Kunze Ekkehard, Wendt Maike, Schlott Thilo
Department of Osteopathology and Haematopathology, University of Göttingen, D-37099 Göttingen, Germany.
Int J Mol Med. 2006 Oct;18(4):547-57.
To explore the significance of epigenetic mechanisms in urinary bladder carcinogenesis mediated by methylation of cytosine in CpG dinucleotides at 5' promoter regions, we analysed the methylation status of a broad panel of different genes in transitional cell carcinomas (TCC) and nonurothelial cancers, among which the 14-3-3 sigma, SYK and CAGE-1 genes were recognised as promising target genes. Using methylation-specific PCR, the rate of DNA hypermethylation proved to be related to the various histopathological cancer subtypes. The higher frequency of promoter methylation of the 14-3-3 sigma (57.1%) and SYK (64.3%) genes in high-grade, high-stage TCC in association with a reduced or even lacking immunohistochemical protein expression than in low-grade, low-stage TCC (28.6% and 42.9%, respectively), indicates that aberrant methylation of these genes plays an essential role in the progression of TCC. The importance of DNA hypermethylation in the conversion of TCC from a low to a high malignant potential was strongly supported by the finding that, unlike superficial low-grade TCC, advanced muscle invasive TCC showed a concurrent promoter methylation of the 14-3-3 sigma, SYK and CAGE-1 genes. Squamous cell carcinomas revealed a peak incidence of hypermethylation of the 14-3-3 sigma gene (80%), and conversely, the lowest methylation frequency of the SYK gene (13.3%). Undifferentiated small cell carcinomas disclosed a promoter methylation of the 14-3-3 sigma, SYK and CAGE-1 genes in only a quarter each for the cases. Although a correlation between the methylation status and gene activity in squamous cell and undifferentiated small cell carcinomas was not observed, the underexpression of the SYK protein products in both cancer types and additionally of the 14-3-3 sigma protein in small cell carcinomas appeared to be related to the aggressive clinical behaviour of both these nonurothelial bladder carcinomas. The relevance of the high frequency of DNA hypermethylation of the CAGE-1 antigen in TCC and squamous cell carcinomas merits further study, particularly in relation to anticancer immunotherapy. The methylation status of the PTEN, COX-2, RUNX-3 and HIC-1 genes was found to be unaltered. In conclusion, the different patterns of aberrant methylation of the 14-3-3 sigma, SYK and CAGE-1 genes in the various histopathological cancer types of the urinary bladder point to a role in tumor cell differentiation, resulting in the phenotypical conversion of TCC into nonurothelial carcinomas and in the progression of TCC to a more malignant potential.
为了探讨由5'启动子区域中CpG二核苷酸的胞嘧啶甲基化介导的表观遗传机制在膀胱癌发生中的意义，我们分析了一系列不同基因在移行细胞癌（TCC）和非尿路上皮癌中的甲基化状态，其中14-3-3 sigma、SYK和CAGE-1基因被认为是有前景的靶基因。使用甲基化特异性PCR，DNA高甲基化率被证明与各种组织病理学癌症亚型有关。14-3-3 sigma基因（57.1%）和SYK基因（64.3%）在高级别、高分期TCC中的启动子甲基化频率高于低级别、低分期TCC（分别为28.6%和42.9%），且免疫组化蛋白表达降低甚至缺失，这表明这些基因的异常甲基化在TCC进展中起重要作用。与浅表低级别TCC不同，进展期肌层浸润性TCC显示14-3-3 sigma、SYK和CAGE-1基因启动子同时甲基化，这一发现有力支持了DNA高甲基化在TCC从低恶性潜能向高恶性潜能转化中的重要性。鳞状细胞癌显示14-3-3 sigma基因高甲基化发生率最高（80%），相反，SYK基因甲基化频率最低（13.3%）。未分化小细胞癌中，仅四分之一的病例显示14-3-3 sigma、SYK和CAGE-1基因启动子甲基化。虽然在鳞状细胞癌和未分化小细胞癌中未观察到甲基化状态与基因活性之间的相关性，但这两种非尿路上皮膀胱癌中SYK蛋白产物的低表达以及小细胞癌中14-3-3 sigma蛋白的低表达似乎与它们侵袭性的临床行为有关。CAGE-1抗原在TCC和鳞状细胞癌中DNA高甲基化频率较高的相关性值得进一步研究，特别是与抗癌免疫治疗相关的研究。发现PTEN、COX-2、RUNX-3和HIC-1基因的甲基化状态未改变。总之，膀胱各种组织病理学癌症类型中14-3-3 sigma、SYK和CAGE-1基因异常甲基化的不同模式表明其在肿瘤细胞分化中起作用，导致TCC向非尿路上皮癌的表型转化以及TCC向更高恶性潜能的进展。
