Elf/Smad4 in Gastrointestinal Cell Proliferation and Cell Cycle Progression

描述（由申请人提供）：tgf - β是培养的哺乳动物细胞G1/S细胞周期进程的重要调节因子。细胞周期蛋白依赖性激酶（cdks）和c-myc的tgf - β依赖性抑制与G1阻滞的信号传导和调节通过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的种系突变导致个体易患胃肠道癌。我们已经证明elf的破坏，β -幽灵素通过smad和Smad4破坏tgf - β信号。此外，elf和Smad4的双杂合子（elf+/-/Smad4+/-）更早发生胃增生和肿瘤。为了进一步了解elf/Smad4在细胞周期调节和肿瘤形成中的作用，我们建议：(1)对elf/~/Smad4+/-小鼠的胃细胞和小鼠胚胎成纤维细胞（MEFs）进行详细的表征，以确定elf缺失对细胞周期动力学、细胞衰老能力、胃细胞和成纤维细胞对凋亡刺激的易感性的影响；以及胃癌细胞和mef对癌基因转化的易感性。(2)确定elf/Smad4+/-小鼠对肿瘤发生易感性增强的分子基础，确定导致肿瘤形成的继发事件的性质。(3)利用elf+/-/Smad4+/-和Smad4+/-小鼠和p53缺失小鼠，研究elf/Smad4和p53通路之间的协同作用。(4)将Aim 1中描述的实验扩展到整个动物模型系统，确定elf/~/Smad4+/-和Smad4+/-小鼠在接受化学致癌物如MNU和/或DMBA以及幽门螺杆菌VacA毒素治疗后对肿瘤发展的易感性增强，并开展旨在确定elf/'/Smad4+/-和Smad4+/-小鼠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.