Differential gene expression in IGFs genes and the risk of breast cancer

描述（由申请人提供）： 癌症遗传病因学的研究主要集中在改变蛋白质功能（蛋白质质量）的序列变异，如截短突变、错义取代和剪接点突变。然而，最近的研究表明，对于复杂的疾病，蛋白质数量的温和变化可能比蛋白质质量的根本变化更重要。越来越多的证据表明，影响基因表达丰度的调节多态性可以改变疾病风险。胰岛素样生长因子（IGF）系统在调节细胞增殖和凋亡中起重要作用。IGF系统的失调导致癌细胞生长和存活。来自遗传流行病学和临床研究的融合数据提供了强有力的证据，即血清中IGF 1蛋白的高循环水平和IGFBP 3蛋白的低循环水平显著预测乳腺癌风险的增加。虽然IGF 1和IGFBP 3循环水平与人群水平的乳腺癌风险增加有关，但个体风险不能通过直接测量血清中的蛋白质浓度容易地分配，因为正常的IGF 1和IGFBP 3蛋白质范围很宽，循环水平受几个个人因素的影响，包括饮食，运动和体重。有限的数据还表明，IGF 1和IGFBP 3都表现出等位基因特异性基因表达（ASGE），这通常是由调节多态性控制。因此，阐明负责增加乳腺癌风险的调节多态性和开发简单的基于DNA的检测方法，可能使我们能够准确地识别未来乳腺癌高风险的健康个体。假设：IGF信号通路中控制等位基因特异性基因表达（ASGE）的基因的调节多态性影响患乳腺癌的风险。具体而言，我们将研究以下假设：1）。IGF 1和IGFBP 3蛋白水平的个体间差异是由于这些基因中的ASGE; 2）. IGF 1基因中的特定单倍型与IGF 1的过表达相关，IGFBP 3中的特定单倍型与IGFBP 3的表达降低相关。此次重新提交的重点是IGF和IGFBP 3基因中的ASGE。在本申请中，我们将在Aim 1中通过最近开发的技术鉴定细胞系中这两种基因的ASGE，在Aim 2中通过重新测序确定与ASGE相关的单倍型，然后在Aim 3中测试mRNA水平的ASGE是否导致蛋白质水平的改变。我们将确定负责ASGE和IGF 1和IGFBP 3蛋白水平的个体间变异的单倍型。这种方法将导致一种新的诊断测试，其中ASGE可以用基于DNA的血液测试进行测定。在未来的工作中，我们将确定是否与乳腺癌风险有关，以及在其他基因中检测ASGE。如果与乳腺癌有关联，这项测试可能是一个有价值的预测标志物，个人的乳腺癌风险。然后，这些知识可以用来帮助临床医生和他们的患者更准确地评估乳腺癌风险，并帮助设计有效的预防策略。

DESCRIPTION (provided by applicant): Investigations of the genetic etiology of cancer have mainly focused on sequence variants that alter protein function (protein quality) such as truncating mutations, missense substitutions, and splice junction mutations. However, recent studies suggest that, for complex diseases, milder changes in protein quantity may be more important than radical changes in the protein quality. Increasing evidence has shown that regulatory polymorphisms that affect gene expression abundance can modify disease risk. The insulin-like growth factor (IGF) system plays an important role in regulating cellular proliferation and apoptosis. Deregulation of the IGF system leads to cancer cell growth and survival. Converging data from genetic epidemiology and clinical studies provide strong evidence that high circulating levels of IGF1 protein and low circulating levels of IGFBP3 protein in serum significantly predict increased risks of breast cancer. Although IGF1 and IGFBP3 circulating levels are associated with increased risk of breast cancer at the population level, individual risk cannot be easily assigned by directly measuring the protein concentration in serum, because the normal IGF1 and IGFBP3 protein ranges are wide and circulating levels are influenced by several personal factors including diet, exercise, and body weight. Limited data also suggest that both IGF1 and IGFBP3 exhibit allele-specific gene expression (ASGE), which is usually controlled by regulatory polymorphisms. Therefore, the elucidation of regulatory polymorphisms responsible for increasing the risk of breast cancer and development of simple DNA-based assays may allow us to accurately identify healthy individuals who are at high risk of breast cancer in the future. Hypothesis: Regulatory polymorphisms in genes in the IGF signaling pathway, which control allele-specific gene expression (ASGE), affect risk of developing breast cancer. Specifically, we will investigate the following hypotheses: 1). the inter-individual variation in IGF1 and IGFBP3 protein levels are due to ASGE in these genes; 2). Specific haplotype(s) in IGF1 gene are correlated with over-expression of IGF1 and specific haplotype(s) in IGFBP3 correlated with reduced expression of IGFBP3. This resubmission is focused on ASGE in the IGF and IGFBP3 genes. In this application, we will identify ASGE in cell lines for these two genes, by recently developed techniques, in Aim 1, determine the haplotypes, correlated to ASGE, through re- sequencing in Aim 2, and then test if the ASGE in mRNA level results in alterations in protein level in Aim 3. We will identify haplotypes responsible for ASGE and inter-individual variation in protein levels of IGF1 and IGFBP3. This approach will lead to a new diagnostic test in which ASGE can be assayed with a DNA-based blood test. In future work, we will then determine if there is an association with breast cancer risk, as well as test for ASGE in additional genes. If there is an association with breast cancer, this test could be a valuable predictive marker of an individual's risk for breast cancer. The knowledge could then be used to assist clinicians and their patients to more accurately assess breast cancer risk and help in designing effective preventative strategies.