Cyclin A Function in Normal Proliferation and in Neoplasia

细胞周期蛋白 A 在正常增殖和肿瘤形成中的功能

• 批准号: 8010621
• 负责人: Peter Sicinski
• 金额: $ 43.6万
• 依托单位: DANA-FARBER CANCER INST
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-04-01 至 2013-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8010621
• 关键词: Ablation; Acute; Address; Animals; Automobile Driving; Belief; Brain; Bypass; Cancer Patient; Cell Cycle; Cell Cycle Progression; Cell Line; Cell Proliferation; Cells; Cerebellum; Cyclin A; Cyclin E; Cyclin-Dependent Kinases; Cyclins; Development; Embryo; Fibroblasts; Health; Hematopoietic stem cells; Human; In Vitro; Knockout Mice; Knowledge; Laboratories; Lead; Lung Adenocarcinoma; Malignant Neoplasms; Malignant neoplasm of lung; Mammalian Cell; Mammals; Molecular; Mus; Neoplasms; Nervous system structure; Normal Cell; Null Lymphocytes; Oncogenic; Pathogenesis; Play; Proliferating; Role; S Phase; Somatic Cell; Staging; Stem cells; Testing; Testis; Textbooks; Therapeutic; Tissues; Work; base; blastomere structure; cancer cell; cell type; cyclin A1; cyclin A2; in vivo; malignant breast neoplasm; mouse development; mouse model; nestin protein; non-oncogenic; novel therapeutic intervention; overexpression; postnatal; therapeutic target; tumorigenesis

DESCRIPTION (provided by applicant): Cyclins are components of the core cell cycle machinery. They serve to activate the associated cyclin-dependent kinases (CDKs). This proposal focuses on cyclin A and its role in normal development and in neoplasia. Mammalian cells express two A-type cyclins: the ubiquitous cyclin A2 and testis-specific cyclin A1. According to our current understanding of the cell cycle machinery, cyclin A represents an essential S-phase cyclin which is required for all embryonic and somatic cell cycles in mammals. This notion is supported by the observation that cyclin A2-null mice die at embryonal day 5.5. Overexpression of cyclin A2 has been shown to play an important role in pathogenesis of many human cancers. Hence, cyclin A might represent a potential therapeutic target in human neoplasia. However, the current notion that cyclin A represents an essential component of the core cell cycle machinery has precluded exploring this possibility. We experimentally tested this notion by generating conditional cyclin A knockout mice (lacking both A-cyclins). This approach allowed us to bypass the early embryonic lethality and to derive cyclin A-null mouse embryonal fibroblasts. Surprisingly, we found that an acute shutdown of A-type cyclins in in vitro cultured fibroblasts had no impact on cell proliferation. Hence, contrary to the current notion, cyclin A is dispensable for normal, non-oncogenic proliferation at least in in vitro cultured fibroblasts. These unexpected findings raise several important issues: (1) What is the molecular basis of the S-progression in the absence of cyclin A? (2) Are A-type cyclins also dispensable for cell cycle progression in vivo, during normal mouse development? (3) Is cyclin A required for the oncogenic proliferation of cancer cells? In the proposed work we will address these issues. The overall hypothesis to be tested is that cyclin A is dispensable for normal, non-oncogenic proliferation of the majority of cell types, but it is critically required for oncogenic proliferation of at least a subset of cancers. If our hypothesis is confirmed, it will change our understanding of the cell cycle machinery, and it may lead to novel therapeutic approaches for cancer patients. In Aim 1 we will test our hypothesis that in mammalian cells A- type and E-type cyclins perform overlapping, redundant roles in driving S phase progression. Consequently, we hypothesize that cyclin A-deficient cells proliferate normally due to the presence of cyclin E. We further hypothesize that ablation of the E-type cyclins in cyclin A-null background would completely halt cell cycle progression. In Aim 2, we will use tissue-specific and inducible Cre strains to bypass the peri-implantational lethality, and to study the requirement for cyclin A function at later stages of development. Lastly in Aim 3, we will study the requirement for cyclin A function in Myc-driven transformation, and in breast and lung cancers in vivo. The Specific Aims are: Aim 1. To study the molecular basis of cyclin A function in cell cycle progression. Aim 2. To determine the requirement for cyclin A function in various lineages during normal development. Aim 3. To determine the requirement for cyclin A function in oncogenic cell proliferation. PUBLIC HEALTH RELEVANCE: The well-documented overexpression of cyclin A in a many human cancers suggests that cyclin A might represent a potential therapeutic target in human neoplasia. However, it is currently a textbook knowledge that cyclin A is essential for normal proliferation of all cells, thereby precluding exploration of anti-cyclin A therapeutic strategies. The work proposed in this application will likely change this notion, and will lead to re-focusing our efforts on cyclin A inhibition in human cancers. Hence, the proposed work will likely lead to novel therapeutic approaches for human cancer patients.

描述（由申请人提供）：细胞周期蛋白是核心细胞周期机制的组成部分。它们用于激活相关的细胞周期蛋白依赖性激酶（CDK）。这个建议的重点是细胞周期蛋白A及其在正常发育和肿瘤形成中的作用。哺乳动物细胞表达两种A型细胞周期蛋白：普遍存在的细胞周期蛋白A2和睾丸特异性细胞周期蛋白A1。根据我们目前对细胞周期机制的理解，细胞周期蛋白A代表哺乳动物所有胚胎和体细胞周期所需的必需S期细胞周期蛋白。这一观点得到了细胞周期蛋白A2缺失小鼠在胚胎第5.5天死亡的观察结果的支持。细胞周期蛋白A2的过表达在许多人类肿瘤的发病机制中起重要作用。因此，细胞周期蛋白A可能是一个潜在的治疗靶点在人类肿瘤。然而，目前认为细胞周期蛋白A代表核心细胞周期机制的重要组成部分，排除了探索这种可能性。我们通过产生条件性细胞周期蛋白A敲除小鼠（缺乏两种细胞周期蛋白）来实验性地测试这一概念。这种方法使我们能够绕过早期胚胎致死性，并获得细胞周期蛋白A无效的小鼠胚胎成纤维细胞。令人惊讶的是，我们发现在体外培养的成纤维细胞中A型细胞周期蛋白的急性关闭对细胞增殖没有影响。因此，与目前的观点相反，至少在体外培养的成纤维细胞中，细胞周期蛋白A对正常的非致癌性增殖是不敏感的。这些意想不到的发现提出了几个重要的问题：（1）在没有细胞周期蛋白A的情况下，S进展的分子基础是什么？(2)在正常小鼠发育过程中，A型细胞周期蛋白是否也参与体内细胞周期进程？(3)细胞周期蛋白A是癌细胞致癌增殖所必需的吗？在拟议的工作中，我们将解决这些问题。待检验的总体假设是，细胞周期蛋白A对于大多数细胞类型的正常、非致癌性增殖是必需的，但它对于至少一个癌症子集的致癌性增殖是关键性需要的。如果我们的假设得到证实，它将改变我们对细胞周期机制的理解，并可能为癌症患者带来新的治疗方法。在目的1中，我们将测试我们的假设，即在哺乳动物细胞中，A型和E型细胞周期蛋白在驱动S期进展中发挥重叠、冗余的作用。因此，我们推测，细胞周期蛋白A缺陷的细胞增殖正常，由于细胞周期蛋白E的存在。我们进一步假设，在细胞周期蛋白A缺失的背景下切除E型细胞周期蛋白将完全停止细胞周期进程。在目标2中，我们将使用组织特异性和诱导型Cre菌株来绕过围产期致死性，并研究在发育后期对细胞周期蛋白A功能的需求。最后，在目标3中，我们将研究Myc驱动的转化以及体内乳腺癌和肺癌中对细胞周期蛋白A功能的需求。具体目标是：目标1。研究细胞周期蛋白A在细胞周期进程中的分子基础。目标2.确定正常发育过程中不同谱系对细胞周期蛋白A功能的需求。目标3。确定致癌细胞增殖对细胞周期蛋白A功能的需求。 公共卫生相关性：许多人类癌症中细胞周期蛋白A的过度表达表明细胞周期蛋白A可能是人类肿瘤的潜在治疗靶点。然而，目前的教科书知识是细胞周期蛋白A是所有细胞的正常增殖所必需的，从而排除了抗细胞周期蛋白A治疗策略的探索。本申请中提出的工作可能会改变这一概念，并将导致我们重新关注人类癌症中的细胞周期蛋白A抑制。因此，拟议的工作可能会为人类癌症患者带来新的治疗方法。