Genetic Epidemiology of Telomere Maintenance and Cancer Etiology

先天性角化不良(DC)[CAS 10374]研究为DC患者及其家人提供全面的临床和分子评估，以更好地了解端粒生物学缺陷在此疾病中的作用。DC是一种遗传性骨髓衰竭综合征(IBMFS)，其特征是指甲异常、网状色素沉着、口腔白斑、端粒非常短，再生障碍性贫血和癌症的风险显著增加。DC的家系表明有多种遗传方式(如X连锁、常染色体显性遗传和常染色体隐性遗传)，尽管许多病例是零星的(即没有家族病史)。我们鉴定了TINF2是一个导致常染色体显性DC的新基因，它是端粒保护蛋白Shelterin复合体的一个组成部分。在NCIS IBMFS研究中登记的所有DC家系都被评估了已知DC基因的突变：TINF2、DKC1、TERC、TERT、NOLA2和NOLA3。在我们的家系队列中，这些基因的阳性比例分别为28%、17%、10%、7%、0%和0%。我们大约40%的患者仍然没有分子特征。这些家系已经被用来证明外周血白细胞亚群中非常短的端粒(通过Flow-FISH)构成了这种疾病的诊断异常。对这些家系的癌症分析表明，其模式与范科尼贫血(即MDS、AML、头/颈鳞状细胞癌和肛门直肠癌)的模式惊人地相似。在分子特征不明的患者中，候选基因测序正在进行中。我们最近发现了一种似乎导致DC的新基因；突变的功能特征正在进行中。我们还在探索与DC发病机制相关的几个新假说，包括表观遗传基因调控和染色体异常。临床表型和医疗并发症的详细特征正在进行中。我们正在分析目标组织中的端粒长度[CAS 10373]，进行了一系列方法学研究，试图阐明端粒长度在个体内的差异，最终目的是改善对不同细胞类型和端粒长度测定方法的可比性的理解。流行病学研究通常使用从血液或口腔细胞中提取的DNA，但尚未发表对血液和口腔细胞DNA端粒长度的直接比较。重要的是要了解在常用标本(血液和口腔细胞)中测量的端粒长度是如何相互比较的，以及如何将端粒长度与癌症风险组织中的端粒长度进行比较。由于Q-PCR和Flow-FISH测量端粒长度的应用越来越广泛，了解这些技术的个体内可比性也是很重要的。我们评估了来自IBMFS研究对象的三个样本(血液、口腔细胞和成纤维细胞DNA)端粒长度的个体内和个体间的差异。一份显示这些个体端粒长度相关的手稿即将提交。这项方法学研究试图确定在不同组织类型中测量的端粒长度是否可以在未来的研究中结合起来。这将形成更大的流行病学研究的基础，端粒长度是癌症和其他疾病的风险因素。我们正在研究端粒长度作为各种癌症的风险因素[CAS 10371]。(1)前列腺癌：我们在PLCO队列中评估端粒长度是前列腺癌的风险因素。未发现前列腺癌风险与端粒长度之间有统计学意义的关联，但发现端粒长度与健康生活方式参数呈正相关(报告已发表)。(2)卵巢癌：我们在波兰对卵巢癌进行的病例对照研究表明，白细胞端粒与高级别浆液性卵巢腺癌密切相关(手稿正在出版中)。采用更大样本量的后续研究正在进行中。(3)骨肉瘤：目前正在分析骨肉瘤患者和对照的白细胞端粒长度的数据。在这项研究中，我们还在评估SNPs在端粒生物学基因中的作用。关于端粒长度作为胶质瘤、胰腺癌和农药暴露的危险因素的合作研究正在进行中。(4)与端粒长度相关的遗传变异正在利用NCI CGEMS前列腺癌和乳腺癌全基因组关联研究的数据进行评估。对端粒生物学中重要基因的单核苷酸多态(SNPs)进行了评估，并确定了与端粒长度相关的潜在候选基因。我们还与哈佛大学合作进行了一项使用相同样本集的全基因组端粒长度关联研究。端粒基因的人口遗传学[CAS 10372]：我们先前已经表明，与其他类型的基因相比，端粒维持途径中的关键蛋白质的核苷酸多样性较低，并且这些基因在物种之间高度保守。由于这些基因似乎受到进化的限制，这些基因中的胚系遗传变异(即单核苷酸多态，SNPs)可能是癌症或其他疾病的重要风险因素。本研究正在评估来自非洲、中东、欧洲、中亚/南亚(C/S)亚洲、东亚、大洋洲和美洲的53个全球人群中1000个个体的37个端粒生物基因的遗传变异。一组来自不同功能途径的比较基因正在被创造出来。这项研究将深入了解这些基因的进化史，阐明可能具有潜在功能的变异，并允许在未来的遗传关联研究中进行量身定制的、基于证据的SNP选择

The Dyskeratosis congenita (DC) [CAS 10374] study provides comprehensive clinical and molecular evaluations to patients with DC and their family members, to better understand the role of telomere biology defects in this disorder. DC is an inherited bone marrow failure syndrome (IBMFS) characterized by abnormal nails, lacey reticular pigmentation, oral leukoplakia, very short telomeres, and significantly elevated risks of aplastic anemia and cancer. Family pedigrees in DC indicate that there are multiple modes of inheritance (e.g. X-linked, autosomal dominant and autosomal recessive), although many cases are sporadic (i.e., lack a family history). We identified TINF2 as a new gene which causes autosomal dominant DC; it is a component of the shelterin complex of telomere protection proteins. All families with DC enrolled in the NCIs IBMFS study are evaluated for mutations in the known DC genes: TINF2, DKC1, TERC, TERT, NOLA2, and NOLA3. In our cohort of families, the proportion positive for these genes are 28%, 17%, 10%, 7%, 0% and 0%, respectively. Approximately 40% of our patients remain molecularly uncharacterized. These families have been used to demonstrate that very short telomeres (by Flow-FISH) in peripheral blood leukocyte subsets comprise a diagnostic abnormality for this disorder. Analysis of the cancers in these families demonstrates a pattern that is strikingly similar to that observed in Fanconi anemia (i.e., MDS, AML, squamous cell cancers of the head/neck and anorectal cancers). Candidate gene sequencing in the molecularly uncharacterized patients is ongoing. We have recently identified a new gene that appears to cause DC; functional characterization of the mutations underway. We are also exploring several new hypotheses related to DC pathogenesis, including epigenetic gene regulation and chromosomal abnormalities. Detailed characterization of the clinical phenotype and medical complications is ongoing. We are analyzing Telomere Length in Target Tissues [CAS 10373] in a series of methodological studies that seeks to clarify intra-individual variability in telomere length, with the ultimate goal being improved understanding of comparability when different cell types and methods of telomere length determination are employed. Epidemiologic studies typically use DNA isolated from either blood or buccal cells, yet direct comparisons of telomere length in blood and buccal cell DNA have not been published. It is important to understand how telomere lengths measured in commonly-used specimens (blood and buccal cells) compare with each other and with telomere lengths in tissues at risk of cancer development. Since telomere length measurement by Q-PCR and flow-FISH are becoming more widely used, it is also important to understand the intra-individual comparability of these techniques. We have evaluated intra- and inter-individual variation in telomere length in specimen trios (blood, buccal cell and fibroblast DNA) from subjects enrolled in the IBMFS study. A manuscript, which shows that telomere length is correlated in these individuals, is nearing submission. This methodological study seeks to determine whether or not telomere length measured in different tissue types can be combined in future studies. It will form the basis for larger epidemiologic studies of telomere length as a risk factor for cancer and other illnesses. We are investigating Telomere Length as a Risk Factor for Various Cancers [CAS 10371].(1) Prostate cancer: We evaluated telomere length as a prostate cancer risk factor in the PLCO cohort. A statistically significant association between prostate cancer risk and telomere length was not identified, but positive associations were found between telomere length and healthy lifestyle parameters (report published).(2) Ovarian Cancer: Our case-control study of ovarian cancer in Poland showed that leukocyte telomeres were strongly associated with high-grade serous ovarian adenocarcinoma (mauscript in press). A follow-up study employing a larger sample size is underway.(3) Osteosarcoma: Data are currently being analyzed on telomere length in leukocytes from osteosarcoma cases and controls. We are also evaluating the role of SNPs in telomere biology genes in this study.Collaborative studies of telomere length as a risk factor in glioma, pancreatic cancer, and pesticide exposures are ongoing. (4) Genetic Variants That Correlate With Telomere Length are being evaluated utilizing data derived from the NCI CGEMS genome-wide association studies of prostate and breast cancer. Single nucleotide polymorphisms (SNPs) in genes important in telomere biology were evaluated and potential candidates associated with telomere length were identified. We are also collaborating with Harvard on a genome-wide association study of telomere length which utilizes the same sample set.Population Genetics of Telomere Genes [CAS 10372]: We have previously shown that nucleotide diversity is low for critical proteins in the telomere maintenance pathway when compared with other types of genes, and that these genes are highly-conserved between species. Because these genes appear to be under evolutionary constraint, it is possible that germ-line genetic variation (i.e., single nucleotide polymorphisms, SNPs) in these genes could be significant risk factors for cancer or other diseases.The present study is evaluating genetic variation in 37 telomere biology genes from 1000 individuals among 53 worldwide populations - Africa, the Middle East, Europe, Central/South (C/S) Asia, East Asia, Oceania, and the Americas. A set of comparison genes from different functional pathways is being created. This study will provide insight into the evolutionary history of these genes, clarify variants which may have potential functional implications, and allow for tailored, evidence-based SNP selection in future genetic association studies