Genetic Association Study in African-American Colorectal Cancer Patients

描述（由申请人提供）：结直肠癌（CRC）是美国癌症发病率和死亡率的重要原因。确定谁处于较高的风险在CRC中尤其重要，因为筛选测试已被证明可以减少死亡。CRC发展的风险是由于遗传和环境因素，这些因素在所有人群中并不均匀。迄今为止，CRC遗传学领域主要集中在高加索人群，而很少有研究包括非洲裔美国人（AA）患者。确定AA的风险因素是一个特别重要的目标，因为该人群的发病率和死亡率并没有像所有其他美国人群那样下降。在芝加哥大学，我们有独特的能力来解决AA中的遗传因素，因为我们已经组装了一个大型的AA CRC病例对照系列。本研究的主要目的是使用候选基因筛选方法鉴定CRC易感等位基因，并在AA CRC患者和对照组中检测相关性。CRC特别适合于候选基因研究，因为在遗传性CRC综合征和腺瘤到癌序列的致癌作用分析中已经鉴定出生物学相关途径。碱基切除修复途径特别有趣，因为最近的工作已经阐明了与MYH基因突变相关的隐性息肉综合征。因此，参与这一途径的基因在生物学上可能是携带CRC易感等位基因的候选基因，但迄今为止，它们尚未在AA中得到充分鉴定或表征。我们的假设是，新的易感等位基因在碱基切除修复基因有助于风险CRC发展的非洲裔美国人。为了验证这一假设，我们将使用高通量异源双链分析筛选候选碱基切除修复基因，并使用测序来表征DNA变化（具体目标1）。为了控制混合AA人群中的人群分层，我们将使用一组高信息量的祖先信息标记物（具体目标2）确定个体祖先估计值。最后，我们将对400例AA CRC病例和400例对照的候选基因筛选中确定的假定CRC易感等位基因进行基因分型，然后通过逻辑回归（具体目标3）进行相关性检验。随着对个体风险的了解和适当的筛查，结直肠癌在很大程度上是一种可预防的疾病。我们研究的目的是更好地了解增加风险的遗传因素，特别是在非洲裔美国人中，他们的癌症发病率和死亡率最高。

DESCRIPTION (provided by applicant): Colorectal cancer (CRC) is a significant cause of cancer morbidity and mortality in the US. Determining who is at higher risk is especially important in CRC because screening tests are available that are proven to reduce death. Risk of CRC development is due to both hereditary and environmental factors which are not uniformly shared between all populations. To date, the field of CRC genetics has focused largely on Caucasian populations, while few studies have included African-American (AA) patients. Determining risk factors in AAs is an especially important goal because both incidence and mortality in this population are not decreasing as they are in all other US populations. At the University of Chicago, we are uniquely equipped to address genetic factors in AAs because we have assembled a large AA CRC case-control series. The main purpose of this study is to identify CRC-susceptibility alleles using a candidate gene screen approach and test for association in AA CRC patients and controls. CRC is particularly amenable to candidate gene studies because biologically relevant pathways have been identified in hereditary CRC syndromes and in the analysis of carcinogenesis in the adenoma to carcinoma sequence. The base excision repair pathway is especially interesting because recent work has elucidated a recessive polyposis syndrome associated with mutations in the gene MYH. Thus, genes involved in this pathway are biologically plausible candidates for harboring CRC-susceptibility alleles, but they have not been adequately identified or characterized in AAs to date. Our hypothesis is that novel susceptibility alleles in base-excision repair genes contribute to risk of CRC development in African-Americans. To test this hypothesis, we will screen candidate base-excision repair genes using high throughput heteroduplex analysis and use sequencing to characterize DNA changes (Specific Aim 1). To control for population stratification in our admixed AA population, we will determine individual ancestry estimates using a set of high informative ancestry informative markers (Specific Aim 2). Finally, we will genotype our putative CRC-susceptibility alleles identified in our candidate gene screens in a series of 400 AA CRC cases and 400 controls and then test for association by logistic regression (Specific Aim 3). With improved understanding of individual risk and proper screening, colorectal cancer is largely a preventable disease. The goal of our study is to better understand hereditary factors that increase risk especially in African-Americans who have the highest incidence and death from this cancer.