Genetic Epidemiological Studies Of Nasopharyngeal Cancer

鼻咽癌在中国南部和台湾的发病率远高于世界其他地区。爱泼斯坦-巴尔病毒被怀疑在疾病病因学中发挥作用，但支持数据相当有限。该病表现出明显的家族聚集性，我们先前报道的分离分析表明，可能与一个隐性传递的主基因有关。我们目前的研究旨在利用分子流行病学方法确定这种疾病的基本原因。我们从大量受试者那里获得了关于这种疾病的家族史以及与危险因素的相关性的问卷数据。到目前为止，我们已经获得了来自297个家庭的1449名受试者的DNA、血清、口腔漱口水、口腔刷子和唾液，这些家庭被确认为两个或两个以上的鼻咽癌成员。我们还从我们的多重家庭成员那里获得了1645份危险因素问卷。正在对所有研究对象的血清样本进行爱泼斯坦-巴尔病毒(EBV)抗体滴度评估。使用应用生物系统2.0版的高信息量短串联重复序列(STR)标记完成了对大约767个DNA样本的全基因组扫描。与国家癌症研究所的科学家合作，对候选基因SNPs的实验室分析也在进行中，其中包括人类白细胞抗原变异体。我们使用在聚合酶链式反应过程中掺入的荧光标记的寡核苷酸引物。产品的大小由应用生物系统(Perkin Elmer)型号373和377自动DNA分析仪上的变性PAGE确定。使用GENESCAN和GENOTYPER计算机程序(应用生物系统)从凝胶图像中识别微卫星等位基因。使用被认为是复杂疾病最强大和最可靠的方法对这些数据进行统计分析，发现了几个非常有希望的候选基因和染色体区域，这些候选基因和染色体区域对鼻咽癌易感性的个体差异具有重大影响。有些分析是一般性的，正在应用于该处正在研究的所有复杂疾病。其他分析涉及针对鼻咽癌的新方法，例如使用EBV滴度作为预测鼻咽癌风险的协变量。正在对候选基因进行传递不平衡测试(TDT)，包括以前被认为与鼻咽癌风险相关的人类白细胞抗原(HL A)基因座上的SNPs和CYP2E1。正在对为所有参与对象收集的大量问卷数据进行评估，以确定导致这种疾病的最重要的环境风险因素。这些分析将使用统计方法，其中考虑到家庭成员之间的关系。EBV抗体滴度正被分析为了解宿主防御的遗传基础的直接感兴趣的依赖变量。这些免疫反应表型的基因图谱研究只需要最低限度的额外成本，因为这些受试者已经有了生物标本和大量的基因类型。石蜡包埋的肿瘤组织切片是从大约一半的鼻咽癌病例中获得的，用于分子分析。

Nasopharyngeal carcinoma (NPC) occurs much more commonly in southern China and Taiwan than in other parts of the world. Epstein-Barr virus is suspected to play a role in disease etiology, but supporting data are quite limited. The disease exhibits clear familial aggregation, and our previously reported segregation analyses suggest that a recessively transmitted major gene may be involved. Our current studies are aimed at determining the basic causes of this disease using molecular epidemiological approaches. We have obtained questionnaire data regarding the family history of this disease and correlation with risk factors from a large number of subjects. To date, we have obtained DNA, serum, oral rinses, oral brushes and saliva for 1,449 subjects from 297 families identified with two or more members affected by NPC. We also obtained 1,645 risk factor questionnaires from our multiplex family members. Epstein Barr Virus (EBV) anitbody titres are being assessed on serum samples from all study subjects. A whole genome scan has been completed for approximately 767 DNA samples using highly informative Short Tandem Repeat (STR) markers of the Applied Biosystems Version 2.0 set. Laboratory assays of candidate gene SNPs including HLA variants are also ongoing, in collaboration with scientists at the NCI. We used fluorescently labeled oligonucleotide primers incorporated during PCR. Products were sized by denaturing PAGE on Applied Biosystems (Perkin Elmer) Model 373 and 377 automated DNA analyzers. GENESCAN and GENOTYPER computer programs (Applied Biosystems) were used to identify microsatellite alleles from the gel images. Statistical analyses of these data using methods thought to be most powerful and robust for complex diseases have identified several genes and chromosomal regions that are very promising candidates for having major influence on differences among individuals in susceptibility to NPC. Some analyses are general and are being applied to all complex diseases under study in the Branch. Other analyses involve novel approaches specific for NPC such as using EBV titres as covariates for predicting NPC risk. Transmission disequilibrium tests (TDTs) are being performed on the candidate genes being assayed including SNPs at HLA loci and CYP2E1 that have been previously suggested to be associated with the risk of NPC. Extensive questionnaire data collected for all participating subjects are being evaluated to identify the most important environmental risk factors for this disease. Statistical methods which account for relationships among family members will be used for these analyses. EBV antibody titres are being analyzed as a dependent variable of direct interest for understanding the genetic basis of host defense. Gene mapping studies of these immune response phenotypes have required minimal additional cost, since biospecimens and substantial numbers of genotypes are already available for these subjects. Sections from paraffin-embedded tumor tissue are being obtained from approximately half of these NPC cases for molecular analyses.