MUCINS AND COLON CANCER PROGRESSION

描述：MUC 2基因座的调节和MUC 2基因缺失的后果。 粘蛋白在结肠肿瘤发生中的作用将通过追踪 Apc基因突变对杯状细胞分化的影响以及 粘蛋白以促进遗传引发的肿瘤中的肿瘤发生。 小说 将使用遗传小鼠模型，其中存在靶向灭活 小鼠Muc 2基因，杯状细胞被特异性标记， 与人MUC 2基因启动子连接的β-gal的表达。 的 该项目源于三个观察结果：（1）在人类异常隐窝病灶中， (ACF)早期癌前病变，杯状细胞减少， 它们产生的粘蛋白的消耗。 (2)基因启动的老鼠 模型Apc 1638，其具有Apc基因的靶向失活， 概括了FAP个体的表型，也发展了ACF， 在人类中，显示杯状细胞减少。 (3)的表型 遗传启动的小鼠（即，在APC中具有突变）被减弱， 环氧合酶2（COX 2）基因失活，提供了令人信服的证据 COX 2与结肠癌的发展有关。 小鼠MUC 2基因座的克隆、结构和功能分析将为进一步研究MUC 2基因的功能奠定基础。 完成的原因有两个：引导转基因建设， 确定谱系特异性表达所需的元素（将使用 目的4）通过比较人和小鼠的调节元件;和 为Muc 2缺失小鼠的开发提供试剂。 由于失去了 粘蛋白是人类和小鼠模型中ACF形成的早期事件， 待开发的Muc 2-/-小鼠，与Apc 1638小鼠（GI 肿瘤发生之前是ACF的发展），将允许 确定粘蛋白损失如何影响肿瘤发展。 的 MUC 2/β-gal转基因小鼠也将允许确定是否 Apc突变干扰杯状细胞分化途径 血统;改变的时间和早期病理病变，这 过程也将被定义。 最后，研究将检验这一假设 保护性粘蛋白的丢失（发生在ACF中， 进展）导致炎症反应，可能与 诱导COX 2（结肠肿瘤发生的关键因素），从而 这表明粘蛋白的丢失可能是APC引发的肿瘤的促进剂。 已经可用的小鼠模型（APC 1638和COX 2-/-），以及那些 在本提案中开发的（MUC 2-/-，MUC 2/β-gal），将用于 测试这个假设。

DESCRIPTION: Regulation of the MUC2 locus and the consequences of loss of mucins in colon tumorigenesis will be investigated by pursuing the effects of an Apc mutation on goblet cell differentiation and the ability of loss of mucins to promote tumorigenesis in genetically initiated tumors. Novel genetic mouse models will be used in which there is targeted inactivation of the mouse Muc2 gene, and goblet cells are specifically labelled by the expression of beta-gal linked to the promoter of the human MUC2 gene. The project stems from three observations: (1) In human aberrant crypt foci (ACF) early preneoplastic lesions, there is depletion of goblet cells and a depletion of the mucins they produce. (2) The genetically initiated mouse model Apc 1638, which has a targeted inactivation of the Apc gene and recapitulates the phenotype of FAP individuals, also develops ACF that, as in humans, show depletion of goblet cells. (3) The phenotype of a genetically initiated mouse (i.e., with a mutation in apc) is attenuated by cyclooxygenase 2 (COX2) gene inactivation, providing compelling evidence that COX2 is involved in the development of colon cancer. The cloning, structural and functional analysis of the mouse MUC2 locus will be completed for two reasons: to guide construction of transgenics to identify the elements necessary for lineage specific expression (to be used under Aim 4) by comparison of the human and mouse regulatory elements; and to provide reagents for development of the Muc2 null mouse. Since a loss of mucins is an early event in ACF formation in human and mouse models, the Muc2-/- mouse to be developed, in combination with the Apc 1638 mouse (GI tumorigenesis is preceded by the development of ACF), will permit the determination of how mucin loss influences tumor development. The MUC2/beta-gal transgenic mice will also allow determination of whether mutation of Apc perturbs the differentiation pathway of the goblet cell lineage; alterations in the timing and early pathological lesions of this process will also be defined. Finally, studies will test the hypothesis that the loss of protective mucins (which happens in ACF, early in progression) leads to an inflammatory response that may be linked to induction of COX2 (a critical element in colon tumorigenesis), thereby demonstrating that loss of mucins can be a promoter of APC-initiated tumors. Mouse models already available (APC 1638 and COX2 -/-), as well as those to be developed in this proposal (Muc2 -/-, MUC2/beta-gal), will be used to test this hypothesis.