Beta-Catenin/NF-kB in Hyperplasia/Neoplasia of Colonic Crypts: Chemoprevention

描述（由申请人提供）： 结肠隐窝的过度增生被认为是结肠癌发生的重要危险因素。慢性肠道炎症，特别是结肠炎，也会显著增加结肠癌的风险。然而，炎症和增殖之间复杂的相互关系，导致粘膜引发肿瘤，是不太清楚。我们将采用由革兰氏阴性细菌啮齿柠檬酸杆菌（CR）引起的增生小鼠模型，即传染性小鼠结肠增生（TMCH）。研究在慢性炎症存在或不存在的情况下，增生如何通过2- catenin/NF-：B影响表观遗传信号。TMCH的特征在于上皮过度增殖和增生。根据遗传背景，不同程度的炎症发生与人类炎症性胃肠道疾病的病理生理相似性。在Swiss-Webster远系杂交小鼠中，TMCH与2-连环蛋白及其下游靶点（细胞周期蛋白D1和c-myc）的增加相关，后者先于NF-：B活性的变化。膳食果胶（6%，丁酸盐来源）阻断2-连环蛋白水平和NF-：B活性的增加，并显著消除增生。有趣的是，通过I：B1的蛋白酶体抑制单独阻断NF-：B活化并不能减少增生。在遗传易感的C3 H/HeNHsd（C3 H）近交系小鼠中，增生的初始阶段之后是响应于CR感染的慢性炎症，伴随着上皮内CD 3 +/CD 103 +T细胞和几种促炎剂（如IL-12、IL-6、KC等）的存在的急剧增加。基于这些发现，我们的假设是：1）活化的2-连环蛋白和NF-：B的相对水平的表观遗传改变在炎症存在或不存在的情况下将是不同的; 2）果胶的相对抑制功效将由表观遗传改变和相关炎症决定。这些假设将在目标1和2中得到检验。导致TMCH模型中2-连环蛋白丰度升高和活化的机制仍然未知。在目标3中，我们将通过利用体内和体外方法来研究其中的一些机制。这些实验将使我们首次了解在存在或不存在炎症的情况下2-连环蛋白和NF-：B的表观遗传学改变是否会影响膳食果胶对增生的相对抑制功效，以及膳食干预如何影响粘膜启动肿瘤形成。增殖速率的增加形成了正常结肠上皮转化为癌症的最早和最可能的必要背景。慢性肠道炎症，特别是结肠炎，也会显著增加患癌症的风险。然而，炎症和增殖之间的复杂的相互关系，导致随后的粘膜引发肿瘤，是不太清楚。利用过度增殖和增生的小鼠模型，TMCH（可传播的小鼠结肠增生），我们将研究在存在或不存在炎症的情况下2-连环蛋白和NF-：B的表观遗传改变如何影响膳食果胶对增生的相对抑制功效以及膳食干预如何影响肿瘤形成的粘膜引发。从最早的，而且很可能是必要的， 正常结肠上皮转化为癌症的背景。慢性肠道炎症，特别是结肠炎，也会显著增加患癌症的风险。然而，炎症和增殖之间的复杂的相互关系，导致随后的粘膜引发肿瘤，是不太清楚。利用小鼠模型的过度增殖和增生，TMCH（可传播的小鼠结肠增生），我们将研究如何表观遗传改变？连环蛋白和NF-？B在存在或不存在炎症的情况下，影响膳食果胶对增生的相对抑制功效，以及膳食干预如何影响肿瘤形成的粘膜引发。

DESCRIPTION (provided by applicant): Hyperproliferation of colonic crypts is recognized as an important risk factor for colon carcinogenesis. Chronic intestinal inflammation, especially of the colon, also significantly increases the risk of colon cancer. However, the complex inter-relationships between inflammation and proliferation, resulting in mucosal priming for neoplasia, are less well understood. We will employ a murine model of hyperplasia, Transmissible Murine Colonic Hyperplasia (TMCH), caused by a Gram-negative bacterium, Citrobacter rodentium (CR.) to study how hyperplasia, in the presence or absence of chronic inflammation affects epigenetic signaling via 2- catenin/NF-:B. TMCH is characterized by epithelial hyperproliferation and hyperplasia. Depending upon the genetic background, varying degrees of inflammation occur with pathophysiological similarities to human inflammatory gastrointestinal diseases. In Swiss-Webster outbred mice, TMCH is associated with increases in 2-catenin and its downstream targets (cyclin D1 and c-myc) that precede changes in NF-:B activity. Dietary pectin (6%, source of butyrate) blocks increases in 2-catenin levels and NF-:B activity and significantly abrogates hyperplasia. Intriguingly, blocking NF-:B activation alone via proteasomal inhibition of I:B1 does not reduce hyperplasia. In genetically susceptible C3H/HeNHsd (C3H) inbred mice, an initial phase of hyperplasia is followed by chronic inflammation in response to CR infection, accompanied by dramatic increases in the presence of intra-epithelial CD3+/CD103+T cells and several pro-inflammatory agents (such as IL-12, IL-6, KC etc). Based on these findings, our hypotheses are: 1) Epigenetic alterations in the relative levels of activated 2-catenin and NF-:B will be different in the presence or absence of inflammation; 2) The relative inhibitory efficacy of pectin will be dictated by the epigenetic alterations and associated inflammation. These hypotheses will be tested in Aims 1 and 2. The mechanisms leading towards elevated abundance and activation of 2-catenin in the TMCH model remains unknown. In Aim 3, we wil examine some of these mechanisms by utilizing both in vivo and in vitro approaches. These experiments will allow us to learn for the first time if epigenetic alterations in 2-catenin and NF-:B in presence or absence of inflammation, impact the relative inhibitory efficacy of dietary pectin on hyperplasia and how dietary intervention affects mucosal priming for neoplasia. Increased rates of proliferation form the earliest and, most probably, the necessary background for the transformation of a normal colonic epithelium to cancer. Chronic intestinal inflammation, especially of the colon, also significantly increases risk of developing cancer. However, the complex inter-relationships among inflammation and proliferation leading subsequently to mucosal priming for neoplasia, is less well understood. Utilizing a mouse model of hyperproliferation and hyperplasia, TMCH (transmissible murine colonic hyperplasia) we will study how epigenetic alterations in 2- catenin and NF-:B in the presence or absence of inflammation, impact the relative inhibitory efficacy of dietary pectin on hyperplasia and how dietary intervention affects mucosal priming for neoplasia. PUBLIC HEALTH RELEVANCE Increased rates of proliferation form the earliest and, most probably, the necessary background for the transformation of a normal colonic epithelium to cancer. Chronic intestinal inflammation, especially of the colon, also significantly increases risk of developing cancer. However, the complex inter-relationships among inflammation and proliferation leading subsequently to mucosal priming for neoplasia, is less well understood. Utilizing a mouse model of hyperproliferation and hyperplasia, TMCH (transmissible murine colonic hyperplasia) we will study how epigenetic alterations in ¿-catenin and NF-?B in the presence or absence of inflammation, impact the relative inhibitory efficacy of dietary pectin on hyperplasia and how dietary intervention affects mucosal priming for neoplasia.