Targeted Chemoprevention of Flat and Polypoid Colitis-associated Dysplasias

 描述（由申请人提供）：尽管溃疡性结肠炎患者中结直肠癌风险增加已得到充分证明，但很少关注针对该高危人群的化学预防方案的开发。基于这一缺陷，迫切需要鉴定用于早期干预的分子靶点并开发用于早期干预的分子靶点。 结肠炎相关肿瘤的化学预防的有效方案。由于该小组先前的几项研究结果提供了强有力的证据，表明结肠炎相关的结直肠肿瘤的两种形态亚型（扁平和息肉样）是通过不同的遗传途径产生的，因此只有深入了解有助于形成每种病变亚型的分子机制，才能实现有效的化学预防。 所提出的实验的假设是结肠炎相关的结肠直肠发育不良的形态亚型由β-连环蛋白介导的增强的增殖（息肉样病变）或p53依赖性凋亡信号传导的缺陷（扁平病变）引起。该假设的基本原理由诱导性结肠炎的葡聚糖硫酸钠（DSS）模型中的初步分析提供，该初步分析表明p53功能的丧失和下游靶基因的表达降低在平坦病变中普遍存在，而β-连环蛋白突变和β-连环蛋白的核定位在携带野生型p53的息肉样病变中占主导地位。提出了一系列机制研究来定义调节扁平与息肉样病变形成的“分子开关”，并评估破坏p53和β-连环蛋白信号传导作为预防结肠炎相关结直肠癌的策略的可行性。在目的1中，将在患有DSS诱导的结肠炎的遗传定义的小鼠中评价突变体β-连环蛋白或p53功能丧失分别驱动息肉样和扁平发育不良形成的能力。通过检查p53表达和活化、β-连环蛋白的亚细胞定位和p53活性的介导物（Siah-1、Mdm 2/X和miR-34）的表达，在β-连环蛋白或p53中具有确定突变的培养的人结肠癌细胞中平行研究发展每种亚型病变倾向的分子机制.在目的2中，将在野生型Tcf 4荧光素酶报告小鼠中测定通过施用再活化p53（CP 31398）或抑制β-连环蛋白介导的TCF信号传导（ICG-001）的试剂提供的针对结肠炎相关瘤形成的化学预防活性。将这些小鼠数据转化为临床环境，首先分析人扁平和息肉样结肠炎相关发育不良的增殖与凋亡能力，并通过每种病变亚型的RNA表达谱进行补充（Aim 3）。由此产生的数据预计将提供新的见解的遗传基础的平坦和息肉样结肠炎相关的发育不良，并告知合理设计的化学预防方案的早期干预结肠炎相关病变的发展，特别是平坦的发育不良，往往逃脱检测。

 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.