Regulation of Intestinal Cell Growth and Differentiation

描述(由申请人提供)： 不断更新的肠上皮依赖于一个良好调节的增殖和分化系统。当细胞从隐窝底部的增殖室迁移出来时，它们就会分化。在结肠肿瘤中，这一过程变得无序。我们这里的目标是研究一种可能的协调这些事件的机制。肠道特异基因的表达需要尾部相关基因CDX1和CDX2。此外，一些研究表明，CDX1和CDX2可以调节肠道细胞的分化和增殖。我们的研究方向是调查这些影响，我们已经开发了研究它们的方法。我们的初步数据将证实，CDX1在大鼠肠道IEC6细胞和人结肠癌DLD1中的瞬时表达可以抑制细胞增殖并诱导G0/G1期阻滞。这种阻断与细胞周期蛋白D1mRNA和蛋白表达的缺失有关。我们已经确定了一个不同的系统来模拟CDX诱导分化。在CDX1或CDX2表达的诱导下，Colo 205结肠癌细胞获得了明显的细胞-细胞黏附表型。这与细胞形态的改变有关，包括极化的柱状形状、顶端微绒毛、粘连、桥粒连接和紧密连接。本研究旨在进一步研究CDX1和CDX2对细胞生长和分化的影响，并基于以下假设：(1)CDX1或CDX2通过下调细胞周期蛋白D1的表达而诱导G0/G1期阻滞；(2)CDX1或CDX2的表达通过诱导细胞与细胞间的黏附相互作用和激活新的CDX转录靶点而促进形态成熟。本研究的具体目的是：(1)研究CDX1或CD2对人结肠癌细胞增殖的影响；(2)研究细胞周期蛋白D1在CDX1生长抑制中的作用；(3)研究CDX1对α-连环蛋白和E2F转录活性的影响；(4)确定CDX1或CDX2对人Colo 205分化和细胞-细胞黏附的影响。这项建议探索CDX因子在调节细胞-细胞黏附、形态成熟和肠道细胞增殖过程中的作用。了解这些机制将提高我们对结肠隐窝正常事件的了解，以及在人类结肠癌中发现的分化和增殖的失调。

DESCRIPTION (provided by applicant): The continuously renewing intestinal epithelium is dependent upon a well-regulated system of proliferation and differentiation. As the cells migrate from the proliferative compartment at the crypt base they differentiate. This process becomes disordered in colonic neoplasms. Our objective here is the study of one possible mechanism coordinating these events. The expression of intestine-specific genes requires the caudal-related genes, Cdx1 and Cdx2. Additionally, several studies suggest Cdx1 and Cdx2 can regulate intestinal cell differentiation and proliferation. Our research has been directed to investigate these effects, and we have developed methods to study them. Our preliminary data will establish that transient expression of Cdx1 in rat intestinal IEC6 cells and human colon cancer DLD1 inhibits proliferation and induces a G0/G1 block. This block was associated with loss of cyclin D1 mRNA and protein expression. We have identified a different system to model Cdx induction of differentiation. Colo 205 colon cancer cells acquired an obvious cell-cell adhesion phenotype with induction of Cdx1 or Cdx2 expression. This was associated with altered cellular morphology including a polarized, columnar shape, apical microvilli, adherens, desmosomal junctions, and tight junctions. This proposal is directed toward characterizing the growth and differentiation effects further and is based on the following hypotheses: (1) Cdxl induces a G0/G1 block by a down-regulation of cyclin D1 gene expression, and (2) Cdxl or Cdx2 expression promotes morphologic maturation by inducing cell-cell adhesive interactions and activating novel Cdx transcriptional targets. The Specific Aims of this proposal are (1) to examine the effects of Cdx1 or Cd2 on the proliferation of human colon cancer cells; (2) to study the role of cyclin D1 in Cdx1 growth inhibition; (3) to characterize the effects of Cdxl on a-catenin and E2F transcriptional activity; and, (4) to determine the effects of Cdxl or Cdx2 on human Colo 205 differentiation and cell-cell adhesion. This proposal explores a role for the Cdx factors in regulating the processes of cell-cell adhesion, morphologic maturation, and proliferation of the intestinal cell. Understanding these mechanisms will improve our knowledge of normal events in the colonic crypts as well as the dysregulation of differentiation and proliferation found in human colon cancers.