title: Inactivation of 14-3-3 sigma by promoter methylation correlates with metastasis in nasopharyngeal carcinoma.
abstract: 14-3-3 sigma, 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 sigma 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 sigma inactivation. Methylation-specific PCR showed 14-3-3 sigma 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 sigma. In tissues, 14-3-3 sigma 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 sigma promoter was detected in NPC but not in any of adjacent NNET. RT-PCR, Western blotting, and immunohistochemistry showed that 14-3-3 sigma 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 sigma gene. In addition, the patients with methylated 14-3-3 sigma presented a higher frequency of lymph node and distant metastasis, and an advanced clinical stage, and overexpression of 14-3-3 sigma 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 sigma is frequently inactivated by promoter methylation in NPC and this aberrant methylation correlates with lymph node and distant metastasis.
authors.affiliation: Key Laboratory of Cancer Proteomics of Chinese Ministry of Health, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Yi
authors.forename: Shuang-Xiang
authors.initials: SX
authors.lastname: Tan
authors.forename: Can-E
authors.initials: CE
authors.lastname: Tang
authors.forename: Wei-Guo
authors.initials: WG
authors.lastname: Huang
authors.forename: Ai-Lan
authors.initials: AL
authors.lastname: Cheng
authors.forename: Cui
authors.initials: C
authors.lastname: Li
authors.forename: Peng-Fei
authors.initials: PF
authors.lastname: Zhang
authors.forename: Mao-Yu
authors.initials: MY
authors.lastname: Li
authors.forename: Jian-Ling
authors.initials: JL
authors.lastname: Li
authors.forename: Hong
authors.initials: H
authors.lastname: Yi
authors.forename: Fang
authors.initials: F
authors.lastname: Peng
authors.forename: Zhu-Chu
authors.initials: ZC
authors.lastname: Chen
authors.forename: Zhi-Qiang
authors.initials: ZQ
authors.lastname: Xiao
mesh_terms: D048948:14-3-3 Proteins; D014408:Biomarkers, Tumor / Q000235:genetics*; D045744:Cell Line, Tumor; D019175:DNA Methylation; D004847:Epithelial Cells; D005092:Exonucleases / Q000235:genetics*; D005095:Exoribonucleases; D020868:Gene Silencing; D006801:Humans; D008207:Lymphatic Metastasis; D009303:Nasopharyngeal Neoplasms / Q000235:genetics / Q000473:pathology; D009362:Neoplasm Metastasis / Q000235:genetics*; D009363:Neoplasm Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic
chemical_list: D048948:14-3-3 Proteins; D014408:Biomarkers, Tumor; D009363:Neoplasm Proteins; D005092:Exonucleases; D005095:Exoribonucleases; C413442:SFN protein, human