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)。我们发现了四个导致DC的新原因：(1)TINF2的胚系突变首次提供了证据，表明Shelterin蛋白保护复合体的破坏可导致人类疾病；(2)WRAP53中导致DC的突变首次证明了端粒酶的错误定位可能导致人类疾病。(3)外显子测序发现DNA螺旋和端粒生物学基因RTEL1突变是引起DC的新原因，(4)我们还发现由ACD编码的另一组分TPP1的突变可引起DC并导致端粒酶活性缺陷。DC队列中的所有参与者都要接受DC相关基因突变的评估。我们进行靶向基因测序和全外显子组测序，以发现所有登记家庭中DC的原因。我们的DC研究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。DC Biospecimen资料库是一个丰富的资源，用于了解端粒生物学异常的分子后果。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。目标组织中的端粒长度[CAS 10373]现已关闭。它评估了来自IBMFS患者的血液、口腔细胞和成纤维细胞的DNA定量聚合酶链式反应测量的个体内端粒长度，以及Flow-FISH和定量聚合酶链式反应的相关性。研究发现，一般而言，成纤维细胞端粒比血液或口腔细胞端粒更长，但组织类型之间存在显著的个体内相关性。这项初步研究为更大规模的端粒生物学与癌症风险的方法学研究奠定了基础。我们还在研究端粒长度作为癌症风险因素[CAS 10371]。大量研究表明，较短的代孕组织TL是癌症的危险因素。我们之前的病例对照研究发现，端粒较短与卵巢癌和胃癌的风险增加有关。然而，我们对TL和前列腺癌的队列研究没有发现同样的关联。我们对代孕组织中TL与癌症风险之间关系的荟萃分析表明，短TL与整体癌症是相关的，但这可能是由特定癌症中更强的作用所驱动的。回溯性研究的OR值远高于前瞻性研究的OR值(2.9比1.16)，这表明在样本采集之前癌症治疗可能有反向因果偏倚。研究的异质性和某些癌症部位的极少或没有数据也是这些分析的局限性。正在进行的工作包括许多关于TL和癌症的协作研究，这些研究旨在1)确定TL是否与特定癌症或癌症相关结果的风险有关，2)在病例对照和队列研究中确定TL和癌症相关性的差异，3)利用这些研究作为生殖系(即代孕)和体组织研究的基础，目的是更好地了解端粒生物学在癌症病因中的作用[CAS 10371]，这些研究已经通过分析来自NCI CGEMS GAs的SNP数据对前列腺癌和乳腺癌的影响进行了评估。我们发现4个基因的13个SNPs与TL相关。我们还与哈佛大学合作进行了TL的全基因组关联研究(GWAS)。这项研究证实了TERC中的一个SNP与TL有关，但与其他研究类似，没有发现其他位点的SNP与TL之间的强烈关联。一项名为获得性重型再生障碍性贫血患者造血干细胞移植后端粒长度[CAS 10508]的新项目被启动，旨在了解端粒生物学在获得性重型再生障碍性贫血造血干细胞移植后预后中的作用。在与国家骨髓捐赠者计划(NMDP)的合作中，我们发现捐赠者TL与接受HCT治疗SAA的患者的临床结果显著相关。正在进行的分析试图在其他接受HCT的患者中验证这些发现。对端粒生物基因的群体遗传学研究[中国科学院10372]继续提供对其进化史的重要见解。正在进行的研究包括表征端粒生物学基因中胚系变异的功能后果以及与临床结果的相关性。

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 have discovered four novel causes of DC: (1) Germline mutations in TINF2 provided the first evidence that disruption of the shelterin protein protection complex can cause human disease; (2) DC-causing mutations in WRAP53 were first proof that mislocalization of telomerase could cause human illness. (3) Exome sequencing discovered mutations in RTEL1, a DNA helices and telomere biology gene, as a novel cause of DC, and (4) We also showed that mutations in another component of shelterin, TPP1, encoded by ACD cause DC and result in telomerase processivity defects. All participants in the DC cohort are evaluated for mutations in the DC-associated genes. We perform targeted gene sequencing and whole exome sequencing to discover the causes of DC in all enrolled families. Our DC studies 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). The DC Biospecimen Repository is a rich resource used to understand the molecular consequences of telomere biology abnormalities. 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. Telomere Length in Target Tissues [CAS 10373] is now closed. It evaluated intra-individual telomere length measured by QPCR of DNA derived from blood, buccal cells, and fibroblasts from IBMFS patients as well as the correlation between flow-FISH and QPCR. It found that in general, fibroblast telomeres were longer than blood or buccal cell telomeres but that there was significant intra-individual correlation between tissue types. This pilot study forms the basis for larger methodological studies of telomere biology and cancer risk. We are also investigating Telomere Length as Cancer Risk Factor [CAS 10371]. Numerous studies suggest that short surrogate tissue TL is a cancer risk factor. Our previous case-control studies found that short telomeres are associated with increased risk of ovarian and gastric cancer. However, our cohort study of TL and prostate cancer did not find the same association. Our meta-analysis on the association between TL in surrogate tissues and cancer risk which suggests short TL and overall cancer are associated but this may be driven by stronger effects in specific cancers. The ORs derived from retrospective studies were much higher than for prospective studies (2.9 versus 1.16), which suggests reverse causation bias and possible contribution of cancer therapy prior to sample collection. Study heterogeneity and minimal or no data on certain cancer sites were also limitations of these analyses. Ongoing work includes many collaborative studies of TL and cancer designed to 1) determine if TL is associated with risk of specific cancers or cancer-related outcomes, 2) determine differences in TL and cancer associations in case-control versus cohort studies, and 3) use these studies as building blocks for germline (i.e., surrogate) and somatic tissue studies aimed at better understanding the contribution of telomere biology to cancer etiology Genetic Variants That Correlate With Telomere Length [CAS 10371] have been evaluated through analyses of SNP data derived from the NCI CGEMS GWAS of prostate and breast cancer. We found that 13 SNPs from 4 genes were associated with TL. We also collaborated with Harvard University on a genome-wide association study (GWAS) of TL. That study confirmed a SNP in TERC as associated with TL, but, similar to other studies, did not find strong associations between SNPs at other sites and TL. A new project, Telomere length after HSCT in patients with acquired severe aplastic anemia [CAS 10508] was initiated which seeks to understand the role of telomere biology in outcomes after hematopoictic stem cell transplant (HCT) for acquired severe aplastic anemia (SAA). In collaboration with the National Marrow Donor Program (NMDP), we showed that donor TL is significantly associated with clinical outcomes in patients undergoing HCT for SAA. Ongoing analyses seek to validate these findings in other patients undergoing HCT. Population genetic studies of telomere biology genes [CAS 10372] continue to provide important insight into their evolutionary history. Ongoing studies include characterization of the functional consequences of germline variants in telomere biology genes and correlation with clinical findings.