In this study, we investigated the expression of 14-3-3σ tumor suppressor gene in a panel of NPC cell lines, xenografts and primary tumors. Our objective was to determine the correlation between 14-3-3σ expression and clinical outcome in NPC. We detected reduced 14-3-3σ expression in 5/6 NPC tumor lines by quantitative RT-PCR and Western blotting. By immunohistochemical staining, significant down-regulation of 14-3-3σ was also found in 26/72 (36.1%) primary tumors of NPC patients, who were treated with curative radiotherapy. Promoter methylation was confirmed in a subset of primary tumors by methylation-specific PCR analysis. Importantly, we demonstrated that 14-3-3σ expression is significantly associated with both overall survival (OS) and cancer-specific survival (CSS), but not with the clinical staging of NPC patients. The low 14-3-3σ expression was associated with improved overall (p=0.029) and cancer-specific survival (p=0.042) on univariate analysis. 14-3-3σ expression and staging were also independent variables to all the prognostic factors under multivariate analysis. In conclusion, low expression of 14-3-3σ appears to be a valuable marker for better survival in patient with NPC. These results provide the evidence that 14-3-3σ expression is a significant prognostic factor for NPC patients.

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