Inactivation of 14-3-3 σ by promoter methylation correlates with metastasis in nasopharyngeal carcinoma |
| |
Authors: | Bin Yi Shuang-Xiang Tan Can-E Tang Wei-Guo Huang Ai-Lan Cheng Cui Li Peng-Fei Zhang Mao-Yu Li Jian-Ling Li Hong Yi Fang Peng Zhu-Chu Chen Zhi-Qiang Xiao |
| |
Institution: | Key Laboratory of Cancer Proteomics of Chinese Ministry of Health, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, China |
| |
Abstract: | 14-3-3 σ, the downstream target of p53, is a negative regulator of cell cycle G2-M phase checkpoint in response to DNA damage. Our previous comparative proteomics study showed that 14-3-3 σ was downregulated or lost in nasopharyngeal carcinoma (NPC) tissue compared with non-cancerous nasopharyngeal epithelial tissue (NNET). In this study, we further investigated for the epigenetic mechanism of 14-3-3 σ inactivation. Methylation-specific PCR showed 14-3-3 σ promoter methylation in 100% of analyzed NPC cell lines (4/4) but not in immortalized human nasopharyngeal epithelial cell line NP69. Treatment of the four NPC cell lines with the methyltransferase inhibitor 5-aza-2′-dC resulted in the demethylation and upregulation of 14-3-3 σ. In tissues, 14-3-3 σ promoter methylation occurred at a higher frequency in NPC, 63/75 (84%), compared to adjacent NNET, 7/25 (28%), and fully methylated 14-3-3 σ promoter was detected in NPC but not in any of adjacent NNET. RT-PCR, Western blotting, and immunohistochemistry showed that 14-3-3 σ expression was downregulated or lost in NPC with methylation, and there was a negative correlation between the expression levels and methylation statuses of 14-3-3 σ gene. In addition, the patients with methylated 14-3-3 σ presented a higher frequency of lymph node and distant metastasis, and an advanced clinical stage, and overexpression of 14-3-3 σ in NPC cell line 5-8F with high metastatic potential was able to inhibit its in vitro invasive ability. Our data are the first to show that 14-3-3 σ is frequently inactivated by promoter methylation in NPC and this aberrant methylation correlates with lymph node and distant metastasis. J. Cell. Biochem. 106: 858–866, 2009. © 2009 Wiley-Liss, Inc. |
| |
Keywords: | nasopharyngeal carcinoma hypermethylation 14-3-3 σ metastasis |
|
|