PKC ISOZYMES AND INTESTINAL EPITHELIAL GROWTH CONTROL

描述(申请人提供)：本申请的长期目标是(A)确定蛋白激酶C(PKC)信号转导分子家族中单个成员在调节肠道上皮细胞自我更新中的功能(S)，以及(B)确定蛋白激酶C同工酶信号通路的变化如何促进肠道疾病的发展。这一新的应用利用了新的信息，表明PKC/PKC a信号在肠上皮细胞中触发了细胞周期退出的协调程序，PKCα活性调节了该系统中的生存途径，PKC a信号的脱敏似乎是肠道癌变的重要组成部分，以及PKC/PKC a表达/活性的丧失促进了肠道细胞的生长。基于这些发现，在这一应用中提出了一些策略来检验这一假设，即PKCα是调节肠上皮细胞生长和细胞生存的信号通路的关键组成部分，并且该分子的活性/表达的特定变化在肠道肿瘤的发展中起着关键作用。因此，PKCα功能的恢复可能有利于肠道肿瘤的预防和/或治疗。为了验证这一假说，将涉及以下特定目标：(1)确定p21waf1/cip1由PKC/PKC a信号在肠上皮细胞中转录诱导的机制，并确定p21waf1/cip1调控通路在肿瘤细胞中是否发生改变；(2)确定PKC a信号在调节肠上皮细胞存活中的作用；(3)确定在肠道癌变过程中PKC a表达缺失的分子机制；以及(4)探索在结肠癌中具有潜在预防和治疗活性的分化药物(即维甲酸，维生素D)以恢复肿瘤肠道细胞中PKCα的表达。这些研究有望加深我们对协调肠上皮细胞更新过程的信号通路的理解，并强调PKC信号通路缺陷在肠道肿瘤中的作用。

DESCRIPTION (provided by applicant): The long-term goals of this application are (a) to define the function(s) of individual members of the protein kinase C (PKC) family of signal transduction molecules in regulation of intestinal epithelial self-renewal, and (b) to determine how alterations in PKC isozyme signaling pathways contribute to the development of intestinal disease. This renewal application draws on new information demonstrating that PKC/PKC a signaling triggers a coordinated program of cell cycle withdrawal in intestinal epithelial cells, that PKC alpha activity regulates survival pathways in this system, that desensitization of PKC a signaling appears to be an important component of intestinal carcinogenesis, and that loss of PKC/PKC a expression/activity promotes the growth of intestinal cells. Based on these findings, strategies are proposed in this application to test the hypothesis that PKC alpha is a key component of signaling pathways that regulate intestinal epithelial cell growth and cell survival, and that specific alterations in the activity/ expression of this molecule play a pivotal role in the development of intestinal neoplasia. Restoration of PKC a function may thus be of benefit for the prevention and/or therapy of intestinal tumors. To test this hypothesis, the following Specific Aims will be addressed: (1) To define the mechanisms involved in transcriptional induction of p21waf1/cip1 by PKC/PKC a signaling in intestinal epithelial cells and determine if p21waf1/cip1 regulatory pathways downstream of PKC alpha signaling are altered in neoplastic intestinal cells, (2) To determine the role of PKC a signaling in regulation of intestinal epithelial cell survival, (3) To define the molecular mechanisms underlying loss of PKC a expression during intestinal carcinogenesis, and (4) To explore the potential of differentiation agents with promising preventive and therapeutic activity in colon cancer (i.e., retinoids, vitamin D) to restore PKC alpha expression in neoplastic intestinal cells. These studies are expected to enhance our understanding of the signaling pathways that orchestrate the process of intestinal epithelial renewal and highlight the contribution of defects in PKC signaling to intestinal neoplasia.