Expression of 14-3-3 sigma, cyclin-dependent kinases 2 and 4, p16, and Epstein-Barr nuclear antigen 1 in nasopharyngeal carcinoma

Abstract Objective: The protein 14-3-3 sigma plays a role in cell cycle arrest by sequestering cyclin-dependent kinase 1 cyclin B1 complexes, as well as cyclin-dependent kinases 2 and 4, hence its definition as a cyclin-dependent kinase inhibitor. However, the nature of the interaction between these biological markers in nasopharyngeal carcinoma is unknown. This study aimed to investigate whether altered expression of these markers contributes to nasopharyngeal carcinogenesis. Methods: The study population consisted of 30 nasopharyngeal carcinoma patients and 10 patients without nasopharyngeal carcinoma. The nasopharyngeal carcinoma cell lines TW02, TW04 and Hone-1 were also assessed. We analysed levels of messenger RNA and protein for the p16 gene and the 14-3-3 sigma, Epstein-Barr nuclear antigen 1, and cyclin-dependent kinase 2 and 4 proteins, in nasopharyngeal carcinoma tissue specimens and cell lines and in normal nasopharyngeal tissue. Results: Protein and messenger RNA levels for cyclin-dependent kinase 2 and Epstein-Barr nuclear antigen 1 were significantly higher in nasopharyngeal carcinoma compared with normal tissue, while levels of cyclin-dependent kinase 4 generally were not; results for 14-3-3 sigma varied. Nasopharyngeal carcinoma patients had diminished p16 gene expression, compared with normal tissue. Conclusion: Levels of cyclin-dependent kinase 2 and Epstein-Barr nuclear antigen 1 were significantly higher in nasopharyngeal carcinoma than in normal tissue, while p16 gene expression was diminished. These three proteins may contribute to nasopharyngeal carcinogenesis.