Epigenomic influences of diet on intestinal neoplasia

描述（由申请人提供）：在这个项目中，我们建议使用小鼠模型系统来探索饮食是否影响癌症的发展。我们的假设是，饮食对基因调控产生长期和累积的影响，即所谓的表观遗传效应，导致从正常的调控模式向早期癌症形成模式的变化。一个关键的基因调控机制是基因组中胞嘧啶的甲基化，通常与基因沉默有关。已经观察到胞嘧啶甲基化在许多癌症中发生了深刻的改变，与基因表达的变化有关，这些变化导致细胞的不受调控的生长。胞嘧啶上甲基的底物是单碳供体分子，如叶酸。研究表明，饮食中叶酸水平的改变对基因组中胞嘧啶甲基化的总体水平有实质性影响，但受影响的精确位点尚未确定。我们开发了一种全基因组检测方法来检测小鼠基因组中约60万个胞嘧啶甲基化位点，使我们能够识别在这种情况下受影响的基因座。我们提出了一项研究，在该研究中，我们测试正常细胞从空肠区域的小肠和腺瘤从同一地区，使用小鼠已被喂养正常或单碳供体缺乏饮食。我们将确定表观遗传变化，发生（a）作为对叶酸，胆碱和蛋氨酸缺乏的饮食的反应，和（B）在良性肿瘤从相同的小鼠（使用Apc 1638模型）。我们将定义每种情况下的变化程度，我们称之为表观基因组距离，并通过寻找每种情况下涉及的位点的一致性来确定正常细胞中饮食诱导的变化是否代表肿瘤转化过程中的中间状态。该项目的成功结果将揭示癌症形成早期阶段的见解，将特定类型的饮食缺乏与异常甲基化和癌症易感性联系起来，并为诊断和预防试验的人类研究奠定基础-可以想象，由于长期饮食影响而获得的表观遗传变化可以通过改变饮食来逆转。这一试点项目将作为一个扩大项目的基础，以解决这些可能性。虽然饮食在引起胃肠道癌症方面显然有影响，但饮食与导致正常细胞成为癌细胞所需的遗传变化之间的联系仍然难以捉摸。在这项研究中，我们建议使用小鼠模型系统，以测试是否基因调控在肠道肿瘤中受到干扰时，暴露于饮食，影响基因表达，胞嘧啶甲基化的调节器之一。这项研究将是第一个全基因组范围的胞嘧啶甲基化研究，以确定饮食诱导的变化是否代表癌症发展的中间阶段。

DESCRIPTION (provided by applicant): In this project, we propose to explore whether diet influences the development of cancer using a mouse model system. Our hypothesis is that diet exerts chronic and cumulative effects on gene regulation, so-called epigenetic effects, to cause a change from a normal pattern of regulation towards the pattern in early cancer formation. One key gene regulatory mechanism is the methylation of cytosines in the genome, usually associated with gene silencing. Cytosine methylation has been observed to be profoundly altered in a number of cancers, associated with gene expression changes that contribute to the cell's unregulated growth. The substrate for the methyl group added to cytosine are single carbon donor molecules like folic acid. It has been shown that altered folate levels in diet have substantial effects on overall levels of cytosine methylation in the genome, but the precise loci affected have not been identified. We developed a genome-wide assay to test ~600,000 sites in the mouse genome for cytosine methylation, allowing us to identify the loci affected in such situations. We propose a study in which we test normal cells from the jejunal area of the small intestine and adenomas from the same area, using mice that have been fed normal or single carbon donor-deficient diets. We will identify the epigenetic changes that occur (a) as a response to the diet deficient in folate, choline and methionine, and (b) in benign tumors from the same mice (using the Apc1638 model). We will define the degree of change in each case, a measure we call epigenomic distance, and determine whether diet-induced changes in normal cells represent an intermediate state on the way to neoplastic transformation by looking for consistency of the loci involved in each case. The successful outcome of this project will reveal insights into the early stages of cancer formation, link a specific type of dietary deficiency with aberrant methylation and cancer susceptibility, and create the basis for human studies for diagnostic and for prophylactic trials - it is conceivable that acquired epigenetic changes due to prolonged dietary influences could be reversed pharmacologically or through changed diet alone. This pilot project will serve as the foundation for an expanded project to address these possibilities. While diet is clearly influential in causing cancer of the gastrointestinal tract, the link between diet and the genetic changes required to cause a normal cell to become a cancer cell have remained elusive. In this study, we propose to use a mouse model system to test whether gene regulation is disturbed in intestinal tumours when exposed to a diet that influences one of the regulators of gene expression, cytosine methylation. The study will be the first genome-wide study of cytosine methylation to see whether diet-induced changes represent an intermediate stage in the development of cancer.