14-3-3σ expression as a prognostic marker in undifferentiated nasopharyngeal carcinoma

In this study, we investigated the expression of 14-3-3 sigma tumor suppressor gene in a panel of NPC cell lines, xenografts and primary tumors. Our objective was to determine the correlation between 14-3-3 sigma expression and clinical outcome in NPC. We detected reduced 14-3-3 sigma expression in 5/6 NPC tumor lines by quantitative RT-PCR and Western blotting. By immunohistochemical staining, significant down-regulation of 14-3-3 sigma 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 14-3-3 sigma 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 14-3-3 sigma expression was associated with improved overall (p=0.029) and cancer-specific survival (p=0.042) on univariate analysis. 14-3-3 sigma expression and staging were also independent variables to all the prognostic factors under multi-variate analysis. In conclusion, low expression of 14-3-3 sigma appears to be a valuable marker for better survival in patient with NPC. These results provide the evidence that 14-3-3 sigma expression is a significant prognostic factor for NPC patients.