结直肠癌遗传易感性的分子流行病学研究
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摘要
背景与目的
结直肠癌与肺癌、乳腺癌并列为目前世界上最常见的三大恶性肿瘤，并且在世界范围内它的发生仍呈现稳定的增长趋势。结直肠癌的发生存在着明显的地域差异：呈现与工业化进程和经济发达水平相一致的阶梯分布，即由发达国家——次发达国家——发展中国家逐级下降。我国虽属低发国家，但随着社会经济的稳步发展增长明显。Yang L等估计2005年我国的结直肠癌年龄标化发病率男性和女性将分别达到15.0／10万和9.7／10万，居常见恶性肿瘤发病率第5位。结直肠癌是至今遗传背景最强、研究最为深入的一类恶性肿瘤，仅约5％的结直肠癌的发生是典型的单基因病。绝大部分结直肠癌的发生发展是一个多步骤、多阶段、多基因参与的过程，是外在的环境因素和机体内在的遗传因素相互作用的结果。机会性因素和环境因素至少可以解释70％的散发性结直肠癌的发生。然而接触同样的环境致癌因子，并不是所有的个体都会发生癌症，每个个体都有特异的遗传易感性，基因组水平的差异即基因多态性是遗传易感性的物质基础。目前，有关人类疾病易感性的评价研究主要的候选基因有DNA修复基因、外源化合物代谢及解毒基因、激素代谢基因、信号传导基因、受体基因、免疫和炎症反应调节基因、介导营养因素基因、参与氧化过程的基因、细胞周期控制基因和细胞死亡控制基因等10个大类。其中，DNA修复基因由于其对细胞基因组的完整和稳定至关重要，居于首位；而P53通路则在DNA修复、信号传导、细胞周期调节和诱导凋亡等多个进程中都起重要作用。体系中单个或多个基因多态性的积累可影响功能的正常发挥而使机体对结直肠癌的易感性发生改变。基于此，主要的研究假设有：DNA修复通路中关键因子的编码基因(OGG1、XRCC1、XPD和XRCC3)常见位点多态性单独或联合作用与散发性结直肠癌易感性有关，并且与不同结直肠癌亚型(根据病理部位、发病年龄和性别等分组)的关系既有共性又有特异性；P53通路中功能性因子(P53)和最重要的调节因子(MDM2)的编码基因单个或多个位点多态性的联合作用与结直肠癌易感性有关；由于P53通路与细胞内多个进程广泛关联，其与DNA修复体系共同的多个基因多态性的联合与结直肠癌的易感性也可能存在关联；遗传因素(基因多态性)与环境暴露(吸烟、饮酒等)在结直肠癌的发生发展过程中可能存在联合作用。
为验证上述研究假设，研究以我国结直肠癌高发县——浙江省嘉善县为研究现场，采用自然人群为基础的病例对照研究设计，以OGG1 Ser326Cys、XRCC1 Arg194Trp、XRCC1Arg280His、XRCC1 Arg399Gln、XPD Lys751Gln和XRCC3 Thr241Met等常见DNA修复基因多态以及P53 Intron3 16bp duplication、P53 Exon4 Arg72Pro、P53 Intron6 G／A transition、MDM2 Del1518和MDM2 SNP309等P53通路常见多态为目的研究因素，同时纳入年龄、性别、BMI和家族肿瘤史等个体特征以及吸烟史、吸烟量、吸烟累计时间、饮酒史和饮酒累计时间等生活方式因子。在描述上述多态在我国自然人群中的分布频率的基础上，明确单位点、单基因以及多基因多态联合与结直肠癌易感性的关联，同时结合常见的环境暴露因子对可能的基因-环境交互作用进行评价。通过以上系统研究，为上述基因多态性与结直肠癌易感性关系提供人群水平的研究证据，明确上述多态作为人群散发性结直肠癌遗传易感性标志的可行性，以将其应用于结直肠癌高危人群筛检，研究结果对于结直肠癌人群预防和干预有重要的现实指导意义。
对象与方法
采用自然人群为基础的病例对照研究设计，以全国结直肠癌调整死亡率最高县——浙江省嘉菩县为研究现场，以该县1990年4月建立的包括10个乡镇的当地居民(64，693人)随访队列为研究人群。以队列内1990年5月至2005年5月发生的，且曾经参加1989～1990年开展的结直肠癌普查的原发性结直肠癌存活病例，排除直肠类癌、继发性结直肠癌、1989～1990年筛查时检出的结直肠癌病例以及不属于队列人群的原发性结直肠癌病例，最终纳入结直肠癌病例206例(结肠癌93例，直肠癌113例)。对照组(队列内正常人群的代表性样本)通过2002年和2005年分别开展的两次抽样调查获得：其中，2002年通过单纯随机抽样方法抽取个体400例，排除死亡16例和结直肠癌病例1例，共须调查383例，实际共调查343例；2005年在基线资料库中，剔除死亡和恶性肿瘤发病个体后，以性别和年龄为分层因素，采用分层随机抽样抽取调查对象550例，最终有效调查个体502例；两组对照人群均衡可比，代表性样本合计845例构成了本次研究的对照人群。通过一对一的上门问卷调查收集个体特征和生活方式等常见环境暴露因素的信息，经调查对象知情同意，采集静脉血5ml，分装储存备用。现场调查的质量控制通过调查前统一培训调查员，调查中统一携带标准的调查员手册，调查后统一对问卷进行复核和以5％的样本量进行电话回访实现。
采用改良盐析法抽提外周血白细胞基因组DNA，-60℃冰箱储存待检；DNA修复各SNP的检测分型均采用聚合酶链式反应-限制性内切酶片段长度多态性(PCR-RFLP)分析技术；P53通路中，P53 Exon4 Arg72Pro和Intron6 G／A transition的基因检测也采用PCR-RFLP分析技术，P53 Intron3 16bp duplication和MDM2 Del1518的检测分型采用PCR扩增后直接电泳分析方法，MDM2 SNP309的检测分型采用PCR-可诱导引物限制性(PIRA)分析技术。实验室的质量控制通过盲法检测和重复检测实现。
调查表经统一编码后，Epidata双遍录入，校对无误后建立数据库，分析前进行必要的变量代换及编码。主要的分析过程和方法包括：病例组和对照组个体具体年龄的差异采用成组t检验；分类变量(性别和基因型分布等)的分布差异采用Pearson x~2分布检验；相关因素的相对危险度估计采用多因素Logisitc回归计算比值比(OR)及其95％可信区间(CI)；采用EH Linkage Software1.2分析各组同一基因多个位点间是否存在连锁不平衡现象；采用PHASE2.0对研究对象的单体型分布进行测算分析；采用叉生分析、相乘交互作用模型和和x~2趋势检验进行基因-环境交互作用的分析；采用多因子降维分析软件MDR进行基因-基因联合作用的初筛。整个统计分析过程结合应用了Excel2003、SPSS 13.0 for Windows、EH Linkage Software1.2、PHASE2.0、MDR-Data Tool Software 0.4.3和MDR Software 1.0.0。
结果
1．个体特征、生活方式与结直肠癌
病例组和对照组的平均年龄分别为65.25±9.47岁和61.84±10.83岁，经成组t检验存在统计学显著性差异(P＜0.01)；采用对照组年龄四分位数分布进行分组；病例组和对照组的年龄分布同样存在统计学显著性差异(P＜0.01)；与最低年龄组(≥42，＜53岁)相比，高(≥61，＜72岁)、最高(≥72岁)年龄组风险增高有统计学意义(P＜0.05)，并且趋势也有统计学意义(P＜0.01)。病例组和对照组在性别、BMI指数和家族肿瘤史等基本因素的分布均不存在统计学显著性差异(P＞0.05)，然而经年龄和性别调整，家族肿瘤史与结直肠癌的发病存在有统计学意义的正相关关系(校正OR：1.51，95％CI：1.05-2.17)。分病理部位考虑，结肠癌和直肠癌病例组在上述各特征因素分布上均衡可比。对各生活方式因子的分析表明，结直肠癌病例组≥20支／天的重度吸烟者比率(24.27％)显著高于对照组(16.18％)，与吸烟量＜20支／天的个体相比，重度吸烟者(≥20支／天)罹患结直肠癌风险增高并有统计学意义(校正OR：1.19，95％CI：1.05-1.35)。
2．DNA修复基因多态性与结直肠癌
OGG1 Ser326Cys、XRCC1 Arg194Trp、XRCC1 Arg280His、XRCC1 Arg399Gln、XPD Lys751Gln和XRCC3 Thr241Met各变异等位基因分布频率在正常对照组为54.91％、34.25％、11.68％、26.19％、8.16％和4.41％，在病例组为54.57％、29.95％、11.22％、28.22％、10.15％和4.90％，所有等位基因和基因型分布两组间均不存在有统计学意义的显著差异(P＞0.05)。与不同特征的结直肠癌关联分析表明，XRCC1 Arg194Trp多态(CT&TT Vs.CC)可显著降低直肠癌、＜60岁结直肠癌和男性结直肠癌的患病风险，校正OR(95％CI)分别为0.66(0.44-0.99)，0.59(0.38-0.92)和0.64(0.41-0.99)。XRCC1单体型分析表明，Arg194Trp、Arg280His和Arg399Gln三位点在病例组和对照组都存在连锁不平衡现象(病例组x~2=36.74，对照组x~2=200.71，df=7，P均＜0.01)，然而在病例组和对照组问不存在有统计学意义的显著性差异(x~2=13.92，df=7，P＞0.05)；对象中8种单体型都有分布，其中CGG、TGG、CAG和CGA是常见的4类单体型；与野生等位基因联合单体型CGG相比，单体型TGG(仅26304位点携变异等位基因T)可使结直肠癌患病风险显著降低，校正OR=0.75(95％CI：0.57-0.99)。基因-环境联合作用分析表明，XRCC1 Arg399Gln多态与吸烟量交互，虽然各交互项风险估计都没有统计学意义，然而x~2趋势检验表明，随着吸烟剂量(支／天)增高，变异等位基因的存在可以使机体结直肠癌的患病风险逐步增高，且趋势有统计学意义(P＜0.05)；相乘交互作用模型分析表明，饮酒史与XPD Lys751Gln交互可使结直肠癌的患病风险增高近1倍且效应临界于统计学显著性水平(校正OR：1.90，95％CI：0.97-3.71，P=0.06)；与不饮酒且携带Asp／Asp野生型人群相比，饮酒累计时间≤32年且携带Asp／Asn或Asn／Asn变异基因型的人群，结直肠癌患病风险增高有统计学意义，校正OR为2.49(95％CI：1.09-5.69)。基因-基因联合作用分析表明，与不携带风险型的个体相比，携带高风险基因型数量多达4个位点时，结直肠癌的患病风险显著增高(校正OR：3.63，95％CI：1.24-10.62，P＜0.05)。
3．P53通路基因多态性与结直肠癌
P53 Intron3 16bp duplication、Exon4 Arg72Pro和Intron6 G／A transition，MDM2 Del1518和SNP309各变异等位基因分布频率在正常对照组为为3.80％、46.49％、5.97％、40.65％和43.78％，在病例组为2.48％、47.26％、4.46％、32.50％和40.59％，其中MDM2 Del1518等位基因和基因型分布在两组间差异有统计学意义(P＜0.05)；该变异纯合基因型与结直肠癌尤其是直肠癌患病风险存在有统计学意义的显著关联，校正OR(95％CI)分别为0.50(0.31-0.81)和0.40(0.20-0.79)。单体型分析表明，P53 Intron3 16bp duplication、Exon4 Arg72Pro和Intron6 G／A transition三位点在正常对照组分布存在连锁不平衡现象(x~2=120.89，df=7，P＜0.001)，而病例组没有(x~2=11.19，df=7，P＞0.05)，并且P53单体型分布在病例组和对照组间有统计学显著性差异(x~2=14.28，df=7，P＜0.05)；对于MDM2 Del1518和SNP309的分析表明，此两多态在病例组和对照组都存在连锁不平衡现象(病例组x~2=29.46，对照组x~2=25.53，df=3，P均＜0.01)，并且MDM2单体型分布在病例组和对照组间也存在统计学显著性差异(x~2=22.78，df=3，P＜0.01)，与野生型等位基因联合单体型“-T”相比，纯变异等位基因联合单体型“+G”可显著降低机体结直肠癌的罹患风险(校正OR：0.25，95％CI：0.14-0.47)。基因-环境联合作用分析表明，P53 Intron3 16bp duplication多态与年龄交互效应有统计学意义(校正OR：0.29，95％CI：0.09-0.98)，另外，P53 Exon4 Arg72Pro与家族肿瘤史交互、P53 Exon4 Arg72Pro或MDM2 SNP309与吸烟量交互对结直肠癌的发生都有一定的危险效应但都没有统计学意义。基因-基因联合作用分析表明，与携带风险型数目≤2的个体相比，随着风险型数目的增大，结直肠癌的患病风险迅速上升，不仅每个亚组的风险增高有统计学意义，并且趋势也有统计学意义(P＜0.05)；MDR分析表明，P53 Intron3 16bp duplication和MDM2 Del 1518交互对结直肠癌的发生具有保护效应，与其他基因型组合相比，野生联合型使结直肠癌患病风险显著增高(校正OR：1.37，95％CI：1.00-1.89)。
基于所有多态位点的基因-基因联合作用分析表明，XRCC1 Arg194Trp和P53 Intron6 G／A transition交互可在一定程度上相互拮抗各自保护效应的发挥，与野生联合型相比，XRCC1 194Trp变异等位基因或P53 Intron6 G／A transition变异等位基因的存在可使机体罹患肠癌风险降低并有统计学意义，然而两变异等位基因同时存在时效应没有统计学意义，校正OR(95％CI)分别为0.69(0.50-0.96)、0.25(0.08-0.85)和0.79(0.43-1.47)；基于所有因子的联合分析表明，年龄是本研究中影响结直肠癌发病的最主要的因素，高年龄组(≥61岁)个体比低年龄组个体(≥42，＜61岁)结直肠癌患病风险增加1倍多(校正OR：2.04，95％CI：1.49-2.80)。
结论
本次在浙江省嘉善县开展的自然人群为基础的病例对照研究，主要的研究结果有：
1．个体特征、生活方式与结直肠癌
年龄是本研究中影响结直肠癌发病的最重要的因子，结直肠癌的患病风险随着年龄的增大而增高；一、二级亲属家族肿瘤史对结直肠癌的发病也具有危险效应；性别和BMI指数分布与结直肠癌的发病没有相关性。是否吸烟／饮酒和吸烟／饮酒累计时间对结直肠癌的发病没有影响；然而重度吸烟者(≥20支／天)对结直肠癌的发病具有危险效应。
2．DNA修复基因多态性与结直肠癌
XRCC1 Arg194Trp多态可降低直肠癌、＜60岁或男性结直肠癌的患病风险；XRCC1单体型中仅Arg194Trp为变异等位基因的单体型“TGG”对结直肠癌的发病也具有保护效应；吸烟量与XRCC1 Arg399Gln的联合作用可增加结直肠癌的患病风险；DNA修复体系多个(≥4)高风险型SNP的积累可使结直肠癌的患病风险增高。
3．P53通路基因多态性与结直肠癌
MDM2 Del1518单位点多态对结直肠癌尤其是直肠癌具有保护效应；MDM2 Del1518和SNP309同为变异等位基因的单体型“+G”对结直肠癌的发病也具有保护效应；P53 Intron3 16bp duplication与年龄交互可逆转年龄对结直肠癌的危险效应；P53 Intron3 16bp duplication和MDM2 Del 1518交互对结直肠癌的发生具有保护效应；另外，XRCC1 Arg194Trp和P53 Intron6 G／A transition交互可在一定程度上相互拮抗各自保护效应的发挥；结直肠癌的患病风险随着P53通路高风险型多态个数的增加而增高，在结直肠癌的发生发展过程中，P53通路基因多态性可能比DNA修复基因体系起着更为重要的作用。
Backgrounds & Objectives
Colorectal cancer including colon and rectum cancer is one of the most common cancers. In 2002, the number of global incident cases was about 1 million accounting for 9.4% of all cancers which is only less than lung cancer (1.35 million) and breast cancer (1.15 million). In terms of prevalence, it is only second to breast cancer (4.4 million, 17.9%) with an estimated 2.8 million persons alive with colorectal cancer diagnosed within 5 years of diagnosis which accouts for 11.5% of all cancers in world. In China, colorectal cancer is the third prevalent cancer both in males and females with an increasing incidence, of which the estimates in 2005 were 15.0 and 9.7 per 100,000 for males and females, respectively.
As for the genetic predisposition to colorectal cancer, high-penetrance genes such as APC and DNA mismatch repair genes may account for hereditary colorectal cancer which is less than 5% of all colorectal cancer, such as familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC) known as monogenic diseases. Low-penetrance cnadidate genes mainly include DNA repair genes, metabolic enzyme genes, cell cycle regulatory genes, immune regulatory genes, oncogenes and tumor suppressing genes that are more common in natural population. Low-penetrance genes have an important influence on genetic predisposition to sporadic colorectal cancer (known as polygenic disease), which have intricate networks with environmental factors in carcinogenesis. DNA repair genes are the most important candidate genes, as the DNA repair system plays an important role in maintaining genome integrity which can protect the genome from carcinogens-induced damage to some extent. The genetic polymorphisms in DNA repair genes have an effect on individual's genetic susceptibility to spontaneous or induced cancer with the altered DNA repair capacity. P53 is a crucial tumor suppressor taking effect on DNA repair, cell cycle arrest and apoptosis in some cases via its stress response way, which is essential for genomic stability, and plays an important role in preventing tumor formation. Inactivating alterations in P53 gene is presented in about 50% of all human cancers. MDM2, encoded by mouse double minute 2 homolog gene (MDM2), is a key negative regulator of P53 stress response way. As a part of an autoregulatory negative feedback loop with P53 protein, overexpression of MDM2 gene can result in excessive
inactivation of P53 by blocking its transcription and mediating its degradation with E3 ubiquitin ligase activity. Polymorphisms in P53 and MDM2 may impair the function of P53 stress response way.
A population-based case-control study was conducted to describe the frequency distribution of polymorphims in DNA repair genes (OGG1 Ser326Cys, XRCC1 Arg194Trp, Arg280His, Arg399Gln, XPD Lys751Gln and XRCC3 Thr241 Met) and in P53 pathway genes (P53 Intron3 16bp duplication, Exon4 Arg72Pro, Intron6 G/A transition, MDM2 Dell518 and SNP309) in natural Chinese population, and to explore the association of colorectal cancer risk with the above single polymorphism, haplotypes of XRCC1, P53 and MDM2, gene-environment interaction between the above polymorphims and common environmental exposure factors, and gene-gene interaction within the same pathway or between the different pathways.
Materials & Methods
In this population-based case-control study, 206 primay colorectal cancer cases and 845 cancer-free healthy controls were enrolled in, and they are all Chinese Han people coming from a follow-up cohort which has been built since 1989 in Jiashan County, the county with the highest age-standardized colorectal cancer mortality in China. After informed consent, all subjects were interviewed with a questionnaire mainly including demographic characteristics, individual lifestyle and family history of cancers by professional trained interviewers with face-to-face method. To ensure the validity of data, a repeat interview by telephone with five percent was performed. Also with the subjects' permission, a total 5ml blood was collected after interview, which was separated into two sections of 2ml blood with sodium citrate anticoagulation and 3ml blood without anticoagulation to gain blood serum. All blood samples were stored at -60°C for long-term conservation. The study was approved by the Medical Ethical Committee of Zhejiang University School of Medicine.
The genomic DNA for each subject was extracted from whole blood using improved salting out procedure. As for the genotyping of polymorphisms in DNA repair genes, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique was used, which also was used for the genotyping of P53 Exon4 Arg72Pro and Intron6 G/A transition. The direct electrophoresis after PCR amplification was used for the genotyping of P53 Intron3 16bp duplication and MDM2 Del1518. Finally, the PCR- primer introduced restriction analysis (PIRA) method was used for the MDM2 SNP309 genotyping. Ten percent of all samples were randomly selected for repeat analysis to ensure obtaining the correct genotype information. All genotyping work was finished under the condition without knowledge of the subjects' case/control status.
Student's t-test was used to evaluate the difference in mean age between cases and controls. Pearson's x~2 test was used to compare the distribution difference in categorial variables (genotype distribution et al) between cases and controls. The Hardy-Weinberg equilibrium test in control group was finished by X~2 goodness-of-fit test. The associations of different factors (0GG1 variants et al) with colorectal cancer risk were estimated by calculating the odds ratios (ORs) and their 95% confidence intervals (95% C/s) with multivariate logistic regression adjusted by age and sex. EH Linkage Software1.2 was used to identify the linkage disequilibrium. PHASE2.0 was used to construct haplotypes and estimate their frequency distributions. At last, MDR Software 1.0.0 was used for analyzing the gene-gene interaction. All statistical analysis was finished in Excel2003, SPSS 13.0 for windows, EH Linkage Softwarel.2, PHASE2.0, MDR-Data Tool Software 0.4.3 and MDR Software 1.0.0. All tests of statistical significance (α=0.05) were two-sided.
Results
1. Demographic characteristics, lifestyle factors and colorectal cancer
The mean age of colorectal cancer cases was 65.25 (SD=9.47) years, which was statistically different
from that of controls (X±SD: 61.84±10.83 years, P<0.01). Based on the quartile distribution of controls, the significant difference between two groups was also observed in the age distribution (P<0.01). As compared with the low age group (<53 years), the higher (>61 years) and the highest age group (≥72 years) had significant risks of colorectal cancer, and the ORs (95% C/s) were 2.89 (1.79-4.68) and 2.37 (1.45-3.88) adjusted by sex, respectively. There was no statistically significant difference in distributions of sex, BMI and family history of cancer in first and second relatives. However, as adjusted by sex and age, family history of cancer in first and second relatives was significantly associated with colorectal cancer risk (OR=1.51, 95%CI=1.05-2.17). As for the lifestyle factors, the frequency of heavy smokers (>20 cigarettes per day) in cases was statistically higher than that in controls (24.27% Vs. 16.18%), and the adjusted OR (95% CI) was 1.19 (1.05-1.35).
2. Genetic polymorphisms of DNA repair genes and risk of colorectal cancer
The polymorphic variants of OGG1 Ser326Cys, XRCC1 Arg194Trp, Arg280His, Arg399Gln, XPD Lys751Gln and XRCC3 Thr241 Met in controls were 54.91%, 34.25%, 11.68%, 26.19%, 8.16% and 4.41%, which in cases were 54.57%, 29.95%, 11.22%, 28.22%, 10.15% and 4.90%, respectively. No significant difference was observed between cases and controls in allels and genotypes distribution. Association analysis for the different sub-type colorectal cancer indicated that 194Trp variant decreased risks of rectum cancer, the comparative early-onset colorectal cancer (age at diagnosis <60 years) and male colorectal cancer significantly, and the adjusted ORs (95% C/s) for variant
heterozygotes and homozygotes as referred to wild homozygotes were 0.66 (0.44-0.99), 0.59 (0.38-0.92) and 0.64 (0.41-0.99), respectively. EH Linkage Software1.2 showed that there existed LD among XRCC1 three locuses, Arg194Trp, Arg280His and Arg399Gln, both in case and control group (Cases: X~2=36.74, Controls: X~2=200.71, df=7, P<0.01). However, no significant difference of the XRCC1 haplotype distribution existed between two groups (X~2=13.92, df=7, P>0.05). The PHASE progrom predicted CGG, TGG, CAG and CGA were the four most common haplotypes among all eight hyplotypes. Adjusted by age and sex, TGG haplotype (only with 194Trp variant) was associated with a statistically significant decreased risk of colorectal cancer compared with CGG hyplotype (without mutant variants), and the OR was 0.75 (95%CI=0.57-0.99). X~2 trend analysis found that 399Gln variant was correlated with the increase of colorectal cancer risk corresponding to the increase of smoke exposure dose (cigarettes per day) (P<0.05). The interaction between XPD 751 Lys/Gln & Gln/Gln genotypes and alcohol drinking (ever or current Vs. never) had an increasing risk of colorectal cancer but didn't reach statistically significant level (OR=1.90, 95%CI=0.97-3.71, P=0.06). Gene-gene interaction revealed that individuals with four putative high-risk genotypes statistically increased colorectal cancer risk (OR=3.63, 95%CI=1.24-10.62, P<0.05).
3. Genetic polymorphisms of P53 pathway genes and risk of colorectal cancer
The polymorphic variants of P53 Intron3 16bp duplication, Exon4 Arg72Pro, Intron6 G/A transition, MDM2 Del1518 and SNP309 in controls were 3.80%, 46.49%, 5.97%, 40.65% and 43.78%, which in cases were 2.48%, 47.26%, 4.46%, 32.50% and 40.59%, respectively. Significant difference was observed between cases and controls in MDM2 Del1518 allels and genotypes distribution (P<0.05). Multivariate logistic regression adjusted by age and sex indicated that MDM2 Del1518 mutant homozygotes statistically decreased colorectal cancer risk especially rectum cancer risk, and ORs (95%C/s) were 0.50 (0.31-0.81) for colorectal cancer and 0.40 (0.20-0.79) for rectum cancer. EH Linkage Softwarel.2 revealed that LD existed among P53 Intron3 16bp duplication, Exon4 Arg72Pro and Intron6 G/A transition three locuses in controls (X~2=120.89, df=7, P<0.001), and between MDM2 Del1518 and SNP309 two locuses both in cases and controls (Cases: X~2=29.46, Controls X~2=25.53, df=3, P<0.01). What's more, statistical differences of the P53 (X~2=14.28, df=7, P<0.05) and MDM2 (X~2=22.78, df=3, P<0.01) haplotypes distribution existed between case and control groups. Compared with "- T" haplotype (both with wild alleles), "+ G" haplotype (both with mutant alleles) made colorectal cancer risk decrease statistically (adjusted OR=0.25, 95%CI=0.14-0.47). Gene-environment interaction analysis found that the interaction of P53 Intron3 16bp duplication and age decreased colorectal cancer risk significantly (OR=0.29, 95%CI=0.09-0.98. On the other hand, the interactions of P53 Exon4 Arg72Pro and family history of cancer or smoke exposure dose, MDM2 SNP309 and smoke exposure dose could increase risk of colorectal cancer but didn't reach the statistical significant level. As compared with individuals having less than three
putative high-risk genotypes, individuals with three or more putative high-risk genotypes had a statistical increased risk of colorectal cancer. And the ORs (95%C/s) were 3.94 (1.18-13.17) for individuals with three high-risk genotypes, 4.63 (1.41-15.17) for individuals with four high-risk genotypes and 6.08 (1.81-20.36) for individuals with five high-risk genotypes, respectively. MDR analysis found that the interaction of P53 Intron3 16bp duplication and MDM2 Del 1518 made colorectal cancer risk decrease statistically. The wild combinative genotype (without variants) was statistically associated with increase of colorectal cancer risk as compared with other three combinative genotypes (OR=1.37, 95%CI= 1.00-1.89). In consideration of all polymorphisms, single XRCC1 Arg194Trp or P53 Intron6 G/A transition polymorphism was associated with a statistical decrease of colorectal cancer risk referred to the wild combinative genotype. However, the mutant combinative genotype also was associated with the decrease of colorectal cancer risk but didn't have statistical significance.
Conclusions
The main findings from this population-based case-control study carried out in Chinese Han population were as follows:
1. Age (≥61 years), family history of cancer in first and second relatives and heavy smoking (≥20 cigarettes per day) may contribute to the colorectal cancer predisposition.
2. XRCC1 Arg194Trp polymorphism may have effect on colorectal cancer especially on rectum cancer, the comparative early-onset colorectal cancer (age at diagnosis <60 years) and male colorectal cancer. The gene-environment interaction between XRCC1 Arg399Gln polymorphism and cigarette smoke exposure may also have effect on the colorectal carcinogenesis. The accumulation of multi-polymorphisms in DNA repair genes has a contribution to the genetic predisposition of colorectal cancer.
3. MDM2 Del1518 polymorphism and its interaction with P53 Intron3 16bp duplication may have influence on colorectal cancer especially on rectum cancer. P53 Intron3 16bp duplication and may be able to counteract the increasing risk of colorectal cancer resulting from age. The accumulation of multi-polymorphisms in P53 pathway genes plays an important role in colorectal cancer susceptibility.
结直肠癌与肺癌、乳腺癌并列为目前世界上最常见的三大恶性肿瘤，并且在世界范围内它的发生仍呈现稳定的增长趋势。结直肠癌的发生存在着明显的地域差异：呈现与工业化进程和经济发达水平相一致的阶梯分布，即由发达国家——次发达国家——发展中国家逐级下降。我国虽属低发国家，但随着社会经济的稳步发展增长明显。Yang L等估计2005年我国的结直肠癌年龄标化发病率男性和女性将分别达到15.0／10万和9.7／10万，居常见恶性肿瘤发病率第5位。结直肠癌是至今遗传背景最强、研究最为深入的一类恶性肿瘤，仅约5％的结直肠癌的发生是典型的单基因病。绝大部分结直肠癌的发生发展是一个多步骤、多阶段、多基因参与的过程，是外在的环境因素和机体内在的遗传因素相互作用的结果。机会性因素和环境因素至少可以解释70％的散发性结直肠癌的发生。然而接触同样的环境致癌因子，并不是所有的个体都会发生癌症，每个个体都有特异的遗传易感性，基因组水平的差异即基因多态性是遗传易感性的物质基础。目前，有关人类疾病易感性的评价研究主要的候选基因有DNA修复基因、外源化合物代谢及解毒基因、激素代谢基因、信号传导基因、受体基因、免疫和炎症反应调节基因、介导营养因素基因、参与氧化过程的基因、细胞周期控制基因和细胞死亡控制基因等10个大类。其中，DNA修复基因由于其对细胞基因组的完整和稳定至关重要，居于首位；而P53通路则在DNA修复、信号传导、细胞周期调节和诱导凋亡等多个进程中都起重要作用。体系中单个或多个基因多态性的积累可影响功能的正常发挥而使机体对结直肠癌的易感性发生改变。基于此，主要的研究假设有：DNA修复通路中关键因子的编码基因(OGG1、XRCC1、XPD和XRCC3)常见位点多态性单独或联合作用与散发性结直肠癌易感性有关，并且与不同结直肠癌亚型(根据病理部位、发病年龄和性别等分组)的关系既有共性又有特异性；P53通路中功能性因子(P53)和最重要的调节因子(MDM2)的编码基因单个或多个位点多态性的联合作用与结直肠癌易感性有关；由于P53通路与细胞内多个进程广泛关联，其与DNA修复体系共同的多个基因多态性的联合与结直肠癌的易感性也可能存在关联；遗传因素(基因多态性)与环境暴露(吸烟、饮酒等)在结直肠癌的发生发展过程中可能存在联合作用。
为验证上述研究假设，研究以我国结直肠癌高发县——浙江省嘉善县为研究现场，采用自然人群为基础的病例对照研究设计，以OGG1 Ser326Cys、XRCC1 Arg194Trp、XRCC1Arg280His、XRCC1 Arg399Gln、XPD Lys751Gln和XRCC3 Thr241Met等常见DNA修复基因多态以及P53 Intron3 16bp duplication、P53 Exon4 Arg72Pro、P53 Intron6 G／A transition、MDM2 Del1518和MDM2 SNP309等P53通路常见多态为目的研究因素，同时纳入年龄、性别、BMI和家族肿瘤史等个体特征以及吸烟史、吸烟量、吸烟累计时间、饮酒史和饮酒累计时间等生活方式因子。在描述上述多态在我国自然人群中的分布频率的基础上，明确单位点、单基因以及多基因多态联合与结直肠癌易感性的关联，同时结合常见的环境暴露因子对可能的基因-环境交互作用进行评价。通过以上系统研究，为上述基因多态性与结直肠癌易感性关系提供人群水平的研究证据，明确上述多态作为人群散发性结直肠癌遗传易感性标志的可行性，以将其应用于结直肠癌高危人群筛检，研究结果对于结直肠癌人群预防和干预有重要的现实指导意义。
对象与方法
采用自然人群为基础的病例对照研究设计，以全国结直肠癌调整死亡率最高县——浙江省嘉菩县为研究现场，以该县1990年4月建立的包括10个乡镇的当地居民(64，693人)随访队列为研究人群。以队列内1990年5月至2005年5月发生的，且曾经参加1989～1990年开展的结直肠癌普查的原发性结直肠癌存活病例，排除直肠类癌、继发性结直肠癌、1989～1990年筛查时检出的结直肠癌病例以及不属于队列人群的原发性结直肠癌病例，最终纳入结直肠癌病例206例(结肠癌93例，直肠癌113例)。对照组(队列内正常人群的代表性样本)通过2002年和2005年分别开展的两次抽样调查获得：其中，2002年通过单纯随机抽样方法抽取个体400例，排除死亡16例和结直肠癌病例1例，共须调查383例，实际共调查343例；2005年在基线资料库中，剔除死亡和恶性肿瘤发病个体后，以性别和年龄为分层因素，采用分层随机抽样抽取调查对象550例，最终有效调查个体502例；两组对照人群均衡可比，代表性样本合计845例构成了本次研究的对照人群。通过一对一的上门问卷调查收集个体特征和生活方式等常见环境暴露因素的信息，经调查对象知情同意，采集静脉血5ml，分装储存备用。现场调查的质量控制通过调查前统一培训调查员，调查中统一携带标准的调查员手册，调查后统一对问卷进行复核和以5％的样本量进行电话回访实现。
采用改良盐析法抽提外周血白细胞基因组DNA，-60℃冰箱储存待检；DNA修复各SNP的检测分型均采用聚合酶链式反应-限制性内切酶片段长度多态性(PCR-RFLP)分析技术；P53通路中，P53 Exon4 Arg72Pro和Intron6 G／A transition的基因检测也采用PCR-RFLP分析技术，P53 Intron3 16bp duplication和MDM2 Del1518的检测分型采用PCR扩增后直接电泳分析方法，MDM2 SNP309的检测分型采用PCR-可诱导引物限制性(PIRA)分析技术。实验室的质量控制通过盲法检测和重复检测实现。
调查表经统一编码后，Epidata双遍录入，校对无误后建立数据库，分析前进行必要的变量代换及编码。主要的分析过程和方法包括：病例组和对照组个体具体年龄的差异采用成组t检验；分类变量(性别和基因型分布等)的分布差异采用Pearson x~2分布检验；相关因素的相对危险度估计采用多因素Logisitc回归计算比值比(OR)及其95％可信区间(CI)；采用EH Linkage Software1.2分析各组同一基因多个位点间是否存在连锁不平衡现象；采用PHASE2.0对研究对象的单体型分布进行测算分析；采用叉生分析、相乘交互作用模型和和x~2趋势检验进行基因-环境交互作用的分析；采用多因子降维分析软件MDR进行基因-基因联合作用的初筛。整个统计分析过程结合应用了Excel2003、SPSS 13.0 for Windows、EH Linkage Software1.2、PHASE2.0、MDR-Data Tool Software 0.4.3和MDR Software 1.0.0。
结果
1．个体特征、生活方式与结直肠癌
病例组和对照组的平均年龄分别为65.25±9.47岁和61.84±10.83岁，经成组t检验存在统计学显著性差异(P＜0.01)；采用对照组年龄四分位数分布进行分组；病例组和对照组的年龄分布同样存在统计学显著性差异(P＜0.01)；与最低年龄组(≥42，＜53岁)相比，高(≥61，＜72岁)、最高(≥72岁)年龄组风险增高有统计学意义(P＜0.05)，并且趋势也有统计学意义(P＜0.01)。病例组和对照组在性别、BMI指数和家族肿瘤史等基本因素的分布均不存在统计学显著性差异(P＞0.05)，然而经年龄和性别调整，家族肿瘤史与结直肠癌的发病存在有统计学意义的正相关关系(校正OR：1.51，95％CI：1.05-2.17)。分病理部位考虑，结肠癌和直肠癌病例组在上述各特征因素分布上均衡可比。对各生活方式因子的分析表明，结直肠癌病例组≥20支／天的重度吸烟者比率(24.27％)显著高于对照组(16.18％)，与吸烟量＜20支／天的个体相比，重度吸烟者(≥20支／天)罹患结直肠癌风险增高并有统计学意义(校正OR：1.19，95％CI：1.05-1.35)。
2．DNA修复基因多态性与结直肠癌
OGG1 Ser326Cys、XRCC1 Arg194Trp、XRCC1 Arg280His、XRCC1 Arg399Gln、XPD Lys751Gln和XRCC3 Thr241Met各变异等位基因分布频率在正常对照组为54.91％、34.25％、11.68％、26.19％、8.16％和4.41％，在病例组为54.57％、29.95％、11.22％、28.22％、10.15％和4.90％，所有等位基因和基因型分布两组间均不存在有统计学意义的显著差异(P＞0.05)。与不同特征的结直肠癌关联分析表明，XRCC1 Arg194Trp多态(CT&TT Vs.CC)可显著降低直肠癌、＜60岁结直肠癌和男性结直肠癌的患病风险，校正OR(95％CI)分别为0.66(0.44-0.99)，0.59(0.38-0.92)和0.64(0.41-0.99)。XRCC1单体型分析表明，Arg194Trp、Arg280His和Arg399Gln三位点在病例组和对照组都存在连锁不平衡现象(病例组x~2=36.74，对照组x~2=200.71，df=7，P均＜0.01)，然而在病例组和对照组问不存在有统计学意义的显著性差异(x~2=13.92，df=7，P＞0.05)；对象中8种单体型都有分布，其中CGG、TGG、CAG和CGA是常见的4类单体型；与野生等位基因联合单体型CGG相比，单体型TGG(仅26304位点携变异等位基因T)可使结直肠癌患病风险显著降低，校正OR=0.75(95％CI：0.57-0.99)。基因-环境联合作用分析表明，XRCC1 Arg399Gln多态与吸烟量交互，虽然各交互项风险估计都没有统计学意义，然而x~2趋势检验表明，随着吸烟剂量(支／天)增高，变异等位基因的存在可以使机体结直肠癌的患病风险逐步增高，且趋势有统计学意义(P＜0.05)；相乘交互作用模型分析表明，饮酒史与XPD Lys751Gln交互可使结直肠癌的患病风险增高近1倍且效应临界于统计学显著性水平(校正OR：1.90，95％CI：0.97-3.71，P=0.06)；与不饮酒且携带Asp／Asp野生型人群相比，饮酒累计时间≤32年且携带Asp／Asn或Asn／Asn变异基因型的人群，结直肠癌患病风险增高有统计学意义，校正OR为2.49(95％CI：1.09-5.69)。基因-基因联合作用分析表明，与不携带风险型的个体相比，携带高风险基因型数量多达4个位点时，结直肠癌的患病风险显著增高(校正OR：3.63，95％CI：1.24-10.62，P＜0.05)。
3．P53通路基因多态性与结直肠癌
P53 Intron3 16bp duplication、Exon4 Arg72Pro和Intron6 G／A transition，MDM2 Del1518和SNP309各变异等位基因分布频率在正常对照组为为3.80％、46.49％、5.97％、40.65％和43.78％，在病例组为2.48％、47.26％、4.46％、32.50％和40.59％，其中MDM2 Del1518等位基因和基因型分布在两组间差异有统计学意义(P＜0.05)；该变异纯合基因型与结直肠癌尤其是直肠癌患病风险存在有统计学意义的显著关联，校正OR(95％CI)分别为0.50(0.31-0.81)和0.40(0.20-0.79)。单体型分析表明，P53 Intron3 16bp duplication、Exon4 Arg72Pro和Intron6 G／A transition三位点在正常对照组分布存在连锁不平衡现象(x~2=120.89，df=7，P＜0.001)，而病例组没有(x~2=11.19，df=7，P＞0.05)，并且P53单体型分布在病例组和对照组间有统计学显著性差异(x~2=14.28，df=7，P＜0.05)；对于MDM2 Del1518和SNP309的分析表明，此两多态在病例组和对照组都存在连锁不平衡现象(病例组x~2=29.46，对照组x~2=25.53，df=3，P均＜0.01)，并且MDM2单体型分布在病例组和对照组间也存在统计学显著性差异(x~2=22.78，df=3，P＜0.01)，与野生型等位基因联合单体型“-T”相比，纯变异等位基因联合单体型“+G”可显著降低机体结直肠癌的罹患风险(校正OR：0.25，95％CI：0.14-0.47)。基因-环境联合作用分析表明，P53 Intron3 16bp duplication多态与年龄交互效应有统计学意义(校正OR：0.29，95％CI：0.09-0.98)，另外，P53 Exon4 Arg72Pro与家族肿瘤史交互、P53 Exon4 Arg72Pro或MDM2 SNP309与吸烟量交互对结直肠癌的发生都有一定的危险效应但都没有统计学意义。基因-基因联合作用分析表明，与携带风险型数目≤2的个体相比，随着风险型数目的增大，结直肠癌的患病风险迅速上升，不仅每个亚组的风险增高有统计学意义，并且趋势也有统计学意义(P＜0.05)；MDR分析表明，P53 Intron3 16bp duplication和MDM2 Del 1518交互对结直肠癌的发生具有保护效应，与其他基因型组合相比，野生联合型使结直肠癌患病风险显著增高(校正OR：1.37，95％CI：1.00-1.89)。
基于所有多态位点的基因-基因联合作用分析表明，XRCC1 Arg194Trp和P53 Intron6 G／A transition交互可在一定程度上相互拮抗各自保护效应的发挥，与野生联合型相比，XRCC1 194Trp变异等位基因或P53 Intron6 G／A transition变异等位基因的存在可使机体罹患肠癌风险降低并有统计学意义，然而两变异等位基因同时存在时效应没有统计学意义，校正OR(95％CI)分别为0.69(0.50-0.96)、0.25(0.08-0.85)和0.79(0.43-1.47)；基于所有因子的联合分析表明，年龄是本研究中影响结直肠癌发病的最主要的因素，高年龄组(≥61岁)个体比低年龄组个体(≥42，＜61岁)结直肠癌患病风险增加1倍多(校正OR：2.04，95％CI：1.49-2.80)。
结论
本次在浙江省嘉善县开展的自然人群为基础的病例对照研究，主要的研究结果有：
1．个体特征、生活方式与结直肠癌
年龄是本研究中影响结直肠癌发病的最重要的因子，结直肠癌的患病风险随着年龄的增大而增高；一、二级亲属家族肿瘤史对结直肠癌的发病也具有危险效应；性别和BMI指数分布与结直肠癌的发病没有相关性。是否吸烟／饮酒和吸烟／饮酒累计时间对结直肠癌的发病没有影响；然而重度吸烟者(≥20支／天)对结直肠癌的发病具有危险效应。
2．DNA修复基因多态性与结直肠癌
XRCC1 Arg194Trp多态可降低直肠癌、＜60岁或男性结直肠癌的患病风险；XRCC1单体型中仅Arg194Trp为变异等位基因的单体型“TGG”对结直肠癌的发病也具有保护效应；吸烟量与XRCC1 Arg399Gln的联合作用可增加结直肠癌的患病风险；DNA修复体系多个(≥4)高风险型SNP的积累可使结直肠癌的患病风险增高。
3．P53通路基因多态性与结直肠癌
MDM2 Del1518单位点多态对结直肠癌尤其是直肠癌具有保护效应；MDM2 Del1518和SNP309同为变异等位基因的单体型“+G”对结直肠癌的发病也具有保护效应；P53 Intron3 16bp duplication与年龄交互可逆转年龄对结直肠癌的危险效应；P53 Intron3 16bp duplication和MDM2 Del 1518交互对结直肠癌的发生具有保护效应；另外，XRCC1 Arg194Trp和P53 Intron6 G／A transition交互可在一定程度上相互拮抗各自保护效应的发挥；结直肠癌的患病风险随着P53通路高风险型多态个数的增加而增高，在结直肠癌的发生发展过程中，P53通路基因多态性可能比DNA修复基因体系起着更为重要的作用。
Backgrounds & Objectives
Colorectal cancer including colon and rectum cancer is one of the most common cancers. In 2002, the number of global incident cases was about 1 million accounting for 9.4% of all cancers which is only less than lung cancer (1.35 million) and breast cancer (1.15 million). In terms of prevalence, it is only second to breast cancer (4.4 million, 17.9%) with an estimated 2.8 million persons alive with colorectal cancer diagnosed within 5 years of diagnosis which accouts for 11.5% of all cancers in world. In China, colorectal cancer is the third prevalent cancer both in males and females with an increasing incidence, of which the estimates in 2005 were 15.0 and 9.7 per 100,000 for males and females, respectively.
As for the genetic predisposition to colorectal cancer, high-penetrance genes such as APC and DNA mismatch repair genes may account for hereditary colorectal cancer which is less than 5% of all colorectal cancer, such as familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC) known as monogenic diseases. Low-penetrance cnadidate genes mainly include DNA repair genes, metabolic enzyme genes, cell cycle regulatory genes, immune regulatory genes, oncogenes and tumor suppressing genes that are more common in natural population. Low-penetrance genes have an important influence on genetic predisposition to sporadic colorectal cancer (known as polygenic disease), which have intricate networks with environmental factors in carcinogenesis. DNA repair genes are the most important candidate genes, as the DNA repair system plays an important role in maintaining genome integrity which can protect the genome from carcinogens-induced damage to some extent. The genetic polymorphisms in DNA repair genes have an effect on individual's genetic susceptibility to spontaneous or induced cancer with the altered DNA repair capacity. P53 is a crucial tumor suppressor taking effect on DNA repair, cell cycle arrest and apoptosis in some cases via its stress response way, which is essential for genomic stability, and plays an important role in preventing tumor formation. Inactivating alterations in P53 gene is presented in about 50% of all human cancers. MDM2, encoded by mouse double minute 2 homolog gene (MDM2), is a key negative regulator of P53 stress response way. As a part of an autoregulatory negative feedback loop with P53 protein, overexpression of MDM2 gene can result in excessive
inactivation of P53 by blocking its transcription and mediating its degradation with E3 ubiquitin ligase activity. Polymorphisms in P53 and MDM2 may impair the function of P53 stress response way.
A population-based case-control study was conducted to describe the frequency distribution of polymorphims in DNA repair genes (OGG1 Ser326Cys, XRCC1 Arg194Trp, Arg280His, Arg399Gln, XPD Lys751Gln and XRCC3 Thr241 Met) and in P53 pathway genes (P53 Intron3 16bp duplication, Exon4 Arg72Pro, Intron6 G/A transition, MDM2 Dell518 and SNP309) in natural Chinese population, and to explore the association of colorectal cancer risk with the above single polymorphism, haplotypes of XRCC1, P53 and MDM2, gene-environment interaction between the above polymorphims and common environmental exposure factors, and gene-gene interaction within the same pathway or between the different pathways.
Materials & Methods
In this population-based case-control study, 206 primay colorectal cancer cases and 845 cancer-free healthy controls were enrolled in, and they are all Chinese Han people coming from a follow-up cohort which has been built since 1989 in Jiashan County, the county with the highest age-standardized colorectal cancer mortality in China. After informed consent, all subjects were interviewed with a questionnaire mainly including demographic characteristics, individual lifestyle and family history of cancers by professional trained interviewers with face-to-face method. To ensure the validity of data, a repeat interview by telephone with five percent was performed. Also with the subjects' permission, a total 5ml blood was collected after interview, which was separated into two sections of 2ml blood with sodium citrate anticoagulation and 3ml blood without anticoagulation to gain blood serum. All blood samples were stored at -60°C for long-term conservation. The study was approved by the Medical Ethical Committee of Zhejiang University School of Medicine.
The genomic DNA for each subject was extracted from whole blood using improved salting out procedure. As for the genotyping of polymorphisms in DNA repair genes, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique was used, which also was used for the genotyping of P53 Exon4 Arg72Pro and Intron6 G/A transition. The direct electrophoresis after PCR amplification was used for the genotyping of P53 Intron3 16bp duplication and MDM2 Del1518. Finally, the PCR- primer introduced restriction analysis (PIRA) method was used for the MDM2 SNP309 genotyping. Ten percent of all samples were randomly selected for repeat analysis to ensure obtaining the correct genotype information. All genotyping work was finished under the condition without knowledge of the subjects' case/control status.
Student's t-test was used to evaluate the difference in mean age between cases and controls. Pearson's x~2 test was used to compare the distribution difference in categorial variables (genotype distribution et al) between cases and controls. The Hardy-Weinberg equilibrium test in control group was finished by X~2 goodness-of-fit test. The associations of different factors (0GG1 variants et al) with colorectal cancer risk were estimated by calculating the odds ratios (ORs) and their 95% confidence intervals (95% C/s) with multivariate logistic regression adjusted by age and sex. EH Linkage Software1.2 was used to identify the linkage disequilibrium. PHASE2.0 was used to construct haplotypes and estimate their frequency distributions. At last, MDR Software 1.0.0 was used for analyzing the gene-gene interaction. All statistical analysis was finished in Excel2003, SPSS 13.0 for windows, EH Linkage Softwarel.2, PHASE2.0, MDR-Data Tool Software 0.4.3 and MDR Software 1.0.0. All tests of statistical significance (α=0.05) were two-sided.
Results
1. Demographic characteristics, lifestyle factors and colorectal cancer
The mean age of colorectal cancer cases was 65.25 (SD=9.47) years, which was statistically different
from that of controls (X±SD: 61.84±10.83 years, P<0.01). Based on the quartile distribution of controls, the significant difference between two groups was also observed in the age distribution (P<0.01). As compared with the low age group (<53 years), the higher (>61 years) and the highest age group (≥72 years) had significant risks of colorectal cancer, and the ORs (95% C/s) were 2.89 (1.79-4.68) and 2.37 (1.45-3.88) adjusted by sex, respectively. There was no statistically significant difference in distributions of sex, BMI and family history of cancer in first and second relatives. However, as adjusted by sex and age, family history of cancer in first and second relatives was significantly associated with colorectal cancer risk (OR=1.51, 95%CI=1.05-2.17). As for the lifestyle factors, the frequency of heavy smokers (>20 cigarettes per day) in cases was statistically higher than that in controls (24.27% Vs. 16.18%), and the adjusted OR (95% CI) was 1.19 (1.05-1.35).
2. Genetic polymorphisms of DNA repair genes and risk of colorectal cancer
The polymorphic variants of OGG1 Ser326Cys, XRCC1 Arg194Trp, Arg280His, Arg399Gln, XPD Lys751Gln and XRCC3 Thr241 Met in controls were 54.91%, 34.25%, 11.68%, 26.19%, 8.16% and 4.41%, which in cases were 54.57%, 29.95%, 11.22%, 28.22%, 10.15% and 4.90%, respectively. No significant difference was observed between cases and controls in allels and genotypes distribution. Association analysis for the different sub-type colorectal cancer indicated that 194Trp variant decreased risks of rectum cancer, the comparative early-onset colorectal cancer (age at diagnosis <60 years) and male colorectal cancer significantly, and the adjusted ORs (95% C/s) for variant
heterozygotes and homozygotes as referred to wild homozygotes were 0.66 (0.44-0.99), 0.59 (0.38-0.92) and 0.64 (0.41-0.99), respectively. EH Linkage Software1.2 showed that there existed LD among XRCC1 three locuses, Arg194Trp, Arg280His and Arg399Gln, both in case and control group (Cases: X~2=36.74, Controls: X~2=200.71, df=7, P<0.01). However, no significant difference of the XRCC1 haplotype distribution existed between two groups (X~2=13.92, df=7, P>0.05). The PHASE progrom predicted CGG, TGG, CAG and CGA were the four most common haplotypes among all eight hyplotypes. Adjusted by age and sex, TGG haplotype (only with 194Trp variant) was associated with a statistically significant decreased risk of colorectal cancer compared with CGG hyplotype (without mutant variants), and the OR was 0.75 (95%CI=0.57-0.99). X~2 trend analysis found that 399Gln variant was correlated with the increase of colorectal cancer risk corresponding to the increase of smoke exposure dose (cigarettes per day) (P<0.05). The interaction between XPD 751 Lys/Gln & Gln/Gln genotypes and alcohol drinking (ever or current Vs. never) had an increasing risk of colorectal cancer but didn't reach statistically significant level (OR=1.90, 95%CI=0.97-3.71, P=0.06). Gene-gene interaction revealed that individuals with four putative high-risk genotypes statistically increased colorectal cancer risk (OR=3.63, 95%CI=1.24-10.62, P<0.05).
3. Genetic polymorphisms of P53 pathway genes and risk of colorectal cancer
The polymorphic variants of P53 Intron3 16bp duplication, Exon4 Arg72Pro, Intron6 G/A transition, MDM2 Del1518 and SNP309 in controls were 3.80%, 46.49%, 5.97%, 40.65% and 43.78%, which in cases were 2.48%, 47.26%, 4.46%, 32.50% and 40.59%, respectively. Significant difference was observed between cases and controls in MDM2 Del1518 allels and genotypes distribution (P<0.05). Multivariate logistic regression adjusted by age and sex indicated that MDM2 Del1518 mutant homozygotes statistically decreased colorectal cancer risk especially rectum cancer risk, and ORs (95%C/s) were 0.50 (0.31-0.81) for colorectal cancer and 0.40 (0.20-0.79) for rectum cancer. EH Linkage Softwarel.2 revealed that LD existed among P53 Intron3 16bp duplication, Exon4 Arg72Pro and Intron6 G/A transition three locuses in controls (X~2=120.89, df=7, P<0.001), and between MDM2 Del1518 and SNP309 two locuses both in cases and controls (Cases: X~2=29.46, Controls X~2=25.53, df=3, P<0.01). What's more, statistical differences of the P53 (X~2=14.28, df=7, P<0.05) and MDM2 (X~2=22.78, df=3, P<0.01) haplotypes distribution existed between case and control groups. Compared with "- T" haplotype (both with wild alleles), "+ G" haplotype (both with mutant alleles) made colorectal cancer risk decrease statistically (adjusted OR=0.25, 95%CI=0.14-0.47). Gene-environment interaction analysis found that the interaction of P53 Intron3 16bp duplication and age decreased colorectal cancer risk significantly (OR=0.29, 95%CI=0.09-0.98. On the other hand, the interactions of P53 Exon4 Arg72Pro and family history of cancer or smoke exposure dose, MDM2 SNP309 and smoke exposure dose could increase risk of colorectal cancer but didn't reach the statistical significant level. As compared with individuals having less than three
putative high-risk genotypes, individuals with three or more putative high-risk genotypes had a statistical increased risk of colorectal cancer. And the ORs (95%C/s) were 3.94 (1.18-13.17) for individuals with three high-risk genotypes, 4.63 (1.41-15.17) for individuals with four high-risk genotypes and 6.08 (1.81-20.36) for individuals with five high-risk genotypes, respectively. MDR analysis found that the interaction of P53 Intron3 16bp duplication and MDM2 Del 1518 made colorectal cancer risk decrease statistically. The wild combinative genotype (without variants) was statistically associated with increase of colorectal cancer risk as compared with other three combinative genotypes (OR=1.37, 95%CI= 1.00-1.89). In consideration of all polymorphisms, single XRCC1 Arg194Trp or P53 Intron6 G/A transition polymorphism was associated with a statistical decrease of colorectal cancer risk referred to the wild combinative genotype. However, the mutant combinative genotype also was associated with the decrease of colorectal cancer risk but didn't have statistical significance.
Conclusions
The main findings from this population-based case-control study carried out in Chinese Han population were as follows:
1. Age (≥61 years), family history of cancer in first and second relatives and heavy smoking (≥20 cigarettes per day) may contribute to the colorectal cancer predisposition.
2. XRCC1 Arg194Trp polymorphism may have effect on colorectal cancer especially on rectum cancer, the comparative early-onset colorectal cancer (age at diagnosis <60 years) and male colorectal cancer. The gene-environment interaction between XRCC1 Arg399Gln polymorphism and cigarette smoke exposure may also have effect on the colorectal carcinogenesis. The accumulation of multi-polymorphisms in DNA repair genes has a contribution to the genetic predisposition of colorectal cancer.
3. MDM2 Del1518 polymorphism and its interaction with P53 Intron3 16bp duplication may have influence on colorectal cancer especially on rectum cancer. P53 Intron3 16bp duplication and may be able to counteract the increasing risk of colorectal cancer resulting from age. The accumulation of multi-polymorphisms in P53 pathway genes plays an important role in colorectal cancer susceptibility.
引文
1. Parkin DM, Bray F, Ferlay J, Pisani P. Global cancer statistics, 2002. CA: a cancer journal for clinicians 2005;55:74-108.
2. Yang L, Parkin DM, Ferlay J, Li L, Chen Y. Estimates of cancer incidence in China for 2000 and projections for 2005. Cancer Epidemiol Biomarkers Prev 2005;14:243-50.
3．卫生部．中国癌症预防与控制规划纲要(2004-2010)．中国肿瘤2004；13：65—8．
4. Sanjoaquin MA, Appleby PN, Thorogood M, Mann JI, Key TJ. Nutrition, lifestyle and colorectal cancer incidence: a prospective investigation of 10998 vegetarians and non-vegetarians in the United Kingdom. British journal of cancer 2004;90:118-21.
5. Norat T, Bingham S, Ferrari P, Slimani N, Jenab M, Mazuir M, Overvad K, Olsen A, Tjonneland A, Clavel F, Boutron-Ruault MC, Kesse E, et al. Meat, fish, and colorectal cancer risk: the European Prospective Investigation into cancer and nutrition. Journal of the National Cancer Institute 2005;97:906-16.
6. McCullough ML, Robertson AS, Rodriguez C, Jacobs EJ, Chao A, Carolyn J, Calle EE, Willett WC, Thun MJ. Calcium, vitamin D, dairy products, and risk of colorectal cancer in the Cancer Prevention Study II Nutrition Cohort (United States). Cancer Causes Control 2003; 14:1-12.
7. Bingham SA, Day NE, Luben R, Ferrari P, Slimani N, Norat T, Clavel-Chapelon F, Kesse E, Nieters A, Boeing H, Tjonneland A, Overvad K, et al. Dietary fibre in food and protection against colorectal cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC): an observational study. Lancet 2003;361:1496-501.
8. Levin B. Nutrition and colorectal cancer. Cancer 1992;70:1723-6.
9. Bodmer WF, Bailey CJ, Bodmer J, Bussey HJ, Ellis A, Gorman P, Lucibello FC, Murday VA, Rider SH, Scambler P, et al. Localization of the gene for familial adenomatous polyposis on chromosome 5. Nature 1987;328:614-6.
10. Bronner CE, Baker SM, Morrison PT, Warren G, Smith LG, Lescoe MK, Kane M, Earabino C, Lipford J, Lindblom A, et al. Mutation in the DNA mismatch repair gene homologue hMLH1 is associated with hereditary non-polyposis colon cancer. Nature 1994;368:258-61.
11. Solomon E. Molecular genetics. Colorectal cancer genes. Nature 1990;343:412-4.
12. Bodmer WF. Cancer genetics: colorectal cancer as a model. Journal of human genetics 2006:51:391-6.
13. Baglioni S, Genuardi M. Simple and complex genetics of colorectal cancer susceptibility. American journal of medical genetics 2004;l 29:35-43.
14. Zhao Z, Zhang F. Sequence context analysis of 8.2 million single nucleotide polymorphisms in the human genome. Gene 2006; 366: 316-24.
15. Sachidanandam R, Weissman D, Schmidt SC, Kakol JM, Stein LD, Marth G, Sherry S, Mullikin JC, Mortimore B J, Willey DL, Hunt SE, Cole CG, et al. A map of human genome sequence variation containing 1.42 million single nucleotide polymorphisms. Nature 2001; 409:928-33.
16．柯杨．相关基因的单核苷酸多态性与肿瘤的遗传易感．中华肿瘤杂志2002；24：105-6．
17. Chen K, Jiang QT, He HQ. Relationship between metabolic enzyme polymorphism and colorectal cancer. World J Gastroenterol 2005;11:331-5.
18. Cotton SC, Sharp L, Little J, Brockton N. Glutathione S-transferase polymorphisms and colorectal cancer: a HuGE review. American journal of epidemiology 2000;151:7-32.
19. Brockton N, Little J, Sharp L, Cotton SC. N-acetyltransferase polymorphisms and colorectal cancer: a HuGE review. American journal of epidemiology 2000;151:846-61.
20. Houlston RS, Yomlinson IP. Polymorphisms and colorectal tumor risk. Gastroenterology 2001;121:282-301.
21. Hubner RA, Muir KR, Liu JF, Sellick GS, Logan RF, Grainge M, Armitage N, Chau I, Houlston RS. Folate metabolism polymorphisms influence risk of colorectal adenoma recurrence. Cancer Epidemiol Biomarkers Prey 2006; 15:1607-13.
22. Sharp L, Little J. Polymorphisms in genes involved in folate metabolism and colorectal neoplasia: a HuGE review. American journal of epidemiology 2004;159:423-43.
23．陈坤，金明娟，范春红，宋亮．大肠癌环境暴露和代谢酶基因多态性的分子流行病学研究．中华流行病学杂志2006；27：905-8．
24. Goode EL, Ulrich CM, Potter JD. Polymorphisms in DNA repair genes and associations with cancer risk. Cancer Epidemiol Biomarkers Prey 2002;11:1513-30.
25. Friedberg EC. DNA damage and repair. Nature 2003;421:436-40.
26. de Jong MM, Nolte IM, te Meerman GJ, van der Graaf WT, de Vries EG, Sijmons RH, Hofstra RM, Kleibeuker JH. Low-penetrance genes and their involvement in colorectal cancer susceptibility. Cancer Epidemiol Biomarkers Prey 2002;11: 1332-52.
27. Hussain SP, Harris CC. p53 biological network: at the crossroads of the cellular-stress response pathway and molecular carcinogenesis. Journal of Nippon Medical School = Nihon Ika Daigaku zasshi 2006;73: 54-64.
28. Soussi T, Dehouche K, Beroud C. p53 website and analysis of p53 gene mutations in human cancer: forging a link between epidemiology and carcinogenesis. Human mutation 2000; 15:105-13.
29. Dumont P, Leu JI, Della Pietra AC, 3rd, George DL, Murphy M. The codon 72 polymorphic variants of p53 have markedly different apoptotic potential. Nature genetics 2003;33:357-65.
30. Wu X, Zhao H, Amos CI, Shete S, Makan N, Hong WK, Kadlubar FF, Spitz MR. p53 Genotypes and Haplotypes Associated With Lung Cancer Susceptibility and Ethnicity. Journal of the National Cancer Institute 2002;94:681-90.
31. Thomas M, Kalita A, Labrecque S, Pim D, Banks L, Matlashewski G. Two polymorphic variants of wild-type p53 differ biochemically and biologically. Molecular and cellular biology 1999;19:1092-100.
32．黄越承，蔡建明．MDM2功能及其调控机制．国外医学肿瘤学分册2004；31：336-9．
33. Kubbutat MH, Jones SN, Vousden KH. Regulation of p53 stability by Mdm2. Nature 1997;387:299-303.
34. Haupt Y, Maya R, Kazaz A, Oren M. Mdm2 promotes the rapid degradation of p53. Nature 1997;387:296-9.
35. Hu Z, Ma H, Lu D, Qian J, Zhou J, Chen Y, Xu L, Wang X, Wei Q, Shen H. Genetic variants in the MDM2 promoter and lung cancer risk in a Chinese population. International journal of cancer 2006;118:1275-8.
36. Bond GL, Hu W, Bond EE, Robins H, Lutzker SG, Arva NC, Bargonetti J, Bartel F, Taubert H, Wuerl P, Oriel K, Yip L, et al. A single nucleotide polymorphism in the MDM2 promoter attenuates the p53 tumor suppressor pathway and accelerates tumor formation in humans. Cell 2004;119:591-602.
37．卫生部肿瘤防治办公室．中国恶性肿瘤死亡回顾调查．人民卫生出版社 1979：198．
38．全国肿瘤防治研究办公室，卫生部卫生信息统计中心．中国试点市、县恶性肿瘤的发病与死亡(1993-1997)．中国医药科技出版社2002．
39．郑树主编．结直肠肿瘤 基础研究与临床实践．北京 人民卫生出版社 2006．
40．陈学敏主编，吴德生，陈秉衡副主编．环境卫生学．北京 人民卫生出版社2004．
41．朱守民，夏昭林．DNA损伤修复基因与遗传易感性．环境与职业医学 2003；20：50-2．
42. Spitz MR, Wei Q, Dong Q, Amos CI, Wu X. Genetic Susceptibility to Lung Cancer: The Role of DNA Damage and Repair Cancer Epidemiol. Biomarkers Prey. 2003;2003:689-98.
43. Kohno T, Shinmura K, Tosaka M, Tani M, Kim SR, Sugimura H, Nohmi T, Kasai H, Yokota J. Genetic polymorphisms and alternative splicing of the hOGG1 gene, that is involved in the repair of 8-hydroxyguanine in damaged DNA. Oncogene 1998;16:3219-25.
44. Shen MR, Jones IM, Mohrenweiser H. Nonconservative amino acid substitution variants exist at polymorphic frequency in DNA repair genes in healthy humans. Cancer research 1998;58:604-8.
45. Khan SG, Metter EJ, Tarone RE, Bohr VA, Grossman L, Hedayati M, Bale SJ, Emmert S, Kraemer KH. A new xeroderma pigmentosum group C poly(AT) insertion/deletion polymorphism. Carcinogenesis 2000; 21: 1821-5.
46．邢德印，林东昕．hOGG1基因与肿瘤．癌症2000；19：499-501．
47．Hung RJ，Hall J，Brennan P，Boffetta P Genetic polymorphisms in the base excision repair pathway and cancer risk: a HuGE review. American journal of epidemiology 2005;162:925-42.
48. Moreno V, Gemignani F, Landi S, Gioia-Patricola L, Chabrier A, Blanco I, Gonzalez S, Guino E, Capella G, Canzian F. Polymorphisms in genes of nucleotide and base excision repair: risk and prognosis of colorectal cancer. Clin Cancer Res 2006;12:2101-8.
49. Hansen R, Saebo M, Skjelbred CF, Nexo BA, Hagen PC, Bock G, Bowitz Lothe IM, Johnson E, Aase S, Hansteen IL, Vogel U, Kure EH. GPX Prol98Leu and OGG1 Ser326Cys polymorphisms and risk of development of colorectal adenomas and colorectal cancer. Cancer letters 2005;229:85-91.
50. Goodman JE, Mechanic LE, Luke BT, Ambs S, Chanock S, Harris CC. Exploring SNP-SNP interactions and colon cancer risk using polymorphism interaction analysis. International journal of cancer 2006; 118:1790-7.
51. Kim JI, Park YJ, Kim KH, Kim JI, Song BJ, Lee MS, Kim CN, Chang SH. hOGG1 Ser326Cys polymorphism modifies the significance of the environmental risk factor for colon cancer. World J Gastroenterol 2003;9:956-60.
52. Abdel-Rahman SZ, Soliman AS, Bondy ML, Omar S, El-Badawy SA, Khaled HM, Seifeldin IA, Levin B. Inheritance of the 194Trp and the 399Gln variant alleles of the DNA repair gene XRCC1 are associated with increased risk of early-onset colorectal carcinoma in Egypt. Cancer letters 2000;159:79-86.
53. Hong YC, Lee KH, Kim WC, Choi SK, Woo ZH, Shin SK, Kim H. Polymorphisms of XRCC1 gene, alcohol consumption and colorectal cancer. International journal of cancer 2005; 116:428-32.
54. Krupa R, Blasiak J. An association of polymorphism of DNA repair genes XRCC1 and XRCC3 with colorectal cancer. J Exp Clin Cancer Res 2004;23:285-94.
55. Yeh CC, Sung FC, Tang R, Chang-Chieh CR, Hsieh LL. Polymorphisms of the XRCC1, XRCC3, & XPD genes, and colorectal cancer risk: a case-control study in Taiwan. BMC cancer 2005;5:12.
56. Mort R, Mo L, McEwan C, Melton DW. Lack of involvement of nucleotide excision repair gene polymorphisms in colorectal cancer. British journal of cancer 2003;89:333-7.
57. Jin MJ, Chen K, Song L, Fan CH, Chen Q, Zhu YM, Ma XY, Yao KY. The association of the DNA repair gene XRCC3 Thr241 Met polymorphism with susceptibility to colorectal cancer in a Chinese population. Cancer genetics and cytogenetics 2005;163:38-43.
58. Hu Z, Ma H, Chen F, Wei Q, Shen H. XRCC1 polymorphisms and cancer risk: a meta-analysis of 38 case-control studies. Cancer Epidemiol Biomarkers Prev 2005;14:1810-8.
59. Thompson LH, West MG. XRCC1 keeps DNA from getting stranded. Mutation research 2000;459:1-18.
60. David-Beabes GL, London SJ. Genetic polymorphism of XRCC1 and lung cancer risk among African-Americans and Caucasians. Lung cancer (Amsterdam, Netherlands) 2001;34:333-9.
61. Stern MC, Umbach DM, van Gils CH, Lunn RM, Taylor JA. DNA repair gene XRCC1 polymorphisms, smoking, and bladder cancer risk. Cancer Epidemiol Biomarkers Prev 2001;10:125-31.
62．金明娟,陈坤．DNA修复基因多态性与肺癌易感性的研究进展．国外医学遗传学分册2005：28：215—20．
63. Seedhouse C, Bainton R, Lewis M, Harding A, Russell N, Das-Gupta E. The genotype distribution of the XRCC1 gene indicates a role for base excision repair in the development of therapy-related acute myeloblastic leukemia. Blood 2002;100:3761-6.
64. Clarkson SG, Wood RD. Polymorphisms in the human XPD (ERCC2) gene, DNA repair capacity and cancer susceptibility: an appraisal. DNA repair 2005;4:1068-74.
65. Spitz MR, Wu X, Wang Y, Wang LE, Shete S, Amos CI, Guo Z, Lei L, Mohrenweiser H, Wei Q. Modulation of nucleotide excision repair capacity by XPD polymorphisms in lung cancer patients. Cancer research 2001 ;61:1354-7.
66. Xing D, Tan W, Wei Q, Lin D. Polymorphisms of the DNA repair gene XPD and risk of lung cancer in a Chinese population. Lung cancer (Amsterdam, Netherlands) 2002;38:123-9.
67. Park JY, Lee SY, Jeon HS, Park SH, Bae NC, Lee EB, Cha SI, Park JH, Kam S, Kim IS, Jung TH. Lys751Gln polymorphism in the DNA repair gene XPD and risk of primary lung cancer. Lung cancer (Amsterdam, Netherlands) 2002;36:15-6.
68. Stern MC, Umbach DM, Lunn RM, Taylor JA. DNA repair gene XRCC3 codon 241 polymorphism, its interaction with smoking and XRCC1 polymorphisms, and bladder cancer risk. Cancer Epidemiol Biomarkers Prev 2002;11:939-43.
69. Matullo G, Palli D, Peluso M, Guarrera S, Carturan S, Celentano E, Krogh V, Munnia A, Tumino R, Polidoro S, Piazza A, Vineis P. XRCC1, XRCC3, XPD gene polymorphisms, smoking and (32)P-DNA adducts in a sample of healthy subjects. Carcinogenesis 2001 ;22:1437-45.
70. Zhang Z, Wan J, Jin X, Jin T, Shen H, Lu D, Xia Z. Genetic polymorphisms in XRCC1, APE1, ADPRT, XRCC2, and XRCC3 and risk of chronic benzene poisoning in a Chinese occupational population. Cancer Epidemiol Biomarkers Prev 2005; 14:2614-9.
71. Shen H, Wang X, Hu Z, Zhang Z, Xu Y, Hu X, Guo J, Wei Q. Polymorphisms of DNA repair gene XRCC3 Thr241Met and risk of gastric cancer in a Chinese population. Cancer letters 2004;206:51-8.
72. Jin S, Levine AJ. The p53 functional circuit. Journal of cell science 2001 ;114:4139-40.
73. Sjalander A, Birgander R, Athlin L, Stenling R, Rutegard J, Beckman L, Beckman G. P53 germ line haplotypes associated with increased risk for colorectal cancer. Carcinogenesis 1995;16:1461-4.
74. Gemignani F, Moreno V, Landi S, Moullan N, Chabrier A, Gutierrez-Enriquez S, Hall J, Guino E, Peinado MA, Capella G, Canzian F. A TP53 polymorphism is associated with increased risk of colorectal cancer and with reduced levels of TP53 mRNA. Oncogene 2004;23:1954-6.
75. Kawajiri K, Nakachi K, Imai K, Watanabe J, Hayashi S. Germ line polymorphisms of p53 and CYPlAl genes involved in human lung cancer. Carcinogenesis 1993;14:1085-9.
76. Koushik A, Tranah GJ, Ma J, Stampfer MJ, Sesso HD, Fuchs CS, Giovannucci EL, Hunter DJ. p53 Arg72Pro polymorphism and risk of colorectal adenoma and cancer. International journal of cancer 2006;l 19:1863-8.
77. Alhopuro P, Ylisaukko-Oja SK, Koskinen WJ, Bono P, Arola J, Jarvinen HJ, Mecklin JP, Atula T, Kontio R, Makitie AA, Suominen S, Leivo I, et al. The MDM2 promoter polymorphism SNP309T→G and the risk of uterine leiomyosarcoma, colorectal cancer, and squamous cell carcinoma of the head and neck. Journal of medical genetics 2005;42:694-8.
78. Menin C, Scaini MC, De Salvo GL, Biscuola M, Quaggio M, Esposito G, Belluco C, Montagna M, Agata S, D'Andrea E, Nitti D, Amadori A, et al. Association between MDM2-SNP309 and age at colorectal cancer diagnosis according to p53 mutation status. Journal of the National Cancer Institute 2006;98:285-8.
79. Alazzouzi H, Suriano G, Guerra A, Plaja A, Espin E, Armengol M, Alhopuro P, Velho S, Shinomura Y, Gonzalez-Aguilera JJ, Yamamoto H, Aaltonen LA, et al. Tumour selection advantage of non-dominant negative P53 mutations in homozygotic MDM2-SNP309 colorectal cancer cells. Journal of medical genetics 2007;44:75-80.
80. Harris CC, Hollstein M. Clinical implications of the p53 tumor-suppressor gene. The New England journal of medicine 1993;329:1318-27.
81． 管立学,杜欣莹,王守训．p53基因CD72 ArgPro多态性与肿瘤易感性研究进展．国外医学遗传学分册2005；28：354-7．
82. Matlashewski GJ, Tuck S, Pim D, Lamb P, Schneider J, Crawford LV. Primary structure polymorphism at amino acid residue 72 of human p53. Molecular and cellular biology 1987;7:961-3.
83. Pietsch EC, Humbey O, Murphy ME. Polymorphisms in the p53 pathway. Oncogene 2006;25:1602-ll.
84. Ohayon T, Gershoni-Baruch R, Papa MZ, Distelman Menachem T, Eisenberg Barzilai S, Friedman E. The R72P P53 mutation is associated with familial breast cancer in Jewish women. British journal of cancer 2005;92:1144-8.
85. Soulitzis N, Sourvinos G, Dokianakis DN, Spandidos DA. p53 codon 72 polymorphism and its association with bladder cancer. Cancer letters 2002; 179:175-83.
86. Shen H, Zheng Y, Sturgis EM, Spitz MR, Wei Q. P53 codon 72 polymorphism and risk of squamous cell carcinoma of the head and neck: a case-control study. Cancer letters 2002;183:123-30.
87. Walsh CS, Miller CW, Karlan BY, Koeffler HP. Association between a functional single nucleotide polymorphism in the MDM2 gene and sporadic endometrial cancer risk. Gynecologic oncology 2007;104:660-4.
88. Ruijs MW, Schmidt MK, Nevanlinna H, Tommiska J, Aittomaki K, Pruntel R, Verhoef S, Van't Veer LJ. The single-nucleotide polymorphism 309 in the MDM2 gene contributes to the Li-Fraumeni syndrome and related phenotypes. Eur J Hum Genet 2007; 15:110-4.
89. Zhang X, Miao X, Guo Y, Tan W, Zhou Y, Sun T, Wang Y, Lin D. Genetic polymorphisms in cell cycle regulatory genes MDM2 and TP53 are associated with susceptibility to lung cancer. Human mutation 2006;27:110-7.
90. Park SH, Choi JE, Kim EJ, Jang JS, Han HS, Lee WK, Kang YM, Park JY. MDM2 309T>G polymorphism and risk of lung cancer in a Korean population. Lung cancer (Amsterdam, Netherlands) 2006;54:19-24.
91. Onat OE, Tez M, Ozcelik T, Toruner GA. MDM2 T309G polymorphism is associated with bladder cancer. Anticancer research 2006;26:3473-5.
92. Ohmiya N, Taguchi A, Mabuchi N, Itoh A, Hirooka Y, Niwa Y, Goto H. MDM2 promoter polymorphism is associated with both an increased susceptibility to gastric carcinoma and poor prognosis. J Clin Oncol 2006;24:4434-40.
93. Millikan RC, Heard K, Winkel S, Hill EJ, Heard K, Massa B, Mayes L, Williams P, Holston R, Conway K, Edmiston S, de Cotret AR. No association between the MDM2 -309 T/G promoter polymorphism and breast cancer in African-Americans or Whites. Cancer Epidemiol Biomarkers Prev 2006; 15:175-7.
94. Bougeard G, Baert-Desurmont S, Tournier I, Vasseur S, Martin C, Brugieres L, Chompret A, Bressac-de Paillerets B, Stoppa-Lyonnet D, Bonaiti-Pellie C, Frebourg T. Impact of the MDM2 SNP309 and p53 Arg72Pro polymorphism on age of tumour onset in Li-Fraumeni syndrome. Journal of medical genetics 2006;43:531-3.
95. Ma H, Hu Z, Zhai X, Wang S, Wang X, Qin J, Jin G, Liu J, Wang X, Wei Q, Shen H. Polymorphisms in the MDM2 promoter and risk of breast cancer: a case-control analysis in a Chinese population. Cancer letters 2006;240:261-7.
96. Miller SA, Dykes DD, Polesky HF. A simple salting out procedure for extracting DNA from human nucleated cells. Nucleic acids research 1988; 16:1215.
97. Le Marchand L, Donlon T, Lum-Jones A, Seifried A, Wilkens LR. Association of the hOGG1 Ser326Cys polymorphism with lung cancer risk. Cancer Epidemiol Biomarkers Prev 2002;l 1:409-12.
98. Abdel-Rahman SZ, El-Zein RA. The 399Gln polymorphism in the DNA repair gene XRCC1 modulates the genotoxic response induced in human lymphocytes by the tobacco-specific nitrosamine NNK. Cancer letters 2000; 159:63-71.
99. Butkiewicz D, Rusin M, Enewold L, Shields PG, Chorazy M, Harris CC. Genetic polymorphisms in DNA repair genes and risk of lung cancer. Carcinogenesis 2001;22:593-7.
100. Sturgis EM, Zheng R, Li L, Castillo EJ, Eicher SA, Chen M, Strom SS, Spitz MR, Wei Q. XPD/ERCC2 polymorphisms and risk of head and neck cancer: a case-control analysis. Carcinogenesis 2000;21:2219-23.
101. David-Beabes GL, Lunn RM, London SJ. No association between the XPD (Lys751Gln) polymorphism or the XRCC3 (Thr241Met) polymorphism and lung cancer risk. Cancer Epidemiol Biomarkers Prey 2001; 10:911-2.
102. Lee JM, Shun CT, Wu MT, Chen YY, Yang SY, Hung HI, Chen JS, Hsu HH, Huang PM, Kuo SW, Lee YC. The associations of p53 overexpression with p53 codon 72 genetic polymorphism in esophageal cancer. Mutation research 2006;594:181-8.
103. Yeh CC, Sung FC, Tang R, Chang-Chieh CR, Hsieh LL. Association between polymorphisms of biotransformation and DNA-repair genes and risk of colorectal cancer in Taiwan. J Biomed Sci 2006.
104. Qing SH, Rao KY, Jiang HY, Wexner SD. Racial differences in the anatomical distribution of colorectal cancer: a study of differences between American and Chinese patients. World J Gastroenterol 2003; 9: 721-5.
105．全国肿瘤防治研究办公室，卫生部卫生信息统计中心．中国试点市、县恶性肿瘤的发病与死亡(1988-1992)．中国医药科技出版社2001．
106. Fuchs CS, Giovannucci EL, Colditz GA, Hunter DJ, Speizer FE, Willett WC. A prospective study of family history and the risk of colorectal cancer. The New England journal of medicine 1994;331:1669-74.
107. Karner-Hanusch J, Mittlbock M, Fillipitsch T, Herbst F. Family history as a marker of risk for colorectal cancer: Austrian experience. World journal of surgery 1997;21:205-9.
108. Chen K, Qiu JL, Zhang Y, Zhao YW. Meta analysis of risk factors for colorectal cancer. World J Gastroenterol 2003; 9: 1598-600.
109. Giacosa A, Franceschi S, La Vecchia C, Favero A, Frascio F, Andreatta R. Overweight and colorectal cancer risk. Minerva gastroenterologica e dietologica 2001; 47: 235-40.
110. Kune GA, Kune S, Watson LF. Body weight and physical activity as predictors of colorectal cancer risk. Nutrition and cancer 1990;13:9-17.
111. Sturmer T, Buring JE, Lee IM, Gaziano JM, Glynn RJ. Metabolic abnormalities and risk for colorectal cancer in the physicians' health study. Cancer Epiderniol Biomarkers Prey 2006;15:2391-7.
112. Samad AK, Taylor RS, Marshall T, Chapman MA. A meta-analysis of the association of physical activity with reduced risk of colorectal cancer. ColorectaI Dis 2005;7:204-13.
113．蒋沁婷，陈坤，邹艳，赵玉婉，马新源，李其龙，姚开颜，郑树．随访队列的结直肠癌危险因素的病例-对照研究．肿瘤2004；24：6-10．
114．张晓慧，许岸高．结直肠癌高危人群的研究现状．中华医学实践杂志 2004；3：39-41．
115. Giovannucci E, Rimm EB, Stampfer MJ, Colditz GA, Ascherio A, Kearney J, Willett WC. A prospective study of cigarette smoking and risk of colorectal adenoma and colorectal cancer in U.S. men. Journal of the National Cancer Institute 1994; 86: 183-91.
116. Martinez ME, McPherson RS, Annegers JF, Levin B. Cigarette smoking and alcohol consumption as risk factors for colorectal adenomatous polyps. Journal of the National Cancer Institute 1995;87:274-9.
117. Wakai K, Hayakawa N, Kojima M, Tamakoshi K, Watanabe Y, Suzuki K, Hashimoto S, Tokudome S, Toyoshima H, Ito Y, Tamakoshi A. Smoking and colorectal cancer in a non-Western population: a prospective cohort study in Japan. Journal of epidemiology/Japan Epidemiological Association 2003; 13: 323-32.
118. Giovannucci E. An updated review of the epidemiological evidence that cigarette smoking increases risk of colorectal cancer. Cancer Epidemiol Biomarkers Prey 2001;10:725-31.
119. Otani T, Iwasaki M, Yamamoto S, Sobue T, Hanaoka T, Inoue M, Tsugane S. Alcohol consumption, smoking, and subsequent risk of colorectal cancer in middle-aged and elderly Japanese men and women: Japan Public Health Center-based prospective study. Cancer Epidemiol Biomarkers Prey 2003; 12:1492-500.
120. Slattery ML, Edwards S, Curtin K, Schaffer D, Neuhausen S. Associations between smoking, passive smoking, GSTM-1, NAT2, and rectal cancer. Cancer Epidemiol Biomarkers Prey 2003;12:882-9.
121. Ravasco P, Monteiro-Grillo I, Marques Vidal P, Camilo ME. Nutritional risks and colorectal cancer in a Portuguese population. Nutr Hosp 2005;20:165-72.
122. Lilla C, Verla-Tebit E, Risch A, Jager B, Hoffmeister M, Brenner H, Chang-Claude J. Effect of NAT1 and NAT2 genetic polymorphisms on colorectal cancer risk associated with exposure to tobacco smoke and meat consumption. Cancer Epidemiol Biomarkers Prey 2006;15:99-107.
123. P S. cancer incidence in North Wales and Liverpool region in relation to habits and environment, 1957.
124. Kune GA, Vitetta L. Alcohol consumption and the etiology of colorectal cancer: a review of the scientific evidence from 1957 to 1991. Nutrition and cancer 1992;18:97-111.
125. Cho E, Smith-Warner SA, Ritz J, van den Brandt PA, Colditz GA, Folsom AR, Freudenheim JL, Giovannucci E, Goldbohm RA, Graham S, Holmberg L, Kim DH, et al. Alcohol intake and colorectal cancer: a pooled analysis of 8 cohort studies. Annals of internal medicine 2004;140:603-13.
126. Wakai K, Kojima M, Tamakoshi K, Watanabe Y, Hayakawa N, Suzuki K, Hashimoto S, Kawado M, Tokudome S, Suzuki S, Ozasa K, Toyoshima H, et al. Alcohol consumption and colorectal cancer risk: findings from the JACC Study. J Epidemiol 2005;15 Suppl 2:S173-9.
127. Ji BT, Dai Q, Gao YT, Hsing AW, McLaughlin JK, Fraumeni JF, Jr., Chow WH. Cigarette and alcohol consumption and the risk of colorectal cancer in Shanghai, China. Eur J Cancer Prev 2002;11:237-44.
128. Ye W, Romelsjo A, Augustsson K, Adami HO, Nyren O. No excess risk of colorectal cancer among alcoholics followed for up to 25 years. British journal of cancer 2003;88:1044-6.
129. Giovannucci E. Alcohol, one-carbon metabolism, and colorectal cancer: recent insights from molecular studies. The Journal of nutrition 2004;134:2475S-81S.
130. Jedrychowski W, Steindorf K, Popiela T, Wahrendorf J, Tobiasz-Adamczyk B, Kulig J, Penar A. Risk of colorectal cancer from alcohol consumption at lower vitamin intakes. A hospital-based case-control study in Poland. Reviews on environmental health 2001 ;16:213-22.
131. Xing DY, Tan W, Song N, Lin DX. Ser326Cys polymorphism in hOGG1 gene and risk of esophageal cancer in a Chinese population. International journal of cancer 2001 ;95:140-3.
132. Yamane A, Kohno T, Ito K, Sunaga N, Aoki K, Yoshimura K, Murakami H, Nojima Y, Yokota J. Differential ability of polymorphic OGG1 proteins to suppress mutagenesis induced by 8-hydroxyguanine in human cell in vivo. Carcinogenesis 2004;25:1689-94.
133. Sugimura H, Kohno T, Wakai K, Nagura K, Genka K, Igarashi H, Morris BJ, Baba S, Ohno Y, Gao C, Li Z, Wang J, et al. hOGGl Ser326Cys polymorphism and lung cancer susceptibility. Cancer Epidemiol Biomarkers Prev 1999;8:669-74.
134. Hanaoka T, Sugimura H, Nagura K, Ihara M, Li XJ, Hamada GS, Nishimoto I, Kowalski LP, Yokota J, Tsugane S. hOGG1 exon7 polymorphism and gastric cancer in case-control studies of Japanese Brazilians and non-Japanese Brazilians. Cancer letters 2001 ;170:53-61.
135. Ito H, Hamajima N, Takezaki T, Matsuo K, Tajima K, Hatooka S, Mitsudomi T, Suyama M, Sato S, Ueda R. A limited association of OGG1 Ser326Cys polymorphism for adenocarcinoma of the lung. Journal of epidemiology / Japan Epidemiological Association 2002;12:258-65.
136. Vogel U, Nexo BA, Wallin H, Overvad K, Tjonneland A, Raaschou-Nielsen O. No association between base excision repair gene polymorphisms and risk of lung cancer. Biochemical genetics 2004;42:453-60.
137. Klungland A, Rosewell I, Hollenbach S, Larsen E, Daly G, Epe B, Seeberg E, Lindahl T, Barnes DE. Accumulation of premutagenic DNA lesions in mice defective in removal of oxidative base damage. Proceedings of the National Academy of Sciences of the United States of America 1999;96:13300-5.
138. Xie Y, Yang H, Cunanan C, Okamoto K, Shibata D, Pan J, Barnes DE, Lindahl T, McIlhatton M, Fishel R, Miller JH. Deficiencies in mouse Myh and Ogg1 result in tumor predisposition and G to T mutations in codon 12 of the K-ras oncogene in lung tumors. Cancer research 2004;64:3096-102.
139. Brem R, Hall J. XRCC1 is required for DNA single-strand break repair in human cells. Nucleic acids research 2005;33:2512-20.
140. Ratnasinghe D, Yao SX, Tangrea JA, Qiao YL, Andersen MR, Barrett MJ, Giffen CA, Erozan Y, Tockman MS, Taylor PR. Polymorphisms of the DNA repair gene XRCC1 and lung cancer risk. Cancer Epidemiol Biomarkers Prev 2001; 10:119-23.
141．宋春英,谭文,林东昕．中国人DNA修复基因XRCC1单核苷酸多态及其与食管癌风险的关系．癌症2001；20：28-31．
142. Lunn RM, Helzlsouer KJ, Parshad R, Umbach DM, Harris EL, Sanford KK, Bell DA. XPD polymorphisms: effects on DNA repair proficiency. Carcinogenesis 2000;21:551-5.
143. Dybdahl M, Vogel U, Frentz G, Wallin H, Nexo BA. Polymorphisms in the DNA repair gene XPD: correlations with risk and age at onset of basal cell carcinoma. Cancer Epidemiol Biomarkers Prev 1999;8:77-81.
144. Tomescu D, Kavanagh G, Ha T, Campbell H, Melton DW. Nucleotide excision repair gene XPD polymorphisms and genetic predisposition to melanoma. Carcinogenesis 2001;22:403-8.
145. Moller P, Knudsen LE, Frentz G, Dybdahl M, Wallin H, Nexo BA. Seasonal variation of DNA damage and repair in patients with non-melanoma skin cancer and referents with and without psoriasis. Mutation research 1998;407:25-34.
146. Hu Z, Wei Q, Wang X, Shen H. DNA repair gene XPD polymorphism and lung cancer risk: a meta-analysis. Lung cancer (Amsterdam, Netherlands) 2004;46:1-10.
147. Liang G, Xing D, Miao X, Tan W, Yu C, Lu W, Lin D. Sequence variations in the DNA repair gene XPD and risk of lung cancer in a Chinese population. International journal of cancer 2003;105:669-73.
148. Winsey SL, Haldar NA, Marsh HP, Bunce M, Marshall SE, Harris AL, Wojnarowska F, Welsh KI. A variant within the DNA repair gene XRCC3 is associated with the development of melanoma skin cancer. Cancer research 2000;60:5612-6.
149. Kuschel B, Auranen A, McBride S, Novik KL, Antoniou A, Lipscombe JM, Day NE, Easton DF, Ponder BA, Pharoah PD, Dunning A. Variants in DNA double-strand break repair genes and breast cancer susceptibility. Human molecular genetics 2002; 11:1399-407.
150. Wang Y, Liang D, Spitz MR, Zhang K, Dong Q, Amos CI, Wu X. XRCC3 genetic polymorphism, smoking, and lung carcinoma risk in minority populations. Cancer 2003 ;98:1701-6.
151. Seedhouse C, Faulkner R, Ashraf N, Das-Gupta E, Russell N. Polymorphisms in genes involved in homologous recombination repair interact to increase the risk of developing acute myeloid leukemia. Clin Cancer Res 2004; 10:2675-80.
152. Shen M, Hung RJ, Brennan P, Malaveille C, Donato F, Placidi D, Carta A, Hautefeuille A. Boffetta P, Porru S. Polymorphisms of the DNA repair genes XRCC1, XRCC3, XPD, interaction with environmental exposures, and bladder cancer risk in a case-control study in northern Italy. Cancer Epidemiol Biomarkers Prev 2003;12:1234-40.
153. Benhamou S, Tuimala J, Bouchardy C, Dayer P, Sarasin A, Hirvonen A. DNA repair gene XRCC2 and XRCC3 polymorphisms and susceptibility to cancers of the upper aerodigestive tract. International journal of cancer 2004; 112:901-4.
154. Han J, Colditz GA, Samson LD, Hunter DJ. Polymorphisms in DNA double-strand break repair genes and skin cancer risk. Cancer research 2004;64:3009-13.
155. Duan Z, Shen H, Lee JE, Gershenwald JE, Ross MI, Mansfield PF, Duvic M, Strom SS, Spitz MR, Wei Q. DNA repair gene XRCC3 241 Met variant is not associated with risk of cutaneous malignant melanoma. Cancer Epidemiol Biomarkers Prev 2002; 11:1142-3.
156. Han J, Hankinson SE, Hunter DJ, De Vivo I. Genetic variations in XRCC2 and XRCC3 are not associated with endometrial cancer risk. Cancer Epidemiol Biomarkers Prev 2004; 13:330-1.
157. Tranah GJ, Giovannucci E, Ma J, Fuchs C, Hankinson SE, Hunter DJ. XRCC2 and XRCC3 polymorphisms are not associated with risk of colorectal adenoma. Cancer Epidemiol Biomarkers Prev 2004;13:1090-1.
158. Wang LE, Bondy ML, Shen H, El-Zein R, Aldape K, Cao Y, Pudavalli V, Levin VA, Yung WK, Wei Q. Polymorphisms of DNA repair genes and risk of glioma. Cancer research 2004;64:5560-3.
159. Manuguerra M, Saletta F, Karagas MR, Berwick M, Veglia F, Vineis P, Matullo G. XRCC3 and XPD/ERCC2 single nucleotide polymorphisms and the risk of cancer: a HuGE review. American journal of epidemiology 2006;164:297-302.
160. Bond GL, Levine AJ. A single nucleotide polymorphism in the p53 pathway interacts with gender, environmental stresses and tumor genetics to influence cancer in humans. Oncogene 2007;26:1317-23.
161. Mendrysa SM, O'Leary KA, McElwee MK, Michalowski J, Eisenman RN, Powell DA, Perry ME. Tumor suppression and normal aging in mice with constitutively high p53 activity. Genes & development 2006;20:16-21.
162. Ritchie MD, Hahn LW, Roodi N, Bailey LR, Dupont WD, Parl FF, Moore JH. Multifactor-dimensionality reduction reveals high-order interactions among estrogen-metabolism genes in sporadic breast cancer. American journal of human genetics 2001;69:138-47.
163. Moore JH, Gilbert JC, Tsai CT, Chiang FT, Holden T, Barney N, White BC. A flexible computational framework for detecting, characterizing, and interpreting statistical patterns of epistasis in genetic studies of human disease susceptibility. Journal of theoretical biology 2006;241:252-61.
164． 唐迅,李娜,胡永华．应用多因子降维法分析基因-基因交互作用．中华流行病学杂志2006：27：437—41．
165. Agirbasli D, Agirbasli M, Williams SM, Phillips JA, 3rd. Interaction among 5,10 methylenetetrahydrofolate reductase, plasminogen activator inhibitor and endothelial nitric oxide synthase gene polymorphisms predicts the severity of coronary artery disease in Turkish patients. Coronary artery disease 2006; 17:413-7.
166. Andrew AS, Nelson HH, Kelsey KT, Moore JH, Meng AC, Casella DP, Tosteson TD, Schned AR, aragas MR. Concordance of multiple analytical approaches demonstrates a complex relationship between DNA repair gene SNPs, smoking and bladder cancer susceptibility. Carcinogenesis 2006;27:1030-7.
167. Hsieh CH, Liang KH, Hung YJ, Huang LC, Pei D, Liao YT, Kuo SW, Bey MS, Chen JL, Chen EY. nalysis of epistasis for diabetic nephropathy among type 2 diabetic patients. Human molecular genetics 2006;15:2701-8.
168. Oestergaard MZ, Tyrer J, Cebrian A, Shah M, Dunning AM, Ponder BA, Easton DF, Pharoah PD. Interactions between genes involved in the antioxidant defence system and breast cancer risk. British journal of cancer 2006;95:525-31.
169. Williams SM, Ritchie MD, Phillips JA, 3rd, Dawson E, Prince M, Dzhura E, Willis A, Semenya A, Summar M, White BC, Addy JH, Kpodonu J, et al. Multilocus analysis of hypertension: a hierarchical approach. Human heredity 2004;57:28-38.
170. Coffey CS, Hebert PR, Ritchie MD, Krumholz HM, Gaziano JM, Ridker PM, Brown NJ, Vaughan DE, Moore JH. An application of conditional logistic regression and multifactor dimensionality reduction for detecting gene-gene interactions on risk of myocardial infarction: the importance of model validation. BMC bioinformatics 2004;5:49.
1. Parkin DM, Bray F, Ferlay J, Pisani P. Global cancer statistics, 2002. CA: a cancer journal for clinicians 2005;55:74-108.
2. Miners JO, McKinnon RA, Mackenzie PI. Genetic polymorphisms of UDP-glucuronosyltransferases and their functional significance. Toxicology 2002; 181-182:453-6.
3. Ando M, Ando Y, Sekido Y, Ando M, Shimokata K, Hasegawa Y. Genetic polymorphisms of the UDP-glucuronosyltransferase 1A7 gene and irinotecan toxicity in Japanese cancer patients. Jpn J Cancer Res 2002;93:591-7.
4. Guillemette C, Ritter JK, Auyeung DJ, Kessler FK, Housman DE. Structural heterogeneity at the UDP-glucuronosyltransferase 1 locus: functional consequences of three novel missense mutations in the human UGT1A7 gene. Pharmacogenetics 2000;10:629-44.
5. Hu Z, Wells PG. In vitro and in vivo biotransformation and covalent binding of benzo(a)pyrene in Gunn and RHA rats with a genetic deficiency in bilirubin uridine diphosphate-glucuronosyltransferase. The Journal of pharmacology and experimental therapeutics 1992;263:334-42.
6. Vogel A, Kneip S, Barut A, Ehmer U, Tukey RH, Manns MP, Strassburg CP. Genetic link of hepatocellular carcinoma with polymorphisms of the UDP-glucuronosyltransferase UGT1A7 gene. Gastroenterology 2001; 121:1136-44.
7. Strassburg CP, Vogel A, Kneip S, Tukey RH, Manns MP. Polymorphisms of the human UDP-glucuronosyltransferase (UGT) 1A7 gene in colorectal cancer. Gut 2002;50:851-6.
8. Vogel A, Ockenga J, Ehmer U, Barut A, Kramer FJ, Tukey RH, Manns MP, Strassburg CP. Polymorphisms of the carcinogen detoxifying UDP-glucuronosyltransferase UGT1A7 in proximal digestive tract cancer. Zeitschrift fur Gastroenterologie 2002;40:497-502.
9. Ockenga J, Vogel A, Teich N, Keim V, Manns MP, Strassburg CP. UDP glucuronosyltransferase (UGT1A7) gene polymorphisms increase the risk of chronic pancreatitis and pancreatic cancer. Gastroenterology 2003; 124:1802-8.
10. Zheng Z, Park JY, Guillemette C, Schantz SP, Lazarus P. Tobacco carcinogen-detoxifying enzyme UGT1A7 and its association with orolaryngeal cancer risk. Journal of the National Cancer Institute 2001;93:1411-8.
2. Yang L, Parkin DM, Ferlay J, Li L, Chen Y. Estimates of cancer incidence in China for 2000 and projections for 2005. Cancer Epidemiol Biomarkers Prev 2005;14:243-50.
3．卫生部．中国癌症预防与控制规划纲要(2004-2010)．中国肿瘤2004；13：65—8．
4. Sanjoaquin MA, Appleby PN, Thorogood M, Mann JI, Key TJ. Nutrition, lifestyle and colorectal cancer incidence: a prospective investigation of 10998 vegetarians and non-vegetarians in the United Kingdom. British journal of cancer 2004;90:118-21.
5. Norat T, Bingham S, Ferrari P, Slimani N, Jenab M, Mazuir M, Overvad K, Olsen A, Tjonneland A, Clavel F, Boutron-Ruault MC, Kesse E, et al. Meat, fish, and colorectal cancer risk: the European Prospective Investigation into cancer and nutrition. Journal of the National Cancer Institute 2005;97:906-16.
6. McCullough ML, Robertson AS, Rodriguez C, Jacobs EJ, Chao A, Carolyn J, Calle EE, Willett WC, Thun MJ. Calcium, vitamin D, dairy products, and risk of colorectal cancer in the Cancer Prevention Study II Nutrition Cohort (United States). Cancer Causes Control 2003; 14:1-12.
7. Bingham SA, Day NE, Luben R, Ferrari P, Slimani N, Norat T, Clavel-Chapelon F, Kesse E, Nieters A, Boeing H, Tjonneland A, Overvad K, et al. Dietary fibre in food and protection against colorectal cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC): an observational study. Lancet 2003;361:1496-501.
8. Levin B. Nutrition and colorectal cancer. Cancer 1992;70:1723-6.
9. Bodmer WF, Bailey CJ, Bodmer J, Bussey HJ, Ellis A, Gorman P, Lucibello FC, Murday VA, Rider SH, Scambler P, et al. Localization of the gene for familial adenomatous polyposis on chromosome 5. Nature 1987;328:614-6.
10. Bronner CE, Baker SM, Morrison PT, Warren G, Smith LG, Lescoe MK, Kane M, Earabino C, Lipford J, Lindblom A, et al. Mutation in the DNA mismatch repair gene homologue hMLH1 is associated with hereditary non-polyposis colon cancer. Nature 1994;368:258-61.
11. Solomon E. Molecular genetics. Colorectal cancer genes. Nature 1990;343:412-4.
12. Bodmer WF. Cancer genetics: colorectal cancer as a model. Journal of human genetics 2006:51:391-6.
13. Baglioni S, Genuardi M. Simple and complex genetics of colorectal cancer susceptibility. American journal of medical genetics 2004;l 29:35-43.
14. Zhao Z, Zhang F. Sequence context analysis of 8.2 million single nucleotide polymorphisms in the human genome. Gene 2006; 366: 316-24.
15. Sachidanandam R, Weissman D, Schmidt SC, Kakol JM, Stein LD, Marth G, Sherry S, Mullikin JC, Mortimore B J, Willey DL, Hunt SE, Cole CG, et al. A map of human genome sequence variation containing 1.42 million single nucleotide polymorphisms. Nature 2001; 409:928-33.
16．柯杨．相关基因的单核苷酸多态性与肿瘤的遗传易感．中华肿瘤杂志2002；24：105-6．
17. Chen K, Jiang QT, He HQ. Relationship between metabolic enzyme polymorphism and colorectal cancer. World J Gastroenterol 2005;11:331-5.
18. Cotton SC, Sharp L, Little J, Brockton N. Glutathione S-transferase polymorphisms and colorectal cancer: a HuGE review. American journal of epidemiology 2000;151:7-32.
19. Brockton N, Little J, Sharp L, Cotton SC. N-acetyltransferase polymorphisms and colorectal cancer: a HuGE review. American journal of epidemiology 2000;151:846-61.
20. Houlston RS, Yomlinson IP. Polymorphisms and colorectal tumor risk. Gastroenterology 2001;121:282-301.
21. Hubner RA, Muir KR, Liu JF, Sellick GS, Logan RF, Grainge M, Armitage N, Chau I, Houlston RS. Folate metabolism polymorphisms influence risk of colorectal adenoma recurrence. Cancer Epidemiol Biomarkers Prey 2006; 15:1607-13.
22. Sharp L, Little J. Polymorphisms in genes involved in folate metabolism and colorectal neoplasia: a HuGE review. American journal of epidemiology 2004;159:423-43.
23．陈坤，金明娟，范春红，宋亮．大肠癌环境暴露和代谢酶基因多态性的分子流行病学研究．中华流行病学杂志2006；27：905-8．
24. Goode EL, Ulrich CM, Potter JD. Polymorphisms in DNA repair genes and associations with cancer risk. Cancer Epidemiol Biomarkers Prey 2002;11:1513-30.
25. Friedberg EC. DNA damage and repair. Nature 2003;421:436-40.
26. de Jong MM, Nolte IM, te Meerman GJ, van der Graaf WT, de Vries EG, Sijmons RH, Hofstra RM, Kleibeuker JH. Low-penetrance genes and their involvement in colorectal cancer susceptibility. Cancer Epidemiol Biomarkers Prey 2002;11: 1332-52.
27. Hussain SP, Harris CC. p53 biological network: at the crossroads of the cellular-stress response pathway and molecular carcinogenesis. Journal of Nippon Medical School = Nihon Ika Daigaku zasshi 2006;73: 54-64.
28. Soussi T, Dehouche K, Beroud C. p53 website and analysis of p53 gene mutations in human cancer: forging a link between epidemiology and carcinogenesis. Human mutation 2000; 15:105-13.
29. Dumont P, Leu JI, Della Pietra AC, 3rd, George DL, Murphy M. The codon 72 polymorphic variants of p53 have markedly different apoptotic potential. Nature genetics 2003;33:357-65.
30. Wu X, Zhao H, Amos CI, Shete S, Makan N, Hong WK, Kadlubar FF, Spitz MR. p53 Genotypes and Haplotypes Associated With Lung Cancer Susceptibility and Ethnicity. Journal of the National Cancer Institute 2002;94:681-90.
31. Thomas M, Kalita A, Labrecque S, Pim D, Banks L, Matlashewski G. Two polymorphic variants of wild-type p53 differ biochemically and biologically. Molecular and cellular biology 1999;19:1092-100.
32．黄越承，蔡建明．MDM2功能及其调控机制．国外医学肿瘤学分册2004；31：336-9．
33. Kubbutat MH, Jones SN, Vousden KH. Regulation of p53 stability by Mdm2. Nature 1997;387:299-303.
34. Haupt Y, Maya R, Kazaz A, Oren M. Mdm2 promotes the rapid degradation of p53. Nature 1997;387:296-9.
35. Hu Z, Ma H, Lu D, Qian J, Zhou J, Chen Y, Xu L, Wang X, Wei Q, Shen H. Genetic variants in the MDM2 promoter and lung cancer risk in a Chinese population. International journal of cancer 2006;118:1275-8.
36. Bond GL, Hu W, Bond EE, Robins H, Lutzker SG, Arva NC, Bargonetti J, Bartel F, Taubert H, Wuerl P, Oriel K, Yip L, et al. A single nucleotide polymorphism in the MDM2 promoter attenuates the p53 tumor suppressor pathway and accelerates tumor formation in humans. Cell 2004;119:591-602.
37．卫生部肿瘤防治办公室．中国恶性肿瘤死亡回顾调查．人民卫生出版社 1979：198．
38．全国肿瘤防治研究办公室，卫生部卫生信息统计中心．中国试点市、县恶性肿瘤的发病与死亡(1993-1997)．中国医药科技出版社2002．
39．郑树主编．结直肠肿瘤 基础研究与临床实践．北京 人民卫生出版社 2006．
40．陈学敏主编，吴德生，陈秉衡副主编．环境卫生学．北京 人民卫生出版社2004．
41．朱守民，夏昭林．DNA损伤修复基因与遗传易感性．环境与职业医学 2003；20：50-2．
42. Spitz MR, Wei Q, Dong Q, Amos CI, Wu X. Genetic Susceptibility to Lung Cancer: The Role of DNA Damage and Repair Cancer Epidemiol. Biomarkers Prey. 2003;2003:689-98.
43. Kohno T, Shinmura K, Tosaka M, Tani M, Kim SR, Sugimura H, Nohmi T, Kasai H, Yokota J. Genetic polymorphisms and alternative splicing of the hOGG1 gene, that is involved in the repair of 8-hydroxyguanine in damaged DNA. Oncogene 1998;16:3219-25.
44. Shen MR, Jones IM, Mohrenweiser H. Nonconservative amino acid substitution variants exist at polymorphic frequency in DNA repair genes in healthy humans. Cancer research 1998;58:604-8.
45. Khan SG, Metter EJ, Tarone RE, Bohr VA, Grossman L, Hedayati M, Bale SJ, Emmert S, Kraemer KH. A new xeroderma pigmentosum group C poly(AT) insertion/deletion polymorphism. Carcinogenesis 2000; 21: 1821-5.
46．邢德印，林东昕．hOGG1基因与肿瘤．癌症2000；19：499-501．
47．Hung RJ，Hall J，Brennan P，Boffetta P Genetic polymorphisms in the base excision repair pathway and cancer risk: a HuGE review. American journal of epidemiology 2005;162:925-42.
48. Moreno V, Gemignani F, Landi S, Gioia-Patricola L, Chabrier A, Blanco I, Gonzalez S, Guino E, Capella G, Canzian F. Polymorphisms in genes of nucleotide and base excision repair: risk and prognosis of colorectal cancer. Clin Cancer Res 2006;12:2101-8.
49. Hansen R, Saebo M, Skjelbred CF, Nexo BA, Hagen PC, Bock G, Bowitz Lothe IM, Johnson E, Aase S, Hansteen IL, Vogel U, Kure EH. GPX Prol98Leu and OGG1 Ser326Cys polymorphisms and risk of development of colorectal adenomas and colorectal cancer. Cancer letters 2005;229:85-91.
50. Goodman JE, Mechanic LE, Luke BT, Ambs S, Chanock S, Harris CC. Exploring SNP-SNP interactions and colon cancer risk using polymorphism interaction analysis. International journal of cancer 2006; 118:1790-7.
51. Kim JI, Park YJ, Kim KH, Kim JI, Song BJ, Lee MS, Kim CN, Chang SH. hOGG1 Ser326Cys polymorphism modifies the significance of the environmental risk factor for colon cancer. World J Gastroenterol 2003;9:956-60.
52. Abdel-Rahman SZ, Soliman AS, Bondy ML, Omar S, El-Badawy SA, Khaled HM, Seifeldin IA, Levin B. Inheritance of the 194Trp and the 399Gln variant alleles of the DNA repair gene XRCC1 are associated with increased risk of early-onset colorectal carcinoma in Egypt. Cancer letters 2000;159:79-86.
53. Hong YC, Lee KH, Kim WC, Choi SK, Woo ZH, Shin SK, Kim H. Polymorphisms of XRCC1 gene, alcohol consumption and colorectal cancer. International journal of cancer 2005; 116:428-32.
54. Krupa R, Blasiak J. An association of polymorphism of DNA repair genes XRCC1 and XRCC3 with colorectal cancer. J Exp Clin Cancer Res 2004;23:285-94.
55. Yeh CC, Sung FC, Tang R, Chang-Chieh CR, Hsieh LL. Polymorphisms of the XRCC1, XRCC3, & XPD genes, and colorectal cancer risk: a case-control study in Taiwan. BMC cancer 2005;5:12.
56. Mort R, Mo L, McEwan C, Melton DW. Lack of involvement of nucleotide excision repair gene polymorphisms in colorectal cancer. British journal of cancer 2003;89:333-7.
57. Jin MJ, Chen K, Song L, Fan CH, Chen Q, Zhu YM, Ma XY, Yao KY. The association of the DNA repair gene XRCC3 Thr241 Met polymorphism with susceptibility to colorectal cancer in a Chinese population. Cancer genetics and cytogenetics 2005;163:38-43.
58. Hu Z, Ma H, Chen F, Wei Q, Shen H. XRCC1 polymorphisms and cancer risk: a meta-analysis of 38 case-control studies. Cancer Epidemiol Biomarkers Prev 2005;14:1810-8.
59. Thompson LH, West MG. XRCC1 keeps DNA from getting stranded. Mutation research 2000;459:1-18.
60. David-Beabes GL, London SJ. Genetic polymorphism of XRCC1 and lung cancer risk among African-Americans and Caucasians. Lung cancer (Amsterdam, Netherlands) 2001;34:333-9.
61. Stern MC, Umbach DM, van Gils CH, Lunn RM, Taylor JA. DNA repair gene XRCC1 polymorphisms, smoking, and bladder cancer risk. Cancer Epidemiol Biomarkers Prev 2001;10:125-31.
62．金明娟,陈坤．DNA修复基因多态性与肺癌易感性的研究进展．国外医学遗传学分册2005：28：215—20．
63. Seedhouse C, Bainton R, Lewis M, Harding A, Russell N, Das-Gupta E. The genotype distribution of the XRCC1 gene indicates a role for base excision repair in the development of therapy-related acute myeloblastic leukemia. Blood 2002;100:3761-6.
64. Clarkson SG, Wood RD. Polymorphisms in the human XPD (ERCC2) gene, DNA repair capacity and cancer susceptibility: an appraisal. DNA repair 2005;4:1068-74.
65. Spitz MR, Wu X, Wang Y, Wang LE, Shete S, Amos CI, Guo Z, Lei L, Mohrenweiser H, Wei Q. Modulation of nucleotide excision repair capacity by XPD polymorphisms in lung cancer patients. Cancer research 2001 ;61:1354-7.
66. Xing D, Tan W, Wei Q, Lin D. Polymorphisms of the DNA repair gene XPD and risk of lung cancer in a Chinese population. Lung cancer (Amsterdam, Netherlands) 2002;38:123-9.
67. Park JY, Lee SY, Jeon HS, Park SH, Bae NC, Lee EB, Cha SI, Park JH, Kam S, Kim IS, Jung TH. Lys751Gln polymorphism in the DNA repair gene XPD and risk of primary lung cancer. Lung cancer (Amsterdam, Netherlands) 2002;36:15-6.
68. Stern MC, Umbach DM, Lunn RM, Taylor JA. DNA repair gene XRCC3 codon 241 polymorphism, its interaction with smoking and XRCC1 polymorphisms, and bladder cancer risk. Cancer Epidemiol Biomarkers Prev 2002;11:939-43.
69. Matullo G, Palli D, Peluso M, Guarrera S, Carturan S, Celentano E, Krogh V, Munnia A, Tumino R, Polidoro S, Piazza A, Vineis P. XRCC1, XRCC3, XPD gene polymorphisms, smoking and (32)P-DNA adducts in a sample of healthy subjects. Carcinogenesis 2001 ;22:1437-45.
70. Zhang Z, Wan J, Jin X, Jin T, Shen H, Lu D, Xia Z. Genetic polymorphisms in XRCC1, APE1, ADPRT, XRCC2, and XRCC3 and risk of chronic benzene poisoning in a Chinese occupational population. Cancer Epidemiol Biomarkers Prev 2005; 14:2614-9.
71. Shen H, Wang X, Hu Z, Zhang Z, Xu Y, Hu X, Guo J, Wei Q. Polymorphisms of DNA repair gene XRCC3 Thr241Met and risk of gastric cancer in a Chinese population. Cancer letters 2004;206:51-8.
72. Jin S, Levine AJ. The p53 functional circuit. Journal of cell science 2001 ;114:4139-40.
73. Sjalander A, Birgander R, Athlin L, Stenling R, Rutegard J, Beckman L, Beckman G. P53 germ line haplotypes associated with increased risk for colorectal cancer. Carcinogenesis 1995;16:1461-4.
74. Gemignani F, Moreno V, Landi S, Moullan N, Chabrier A, Gutierrez-Enriquez S, Hall J, Guino E, Peinado MA, Capella G, Canzian F. A TP53 polymorphism is associated with increased risk of colorectal cancer and with reduced levels of TP53 mRNA. Oncogene 2004;23:1954-6.
75. Kawajiri K, Nakachi K, Imai K, Watanabe J, Hayashi S. Germ line polymorphisms of p53 and CYPlAl genes involved in human lung cancer. Carcinogenesis 1993;14:1085-9.
76. Koushik A, Tranah GJ, Ma J, Stampfer MJ, Sesso HD, Fuchs CS, Giovannucci EL, Hunter DJ. p53 Arg72Pro polymorphism and risk of colorectal adenoma and cancer. International journal of cancer 2006;l 19:1863-8.
77. Alhopuro P, Ylisaukko-Oja SK, Koskinen WJ, Bono P, Arola J, Jarvinen HJ, Mecklin JP, Atula T, Kontio R, Makitie AA, Suominen S, Leivo I, et al. The MDM2 promoter polymorphism SNP309T→G and the risk of uterine leiomyosarcoma, colorectal cancer, and squamous cell carcinoma of the head and neck. Journal of medical genetics 2005;42:694-8.
78. Menin C, Scaini MC, De Salvo GL, Biscuola M, Quaggio M, Esposito G, Belluco C, Montagna M, Agata S, D'Andrea E, Nitti D, Amadori A, et al. Association between MDM2-SNP309 and age at colorectal cancer diagnosis according to p53 mutation status. Journal of the National Cancer Institute 2006;98:285-8.
79. Alazzouzi H, Suriano G, Guerra A, Plaja A, Espin E, Armengol M, Alhopuro P, Velho S, Shinomura Y, Gonzalez-Aguilera JJ, Yamamoto H, Aaltonen LA, et al. Tumour selection advantage of non-dominant negative P53 mutations in homozygotic MDM2-SNP309 colorectal cancer cells. Journal of medical genetics 2007;44:75-80.
80. Harris CC, Hollstein M. Clinical implications of the p53 tumor-suppressor gene. The New England journal of medicine 1993;329:1318-27.
81． 管立学,杜欣莹,王守训．p53基因CD72 ArgPro多态性与肿瘤易感性研究进展．国外医学遗传学分册2005；28：354-7．
82. Matlashewski GJ, Tuck S, Pim D, Lamb P, Schneider J, Crawford LV. Primary structure polymorphism at amino acid residue 72 of human p53. Molecular and cellular biology 1987;7:961-3.
83. Pietsch EC, Humbey O, Murphy ME. Polymorphisms in the p53 pathway. Oncogene 2006;25:1602-ll.
84. Ohayon T, Gershoni-Baruch R, Papa MZ, Distelman Menachem T, Eisenberg Barzilai S, Friedman E. The R72P P53 mutation is associated with familial breast cancer in Jewish women. British journal of cancer 2005;92:1144-8.
85. Soulitzis N, Sourvinos G, Dokianakis DN, Spandidos DA. p53 codon 72 polymorphism and its association with bladder cancer. Cancer letters 2002; 179:175-83.
86. Shen H, Zheng Y, Sturgis EM, Spitz MR, Wei Q. P53 codon 72 polymorphism and risk of squamous cell carcinoma of the head and neck: a case-control study. Cancer letters 2002;183:123-30.
87. Walsh CS, Miller CW, Karlan BY, Koeffler HP. Association between a functional single nucleotide polymorphism in the MDM2 gene and sporadic endometrial cancer risk. Gynecologic oncology 2007;104:660-4.
88. Ruijs MW, Schmidt MK, Nevanlinna H, Tommiska J, Aittomaki K, Pruntel R, Verhoef S, Van't Veer LJ. The single-nucleotide polymorphism 309 in the MDM2 gene contributes to the Li-Fraumeni syndrome and related phenotypes. Eur J Hum Genet 2007; 15:110-4.
89. Zhang X, Miao X, Guo Y, Tan W, Zhou Y, Sun T, Wang Y, Lin D. Genetic polymorphisms in cell cycle regulatory genes MDM2 and TP53 are associated with susceptibility to lung cancer. Human mutation 2006;27:110-7.
90. Park SH, Choi JE, Kim EJ, Jang JS, Han HS, Lee WK, Kang YM, Park JY. MDM2 309T>G polymorphism and risk of lung cancer in a Korean population. Lung cancer (Amsterdam, Netherlands) 2006;54:19-24.
91. Onat OE, Tez M, Ozcelik T, Toruner GA. MDM2 T309G polymorphism is associated with bladder cancer. Anticancer research 2006;26:3473-5.
92. Ohmiya N, Taguchi A, Mabuchi N, Itoh A, Hirooka Y, Niwa Y, Goto H. MDM2 promoter polymorphism is associated with both an increased susceptibility to gastric carcinoma and poor prognosis. J Clin Oncol 2006;24:4434-40.
93. Millikan RC, Heard K, Winkel S, Hill EJ, Heard K, Massa B, Mayes L, Williams P, Holston R, Conway K, Edmiston S, de Cotret AR. No association between the MDM2 -309 T/G promoter polymorphism and breast cancer in African-Americans or Whites. Cancer Epidemiol Biomarkers Prev 2006; 15:175-7.
94. Bougeard G, Baert-Desurmont S, Tournier I, Vasseur S, Martin C, Brugieres L, Chompret A, Bressac-de Paillerets B, Stoppa-Lyonnet D, Bonaiti-Pellie C, Frebourg T. Impact of the MDM2 SNP309 and p53 Arg72Pro polymorphism on age of tumour onset in Li-Fraumeni syndrome. Journal of medical genetics 2006;43:531-3.
95. Ma H, Hu Z, Zhai X, Wang S, Wang X, Qin J, Jin G, Liu J, Wang X, Wei Q, Shen H. Polymorphisms in the MDM2 promoter and risk of breast cancer: a case-control analysis in a Chinese population. Cancer letters 2006;240:261-7.
96. Miller SA, Dykes DD, Polesky HF. A simple salting out procedure for extracting DNA from human nucleated cells. Nucleic acids research 1988; 16:1215.
97. Le Marchand L, Donlon T, Lum-Jones A, Seifried A, Wilkens LR. Association of the hOGG1 Ser326Cys polymorphism with lung cancer risk. Cancer Epidemiol Biomarkers Prev 2002;l 1:409-12.
98. Abdel-Rahman SZ, El-Zein RA. The 399Gln polymorphism in the DNA repair gene XRCC1 modulates the genotoxic response induced in human lymphocytes by the tobacco-specific nitrosamine NNK. Cancer letters 2000; 159:63-71.
99. Butkiewicz D, Rusin M, Enewold L, Shields PG, Chorazy M, Harris CC. Genetic polymorphisms in DNA repair genes and risk of lung cancer. Carcinogenesis 2001;22:593-7.
100. Sturgis EM, Zheng R, Li L, Castillo EJ, Eicher SA, Chen M, Strom SS, Spitz MR, Wei Q. XPD/ERCC2 polymorphisms and risk of head and neck cancer: a case-control analysis. Carcinogenesis 2000;21:2219-23.
101. David-Beabes GL, Lunn RM, London SJ. No association between the XPD (Lys751Gln) polymorphism or the XRCC3 (Thr241Met) polymorphism and lung cancer risk. Cancer Epidemiol Biomarkers Prey 2001; 10:911-2.
102. Lee JM, Shun CT, Wu MT, Chen YY, Yang SY, Hung HI, Chen JS, Hsu HH, Huang PM, Kuo SW, Lee YC. The associations of p53 overexpression with p53 codon 72 genetic polymorphism in esophageal cancer. Mutation research 2006;594:181-8.
103. Yeh CC, Sung FC, Tang R, Chang-Chieh CR, Hsieh LL. Association between polymorphisms of biotransformation and DNA-repair genes and risk of colorectal cancer in Taiwan. J Biomed Sci 2006.
104. Qing SH, Rao KY, Jiang HY, Wexner SD. Racial differences in the anatomical distribution of colorectal cancer: a study of differences between American and Chinese patients. World J Gastroenterol 2003; 9: 721-5.
105．全国肿瘤防治研究办公室，卫生部卫生信息统计中心．中国试点市、县恶性肿瘤的发病与死亡(1988-1992)．中国医药科技出版社2001．
106. Fuchs CS, Giovannucci EL, Colditz GA, Hunter DJ, Speizer FE, Willett WC. A prospective study of family history and the risk of colorectal cancer. The New England journal of medicine 1994;331:1669-74.
107. Karner-Hanusch J, Mittlbock M, Fillipitsch T, Herbst F. Family history as a marker of risk for colorectal cancer: Austrian experience. World journal of surgery 1997;21:205-9.
108. Chen K, Qiu JL, Zhang Y, Zhao YW. Meta analysis of risk factors for colorectal cancer. World J Gastroenterol 2003; 9: 1598-600.
109. Giacosa A, Franceschi S, La Vecchia C, Favero A, Frascio F, Andreatta R. Overweight and colorectal cancer risk. Minerva gastroenterologica e dietologica 2001; 47: 235-40.
110. Kune GA, Kune S, Watson LF. Body weight and physical activity as predictors of colorectal cancer risk. Nutrition and cancer 1990;13:9-17.
111. Sturmer T, Buring JE, Lee IM, Gaziano JM, Glynn RJ. Metabolic abnormalities and risk for colorectal cancer in the physicians' health study. Cancer Epiderniol Biomarkers Prey 2006;15:2391-7.
112. Samad AK, Taylor RS, Marshall T, Chapman MA. A meta-analysis of the association of physical activity with reduced risk of colorectal cancer. ColorectaI Dis 2005;7:204-13.
113．蒋沁婷，陈坤，邹艳，赵玉婉，马新源，李其龙，姚开颜，郑树．随访队列的结直肠癌危险因素的病例-对照研究．肿瘤2004；24：6-10．
114．张晓慧，许岸高．结直肠癌高危人群的研究现状．中华医学实践杂志 2004；3：39-41．
115. Giovannucci E, Rimm EB, Stampfer MJ, Colditz GA, Ascherio A, Kearney J, Willett WC. A prospective study of cigarette smoking and risk of colorectal adenoma and colorectal cancer in U.S. men. Journal of the National Cancer Institute 1994; 86: 183-91.
116. Martinez ME, McPherson RS, Annegers JF, Levin B. Cigarette smoking and alcohol consumption as risk factors for colorectal adenomatous polyps. Journal of the National Cancer Institute 1995;87:274-9.
117. Wakai K, Hayakawa N, Kojima M, Tamakoshi K, Watanabe Y, Suzuki K, Hashimoto S, Tokudome S, Toyoshima H, Ito Y, Tamakoshi A. Smoking and colorectal cancer in a non-Western population: a prospective cohort study in Japan. Journal of epidemiology/Japan Epidemiological Association 2003; 13: 323-32.
118. Giovannucci E. An updated review of the epidemiological evidence that cigarette smoking increases risk of colorectal cancer. Cancer Epidemiol Biomarkers Prey 2001;10:725-31.
119. Otani T, Iwasaki M, Yamamoto S, Sobue T, Hanaoka T, Inoue M, Tsugane S. Alcohol consumption, smoking, and subsequent risk of colorectal cancer in middle-aged and elderly Japanese men and women: Japan Public Health Center-based prospective study. Cancer Epidemiol Biomarkers Prey 2003; 12:1492-500.
120. Slattery ML, Edwards S, Curtin K, Schaffer D, Neuhausen S. Associations between smoking, passive smoking, GSTM-1, NAT2, and rectal cancer. Cancer Epidemiol Biomarkers Prey 2003;12:882-9.
121. Ravasco P, Monteiro-Grillo I, Marques Vidal P, Camilo ME. Nutritional risks and colorectal cancer in a Portuguese population. Nutr Hosp 2005;20:165-72.
122. Lilla C, Verla-Tebit E, Risch A, Jager B, Hoffmeister M, Brenner H, Chang-Claude J. Effect of NAT1 and NAT2 genetic polymorphisms on colorectal cancer risk associated with exposure to tobacco smoke and meat consumption. Cancer Epidemiol Biomarkers Prey 2006;15:99-107.
123. P S. cancer incidence in North Wales and Liverpool region in relation to habits and environment, 1957.
124. Kune GA, Vitetta L. Alcohol consumption and the etiology of colorectal cancer: a review of the scientific evidence from 1957 to 1991. Nutrition and cancer 1992;18:97-111.
125. Cho E, Smith-Warner SA, Ritz J, van den Brandt PA, Colditz GA, Folsom AR, Freudenheim JL, Giovannucci E, Goldbohm RA, Graham S, Holmberg L, Kim DH, et al. Alcohol intake and colorectal cancer: a pooled analysis of 8 cohort studies. Annals of internal medicine 2004;140:603-13.
126. Wakai K, Kojima M, Tamakoshi K, Watanabe Y, Hayakawa N, Suzuki K, Hashimoto S, Kawado M, Tokudome S, Suzuki S, Ozasa K, Toyoshima H, et al. Alcohol consumption and colorectal cancer risk: findings from the JACC Study. J Epidemiol 2005;15 Suppl 2:S173-9.
127. Ji BT, Dai Q, Gao YT, Hsing AW, McLaughlin JK, Fraumeni JF, Jr., Chow WH. Cigarette and alcohol consumption and the risk of colorectal cancer in Shanghai, China. Eur J Cancer Prev 2002;11:237-44.
128. Ye W, Romelsjo A, Augustsson K, Adami HO, Nyren O. No excess risk of colorectal cancer among alcoholics followed for up to 25 years. British journal of cancer 2003;88:1044-6.
129. Giovannucci E. Alcohol, one-carbon metabolism, and colorectal cancer: recent insights from molecular studies. The Journal of nutrition 2004;134:2475S-81S.
130. Jedrychowski W, Steindorf K, Popiela T, Wahrendorf J, Tobiasz-Adamczyk B, Kulig J, Penar A. Risk of colorectal cancer from alcohol consumption at lower vitamin intakes. A hospital-based case-control study in Poland. Reviews on environmental health 2001 ;16:213-22.
131. Xing DY, Tan W, Song N, Lin DX. Ser326Cys polymorphism in hOGG1 gene and risk of esophageal cancer in a Chinese population. International journal of cancer 2001 ;95:140-3.
132. Yamane A, Kohno T, Ito K, Sunaga N, Aoki K, Yoshimura K, Murakami H, Nojima Y, Yokota J. Differential ability of polymorphic OGG1 proteins to suppress mutagenesis induced by 8-hydroxyguanine in human cell in vivo. Carcinogenesis 2004;25:1689-94.
133. Sugimura H, Kohno T, Wakai K, Nagura K, Genka K, Igarashi H, Morris BJ, Baba S, Ohno Y, Gao C, Li Z, Wang J, et al. hOGGl Ser326Cys polymorphism and lung cancer susceptibility. Cancer Epidemiol Biomarkers Prev 1999;8:669-74.
134. Hanaoka T, Sugimura H, Nagura K, Ihara M, Li XJ, Hamada GS, Nishimoto I, Kowalski LP, Yokota J, Tsugane S. hOGG1 exon7 polymorphism and gastric cancer in case-control studies of Japanese Brazilians and non-Japanese Brazilians. Cancer letters 2001 ;170:53-61.
135. Ito H, Hamajima N, Takezaki T, Matsuo K, Tajima K, Hatooka S, Mitsudomi T, Suyama M, Sato S, Ueda R. A limited association of OGG1 Ser326Cys polymorphism for adenocarcinoma of the lung. Journal of epidemiology / Japan Epidemiological Association 2002;12:258-65.
136. Vogel U, Nexo BA, Wallin H, Overvad K, Tjonneland A, Raaschou-Nielsen O. No association between base excision repair gene polymorphisms and risk of lung cancer. Biochemical genetics 2004;42:453-60.
137. Klungland A, Rosewell I, Hollenbach S, Larsen E, Daly G, Epe B, Seeberg E, Lindahl T, Barnes DE. Accumulation of premutagenic DNA lesions in mice defective in removal of oxidative base damage. Proceedings of the National Academy of Sciences of the United States of America 1999;96:13300-5.
138. Xie Y, Yang H, Cunanan C, Okamoto K, Shibata D, Pan J, Barnes DE, Lindahl T, McIlhatton M, Fishel R, Miller JH. Deficiencies in mouse Myh and Ogg1 result in tumor predisposition and G to T mutations in codon 12 of the K-ras oncogene in lung tumors. Cancer research 2004;64:3096-102.
139. Brem R, Hall J. XRCC1 is required for DNA single-strand break repair in human cells. Nucleic acids research 2005;33:2512-20.
140. Ratnasinghe D, Yao SX, Tangrea JA, Qiao YL, Andersen MR, Barrett MJ, Giffen CA, Erozan Y, Tockman MS, Taylor PR. Polymorphisms of the DNA repair gene XRCC1 and lung cancer risk. Cancer Epidemiol Biomarkers Prev 2001; 10:119-23.
141．宋春英,谭文,林东昕．中国人DNA修复基因XRCC1单核苷酸多态及其与食管癌风险的关系．癌症2001；20：28-31．
142. Lunn RM, Helzlsouer KJ, Parshad R, Umbach DM, Harris EL, Sanford KK, Bell DA. XPD polymorphisms: effects on DNA repair proficiency. Carcinogenesis 2000;21:551-5.
143. Dybdahl M, Vogel U, Frentz G, Wallin H, Nexo BA. Polymorphisms in the DNA repair gene XPD: correlations with risk and age at onset of basal cell carcinoma. Cancer Epidemiol Biomarkers Prev 1999;8:77-81.
144. Tomescu D, Kavanagh G, Ha T, Campbell H, Melton DW. Nucleotide excision repair gene XPD polymorphisms and genetic predisposition to melanoma. Carcinogenesis 2001;22:403-8.
145. Moller P, Knudsen LE, Frentz G, Dybdahl M, Wallin H, Nexo BA. Seasonal variation of DNA damage and repair in patients with non-melanoma skin cancer and referents with and without psoriasis. Mutation research 1998;407:25-34.
146. Hu Z, Wei Q, Wang X, Shen H. DNA repair gene XPD polymorphism and lung cancer risk: a meta-analysis. Lung cancer (Amsterdam, Netherlands) 2004;46:1-10.
147. Liang G, Xing D, Miao X, Tan W, Yu C, Lu W, Lin D. Sequence variations in the DNA repair gene XPD and risk of lung cancer in a Chinese population. International journal of cancer 2003;105:669-73.
148. Winsey SL, Haldar NA, Marsh HP, Bunce M, Marshall SE, Harris AL, Wojnarowska F, Welsh KI. A variant within the DNA repair gene XRCC3 is associated with the development of melanoma skin cancer. Cancer research 2000;60:5612-6.
149. Kuschel B, Auranen A, McBride S, Novik KL, Antoniou A, Lipscombe JM, Day NE, Easton DF, Ponder BA, Pharoah PD, Dunning A. Variants in DNA double-strand break repair genes and breast cancer susceptibility. Human molecular genetics 2002; 11:1399-407.
150. Wang Y, Liang D, Spitz MR, Zhang K, Dong Q, Amos CI, Wu X. XRCC3 genetic polymorphism, smoking, and lung carcinoma risk in minority populations. Cancer 2003 ;98:1701-6.
151. Seedhouse C, Faulkner R, Ashraf N, Das-Gupta E, Russell N. Polymorphisms in genes involved in homologous recombination repair interact to increase the risk of developing acute myeloid leukemia. Clin Cancer Res 2004; 10:2675-80.
152. Shen M, Hung RJ, Brennan P, Malaveille C, Donato F, Placidi D, Carta A, Hautefeuille A. Boffetta P, Porru S. Polymorphisms of the DNA repair genes XRCC1, XRCC3, XPD, interaction with environmental exposures, and bladder cancer risk in a case-control study in northern Italy. Cancer Epidemiol Biomarkers Prev 2003;12:1234-40.
153. Benhamou S, Tuimala J, Bouchardy C, Dayer P, Sarasin A, Hirvonen A. DNA repair gene XRCC2 and XRCC3 polymorphisms and susceptibility to cancers of the upper aerodigestive tract. International journal of cancer 2004; 112:901-4.
154. Han J, Colditz GA, Samson LD, Hunter DJ. Polymorphisms in DNA double-strand break repair genes and skin cancer risk. Cancer research 2004;64:3009-13.
155. Duan Z, Shen H, Lee JE, Gershenwald JE, Ross MI, Mansfield PF, Duvic M, Strom SS, Spitz MR, Wei Q. DNA repair gene XRCC3 241 Met variant is not associated with risk of cutaneous malignant melanoma. Cancer Epidemiol Biomarkers Prev 2002; 11:1142-3.
156. Han J, Hankinson SE, Hunter DJ, De Vivo I. Genetic variations in XRCC2 and XRCC3 are not associated with endometrial cancer risk. Cancer Epidemiol Biomarkers Prev 2004; 13:330-1.
157. Tranah GJ, Giovannucci E, Ma J, Fuchs C, Hankinson SE, Hunter DJ. XRCC2 and XRCC3 polymorphisms are not associated with risk of colorectal adenoma. Cancer Epidemiol Biomarkers Prev 2004;13:1090-1.
158. Wang LE, Bondy ML, Shen H, El-Zein R, Aldape K, Cao Y, Pudavalli V, Levin VA, Yung WK, Wei Q. Polymorphisms of DNA repair genes and risk of glioma. Cancer research 2004;64:5560-3.
159. Manuguerra M, Saletta F, Karagas MR, Berwick M, Veglia F, Vineis P, Matullo G. XRCC3 and XPD/ERCC2 single nucleotide polymorphisms and the risk of cancer: a HuGE review. American journal of epidemiology 2006;164:297-302.
160. Bond GL, Levine AJ. A single nucleotide polymorphism in the p53 pathway interacts with gender, environmental stresses and tumor genetics to influence cancer in humans. Oncogene 2007;26:1317-23.
161. Mendrysa SM, O'Leary KA, McElwee MK, Michalowski J, Eisenman RN, Powell DA, Perry ME. Tumor suppression and normal aging in mice with constitutively high p53 activity. Genes & development 2006;20:16-21.
162. Ritchie MD, Hahn LW, Roodi N, Bailey LR, Dupont WD, Parl FF, Moore JH. Multifactor-dimensionality reduction reveals high-order interactions among estrogen-metabolism genes in sporadic breast cancer. American journal of human genetics 2001;69:138-47.
163. Moore JH, Gilbert JC, Tsai CT, Chiang FT, Holden T, Barney N, White BC. A flexible computational framework for detecting, characterizing, and interpreting statistical patterns of epistasis in genetic studies of human disease susceptibility. Journal of theoretical biology 2006;241:252-61.
164． 唐迅,李娜,胡永华．应用多因子降维法分析基因-基因交互作用．中华流行病学杂志2006：27：437—41．
165. Agirbasli D, Agirbasli M, Williams SM, Phillips JA, 3rd. Interaction among 5,10 methylenetetrahydrofolate reductase, plasminogen activator inhibitor and endothelial nitric oxide synthase gene polymorphisms predicts the severity of coronary artery disease in Turkish patients. Coronary artery disease 2006; 17:413-7.
166. Andrew AS, Nelson HH, Kelsey KT, Moore JH, Meng AC, Casella DP, Tosteson TD, Schned AR, aragas MR. Concordance of multiple analytical approaches demonstrates a complex relationship between DNA repair gene SNPs, smoking and bladder cancer susceptibility. Carcinogenesis 2006;27:1030-7.
167. Hsieh CH, Liang KH, Hung YJ, Huang LC, Pei D, Liao YT, Kuo SW, Bey MS, Chen JL, Chen EY. nalysis of epistasis for diabetic nephropathy among type 2 diabetic patients. Human molecular genetics 2006;15:2701-8.
168. Oestergaard MZ, Tyrer J, Cebrian A, Shah M, Dunning AM, Ponder BA, Easton DF, Pharoah PD. Interactions between genes involved in the antioxidant defence system and breast cancer risk. British journal of cancer 2006;95:525-31.
169. Williams SM, Ritchie MD, Phillips JA, 3rd, Dawson E, Prince M, Dzhura E, Willis A, Semenya A, Summar M, White BC, Addy JH, Kpodonu J, et al. Multilocus analysis of hypertension: a hierarchical approach. Human heredity 2004;57:28-38.
170. Coffey CS, Hebert PR, Ritchie MD, Krumholz HM, Gaziano JM, Ridker PM, Brown NJ, Vaughan DE, Moore JH. An application of conditional logistic regression and multifactor dimensionality reduction for detecting gene-gene interactions on risk of myocardial infarction: the importance of model validation. BMC bioinformatics 2004;5:49.
1. Parkin DM, Bray F, Ferlay J, Pisani P. Global cancer statistics, 2002. CA: a cancer journal for clinicians 2005;55:74-108.
2. Miners JO, McKinnon RA, Mackenzie PI. Genetic polymorphisms of UDP-glucuronosyltransferases and their functional significance. Toxicology 2002; 181-182:453-6.
3. Ando M, Ando Y, Sekido Y, Ando M, Shimokata K, Hasegawa Y. Genetic polymorphisms of the UDP-glucuronosyltransferase 1A7 gene and irinotecan toxicity in Japanese cancer patients. Jpn J Cancer Res 2002;93:591-7.
4. Guillemette C, Ritter JK, Auyeung DJ, Kessler FK, Housman DE. Structural heterogeneity at the UDP-glucuronosyltransferase 1 locus: functional consequences of three novel missense mutations in the human UGT1A7 gene. Pharmacogenetics 2000;10:629-44.
5. Hu Z, Wells PG. In vitro and in vivo biotransformation and covalent binding of benzo(a)pyrene in Gunn and RHA rats with a genetic deficiency in bilirubin uridine diphosphate-glucuronosyltransferase. The Journal of pharmacology and experimental therapeutics 1992;263:334-42.
6. Vogel A, Kneip S, Barut A, Ehmer U, Tukey RH, Manns MP, Strassburg CP. Genetic link of hepatocellular carcinoma with polymorphisms of the UDP-glucuronosyltransferase UGT1A7 gene. Gastroenterology 2001; 121:1136-44.
7. Strassburg CP, Vogel A, Kneip S, Tukey RH, Manns MP. Polymorphisms of the human UDP-glucuronosyltransferase (UGT) 1A7 gene in colorectal cancer. Gut 2002;50:851-6.
8. Vogel A, Ockenga J, Ehmer U, Barut A, Kramer FJ, Tukey RH, Manns MP, Strassburg CP. Polymorphisms of the carcinogen detoxifying UDP-glucuronosyltransferase UGT1A7 in proximal digestive tract cancer. Zeitschrift fur Gastroenterologie 2002;40:497-502.
9. Ockenga J, Vogel A, Teich N, Keim V, Manns MP, Strassburg CP. UDP glucuronosyltransferase (UGT1A7) gene polymorphisms increase the risk of chronic pancreatitis and pancreatic cancer. Gastroenterology 2003; 124:1802-8.
10. Zheng Z, Park JY, Guillemette C, Schantz SP, Lazarus P. Tobacco carcinogen-detoxifying enzyme UGT1A7 and its association with orolaryngeal cancer risk. Journal of the National Cancer Institute 2001;93:1411-8.