Genetic interactions in colorectal cancer susceptibility

描述（由申请人提供）：大约30%的结直肠癌（CRC）风险是由遗传因素引起的。利用小鼠模型，上位效应（仅在存在第二种遗传变异时观察到的风险）和协同效应（遗传变异之间的倍增效应）已被证明是癌症风险的重要决定因素。利用全基因组关联研究的基因型鉴定上位性和协同性相互作用是困难的，因为有大量可能的组合。我们提出了一种小鼠-人类策略，以人类基因组中的目标区域进行遗传相互作用分析，以减少这些研究的复杂性。来自人类病例/对照研究的数据表明，AURKA和PTPRJ两个基因的变异会增加结直肠癌的风险。在小鼠中，这两个基因映射到与其他位点相互作用以协同增加癌症风险的位点（遗传区域）。本提案的目标是确定与AURKA和PTPRJ相互作用以增加结直肠癌风险的易感性变异。我们假设人类与小鼠CRC易感位点的等效位点将与AURKA和PTPRJ相互作用。为了验证这一假设并确定结直肠癌风险的相互作用遗传变异，我们将：从AURKA-和ptprj相互作用位点的编码和调控区域检测肿瘤中变异的特异性变化。以往的研究表明，肿瘤易感变异优先获得，耐药变异优先丢失，从而为识别这些变异提供了一种工具。使用来自600个个体的匹配的正常和结直肠癌肿瘤DNA，映射到候选AURKA和PTPRJ相互作用位点的变异将被评估为变异特异性的增益或损失。2. 对从小鼠模型中鉴定出的相互作用的CRC基因座进行双向相互作用研究。将使用来自2200例结直肠癌病例和对照组的已发表全基因组关联数据，对映射到四个相互作用小鼠易感位点的人类等效区域的变异进行人类遗传相互作用测试。目标1和目标2的重要发现将通过用于绘制易感位点的小鼠品系的序列和基因表达研究得到验证。显示癌症风险证据的变异将是未来基于人群的病例对照研究和机制研究的重点。这项工作将导致识别增加CRC风险的相互作用遗传变异，并将为CRC提供更好的风险评估工具。由于结肠镜筛查期间切除前体息肉可显著降低结直肠癌的癌症死亡率，因此识别高危个体将降低该疾病的发病率和死亡率。从这些研究中发现的基因和途径将为结直肠癌的治疗提供新的治疗靶点。

DESCRIPTION (provided by applicant): Approximately 30% of colorectal cancer (CRC) risk s due to genetic (inherited) factors. Using mouse models, epistatic effects (risks observed only in the presence of a second genetic variant) and synergistic effects (multiplicative effects between genetic variants) have been shown to be important determinants of cancer risk. Identification of epistatic and synergistic interactions using genotypes from whole genome association studies is difficult due to the large number of possible combinations. We propose a mouse- human strategy to target regions in the human genome for genetic interaction analyses to reduce the complexity of these studies. Data from human case/control studies show that variants in two genes, AURKA and PTPRJ, increase CRC risk. In the mouse, both genes map to loci (genetic regions) that interact with other loci to synergistically increase cancer risk. The goal of this proposal is to identify susceptibility variants that interact with AURKA and PTPRJ to increase CRC risk. We hypothesize that the human equivalent loci to mouse CRC susceptibility loci will interact with AURKA and PTPRJ. To test this hypothesis and to identify interacting genetic variants for CRC risk we will: 1. Test variants from coding and regulatory regions of AURKA- and PTPRJ-interacting loci for variant specific changes in tumors. Previous studies show that cancer susceptibility variants are preferentially gained and cancer resistance variants are preferentially lost in tumors, thus providing a tool to identify these variants. Using matched normal and CRC tumor DNA from 600 individuals, variants that map to candidate AURKA and PTPRJ- interacting loci will be assessed for variant specific gains or losses. 2. Conduct two-way interaction studies of interacting CRC loci identified from mouse models. Variants that map to human equivalent regions of four interacting mouse susceptibility loci will be tested for genetic interactions in humans using published whole genome association data from 2200 CRC cases and controls. Significant findings from Aims 1 and 2 will be validated by sequence and gene expression studies in the strains of mice used to map the susceptibility loci. Variants showing evidence of cancer risk will be the focus of future population-based case control studies and mechanistic studies. This work will lead to the identification of interacting genetic variants which increase CRC risk and will result in better risk assessment tools for CRC. Since cancer mortality for CRC can be significantly reduced by the removal of precursor polyps during screening colonoscopy, identification of at risk individuals will decrease the incidence and mortality of this disease. Genes and pathways identified from these studies will provide new therapeutic targets for CRC treatment. PUBLIC HEALTH RELEVANCE: This work has the potential to identify combinations of genetic variants that work together to increase susceptibility to colorectal cancer. Identification of these variants will lead to better risk assessments for colorectal cancer, a more complete understanding of the mechanisms of colorectal tumorigenesis and new therapeutic targets.