Wnt antagonist DKK1 acts as a tumor suppressor gene that induces apoptosis and inhibits proliferation in human renal cell carcinoma
Wnt antagonist DKK1 acts as a tumor suppressor gene that induces apoptosis and inhibits proliferation in human renal cell carcinoma
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DOI：
10.1002/ijc.25507
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发表时间：
2011-04-15
影响因子：
6.4
通讯作者：
Dahiya, Rajvir
中科院分区：
文献类型：
--
作者：
Hirata, Hiroshi;Hinoda, Yuji;Dahiya, Rajvir
Wnt拮抗剂Dkk1在肾细胞癌(RCC)中的功能意义尚未被研究。因此，我们推测Dkk1可能是一个肿瘤抑制基因，并且在表观遗传上是沉默的，因此Dkk1的降低可能导致肾癌的进展。为了评估Dkk1的功能，我们建立了稳定的Dkk1转基因细胞，并对它们的细胞活力、克隆形成、细胞凋亡、细胞周期和侵袭能力进行了监测。5-氮-20-脱氧胞苷和曲古抑素A处理后，Dkk1的表达水平降低，5-氮-20-脱氧胞苷和曲古抑素A处理后，Dkk1的表达水平升高。染色质免疫沉淀实验显示，5-氮-20-脱氧胞苷/曲古抑素A处理的肾癌细胞株中二甲基H3K9和三甲基H3K27的表达水平降低。在原发肾细胞癌组织中，甲基化增加也与较高的病理分期有关。Dkk1转染组T细胞因子/淋巴增强因子活性和核β-连环素表达无明显变化。Dkk1转染组细胞周期蛋白D1和c-Myc的表达无明显变化。这些结果提示Dkk1可能不参与β-连环蛋白依赖途径。我们还检测了各种相关基因的表达情况。切割后的caspase3、p53、p21和PUMA在Dkk1细胞中的表达显著上调。在稳定的Dkk1细胞中，凋亡细胞的数量增加，在裸鼠体内也观察到肿瘤生长受到抑制。综上所述，这是首次报道Dkk1在肾癌中的表达在表观遗传上是沉默的，它的重新表达诱导了肾癌的细胞凋亡和细胞周期停滞。
The functional significance of Wnt antagonist DKK1 has not been investigated in renal cell carcinoma (RCC). Therefore, we hypothesized that DKK1 may be a tumor suppressor gene and is epigenetically silenced, thus decreased DKK1 may cause progression of RCC. To assess the function of DKK1, we established stable DKK1 transfected cells and monitored them regarding cell viability, colony formation, apoptosis, cell cycle, and invasive capability. RCC cell lines had decreased levels of DKK1, which were increased after treatment with 5-Aza-20-deoxycytidine and trichostatin A. In chromatin immunoprecipitation assay, the level of dimethyl H3K9 and trimethyl H3K27 was decreased after 5-Aza-20-deoxycytidine/ trichostatin A treatment in RCC cell lines. Increased methylation was also associated with higher pathological stages in primary RCC tissues. T-cell factor/ lymphoid enhancer factor activity and nuclear beta-catenin expression were not changed in DKK1 transfectants. Also the expression of cyclinD1 and c-Myc was not changed in DKK1 transfectants. These results suggest that DKK1 may not be involved in the beta-catenin dependent pathway. We also evaluated the expression of various related genes. Cleaved caspase3, p53, p21 and puma expression were significantly upregulated in the DKK1 transfected cells. The population of apoptotic cells was increased in stable DKK1 cells and tumor growth suppression was also observed in nude mice with DKK1 transfected cells. In conclusion, this is the first report to show that DKK1 expression is epigenetically silenced in kidney cancer and its reexpression induces apoptosis and cell cycle arrest in RCC.