Mechanisms of Cell Cycle Associated Neoplasia

描述（由申请人提供）：调节细胞周期的基因突变是肿瘤发生的基本机制。这些突变涉及内在细胞周期组分本身（细胞周期蛋白、Cdk抑制剂）以及癌基因（例如，c-Myc）和影响细胞周期机制的肿瘤抑制因子（例如p53、Fbw 7）。该提案侧重于这些癌症相关细胞周期途径的功能和调节。 Fbw 7肿瘤抑制因子靶向细胞周期蛋白E、Notch和c-Jun，在它们被磷酸化后降解。在初步研究中，我们发现Fbw 7也调节磷酸化依赖的c-Myc周转，并且三种Fbw 7亚型（Fbw 7 α，Fbw 7 β，Fbw 7 γ）表现出独特的亚细胞定位。在目标1中，我们将通过在小鼠中产生Fbw 7 α和Fbw 7 γ的条件无效突变来检验Fbw 7亚型在这些隔室中执行不同生物学功能的假设。我们将检查每个异构体在调节特定Fbw 7底物中的作用，我们将测试Fbw 7 γ在核仁中调节c-Myc功能的假设。在目标2中，我们将确定Fbw 7 α或Fbw 7 γ是否是肿瘤抑制因子。这些实验将确定Fbw 7 γ和Fbw 7 α的正常和肿瘤功能。 影响苏氨酸58（T58）的突变是淋巴瘤中最常见的c-Myc突变，并且T58磷酸化调节c-Myc稳定性。我们已经发现GSK-3对T58的磷酸化调节Fbw 7介导的c-Myc更新。在目标3中，我们将检验T58突变通过阻止c-Myc与Fbw 7的相互作用而促成c-Myc相关瘤形成的假设。我们将开发T58突变的敲入小鼠，用于研究T58磷酸化在调节c-Myc丰度和功能中的作用，并确定其在c-Myc相关肿瘤发生中的作用。 p27 Cdk抑制剂在人类癌症中的表达减少意味着预后不良，并且p27在小鼠中是肿瘤抑制剂。在上一个资助期，我们在p27-null小鼠中使用插入突变来鉴定与p27- 1 oss合作的癌基因，并鉴定了三个候选癌基因（c-myc，Jdpl，GPC 3/XpcI 1）。目的4的目标是利用小鼠移植模型来确定血细胞中Jdp 2和GPC 3/Xpc 11表达失调的后果，研究Jdp 2或GPC 3/Xpc 11激活与p27丢失之间的协同性，并了解这种协同性的机制。

DESCRIPTION (provided by applicant): Mutation of genes that regulate the cell cycle is a fundamental mechanism underlying tumorigenesis. These mutations involve intrinsic cell cycle components themselves (cyclins, Cdk inhibitors) as well as oncogenes (e.g., c-Myc) and tumor suppressors (e.g. p53, Fbw7) that impact upon the cell cycle machinery. This proposal focuses on the functions and regulation of these cancer-associated cell cycle pathways. The Fbw7 tumor suppressor targets cyclin E, Notch, and c-Jun for degradation after they have been phosphorylated. In preliminary studies, we found that Fbw7 also regulates phosphorylation-dependent c-Myc turnover and that the three Fbw7 isoforms (Fbw7alpha, Fbw7beta, Fbw7gamma) exhibit unique subcellular Iocalizations. In Aim 1 we will test the hypothesis that the Fbw7 isoforms perform distinct biologic functions in these compartments by developing conditional-null mutations of Fbw7alpha and Fbw7gamma in the mouse. We will examine the roles of each isoform in regulating specific Fbw7 substrates, and we will test the hypothesis that Fbw7gamma, regulates c-Myc function in the nucleolus. In Aim 2 we will determine if Fbw7alpha or Fbw7gamma are tumor suppressors. These experiments will define the normal and neoplastic functions of Fbw7gamma and Fbw7alpha. Mutations affecting threonine 58 (T58) are the most common c-Myc mutations in lymphomas and T58 phosphorylation regulates c-Myc stability. We have found that T58 phosphorylation by GSK-3 regulates Fbw7-mediated c-Myc turnover. In Aim 3 we will test the hypothesis that T58 mutations contribute to c-Myc associated neoplasia by preventing the interaction of c-Myc with Fbw7. We will develop knock-in mice in which T58 is mutated that will than be used to study the role of T58 phosphorylation in regulating c-Myc abundance and function, and to determine its role in c-Myc-associated tumorigenesis. Reduced expression of the p27 Cdk inhibitor in human cancers connotes poor prognosis, and p27 is a tumor suppressor in mice. In the last funding period we used insertional mutagenesis in p27-null mice to identify oncogenes that cooperate with p27-1oss, and identified three candidate oncogenes (c-myc, Jdpl, GPC3/XpcI1). The goals of Aim 4 are to utilize murine transplant models to determine the consequences of deregulated Jdp2 and GPC3/Xpcl1 expression in blood cells, to study the cooperativity between Jdp2 or GPC3/Xpcl1 activation and p27-loss, and to understand the mechanisms of this cooperativity.