Restoring Guanylin-Guanylate cyclase C Signaling to Prevent Colorectal Cancer

摘要 结直肠癌是美国第四大发病率最高的癌症，也是癌症死亡的第二大原因， 代表了对预防策略的未满足的临床需求。在这种情况下，一种新的肿瘤抑制剂， 鸟苷酸环化酶C（GUCY 2C），提供了一个机会，以推进预防和治疗结直肠癌 癌GUCY 2C是在肠上皮的腔面上表达的跨膜受体。 它与内源性配体鸟苷素一起调节肠液分泌、组织结构和肠道免疫功能。 几个典型的癌症信号网络。有趣的是，鸟苷素是最常见的基因丢失， 散发性结直肠癌的治疗。它的丢失发生在转化的早期，并出现在病变中， 腺瘤性结肠息肉病（APC）或其下游靶点β-连环蛋白的突变， >90%的散发性结直肠癌。这些突变导致稳定和β- 连环蛋白，驱动肿瘤发生的转录程序。虽然异常的APC/β-catenin信号传导是 作为结直肠癌的一个公认的驱动因素，调控转化的下游机制仍然存在， 不完全理解。我们的初步数据表明，强制转基因鸟苷素表达消除 APC/β-连环蛋白驱动的癌症小鼠模型中肿瘤的发展，表明这些之间的联系 两个信号轴。因此，我们假设异常的APC/β-catenin信号传导驱动的结直肠癌， 反映鸟苷素损失，其使GUCY 2C肿瘤抑制因子沉默。本项目将探讨 结直肠癌中鸟苷素损失，最终目的是证明GUCY 2C配体的效用 作为预防结直肠癌的一种手段。为此，我们提出两个具体目标。在目标1中， 我们将鸟苷素损失定义为APC/β-连环蛋白依赖性肠肿瘤发生中的必需步骤， 这可以通过激素替代疗法来克服。使用条件性小鼠肠道模型 我们实验室开发的癌症，我们将诱导双等位基因APC丢失或β-连环蛋白激活突变， 研究转基因鸟苷素或口服GUCY 2C配体对抗肿瘤发生的潜力。结果将 告知化学预防策略以预防结直肠癌。在目标2中，我们将阐明 APC/β-catenin信号通过其抑制鸟苷素。使用人类癌细胞和小鼠模型， 结直肠癌，我们将定义APC/β-连环蛋白抑制鸟苷素的转录机制， 允许肿瘤发生。结果将揭示可逆的机制，有助于结直肠癌（鸟苷素 损失），这将扩大肠道肿瘤发生的病理生理学模型。这些研究将 携带APC/β-连环蛋白突变的患者（>90%的结直肠癌）的直接翻译潜力， 由于最近FDA批准了口服GUCY 2C配体利那洛肽（LinzessTM）或普坎替林 （TrulanceTM），其可用于激素替代疗法。

ABSTRACT Colorectal cancer is the 4th most incident cancer in the U.S. and the second leading cause of cancer mortality, representing an unmet clinical need for prevention strategies. In this context, a novel tumor suppressor, guanylate cyclase C (GUCY2C), offers an opportunity to advance the prevention and treatment of colorectal cancer. GUCY2C is a transmembrane receptor expressed on the luminal aspect of the intestinal epithelium. Together with its endogenous ligand, guanylin, it regulates intestinal fluid secretion, tissue architecture, and several canonical cancer signaling networks. Intriguingly, guanylin is among the most commonly lost gene products in sporadic colorectal cancer. Its loss occurs early in transformation and arises in lesions harboring mutations of adenomatous polyposis coli (APC) or its downstream target, β-catenin, which are responsible for >90% of sporadic colorectal cancers. These mutations lead to stabilization and nuclear accumulation of β- catenin, driving a transcriptional program underlying tumorigenesis. While aberrant APC/β-catenin signaling is a well-established driver of colorectal cancer, downstream mechanisms regulating transformation remain incompletely understood. Our preliminary data indicate that enforced transgenic guanylin expression eliminates the development of tumors in mouse models of APC/β-catenin-driven cancer, suggesting a link between these two signaling axes. Hence, we hypothesize that colorectal cancer driven by aberrant APC/β-catenin signaling reflects guanylin loss, which silences the GUCY2C tumor-suppressor. This project will explore the role of guanylin loss in colorectal cancer, with the ultimate intent to demonstrate the utility of GUCY2C ligand replacement as a means of colorectal cancer prevention. To this end, we propose two specific aims. In Aim 1, we will define guanylin loss as a required step in APC/β-catenin-dependent intestinal tumorigenesis, which can be overcome by hormone replacement therapy. Using conditional mouse models of intestinal cancer developed by our laboratory, we will induce biallelic APC loss or β-catenin activating mutations and examine the potential for transgenic guanylin or oral GUCY2C ligands to oppose tumorigenesis. Results will inform chemopreventive strategies to prevent colorectal cancer. In Aim 2, we will elucidate the mechanisms by which APC/β-catenin signaling suppresses guanylin. Using human cancer cells and mouse models of colorectal cancer, we will define the transcriptional mechanisms by which APC/β-catenin suppress guanylin, permitting tumorigenesis. Results will reveal reversible mechanisms contributing to colorectal cancer (guanylin loss) that would expand the pathophysiological model of intestinal tumorigenesis. These studies will have immediate translational potential for patients harboring APC/β-catenin mutations (>90% of colorectal cancers), due to the recent FDA-approval of the oral GUCY2C ligands, linaclotide (LinzessTM) or plecanatide (TrulanceTM), which could be leveraged for hormone replacement therapy.