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

描述（由申请人提供）：已知用于调节参与细胞增殖、迁移、自我更新和存活的基因的Wnt信号转导途径在许多类型的癌症中失调，特别是结肠直肠癌（CRC），其中该途径中的激活突变发生在超过80%的散发性结肠直肠癌中。因此，抑制该途径的药物作为新一代创新治疗剂的基础而备受追捧。不幸的是，在用小的药物样分子靶向该途径的能力方面存在差距，这一差距是发现靶向该途径缺陷的药物的障碍。作为我们从床到床的努力的一部分，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/β-连环蛋白信号传导，该机制涉及Frizzled受体的内化和Dishevelled和β-连环蛋白的下调。随后的研究表明，氯硝柳胺有望治疗结直肠癌。具体而言，我们证明氯硝柳胺选择性地抑制结肠直肠癌细胞系和新鲜切除的人结肠直肠肿瘤中的肿瘤细胞增殖，包括APC和β-连环蛋白中携带突变的细胞。重要的是，氯硝柳胺还在体内抑制Wnt/β-连环蛋白信号传导和结肠直肠肿瘤生长，而在小鼠异种移植模型中没有明显的毒性迹象。基于我们的发现，正在开发拟议的临床试验，其中氯硝柳胺在息肉中的Wnt抑制活性将在结肠镜检查前的磨合期后进行组织化学评估。鉴于长期以来的努力和在生物化学靶点上的差距，FDA批准的药物氯硝柳胺抑制该途径的发现非常重要，并为开发创新的临床药物提供了机会。尽管如此，氯硝柳胺用于治疗转移性CRC可能受到其驱虫作用机制和次优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标和抑制剂的鉴定提供了改善CRC治疗的潜力。我们的工作导致了这样的假设，即通过氯硝柳胺和优化的衍生物调节Wnt信号传导可用于治疗CRC，并且通过结合可用于药物发现的特定蛋白质靶标来抑制。该提案的目的是确定氯硝柳胺介导的Wnt信号抑制的靶点并定义其机制，以便为氯硝柳胺的临床试验设计提供信息，并开发具有适当PK特性的更有效和选择性的同类最佳Wnt信号抑制剂用于未来的临床研究。具体目标是：（1）界定结构-活动 本研究的目的是：（1）确定氯硝柳胺驱动Wnt抑制活性的相关性（SAR），并鉴定更有效和选择性的Wnt信号传导抑制剂;（2）描述氯硝柳胺介导的Wnt信号传导抑制的分子机制，并鉴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。该提案的资助将使我们能够确定生物靶点并确定抑制剂，以向临床研究进展，以克服发现Wnt/β-连环蛋白抑制剂的障碍。从而加速氯硝柳胺及其衍生物的转化应用，以提高患者生存率。

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.