Analysis of STAG2 Inactivation and Aneuploidy in Human Cancer

描述（由申请人提供）：将癌细胞与正常细胞区分开来的最常见特征之一是存在非整倍体。我们最近在相当一部分恶性人类肿瘤中发现了非整倍体的原因——缺失、体细胞突变和STAG2基因表达缺失（Science 336:1039-1043, 2011）。编码的STAG2蛋白是多蛋白内聚复合物的关键组成部分，它调节姐妹染色单体内聚并帮助确保有丝分裂过程中染色体的忠实分离。在这项资助中，我们提出了多方面的努力，以进一步确定STAG2失活导致染色体不稳定、非整倍体和癌症的机制。在目标1中，我们将评估肿瘤来源的STAG2突变对姐妹染色单体内聚和蛋白-蛋白相互作用的影响。目的是对STAG2突变进行功能评估，以揭示在肿瘤发生过程中丢失的STAG2关键活性。在Aim #2中，我们将确定STAG2截断突变对内聚蛋白的蛋白质组成及其在细胞周期不同阶段与染色质相互作用的能力的影响。这些实验将使我们能够确定STAG2失活导致染色体不稳定和非整倍体的关键机制。在Aim #3中，我们将确定STAG2失活在人类星形胶质细胞和GBM细胞中转化的启动和维持中的作用。这些实验将使我们能够确定STAG2失活是否会导致恶性转化的易感性增强。在Aim #4中，我们将确定STAG2突变是否会导致GBM细胞对电离辐射和DNA损伤化疗药物敏感。该研究计划的总体目标是确定STAG2失活导致染色体不稳定、非整倍体和细胞转化的机制，从而有可能开发出专门针对非整倍体细胞的新型抗癌疗法。

DESCRIPTION (provided by applicant): One of the most common features that distinguishes cancer cells from normal cells is the presence of aneuploidy. We have recently discovered a cause of aneuploidy in a substantial fraction of malignant human tumors - deletions, somatic mutations, and loss of expression of the STAG2 gene (Science 336:1039-1043, 2011). The encoded STAG2 protein is a key component of the multi-protein cohesin complex which regulates sister chromatid cohesion and helps ensure faithful chromosome segregation during mitosis. In this grant we propose a multi-faceted effort to further define the mechanism through which STAG2 inactivation leads to chromosomal instability, aneuploidy, and cancer. In Aim #1 we will evaluate the effects of tumor-derived mutations in STAG2 on sister chromatid cohesion and protein-protein interactions. The goal is to functionally evaluate mutations in STAG2 to reveal the key activities of STAG2 that are lost during tumorigenesis. In Aim #2 we will determine the effect of STAG2 truncating mutations on the protein composition of cohesin and its ability to interact with chromatin at different phases of the cell cycle. These experiments wil enable us to identify key mechanisms by which STAG2 inactivation leads to chromosomal instability and aneuploidy. In Aim #3 we will determine the role of STAG2 inactivation on the initiation and maintenance of transformation in human astrocytes and GBM cells. These experiments will enable us to determine if STAG2 inactivation results in enhanced susceptibility to malignant transformation. In Aim #4 we will determine if mutations in STAG2 cause GBM cells to be sensitized to ionizing radiation and DNA damaging chemotherapeutic drugs. The broad goal of the proposed research program is to determine the mechanism through which STAG2 inactivation leads to chromosomal instability, aneuploidy, and cellular transformation, making it possible to develop strategies for identifying novel anticancer therapeutics that specifically target aneuploid cells.