Homologous Recombination in Genome Stability and Tumor Suppression

描述（由申请人提供）：本提案的目的是确定同源重组在基因组稳定性、肿瘤抑制和正常发育中的作用。染色体不稳定性是许多癌症的主要标志，染色体畸变是重要的预后标志，不稳定性越大，通常意味着预后越差。不幸的是，预防或促进染色体不稳定的潜在分子机制在很大程度上仍然未知。越来越多的证据表明未修复的DNA双链断裂（DSB）与基因组不稳定有关。同源重组（HR）是一种重要的DSB修复途径，在细胞增殖过程中尤为重要。我们的中心假设是，在快速分裂的细胞中，同源重组对于预防癌症相关的基因组不稳定至关重要。我们将通过关注淋巴细胞中一个重要的HR通路成分XRCC2的功能来验证这一假设。我们最近使用一种适用于体外和体内研究的淋巴细胞培养系统，发现XRCC2是正常b细胞发育所必需的。我们现在将使用相同的系统来实现以下具体目标：1)测试XRCC2在多大程度上阻止与复制相关的基因组不稳定性和肿瘤发生。采用体外和体内两种方法，我们将测试xrcc2缺陷细胞的自发或诱导染色体异常，并测量xrcc2缺陷对肿瘤抑制的影响。2)明确XRCC2与p53蛋白相互作用的机制。我们的数据表明Xrcc2和编码p53的基因（Trp53）之间存在遗传相互作用。我们将使用多种方法来测试这是否涉及蛋白质的直接或间接物理相互作用。3)检测XRCC2在正常淋巴细胞发育中的功能。我们的数据表明，XRCC2不仅在防止基因组不稳定方面具有关键功能，而且在促进正常淋巴细胞发育方面也具有关键功能。为了更好地理解肿瘤抑制的机制，我们将使用体外和体内方法精确定义XRCC2在正常淋巴细胞发育中的作用。这项工作对于理解染色体异常的分子起源以及它们如何驱动癌症发展至关重要。公共卫生相关性：染色体畸变是人类癌症的一个标志，可以作为病人预后的有用指标。在这个建议中，我们将研究癌症相关染色体畸变的起源和它们发生的机制。确定这些机制将是设计更好的癌症诊断测试的关键；改善预后指标；并根据肿瘤特异性开发新的癌症治疗方法。

DESCRIPTION (provided by applicant): The objectives of this proposal are to determine the roles for homologous recombination in genome stability, tumor suppression, and normal development. Chromosomal instability is a major hallmark of many cancers, and chromosome aberrations can be important prognostic markers, with greater instability usually corresponding to poorer outlook. Unfortunately, the underlying molecular mechanisms that prevent or promote chromosomal instability remain largely unknown. Growing evidence implicates unrepaired DNA double strand breaks (DSB) in genome instability. Homologous recombination (HR) represents one critical DSB repair pathway that may be especially important as cells are multiplying. Our central hypothesis is that homologous recombination is crucial for preventing cancer-related genome instability in rapidly dividing cells. We will test this hypothesis by focusing on the function of one important HR pathway component, XRCC2, in lymphocytes. Using a lymphocyte culture system amenable to both in vitro and in vivo studies, we recently showed that XRCC2 is required for normal B-cell development. We will employ this same system to now carry out the specific aims of: 1) Testing the extent to which XRCC2 prevents replication-associated genome instability and tumorigenesis. Using both in vitro and in vivo approaches, we will test Xrcc2-defective cells for spontaneous or induced chromosomal abnormalities, and measure the effects of Xrcc2-deficiency on tumor suppression. 2) Defining the mechanisms of interaction between XRCC2 and the p53 protein. Our data indicate a genetic interaction between Xrcc2 and the gene encoding p53 (Trp53). We will use multiple approaches to test whether this involves direct or indirect physical interaction of the proteins. 3) Measuring the functions of XRCC2 in normal lymphocyte development. Our data suggest that XRCC2 has critical functions, not just in preventing genome instability, but also in promoting normal lymphoid development. To better understand the mechanisms of tumor suppression, we will precisely define the normal lymphoid developmental roles of XRCC2, using in vitro and in vivo approaches. This work will be essential to understanding the molecular origins of chromosomal abnormalities and how they may function to drive cancer development. PUBLIC HEALTH RELEVANCE: Chromosome aberrations are a hallmark of human cancer, and can be useful indicators of patient prognosis. In this proposal we will investigate the origins of cancer-related chromosome aberrations and the mechanisms by which they occur. Identifying these mechanisms will be key to designing better cancer diagnostic tests; refining prognostic markers; and developing new cancer therapies based on tumor-specific properties.