Cell Growth Signaling in Cancer Development

描述(申请人提供)：生长是细胞积累质量和增大大小的过程。MTORC1是一种蛋白激酶，由mTOR催化亚基及其相关蛋白Raptor和mLST8组成，是调节生长对生长因子、营养物质和压力反应的信号网络的中心组成部分。越来越明显的是，许多促进癌症的病变激活了mTORC1途径。最值得注意的是，TSC1-TSC2肿瘤抑制复合体--其失活会导致肿瘤倾向综合征结节性硬化症(TSC)和相关疾病淋巴管肌瘤病(LAM)--是mTORC1的主要负调控因子。TSC1-TSC2异源二聚体是一种GTP酶激活蛋白(GAP)，可以抑制Rheb，Rheb是一种GTP结合蛋白，通过一种鲜为人知的机制激活mTORC1。TSC1-TSC2和Rheb对于失去PTEN、NF1、LKB1或P53抑癌基因的细胞中mTORC1的激活也是重要的。我们建议解决我们对mTORC1生物学理解中的关键差距。首先，我们将确定在生长因子或TSC1-TSC2或PTEN失活的情况下激活mTORC1的分子机制。其次，利用我们正在开发的小鼠模型，我们将严格测试mTORC1在PTEN失活导致的肿瘤发生中的作用。第三，我们将获得完整的mTORC1和mTOR激动域的结构信息。我们将通过利用生物化学、分子生物学、癌症小鼠模型和结构生物学等工具的多学科协作方法来实现我们的目标。我们相信，我们的结果可能对结节性硬化症的治疗具有重要的医学意义。了解TSC1-TSC2失活是如何激活mTORC1的，对于合理开发TSC的治疗方法是必要的。通过我们的动物模型，我们将获得一个明确的遗传学答案，说明在PTEN缺失的肿瘤患者中抑制mTORC1的潜在价值。最后，我们新颖的mTORC1激酶分析的改进版本可能有助于高通量筛选抑制mTORC1的小分子，我们的结构工作将为mTOR激酶抑制剂的开发提供信息。与公共卫生相关：生长是细胞和有机体积累质量并增大大小的过程。越来越明显的是，这一基本的生物学过程在常见的人类疾病中被放松了管制，最明显的是在癌症中。在这项应用中，我们打算研究哺乳动物中的一种主要生长调节因子，一种由几种蛋白质组成的复合体，称为mTORC1。我们建议阐明在癌症和正常细胞中激活mTORC1的分子机制，确定抑制mTORC1是否可能是治疗具有常见致癌基因改变的肿瘤的良好方法，最后，确定mTORC1的分子结构。我们提议的工作的总体目标是增加肿瘤学社区在癌症治疗中合理利用mTORC1的能力。我们预计，我们的工作将有助于了解哪些肿瘤类型应该使用mTORC1抑制剂治疗，有助于开发更具特异性的mTORC1抑制剂，并导致发现可能成为未来药物开发目标的机制。

DESCRIPTION (provided by applicant): Growth is the process through which cells accumulate mass and increase in size. mTORC1 is a protein kinase composed of the mTOR catalytic subunit and the associated proteins raptor and mLST8 and the central component of a signaling network that regulates growth in response to growth factors, nutrients, and stress. It is increasingly apparent that many cancer-promoting lesions activate the mTORC1 pathway. Most notably, the TSC1-TSC2 tumor suppressor complex--whose inactivation causes the tumor- prone syndrome Tuberous Sclerosis Complex (TSC) and the related disease Lymphangioleiomyomatosis (LAM)--is a major negative regulator of mTORC1. The TSC1-TSC2 heterodimer is a GTPase activating protein (GAP) that inhibits rheb, a GTP-binding protein that activates mTORC1 through a poorly understood mechanism. TSC1-TSC2 and rheb are also important for the activation of mTORC1 that occurs in cells that have lost the PTEN, NF1, LKB1, or p53 tumor suppressors. We propose to address key gaps in our understanding of mTORC1 biology. First, we will determine the molecular mechanisms that activate mTORC1 in response to growth factors or inactivation of TSC1- TSC2 or PTEN. Second, using mouse models we are developing, we will rigorously test the role of mTORC1 in tumorigenesis caused by inactivation of PTEN. Third, we will obtain structural information about intact mTORC1 and the mTOR kinase domain. We will accomplish our goals with a collaborative multi-disciplinary approach that exploits the tools of biochemistry, molecular biology, mouse models of cancer, and structural biology. We believe that our results are likely to have significant medical implications for the treatment of Tuberous Sclerosis Complex. An understanding of how the inactivation of TSC1-TSC2 activates mTORC1 is necessary for the rational development of therapies for TSC. With our animal models we will obtain a definitive genetic answer to the potential value of inhibiting mTORC1 in patients with tumors missing PTEN. Lastly, modified versions of our novel mTORC1 kinase assay may be useful for the high- throughput screening of small molecules that inhibit mTORC1 and our structural work will inform the development of inhibitors of the mTOR kinase. PUBLIC HEALTH RELEVANCE: Growth is the process through which cells and organisms accumulate mass and increase in size. It is increasingly apparent that this basic biological process is deregulated in common human diseases, most notably in cancer. In this application we propose to study one of the major growth regulators in mammals, a complex of several proteins called mTORC1. We propose to elucidate the molecular mechanisms that activate mTORC1 in cancer and normal cells, to determine if inhibiting mTORC1 is likely to be a good treatment for tumors that have a common cancer-causing genetic alteration, and, lastly, to determine the molecular structure of mTORC1. The overall goal of our proposed work is to increase the capacity of the oncology community to rationally exploit mTORC1 in the treatment of cancer. We anticipate that our work will help understand which tumor classes should be treated with mTORC1 inhibitors, aid in the development of more specific mTORC1 inhibitors, and lead to the discovery of mechanisms that may be targets for future drug development.