Targeted Chemoprevention of Flat and Polypoid Colitis-associated Dysplasias

 描述(申请人提供)：尽管溃疡性结肠炎患者患结直肠癌的风险增加是有充分证据的，但很少有人注意到为这一高危人群开发一种化学预防方案。基于这一缺陷，迫切需要确定早期干预和发展的分子靶点。 化学预防结肠炎相关肿瘤的有效方案。由于该小组先前的几项研究结果提供了强有力的证据，表明结肠炎相关结直肠肿瘤的两种形态亚型(扁平和息肉样)是通过不同的Geneti途径发生的，因此只有在深入了解导致每种病变亚型形成的分子机制后，才能实现有效的化学预防。拟议实验的假设是，结肠炎相关的结直肠发育不良的形态亚型要么源于？连环蛋白介导的增殖增强(息肉样病变)，要么源于p53依赖的凋亡信号的缺陷(扁平病变)。对葡聚糖硫酸钠(DSS)诱导的结肠炎模型的初步分析表明，p53功能丧失和下游靶基因表达减少在扁平病变中普遍存在，而在含有野生型p53的息肉样病变中，？连环蛋白突变和？连环蛋白的核定位占主导地位。建议进行一系列机制研究，以确定调节扁平和息肉病变形成的“分子开关”，并评估干扰P53和？连环蛋白向S发送预防结肠炎相关性结直肠癌策略的可行性。在目标1中，将在DSS诱导的结肠炎的基因定义的小鼠中评估突变型连环蛋白或p53功能丧失分别驱动息肉样变和扁平异型增生的形成的能力。通过检测P53的表达和激活、B型连环蛋白的亚细胞定位以及P53活性的介体(Siah-1、MDM2/X和miR-34)的表达，将在培养的具有明确p53突变的人结肠癌细胞中平行研究导致每种亚型病变倾向的分子机制。在目标2中，将在野生型TCF4荧光素酶报告小鼠中确定通过重新激活P53(CP31398)或抑制？连环蛋白介导的TCF信号转导(ICG-001)的药物对结肠炎相关肿瘤的化学预防活性。将这些小鼠数据转换到临床环境将首先分析人类扁平和息肉样结肠炎相关异型增生的增殖和凋亡能力，并辅之以每种病变亚型的RNA表达谱(目标3)。由此产生的数据有望为扁平和息肉样结肠炎相关发育不良的遗传基础提供新的见解，并为合理设计化学预防方案以早期干预结肠炎相关损害的发展，特别是经常漏诊的扁平发育不良提供信息。

 DESCRIPTION (provided by applicant): Although the increased risk of colorectal cancer among patients with ulcerative colitis is well documented, little attention has been given to the development of a chemopreventive regimen for this high- risk population. Based on this deficiency, a critical need exists to identify molecular targets for early intervention and develop efficacious regimens for the chemoprevention of colitis-associated neoplasia. Because results from several prior studies by this group provide strong evidence that the two morphological subtypes of colitis-associated colorectal neoplasias (flat and polypoid) arise via different geneti pathways, effective chemoprevention will only be realized once an in-depth understanding of the molecular mechanisms that contribute to the formation of each lesion subtype has been achieved. The hypothesis of the proposed experimentation is that morphological subtypes of colitis-associated colorectal dysplasias arise from either ß-catenin-mediated enhanced proliferation (polypoid lesions) or deficiencies in p53-dependent apoptotic signaling (flat lesions. Rationale for this hypothesis is provided by preliminary analyses in the dextran sulfate sodium (DSS) model of induced colitis that indicate that loss of p53 function and decreased expression of downstream target genes are prevalent in flat lesions, while ß-catenin mutations and nuclear localization of ß-catenin predominate in polypoid lesions bearing wild-type p53. A series of mechanistic studies are proposed to define the "molecular switch" that regulates the formation of flat vs. polypoid lesions and assess the feasibility of disrupting p53 and ß-catenin signaling s a strategy for the prevention of colitis-associated colorectal cancer. The ability of mutant ß-catenin or loss of function of p53 to drive the formation of polypoid and flat dysplasias, respectively, will be evaluated in Aim 1 in genetically defined mice with DSS-induced colitis. The molecular mechanisms underlying the propensity to develop each subtype of lesion will be investigated in parallel in cultured human colon carcinoma cells with defined mutations in ß-catenin or p53 by examining p53 expression and activation, subcellular localization of ß-catenin and the expression of mediators of p53 activity (Siah-1, Mdm2/X and miR-34). In Aim 2, the chemopreventive activity afforded against colitis-associated neoplasia by administering agents that reactivate p53 (CP31398) or inhibit ß-catenin-mediated TCF signaling (ICG-001) will be determined in wild-type Tcf4 luciferase reporter mice. Translation of these murine data to a clinical setting will be initiated with an analysis of the proliferative vs. apoptotic capacity of human flat and polypoid colitis-associated dysplasias and complemented by RNA expression profiling of each lesion subtype (Aim 3). The resulting data are anticipated to provide novel insight into the genetic basis of flat and polypoid colitis-associated dysplasias and inform the rational design of chemopreventive regimens for early intervention in the development of colitis-associated lesions, in particular flat dysplasias that often escape detection.