a run-in phase prior to colonoscopy. Given the long-standing efforts and gap in biochemical targets amenable to drug discovery, the finding that a FDA-approved drug niclosamide inhibits the pathway is highly significant and offers an opportunity to develop innovative clinical agents. Nonetheless, repurposing niclosamide to treat metastatic CRC may be limited by its anthelmintic mechanism of action and suboptimal systemic bioavailability. Identification of the biochemical target and inhibitors with better potency, selectivity and pharmacokinetic properties offer the potential to improve treatment of CRC. Our work led to the hypothesis that modulating Wnt signaling by niclosamide and optimized derivatives are useful to treat CRC and that inhibition occurs by binding a specific protein target that can be exploited for drug discovery. The objective of this proposal is to identify the target and define the mechanism of niclosamide-mediated inhibition of Wnt signaling in order to inform clinical trial designs with niclosamide, and to develop more potent and selective best-in-class Wnt signaling inhibitors with appropriate PK properties for future clinical studies. The specific aims of the proposal are to: (1) To define Structure-Activity Relationships (SAR) of niclosamide driving Wnt inhibitory activity and to identify more potent and selective inhibitors of Wnt signaling; (2) To delineate the molecular mechanism underlying niclosamide-mediated inhibition of Wnt signaling and to identify the molecular target of niclosamide; and (3) To determine the tumor inhibitory effect of novel niclosamide derivatives in vivo. Funding of this proposal will enable us to identify the biological target and identify inhibiors to progress toward clinical studies to overcome a barrier in the discovery of Wnt/ß-catenin inhibitors. Thus accelerate the translational application of niclosamide and its derivatives to improve patient survival.