Genetic Susceptibility And The Environment In Cancer Ris

癌症风险的遗传易感性和环境

• 批准号: 6681961
• 负责人: JACK A TAYLOR
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF ENVIRONMENTAL HEALTH SCIENCES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6681961
• 关键词: DNA repair; bladder neoplasm; cancer risk; carcinogenesis; clinical research; environment related neoplasm /cancer; flow cytometry; gene environment interaction; gene expression; gene interaction; genetic polymorphism; genetic susceptibility; green fluorescent proteins; hormone metabolism; human subject; neoplasm /cancer genetics; polymerase chain reaction; population genetics; prostate neoplasms; restriction fragment length polymorphism; vitamin D receptors

Our molecular epidemiology studies are focused on DNA repair gene polymorphisms and on the measurement of repair capacity; to identify important risks for environmentally-associated cancers. The group of Intramural laboratories working on repair provides a strong basic science foundation of expert colleagues that facilitates our ability to translate studeis to the population level and examine the effects of polymorphisms and repair capacity on mutation and cancer risk. Research on genetic susceptibility and gene-environment interaction may identify variants of genes important to carcinogenesis and the pathways by which environmental agents damage DNA. The study of genetically susceptible subgroups may allow a more precise identification of environmental exposures that cause disease and the risk from such exposure. Finally, if important susceptibility genes are identified, it could lead to public health programs for protecting susceptible populations, and for targeted screening of groups at higher risk of disease. Bladder Cancer XRCC3. We examined the role of a common polymorphism in the XRCC3 gene (codon 241: threonine to methionine change) and bladder cancer risk. This gene plays a role in the homologous recombination pathway, that repairs double strand breaks (DSBs). We hypothesized that the codon 241 polymorphism could affect repair of smoking-associated DNA damage and could thereby affect bladder cancer risk. We genotyped 233 bladder cancer cases and 209 controls who had been frequency matched to cases on age, sex, and ethnicity. We observed a weak positive association between subjects who carried at least one copy of the codon 241 Met allele and bladder cancer (OR: 1.3; 95% CI: 0.9-1.9). Among heavy-smokers, individuals with the Met allele had about twice the risk of those without it. Previously, we observed in these subjects an association between bladder cancer risk and allelic variants of the XRCC1 gene, which is involved in the repair of base damage and single strand breaks (SSBs). Interestingly, we find evidence of interaction between these two genes on bladder cancer risk and some support for a gene-gene-smoking exposure interaction on risk. XPD. We hypothesized that an XPD codon 751 polymorphism (Lys to Gln amino acid change) could affect the repair of smoking-induced DNA damage and could be associated with bladder cancer risk. We determined the XPD codon 751 genotype for 228 bladder cancer cases and 210 controls who were frequency matched to cases by age, sex, and ethnicity. We found a slight decrease in risk for the XPD codon 751 Gln/Gln genotype (adjusted OR: 0.8; 95% CI: 0.4-1.3) compared to subjects with the Lys/Lys or Lys/Gln genotypes. The analysis with smoking showed that smokers with the Lys/Lys or Lys/Gln genotypes were twice as likely to have bladder cancer than smokers with the Gln/Gln genotype (test of interaction p= 0.03). HRAS1. To examine whether individuals with rare HRAS1 VNTR alleles are at increased risk of bladder cancer, we carried out a case-control study with 230 bladder cancer cases and 203 hospital-based controls. HRAS1 genotype may be related to the prognosis of bladder cancer because incident cases had a higher frequency of rare alleles than did prevalent cases. Prostate cancer. We proposed a hypothesis that reduced base excision repair capacity modulates the effect of diet-associated oxidative damage on prostate cancer risk. We examined whether polymorphisms in the XRCC1 gene affect prostate cancer risk. Men who were homozygous for the XRCC1 codon 399 Arg allele showed a slightly higher prostate cancer risk than those with one or two copies of the GLN allele. Across different strata of dietary intake, this risk was slightly but remarkably consistently increased. The risk was highest among men with the Arg/Arg genotype and low dietary intake of vitamin E or lycopene; whereas low intake of these antioxidants in men without this genotype hardly increased prostate cancer risk. Functional Measures of DNA Repair for Population Studies Measure of Recombinational Repair. In order to be able to measure individual differences in recombinational DNA repair we developed a novel assay based on recombination between two Green Fluorescent Protein (GFP) sequences in transiently transfected plasmid DNA. The plasmid construct contains an intact, emission-shifted, 'blue' variant of GFP (BFP), with a 300 nucleotide stretch of homology to a nonfunctional copy of GFP. In the absence of homologous recombination only BFP is present, but homologous recombination can create a functional GFP. The homologous regions in the plasmid were constructed in both the direct and the inverted orientation of transcription to detect possible differences in the recombination mechanisms involved. A panel of human tumor cell lines was chosen on the basis of genetic background and chromosome integrity and tested for homologous recombination using this assay. The panel included cell lines with varying levels of karyotypic abnormalities, isogenic cell lines with normal and mutant p53, isogenic cell lines with or without DNA mismatch repair, BRCA1 and -2 mutant cell lines, and the lymphoma cell line DT40. With this assay, the observed differences between cell lines with the lowest and highest levels of recombination were about 100-fold. Increased levels of recombination were associated with mutant p53, whereas a low level of recombination was found in the BRCA1 mutant cell line. In the cell line HT1080TG, a mutagenized derivative of HT1080 with two mutant alleles of p53, high levels of recombination were found with the direct orientation but not with the inverted orientation plasmid. No difference in recombination was detected between two isogenic cell lines that only differed in DNA mismatch repair capability. Functional Measure of DNA Repair: We have established the Single Cell Gel Electrophoresis (Comet) assay in my laboratory for measuring DNA damage and repair. ). In this assay, DNA is damage introduced through in vitro exposure of cells to different chemical carcinogens. Cells are embedded in agarose on a microscope slide, lysed, and the remaining nucleoids are subject to electrophoresis. Nucleoids from cells without DNA damage remain spherical, while those with damaged DNA have migration of the free DNA strands through the agarose. When visualized using a fluorescent microscope these cells have a comet-like shape, with the tail formed from broken DNA. The amount of DNA in the tails of individual cells can be rapidly and precisely measured using image analysis software. By allowing different lengths of repair time before cells are lysed, we can precisely measure repair kinetics. We are beginning to apply these measures to lymphocytes from cases and controls in the bladder cancer study in order to assess risk from decreased repair capacity and to assess the consequences of newly described polymorphisms in repair gene on direct functional measures of repair. Part of the power of Comet analysis coupled with automated image analysis software is that it provides multiple DNA damage outcome measurements on each of 100 individual cells from a particular treatment. Data Analysis. Motivated by the single cell gel or comet assay application, we proposed a general approach for Bayesian quantile regression of clustered data. To simplify modeling, the likelihood is approximated by a substitution likelihood, which depends on a vector of unknown quantiles. Covariate effects and heterogeneity among samples in these quantiles are modeled using a Gaussian hierarchical model, with appropriate order constraints, and a Markov chain Monte Carlo algorithm for a posterior computation.

我们的分子流行病学研究重点是DNA修复基因多态性和修复能力的测量；确定与环境相关的癌症的重要风险。从事修复工作的校内实验室小组为专家同事提供了强大的基础科学基础，有助于我们将研究成果转化为人群水平，并检查多态性和修复能力对突变和癌症风险的影响。对遗传易感性和基因-环境相互作用的研究可能会识别对致癌作用重要的基因变异以及环境因素损伤 DNA 的途径。对遗传易感亚群的研究可以更准确地识别导致疾病的环境暴露以及此类暴露的风险。最后，如果识别出重要的易感基因，可能会导致制定保护易感人群的公共卫生计划，并对患病风险较高的群体进行有针对性的筛查。 膀胱癌 XRCC3。我们研究了 XRCC3 基因中常见多态性（密码子 241：苏氨酸变为蛋氨酸）与膀胱癌风险的作用。该基因在同源重组途径中发挥作用，修复双链断裂 (DSB)。我们假设密码子 241 多态性可能影响吸烟相关 DNA 损伤的修复，从而影响膀胱癌风险。我们对 233 名膀胱癌病例和 209 名对照者进行了基因分型，这些对照者的年龄、性别和种族与病例进行了频率匹配。我们观察到携带至少一份密码子 241 Met 等位基因的受试者与膀胱癌之间存在弱正相关（OR：1.3；95% CI：0.9-1.9）。在重度吸烟者中，携带 Met 等位基因的人的风险大约是不携带 Met 等位基因的人的两倍。此前，我们在这些受试者中观察到膀胱癌风险与 XRCC1 基因的等位基因变异之间存在关联，该基因参与碱基损伤和单链断裂 (SSB) 的修复。有趣的是，我们发现了这两个基因之间相互作用对膀胱癌风险的影响的证据，以及基因-基因-吸烟暴露对风险的相互作用的一些支持。 XPD。我们假设 XPD 密码子 751 多态性（Lys 至 Gln 氨基酸变化）可能影响吸烟引起的 DNA 损伤的修复，并可能与膀胱癌风险相关。我们确定了 228 例膀胱癌病例和 210 例对照的 XPD 密码子 751 基因型，这些对照按年龄、性别和种族与病例进行频率匹配。我们发现与具有 Lys/Lys 或 Lys/Gln 基因型的受试者相比，XPD 密码子 751 Gln/Gln 基因型的风险略有降低（调整后 OR：0.8；95% CI：0.4-1.3）。对吸烟的分析表明，具有 Lys/Lys 或 Lys/Gln 基因型的吸烟者患膀胱癌的可能性是具有 Gln/Gln 基因型的吸烟者的两倍（交互作用检验 p= 0.03）。 HRAS1。为了检查具有罕见 HRAS1 VNTR 等位基因的个体患膀胱癌的风险是否增加，我们对 230 例膀胱癌病例和 203 例医院对照进行了病例对照研究。 HRAS1 基因型可能与膀胱癌的预后相关，因为发病病例的罕见等位基因频率高于流行病例。 前列腺癌。我们提出了一个假设，即碱基切除修复能力的降低可以调节饮食相关的氧化损伤对前列腺癌风险的影响。我们检查了 XRCC1 基因的多态性是否会影响前列腺癌风险。 XRCC1 密码子 399 Arg 等位基因纯合的男性比具有一两个 GLN 等位基因的男性患前列腺癌的风险略高。在不同的饮食摄入层次中，这种风险略有但显着地持续增加。在具有 Arg/Arg 基因型且饮食中维生素 E 或番茄红素摄入量较低的男性中，该风险最高；而没有这种基因型的男性，这些抗氧化剂的摄入量低几乎不会增加前列腺癌的风险。 人口研究中 DNA 修复的功能测量 重组修复的测量。为了能够测量重组 DNA 修复中的个体差异，我们开发了一种基于瞬时转染质粒 DNA 中两个绿色荧光蛋白 (GFP) 序列之间重组的新型测定方法。该质粒构建体包含完整的、发射位移的“蓝色”GFP 变体 (BFP)，具有与 GFP 的非功能性副本同源的 300 个核苷酸序列。在没有同源重组的情况下，仅存在 BFP，但同源重组可以产生功能性 GFP。质粒中的同源区域以正向和反向转录方向构建，以检测所涉及的重组机制中可能存在的差异。根据遗传背景和染色体完整性选择一组人类肿瘤细胞系，并使用该测定法测试同源重组。该小组包括具有不同水平核型异常的细胞系、具有正常和突变p53的同基因细胞系、具有或不具有DNA错配修复的同基因细胞系、BRCA1和-2突变细胞系以及淋巴瘤细胞系DT40。通过该测定，观察​​到重组水平最低和最高的细胞系之间的差异约为 100 倍。重组水平的增加与突变型 p53 相关，而在 BRCA1 突变细胞系中发现重组水平较低。在细胞系 HT1080TG（具有两个 p53 突变等位基因的 HT1080 的诱变衍生物）中，在直接方向而非反向方向质粒中发现了高水平的重组。两个同基因细胞系之间没有检测到重组差异，只是 DNA 错配修复能力不同。 DNA 修复的功能测量：我们在实验室建立了单细胞凝胶电泳（彗星）测定法，用于测量 DNA 损伤和修复。 ）。在此测定中，DNA 是通过细胞在体外暴露于不同化学致癌剂而引起的损伤。将细胞包埋在显微镜载玻片上的琼脂糖中，裂解，并对剩余的核进行电泳。未受 DNA 损伤的细胞中的类核仍保持球形，而 DNA 受损的细胞中的游离 DNA 链会通过琼脂糖迁移。当使用荧光显微镜观察时，这些细胞呈彗星状，尾巴由断裂的 DNA 形成。使用图像分析软件可以快速、精确地测量单个细胞尾部的 DNA 量。通过在细胞裂解之前允许不同长度的修复时间，我们可以精确测量修复动力学。我们开始将这些措施应用于膀胱癌研究中病例和对照的淋巴细胞，以评估修复能力下降的风险，并评估新描述的修复基因多态性对修复的直接功能测量的影响。彗星分析与自动图像分析软件相结合的部分功能在于，它可以对来自特定处理的 100 个单独细胞中的每一个细胞提供多个 DNA 损伤结果测量。 数据分析。受单细胞凝胶或彗星测定应用的启发，我们提出了一种聚类数据贝叶斯分位数回归的通用方法。为了简化建模，通过替换似然来近似似然，该替换似然取决于未知分位数的向量。这些分位数中样本之间的协变量效应和异质性使用具有适当阶数约束的高斯分层模型以及用于后验计算的马尔可夫链蒙特卡罗算法进行建模。