权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Role of ornithine decarboxylase in Ras transformation

鸟氨酸脱羧酶在 Ras 转化中的作用

基本信息

批准号：
7081242
负责人：
LISA M SHANTZ
金额：
$ 20.58万
依托单位：
PENNSYLVANIA STATE UNIV HERSHEY MED CTR
依托单位国家：
美国
项目类别：
财政年份：
1999
资助国家：
美国
起止时间：
1999-07-01 至 2008-06-30
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): The goal of this work is to understand the mechanism by which ornithine decarboxylase (ODC) activity is induced during carcinogenesis by oncogenic ras, andto define the role of ODC in this process. Results in the Progress Report show for the first time that induction of ODC activity in Ras-transformed cells requires the coordinate activation of the Raf/MEK/ERK and PI 3-kinase pathways. ODC RNA and protein are increased, with the primary regulation being post-transcriptional. We will use constitutively active forms of Ras, Raf and Akt to activate the effector pathways of interest in RIE-1 epithelial cells. These cells are appropriate since the Raf/ME/ERK and PI 3-kinase pathways cooperate in their transformation. We will use this model to study translational regulation of ODC in response to these signaling cascades, and to assess the role of sustained ODC activation in transformation, cell cycle control, and survival. We also show that inhibiting ODC with the irreversible inactivator alpha-difluoromethylornithine (DFMO) delays the onset of spontaneous tumors in mice overexpressing an active MEK mutant in the skin (K14-MEK mice), and causes regression of established tumors. To test the hypothesis that suppression of ODC blocks the promotion of target cells initiated by the Raf/MEK/ERK pathway, we will cross K14-MEK mice with two transgenic lines overexpressing antizyme (AZ), which binds to ODC and targets it for degradation. We have shown using K5-AZ and K6-AZ mice that AZ suppresses tumor growth in the two-stage model of skin carcinogenesis. The K6 promoter requires hyperproliferation for maximal expression. Since MEK overexpression causes hyperplasia, MEK/K6-AZ mice represent a model to test if ODC inhibition is effective in preventing tumor formation after establishment of a carcinogenic environment. The K5 promoter is constitutive, and MEK/K5-AZ mice have a constant expression of AZ from birth. These mice represent a chemoprevention model, in which ODC is inhibited at the time of the initiating stimulus. We will examine tumors from MEK/AZ mice to determine effects on cell cycle proteins, apoptosis, and proliferation. To specifically address the role of ODC in cell cycle progression during tumorigenesis, we will use transgenic mice that overexpress AZ and cyclin D1 in the skin. Keratinocytes from D1/AZ mice will also be used to analyze direct interactions of AZ with cyclin D1, to test whether other properties of AZ are important for deregulation of cell proliferation in tumor development.

描述（由申请人提供）：本研究的目的是了解致癌ras在致癌过程中诱导鸟氨酸脱羧酶（ODC）活性的机制，并确定ODC在此过程中的作用。进展报告中的结果首次表明，Ras转化细胞中ODC活性的诱导需要Raf/MEK/ERK和PI 3-激酶途径的协同激活。ODC RNA和蛋白质增加，主要调控是转录后。我们将使用Ras、Raf和Akt的组成型活性形式来激活RIE-1上皮细胞中感兴趣的效应子途径。这些细胞是合适的，因为Raf/ME/ERK和PI 3-激酶途径在它们的转化中合作。我们将使用这个模型来研究响应这些信号级联的ODC的翻译调节，并评估持续的ODC激活在转化，细胞周期控制和存活中的作用。我们还表明，用不可逆灭活剂α-二氟甲基鸟氨酸（DFMO）抑制ODC可延迟皮肤中过度表达活性MEK突变体的小鼠（K14-MEK小鼠）中自发性肿瘤的发作，并导致已建立的肿瘤消退。为了检验抑制ODC阻断Raf/MEK/ERK途径启动的靶细胞促进的假设，我们将K14-MEK小鼠与两个过表达抗酶（AZ）的转基因系杂交，所述抗酶结合ODC并靶向其降解。我们已经使用K5-AZ和K6-AZ小鼠证明AZ在皮肤癌发生的两阶段模型中抑制肿瘤生长。K6启动子需要过度增殖以获得最大表达。由于MEK过表达导致增生，因此MEK/K6-AZ小鼠代表了测试在建立致癌环境后ODC抑制是否有效预防肿瘤形成的模型。K5启动子是组成型的，并且MEK/K5-AZ小鼠从出生起就具有AZ的恒定表达。这些小鼠代表了化学预防模型，其中ODC在起始刺激时被抑制。我们将检查来自MEK/AZ小鼠的肿瘤，以确定对细胞周期蛋白、凋亡和增殖的影响。为了明确ODC在肿瘤发生过程中细胞周期进展中的作用，我们将使用皮肤中过表达AZ和细胞周期蛋白D1的转基因小鼠。来自D1/AZ小鼠的角质形成细胞也将用于分析AZ与细胞周期蛋白D1的直接相互作用，以测试AZ的其他特性是否对肿瘤发展中细胞增殖的失调很重要。