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

描述(由申请人提供)： 结肠隐窝过度增殖被认为是结肠癌发生的重要危险因素。慢性肠炎，尤其是结肠炎症，也会显著增加患结肠癌的风险。然而，炎症和增殖之间复杂的相互关系，导致粘膜对肿瘤的启动，还不太清楚。我们将使用由革兰氏阴性杆菌罗氏柠檬酸杆菌(CR)引起的小鼠增生性传播性结肠增生症(TMCH)的小鼠模型。研究在慢性炎症存在或不存在的情况下，增殖如何通过2-连环蛋白/核因子-B影响表观遗传信号。TMCH以上皮过度增殖和增殖为特征。根据遗传背景的不同，会发生不同程度的炎症，其病理生理与人类炎症性胃肠道疾病相似。在瑞士-韦氏近交系小鼠中，TMCH与2-连环素及其下游靶标(细胞周期蛋白D1和c-myc)的增加有关，这些靶标先于核因子-：B活性的变化。饮食中的果胶(6%，丁酸的来源)阻止了2-连环蛋白水平和核因子：B活性的增加，并显著地阻止了增生。有趣的是，仅通过蛋白酶体抑制I：B1来阻断NF-：B的激活并不能减少增生。在遗传易感的C3H/HeNHsd(C3H)近交系小鼠中，伴随着慢性炎症反应的慢性炎症反应，伴随着上皮内CD3+/CD103+T细胞和几种促炎因子(如IL-12、IL-6、KC等)的急剧增加。基于这些发现，我们的假设是：1)有或没有炎症时，激活的2-连环蛋白和核因子-B的相对水平的表观遗传变化将不同；2)果胶的相对抑制效果将由表观遗传变化和相关的炎症决定。这些假说将在目标1和目标2中得到验证。在TMCH模型中，导致2-连环蛋白丰度增加和激活的机制尚不清楚。在目标3中，我们将利用体内和体外的方法来研究其中的一些机制。这些实验将使我们第一次了解在存在或不存在炎症的情况下，2-连环蛋白和核因子：B的表观遗传变化是否影响饮食果胶对增殖的相对抑制效果，以及饮食干预如何影响粘膜对肿瘤的启动。增殖率的增加是正常结肠上皮向癌症转化的最早的，也是最有可能的必要背景。慢性肠炎，尤其是结肠炎症，也会显著增加罹患癌症的风险。然而，炎症和增殖之间复杂的相互关系导致随后粘膜启动肿瘤，还不太清楚。利用一种小鼠的过度增殖和增殖模型，TMCH(传递性小鼠结肠增生)，我们将研究在存在或不存在炎症的情况下，2-连环蛋白和核因子：B的表观遗传学变化如何影响饮食果胶对增殖的相对抑制效果，以及饮食干预如何影响黏膜对肿瘤的启动。与公共卫生相关的核扩散速度的增加形成了最早也最有可能是必要的 正常结肠上皮向癌症转化的背景。慢性肠炎，尤其是结肠炎症，也会显著增加罹患癌症的风险。然而，炎症和增殖之间复杂的相互关系导致随后粘膜启动肿瘤，还不太清楚。利用一种小鼠过度增殖和增殖的模型，TMCH(传递性小鼠结肠增生)，我们将研究在有或没有炎症的情况下，连环蛋白和核因子-β的表观遗传学变化如何影响饮食果胶对增殖的相对抑制效果，以及饮食干预如何影响粘膜对肿瘤的启动。

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.