Institute of Pathology, Medical University of Graz, Auenbruggerplatz 25, 8036 Graz, Austria.
Hum Pathol. 2013 Mar;44(3):336-45. doi: 10.1016/j.humpath.2012.05.021. Epub 2012 Sep 17.
Embryonal renal mesenchyme contains pluripotent progenitor cells characterized by expression of SIX2, which suppresses cellular differentiation. Additionally hypomethylation of the promotor region in renal neoplasms indicates a role of SIX2 in tumorigenesis. This study focuses therefore on the investigation of SIX2 in different renal neoplasms and the mode and consequences of SIX2 activation. Expression of SIX2 was determined in renal cell carcinomas, nephroblastomas, and dysplastic kidneys using immunohistochemistry and quantitative real-time polymerase chain reaction. Its potential mode of activation was assessed by measuring upstream activators by quantitative real-time polymerase chain reaction and the level of methylation of the promoter region by quantitative DNA methylation analysis. Consequences of SIX2 activation were investigated by overexpressing SIX2 in a cell line. Forty-seven of 49 renal clear cell carcinomas showed nuclear staining of SIX2, whereas all papillary carcinomas were negative. In nephroblastomas of various subtypes blastema showed a significant up-regulation (P < .01) and a strong nuclear protein expression of SIX2 in contrast to negative epithelial and mesenchymal areas. 11 cases of dysplastic kidneys were entirely negative. Upstream activators of SIX2 indicated an activation of the signal transduction pathway in most samples. No difference of promoter methylation status was observed between blastema and epithelial structures. A significantly higher percentage of cells in the S-phase and an increased migration were detected in the cell-line overexpressing SIX2. Our study suggests that activation of SIX2 might contribute to the pathogenesis of renal clear cell carcinomas and nephroblastomas. SIX2 also appears to be a valuable marker for minimal residual blastema contributing to the prognosis of nephroblastomas.
胚胎肾间质包含多能祖细胞，其特征在于表达 SIX2，其抑制细胞分化。此外，肾肿瘤中启动子区域的低甲基化表明 SIX2 在肿瘤发生中的作用。因此，本研究重点研究了 SIX2 在不同肾肿瘤中的表达以及 SIX2 激活的模式和后果。使用免疫组织化学和实时定量聚合酶链反应测定肾细胞癌、肾母细胞瘤和发育不良肾脏中 SIX2 的表达。通过实时定量聚合酶链反应测量上游激活剂并通过定量 DNA 甲基化分析测量启动子区域的甲基化水平来评估其潜在的激活模式。通过在细胞系中过表达 SIX2 来研究 SIX2 激活的后果。49 例肾透明细胞癌中有 47 例显示 SIX2 的核染色，而所有乳头状癌均为阴性。在各种亚型的肾母细胞瘤中，胚细胞瘤显示出明显的上调（P <.01），并且 SIX2 的核蛋白表达强烈，与阴性上皮和间充质区域形成对比。11 例发育不良的肾脏完全为阴性。SIX2 的上游激活剂表明大多数样本中信号转导途径的激活。胚细胞瘤和上皮结构之间未观察到启动子甲基化状态的差异。在过表达 SIX2 的细胞系中，检测到 S 期的细胞百分比显著增加和迁移增加。我们的研究表明，SIX2 的激活可能有助于肾透明细胞癌和肾母细胞瘤的发病机制。SIX2 似乎也是有助于肾母细胞瘤预后的最小残留胚细胞瘤的有价值标志物。
