Molecular Epidemiology of Pediatric Germ Cell Tumors

描述（由申请人提供）：儿童生殖细胞肿瘤（gct）是一种异质肿瘤，被假设为子宫内事件的结果，这表明正常胚胎发育所需过程的改变可能与病因学特别相关。近年来，儿童gct的发病率在某些亚组中有所增加，其根本原因尚不清楚。考虑到发病年龄较早，遗传因素似乎是有可能的。异常DNA甲基化与多种类型癌症的病因有关，由于在正常发育过程中生殖系和早期胚胎中发生了广泛的表观遗传重编程，因此可能与gct特别相关。本提案的主要目的是利用美国和加拿大儿童肿瘤小组（COG）和儿童癌症研究网络（CCRN）的资源，对儿童gct的遗传和表观遗传改变进行一项全面的病例-父母三合一研究。2008年7月1日至2015年12月31日诊断的儿童GCT（0-19岁）病例将通过CCRN进行识别，并将被邀请参加。我们预计将招收大约930例病例。将收集病例及其父母的DNA样本用于基因分析，获得肿瘤样本用于评估表观遗传改变，并通过邮寄问卷评估生活方式和环境风险因素。我们假设与生殖细胞发育相关的关键通路的遗传变异将与儿童GCT有关。我们进一步假设，由于肿瘤的组织学亚型取决于在转化时发生的分化程度，DNA甲基化模式将因肿瘤组织学而异。我们的主要目标将是：1)使用病例-亲本三联体设计评估生殖细胞发育关键通路的遗传变异（包括选定基因的深度测序）与儿童GCT之间的关系；2)通过肿瘤组织学探索DNA甲基化的异质性。我们将使用Illumina平台对来自相关生物学途径的单核苷酸多态性（snp）进行基因分型。候选snp将使用标记snp方法选择，并辅以先前报道的具有功能意义的snp。此外，深度重测序将用于鉴定与我们的试点数据中的儿童gct相关的四个基因的变异，分别是KITLG、SPRY4、BAK1和DMRT1。我们将使用Illumina HumanMethylation27 BeadChip评估全基因组DNA甲基化，这将使我们能够选择具有gct特征的CpG位点。本申请中提出的研究具有重要意义，因为它将是迄今为止最大的儿科gct遗传流行病学研究，并将评估遗传易感性方面的新关联。此外，了解儿童gct的甲基化模式可能表明肿瘤发生的发育阶段。

DESCRIPTION (provided by applicant): Pediatric germ cell tumors (GCTs) are a heterogeneous group of tumors that are hypothesized to occur as a result of events in utero, which suggests that alterations in processes required for normal embryonic development are likely to be especially relevant to etiology. The incidence of pediatric GCTs has increased in recent years in certain subgroups, and the underlying causes are unknown. Given the early age of onset, genetic contributions seem likely. Aberrant DNA methylation, which has been implicated in the etiology of multiple types of cancer, has the potential to be especially relevant in GCTs due to the extensive epigenetic reprogramming that occurs in the germ line and early embryo during normal development. The primary objective for this proposal is to conduct a comprehensive case-parent triad study of genetic and epigenetic alterations in pediatric GCTs using the resources of the Children's Oncology Group (COG) and the Childhood Cancer Research Network (CCRN) in the United States and Canada. Cases of pediatric GCT (ages 0-19 years) diagnosed from July 1, 2008-December 31, 2015 will be identified through the CCRN and will be invited to participate. We expect to enroll approximately 930 cases. DNA samples will be collected from the cases and their parents for use in genetic analyses, tumor specimens will be obtained for evaluation of epigenetic alterations, and lifestyle and environmental risk factors will be assessed using mailed questionnaires. We hypothesize that genetic variation in key pathways relevant to germ cell development will be associated with pediatric GCT. We further hypothesize that because the histologic subtype of the tumor is dependent on the degree of differentiation that has occurred at the time of transformation, DNA methylation patterns will differ by tumor histology. Our primary aims will be to: 1) Evaluate associations between genetic variation (including deep sequencing of selected genes) in key pathways involved in germ cell development and pediatric GCT using a case-parent triad design and 2) Explore heterogeneity in DNA methylation by tumor histology. We will genotype single nucleotide polymorphisms (SNPs) from relevant biological pathways using the Illumina platform. Candidate SNPs will be selected using a tagSNP approach supplemented with SNPs that have been previously reported to have functional significance. In addition, deep re-sequencing will be used to identify variants in four genes that are associated with pediatric GCTs in our pilot data, KITLG, SPRY4, BAK1, and DMRT1. We will evaluate genome wide DNA methylation using the Illumina HumanMethylation27 BeadChip, which will allow us to select CpG sites that are characteristic of GCTs. The research proposed in this application is significant because it will be the largest genetic epidemiology study of pediatric GCTs to date and it will evaluate novel associations with respect to genetic susceptibility. In addition, understanding methylation patterns in pediatric GCTs may indicate the developmental stage at which the tumor arose.