Lind G E, Skotheim R I, Fraga M F, Abeler V M, Esteller M, Lothe R A
Department of Cancer Prevention, Institute for Cancer Research, Rikshospitalet-Radiumhospitalet Medical Centre, Oslo, Norway.
J Pathol. 2006 Dec;210(4):441-9. doi: 10.1002/path.2064.
Testicular germ cell tumours (TGCTs) are classified into two main histological subgroups: seminomas and non-seminomas. The latter comprise several subtypes: embryonal carcinomas, yolk sac tumours, choriocarcinomas, and teratomas. These embryonal and extra-embryonal-like differentiation lineages represent a caricature of early normal development, and inactivation of gene expression through promoter hypermethylation may therefore be of particular importance in germ cell tumourigenesis. The promoter methylation status of ten candidate genes-CDH13, DLX6, EMX2, HOXA9, HOXB5, MSX1, MSX2, RASSF1A, RUNX3, and SCGB3A1 (alias HIN-1)-was assessed by methylation-specific PCR in seven intratubular germ cell neoplasias and 55 primary TGCTs. Furthermore, by a discovery-based global approach, comparing cDNA microarray expression profiles of two germ cell tumour cell lines before and after treatment with the demethylating agent 5-aza-2'-deoxycytidine, a gene list of potentially epigenetic targets was identified, from which CGGBP1, CGRRF1, SMARCC2, SORBS1, and XPA were analysed further. Overall, the non-seminomas were significantly more often methylated than were seminomas (p < 0.001). The three most frequently methylated genes among this subtype were SCGB3A1 (54%), RASSF1A (29%), and HOXA9 (26%). CDH13 and HOXB5 were methylated at low frequencies (10-15%), and EMX2, MSX1, RUNX3, SORBS1, and XPA only rarely (<10%). In conclusion, this study has identified several novel epigenetically deregulated target genes in TGCT development, including homeobox genes and SCGB3A1, suggesting that epigenetic inactivation of key genes in normal development also has an important role in TGCTs.
睾丸生殖细胞肿瘤（TGCTs）主要分为两个组织学亚组：精原细胞瘤和非精原细胞瘤。后者包括几种亚型：胚胎癌、卵黄囊瘤、绒毛膜癌和畸胎瘤。这些胚胎样和胚外样分化谱系代表了早期正常发育的一种夸张表现，因此通过启动子高甲基化导致的基因表达失活在生殖细胞肿瘤发生过程中可能尤为重要。通过甲基化特异性PCR评估了7例管内生殖细胞肿瘤和55例原发性TGCT中10个候选基因（CDH13、DLX6、EMX2、HOXA9、HOXB5、MSX1、MSX2、RASSF1A、RUNX3和SCGB3A1（别名HIN-1））的启动子甲基化状态。此外，通过基于发现的全局方法，比较了两种生殖细胞肿瘤细胞系在用去甲基化剂5-氮杂-2'-脱氧胞苷处理前后的cDNA微阵列表达谱，确定了一份潜在的表观遗传靶点基因列表，并对其中的CGGBP1、CGRRF1、SMARCC2、SORBS1和XPA进行了进一步分析。总体而言，非精原细胞瘤的甲基化频率显著高于精原细胞瘤（p < 0.001）。该亚型中甲基化最频繁的三个基因是SCGB3A1（54%）、RASSF1A（29%）和HOXA9（26%）。CDH13和HOXB5的甲基化频率较低（10 - 15%），而EMX2、MSX1、RUNX3、SORBS1和XPA仅偶尔出现甲基化（<10%）。总之，本研究在TGCT发展过程中鉴定出了几个新的表观遗传失调靶点基因，包括同源盒基因和SCGB3A1，这表明正常发育过程中关键基因的表观遗传失活在TGCT中也起着重要作用。
