Role of Claudin-1 in Colon Cancer

描述(由申请人提供)： 结直肠癌(CRC)是退伍军人癌症相关死亡的主要原因之一，退伍军人事务部每年管理和治疗约17.5万名结直肠癌患者[1]。尽管在疾病的筛查/诊断方面取得了重大进展，但治疗方案仍然只取得了一定的成功，主要包括手术切除和化疗。重要的是，疾病的进展和转移仍然是VA-CRC患者发病率和死亡率的主要原因。因此，迫切需要有希望抑制CRC进展的新疗法。我们的研究是朝着这个方向迈出的重要一步。值得注意的是，我们和其他实验室的大量工作已经证实，claudin-1在结直肠癌中的表达以一种具有阶段特异性的方式高度上调，并与结直肠癌的生长和进展有关。现在，利用一种新的肠道特异性claudin-1过表达的小鼠模型，我们展示了claudin-1在Notch信号和结肠细胞成熟/杯状细胞分化/MUC-2表达调节中的新作用。我们进一步证明，通过APCmin和claudin-1转基因小鼠的杂交，结肠癌负担(肿瘤的发生率和生长)和后代的侵袭性增加了数倍。在我们的持续研究中，我们现在已经产生了证据表明，Notch-和Wnt-信号以claudin-1依赖的方式协同增强APCmin/CL-1小鼠的CRC，这可能是通过调节癌症干细胞来实现的。综上所述，我们的假设是，Claudin-1表达增加导致Notch-hyper激活，从而扰乱正常的结肠分化和动态平衡，从而通过Notch和Wnt-信号之间的协同作用，诱导对结直肠癌生长和进展的易感性。为了验证我们的假设，我们提出了以下特定的目标：特定的目标1.确定claudin-1的表达调节Notch信号来调节结肠肿瘤的发生。在这里，我们将：a)确定Notch信号调节APCmin/CL-1小鼠肿瘤形成的增加；b)确定黏膜炎症是否有助于Claudin-1依赖的结肠肿瘤形成和/或侵袭性的增加；c)确定Claudin-1依赖调控Notch激活的机制/S。具体目的2.确定Notch与Wnt/b-catenin信号协同调节Claudin-1在结肠肿瘤发生中依赖的增加。在这里，我们将确定：a)抑制Wnt/b-catenin信号在APCmin/CL-1小鼠结肠肿瘤发生中的影响；b)依赖claudin-1的Wnt/b-catenin信号的增加依赖于Notch-激活，并探讨其潜在机制/S；c)在结肠癌患者中，claudin-1的表达是否与Notch和b-catenin/Wnt-激活相关，及其与癌症侵袭性的潜在关联。具体目的3.探讨APC/Wnt信号在结肠Claudin-1表达调控中的作用。在这里，我们将：a)研究APC(WT)-Smad4轴在Claudin-1表达调控中的作用；b)确定APC和Smad4在Claudin-1转录调控中的相互作用细节。我们的短期目标是更好地了解claudin-1表达异常如何调节结肠癌细胞形成肿瘤和进一步进展的能力。我们的长期目标是开发Claudin-1特异性抑制剂，这种抑制剂可以特异性地输送到结肠癌细胞，从而创造出一种无毒、抑制疾病进展的抗结直肠癌药物。我们相信，这样的治疗干预可以显着提高患有结直肠癌的美国退伍军人的存活率和生活质量。

DESCRIPTION (provided by applicant): Colorectal cancer (CRC) is one of the leading causes of cancer-related deaths in the Veterans armed forces personnel and each year Veterans affairs manages and treats ~175,000 colorectal cancer patients [1]. Although, significant advances are made in the screening/diagnosis of the disease, treatment options remain only moderately successful and primarily include surgical resection and chemotherapy. Importantly, disease progression and metastasis remain the prime cause of the morbidity and mortality among VA-CRC patients. Thus, new therapies with the promise to inhibit CRC progression are urgently needed. Our studies are an important step in that direction. Notably, extensive work from our and other laboratories has confirmed that expression of claudin-1 is highly upregulated in CRC in a stage-specific manner, and is causally associated with CRC growth and progression. Now, using a novel mouse model of intestine-specific claudin-1 overexpression, we show novel role of claudin-1 in the regulation of Notch-signaling and colonocyte maturation/goblet cell differentiation/Muc-2 expression. We further demonstrate multi-fold increase in colonic tumor burden (tumor incidence and growth) and aggressiveness in the offspring generated through the cross between APCmin and claudin-1 transgenic mice. In our continued study, we have now generated evidence that Notch- and Wnt-signaling synergize in claudin-1-dependent manner to augment CRC in APCmin/Cl-1 mice, possibly through the regulation of cancer stem cells. Taken together, our hypothesis is that increased claudin-1 expression induces Notch-hyper activation to dysregulate normal colonic differentiation and homeostasis, and thus induces susceptibility to CRC growth & progression through the synergy between Notch and Wnt- signaling. To test our hypothesis, we propose following specific aims: Specific Aim 1. Determine that claudin-1 expression modulates Notch-signaling to regulate colon tumorigenesis. Here we will: a) determine that Notch-signaling regulates increased tumorigenesis in APCmin/Cl-1 mice; b) determine whether mucosal inflammation contributes to Claudin-1-dependent increase in colon tumorigenesis and/or aggressiveness; c) determine the mechanism/s underlying Claudin-1-dependent regulation of Notch-activation. Specific Aim 2. To determine that Notch synergizes with Wnt/b-catenin signaling to regulate claudin-1- dependent increase in colon tumorigenesis. Here, we will determine: a) the impact of inhibition of Wnt/b- catenin-signaling on colon tumorigenesis in APCmin/Cl-1 mice.; b) that claudin-1-dependent increase in Wnt/b- catenin signaling depends upon Notch-activation and to examine the underlying mechanism/s; c) whether claudin-1 expression correlates with Notch and b-catenin/Wnt-activation in colon cancer patients and its potential association with the aggressiveness of cancer. Specific Aim 3. To investigate the role of APC/ Wnt-signaling in the regulation of colonic Claudin-1 expression. Here, we will: a) examine the role of APC (WT)-Smad4 axis in the regulation of Claudin-1 expression; b) determine the details of the cross-talk between APC and Smad4 in transcriptional regulation of Claudin-1. Our short term goal is to better understand how dysregulation of claudin-1 expression modulates the ability of colon cancer cells to form tumor and further progression. Our long term goal is to develop claudin-1-specific inhibitors that can be delivered specifically to the colon cancer cells and thus to create an anti-CRC drug that is not toxic and inhibits disease progression. We believe such therapeutic interventions can significantly increase survival and quality of life US Veterans who are suffering from colorectal cancer.