Gastrointestinal Cell Proliferation and Cell Cycle

描述(申请人提供)：转化生长因子-β是哺乳动物细胞培养中G1/S细胞周期进程的重要调节因子。细胞周期蛋白依赖性蛋白依赖性激酶(CDKs)和c-myc抑制细胞周期蛋白依赖性蛋白依赖性蛋白激酶(CDKs)和c-myc的信号转导和调控通过Smads发生。Smad2、Smads和Smad4是参与胃肠道细胞增殖的关键蛋白。Smad2和Smad4的胚系突变导致个体易患胃肠癌。我们已经证明，破坏ELF，一种β-幽灵蛋白，通过Smads和Smad4干扰转化生长因子-β信号。此外，ELF和Smad4的双重杂合子(ELF/-/Smad4/-)会更早地发展为胃增生症和肿瘤。为了进一步了解ELF/Smad4在细胞周期调控和肿瘤发生中的作用，我们建议：(1)对来自ELF/~/Smad4/-小鼠的胃细胞和小鼠胚胎成纤维细胞(MEF)进行详细的鉴定，以确定ELF缺失对细胞周期动力学的影响，这些细胞经历衰老的能力，胃细胞和成纤维细胞对凋亡刺激的敏感性；以及胃细胞和MEF对癌基因癌变的敏感性。(2)确定ELF/Smad4/-小鼠对肿瘤易感性增强的分子基础，并确定导致肿瘤形成的次要事件的性质。(3)利用ELF/-/Smad4/-和Smad4/-小鼠以及P53基因缺陷小鼠，研究ELF/Smad4和P53信号通路之间的协同作用。(4)将目标1中描述的实验扩展到整个动物模型系统，通过确定精灵/~/Smad4/-和Smad4/-小鼠在化学致癌物如MNU和/或DMBA以及幽门螺杆菌VacA毒素治疗后对癌症发展的增强敏感性，并开展旨在确定精灵/‘/Smad4/-和Smad4/-小鼠对肿瘤易感性增强的分子基础的实验。

DESCRIPTION (provided by applicant): TGF-beta is an important regulator of G1/S cell cycle progression of mammalian cells in culture. Signaling and modulation of TGF-beta dependent inhibition of cyclin-dependent kinases (cdks) and c-myc with G1 arrest, occurs through Smads. Smad2, SmadS and Smad4 are key proteins involved in gastrointestinal cell proliferation. Germline mutations in Smad2 and Smad4 result in a predisposition of the individuals to the development of gastrointestinal carcinoma. We have shown that disruption of elf, a beta-Spectrin disrupts TGF-beta signaling through SmadS and Smad4. Moreover, double heterozygotes of elf and Smad4 (elf+/-/Smad4+/-) develop earlier gastric hyperplasia and tumors. To gain further insight into the role of elf/Smad4 in cell cycle regulation and neoplasia, we propose: (1) to carry out a detailed characterization of gastric cells and mouse embryonic fibroblasts (MEFs) derived from elf/~/Smad4+/- mice to determine the effect of loss of ELF on cell cycle kinetics, ability of these cells to undergo senescence, susceptibility of gastric cells and fibroblasts to apoptotic stimuli; and susceptibility of gastric cells and MEFs to neoplastic transformation by oncogenes. (2) To determine the molecular basis for the enhanced susceptibility of the elf/Smad4+/- mice to the development of tumors and determine the nature of secondary events that lead to tumor formation. (3) To investigate the collaboration between the elf/Smad4 and p53 pathways, using elf+/-/Smad4+/- and Smad4+/- mice and mice deficient in p53. (4) To extend experiments described in Aim 1 to whole animal model systems by determining enhanced susceptibility of the elf/~/Smad4+/- and Smad4+/- mice to the development of carcinomas following treatment with chemical carcinogens such as MNU and/or DMBA, and H. pylori VacA toxin, and carrying out experiments aimed at determining the molecular basis for enhanced susceptibility to neoplasia in the elf/'/Smad4+/- and Smad4+/- mice.