ATM mutations in breas cancer - a functional approach

说明(申请人提供)：电离辐射(IR)是一种在动物和人类中都已知的乳腺癌致癌物质。暴露于红外线会引起DNA的各种损伤，其中最危险的是DNA双链断裂(DSB)。基因组不稳定可能是由于未修复的DSB的存在导致细胞死亡或恶性转化。真核生物已经进化出有效的系统来监测基因组的完整性，并通过细胞周期停滞、修复和/或凋亡机制对它们的存在做出快速反应。哺乳动物细胞DNA DSB反应途径的主要调节因子是ATM蛋白。ATM是这一途径中的几种蛋白质之一，这些蛋白质由与乳腺癌易感性有关的基因编码。尽管IR、乳腺癌和这些基因之间存在有趣的关系，但对于这种特殊的生化途径如何对乳腺癌风险产生特定影响，目前还没有明确的模型。我们现在已经为ATM的角色开发了一个模型。在这个“错义突变”模型中，我们提出ATM突变的一个子集通过显性干扰起作用，降低ATM的内在激酶活性，和/或扰乱包括ATM的蛋白质复合体。该模型预测，ATM介导的乳腺癌风险仅限于此类突变的携带者，并表明IR等制剂可能会增强此类个体的致癌作用。IR是ATM的有效诱导剂。为了探索ATM、辐射暴露与乳腺癌之间的复杂关系，我们发起了WeCARE(女性环境癌症与辐射暴露)研究，2100名患有单侧或非同步双侧乳腺癌的妇女参加了研究。在这个收集中，乳腺癌危险因素通过问卷调查进行了评估；进行了全面的辐射剂量重建和ATM基因的完全突变筛查。对ATM数据的初步分析显示，在接受放射治疗并携带ATM错义突变的受试者中，患第二原发乳腺癌的风险显著增加。然而，突变状态的确定仅基于序列保守性的考虑-原始研究中没有对突变状态的功能确认。在这一新的应用中，我们建议在这些初步发现的基础上，通过直接测试这一假设，即在接受放射治疗作为第一次原发乳腺癌治疗的女性中，对侧乳腺癌的发病率增加，并且这些女性携带特定的ATM等位基因，这种等位基因主要干扰细胞对IR的反应。我们的研究将表征在WeCare筛选过程中发现的假定ATM突变对DNA损伤反应途径的功能影响，然后将这些信息纳入整个WeCare研究的变量分析中。

DESCRIPTION (provided by applicant): Ionizing radiation (IR) is a known breast carcinogen in both animals and humans. IR exposure generates a variety of lesions in DNA of which the most dangerous are DNA double strand breaks (DSBs). Genomic instability can result from the presence of unrepaired DSBs leading to cell death or malignant transformation. Eukaryotes have evolved efficient systems for monitoring genomic integrity and responding rapidly to their presence via cell cycle arrest, repair, and/or apoptotic mechanisms. The master regulator of the mammalian cellular DNA DSB response pathway is the protein ATM. ATM is one of several proteins in this pathway encoded by genes implicated in breast cancer susceptibility. Despite the intriguing relationship between IR, breast cancer, and these genes, there is no clear model for how this particular biochemical pathway has specific effects on breast cancer risk. We have now developed a model for the role of ATM. In this "missense-mutation" model we propose that a subset of ATM mutations act by dominant interference, reducing the intrinsic kinase activity of ATM, and/or disrupting protein complexes that include ATM. The model predicts that ATM-mediated risk for breast cancer is specific to carriers of this class of mutation and suggests that agents such as IR, which are potent inducers of ATM, may have enhanced carcinogenic effects in such individuals. In order to explore the complex relationship between ATM, radiation exposure and breast cancer, we initiated the WECARE (Women's Environment Cancer and Radiation Exposure) study in which 2100 women with either unilateral or asynchronous bilateral breast cancer are enrolled. In this collection, breast cancer risk factors have been assessed by questionnaire; both full radiation dosimetry reconstruction, and full mutation screening of the ATM gene have been carried out. Preliminary analysis of the ATM data reveals a significant increase in risk for second primary breast cancers in subjects who received radiation therapy and carry ATM missense mutations. However, mutation status determination was based only on consideration of sequence conservation-no functional confirmation of mutation status was included in the original study. In this new application, we propose to build upon these preliminary findings by directly testing the hypothesis that the incidence of contralateral breast cancer is increased among women who received radiation therapy as a treatment for their first primary breast cancer and who are carriers of specific ATM alleles which dominantly interfere with the cellular response to IR. Our studies will characterize putative ATM mutations identified in the course of WECARE screening for their functional effects on DNA damage response pathways, and then incorporate this information into the analysis of variables for the overall WECARE study.