Molecular Epidemiology of Colorectal Adenomas

描述(申请人提供)：我们的总体目标是在结直肠腺瘤的病因学中对基因的主要作用以及基因-基因和基因环境之间的相互作用进行更直接的研究，这些代谢途径是结直肠癌的公认先兆。在这项应用的父母研究中，我们有1610名受试者(778例和832名对照)的DNA和风险因素数据。我们有以下具体目标：1)研究与叶酸相关途径相关的选定基因和环境因素。具体地说，我们建议研究可能影响叶酸代谢的MTHFR、MTRR、ADH3，以及可能参与与叶酸代谢相关的DNA修复的XRCC1、XRCC3、OGG1和MGMT。此外，我们已经掌握了有关红细胞叶酸、同型半胱氨酸和DNA甲基化的数据，这些数据将在适当的时候纳入这些数据的统计分析中。2)研究可能参与胆汁酸代谢或运输的基因。具体地说，我们建议研究编码回肠钠依赖胆汁酸转运体(ISBT)的SLC10A2基因，以及VDR和EPHX1基因。我们还将进行分析，以调查这些基因的主要作用是否似乎被选定的环境因素所改变，这些环境因素被假设通过对胆汁酸的影响来影响结直肠腺瘤或癌症的风险。3)通过克隆酶的定点突变、过度表达和适当的检测，在体外系统地研究了EPHX1(别名meh)和MTHFR等流行病学相关基因中的所有非同义SNP，并在体外系统地表征了流行病学相关基因5‘和3’UTRs(非翻译区)上的所有SNPs的特征，例如表达修饰的萤火虫荧光素酶。我们选择要表征的等位基因的理论基础在研究设计和方法部分进行了描述；4)由于Thomas博士和Cortessis博士进一步发展了一种更好地分析复杂代谢途径的统计方法，我们将把这种方法应用于本研究产生的数据。

DESCRIPTION (provided by applicant): Our overall objective is to conduct more directed studies of main effects of genes and gene-gene and gene environment interactions within selected metabolic pathways of interest in the etiology of colorectal adenomas, accepted precursors of colorectal cancer (CRC). In the parent study for this application, we have DNA and risk factor data on 1,610 subjects (778 cases and 832 controls). We have the following specific aims: 1) Study selected genes and environmental factors relevant to a folate-related pathway. Specifically, we propose to study MTHFR, MTRR, ADH3, which may affect folate metabolism, and XRCC1, XRCC3, OGG1, and MGMT, which may be involved in DNA repair of damage associated with folate metabolism. In addition, we have data already in hand on RBC folates, homocysteine, and DNA methylation that will be incorporated into statistical analyses of these data where appropriate. 2) Study genes that may be involved in the metabolism or transport of bile acids. Specifically, we propose to study SLC10A2, the gene encoding the ilieal sodium-dependent bile acid transporter (ISBT), along with the VDR and EPHX1 genes. We will also conduct analyses to investigate if the main effects of these genes appear to be modified by selected environmental factors that have been hypothesized to affect risk of colorectal adenomas or cancer via an effect on bile acids. 3) To characterize systematically in vitro all non-synonymous SNPs in selected genes of epidemiologic interest, such as EPHXl (alias mEH) and MTHFR, by site-directed mutagenesis of the cloned enzyme, overexpression and appropriate assays, and to characterize systematically in vitro all SNPs in the 5' and 3' UTRs (untranslated region) of selected genes of epidemiologic interest in appropriate reporter constructs, e.g. expressing modified firefly luciferase. Our rationale for selecting alleles to be characterized is described in the Study Design and Methods section; 4) As a statistical method to better analyze complex metabolic pathways is further developed by Drs. Thomas and Cortessis, we will apply this method to data generated by this study.