PTEN TUMOR SUPPRESSOR AND CELL CYCLE REGULATION

PTEN 肿瘤抑制剂和细胞周期调节

• 批准号: 6376738
• 负责人: HONG SUN
• 金额: $ 32.75万
• 依托单位: YALE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-07-01 至 2004-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6376738
• 关键词: 3T3 cells; SDS polyacrylamide gel electrophoresis; autoradiography; biological signal transduction; carcinogenesis; cell cycle; cell cycle proteins; cell growth regulation; embryonic stem cell; enzyme inhibitors; high performance liquid chromatography; immunoprecipitation; laboratory mouse; laboratory rabbit; nucleic acid sequence; oncoproteins; phosphatidylinositol 3 kinase; protein kinase; protein purification; protein structure function; tissue /cell culture; tumor suppressor proteins

Elucidation of tumor suppressor function provides much valuable insights into the mechanism of tumorigenesis. We have previously identified a novel phosphatase, TEP1, that shares substantial homology to several cytoskeletal proteins such as tensin. The gene encoding TEP1 is mapped to chromosome 10q23, a locus frequently deleted in human cancers. TEP1 is identical to the candidate tumor suppressor PTEN or MMAC1, which was isolated by positional cloning method. PTEN/MMAC1/TEP1 is deleted or mutated in many primary human cancers including glioblastma, endometric tumor, breast and prostate cancers and in several cancer predisposition syndromes such as Cowden disease. The broad, long term objective of this application is to elucidate the molecular mechanisms by which the cellular signaling pathways are linked to the regulatory processes for cell cycle progression and cell survival. In particular, this proposal is focused on investigating the mechanism by which the tumor suppressor protein PTEN functions to regulate cell cycle progression and how the inactivation of this tumor suppressor contributes to the genesis of human cancer. Our recent studies strongly suggest that in vivo, PTEN acts as a specific phosphatase towards phosphatidylinositol 3,4,5-trisphosphate (PIP3). We have generated the mouse embryonic stem cells in which the Pten gene was deleted by homologous recombination (Pten-/- cells). We have shown that Pten-/- cells contained elevated level of PIP3 and increased activation of Akt/PKB, a downstream signaling molecule in the PI 3-kinase pathway. Consequently, Pten-/- cells exhibited enhanced cell proliferation and cell survival. We further demonstrated that PTEN deletion caused advanced cell cycle progression into S-phase and a critical target for PTEN effect on cell cycle is p27KIP1, a CDK inhibitor. We propose to elucidate the molecular mechanism by which PTEN regulates p27 level and cell cycle progression. Our specific aims are: 1) To determine how the PTEN pathway regulates p27 level; 2) To analyze the PI 3-kinase downstream factors involved in regulation of p27; 3) To establish biochemical and molecular assays to identify the PTEN responsive factors that control p27; 4) To investigate the regulation of PTEN activity using structure and function analysis. The proposed research program in this application should provide novel insights into the molecular mechanisms that underlie the PTEN tumor suppressor function. Such knowledge should also help to provide a molecular basis for designing novel strategies for the diagnosis and treatment of human cancer.

肿瘤抑制功能的阐明为肿瘤的发生机制提供了许多有价值的见解。我们之前已经鉴定出一种新的磷酸酶TEP1，它与几种细胞骨架蛋白如张力蛋白有很大的同源性。编码TEP1的基因被定位在染色体10q23上，这是一个在人类癌症中经常缺失的基因。TEP1与用定位克隆法分离得到的候选抑癌基因PTEN或MMAC1相同。PTEN/MMAC1/TEP1在许多人类原发肿瘤中缺失或突变，包括胶质母细胞瘤、子宫内膜癌、乳腺癌和前列腺癌，以及一些癌症易感综合征，如考登病。这一应用的广泛的、长期的目标是阐明细胞信号通路与细胞周期进展和细胞生存的调控过程相联系的分子机制。特别是，这项建议侧重于研究抑癌蛋白PTEN调节细胞周期进展的机制，以及该抑癌蛋白的失活如何促进人类癌症的发生。我们最近的研究有力地表明，在体内，PTEN是磷脂酰肌醇3，4，5-三磷酸(PIP3)的特异性磷酸酶。我们已经通过同源重组获得了Pten基因缺失的小鼠胚胎干细胞(Pten-/-cell)。我们发现Pten-/-细胞中存在PIP3水平升高和Akt/PKB的激活，Akt/PKB是PI3K途径的下游信号分子。因此，Pten-/-细胞表现出促进细胞增殖和细胞存活的作用。我们进一步证明PTEN的缺失导致细胞周期提前进入S期，并且PTEN对细胞周期的影响的一个关键靶点是CDK抑制剂p27KIP1。我们建议阐明PTEN调节p27水平和细胞周期进程的分子机制。我们的具体目标是：1)确定PTEN通路如何调节p27水平；2)分析参与p27调控的PI3-激酶下游因素；3)建立生化和分子检测方法，以确定控制p27的PTEN反应因子；4)利用结构和功能分析来研究PTEN活性的调节。在这项申请中提出的研究计划将为PTEN肿瘤抑制功能的分子机制提供新的见解。这些知识也应该有助于为人类癌症的诊断和治疗设计新的策略提供分子基础。