Abstract: Objective: To ascertain the possible roles of COX-2，PCNA and p53 in the tumorigenesis and development of nasopharyngeal carcinoma, and to evalulate their impact on the prognosis of nasopharyngeal carcinoma. Methods: Immunohistochemical assay was used to determine COX-2, PCNA and p53 in all specimens, including 60 cases of nasopharyngeal carcinoma and 30 cases of normal nasopharynx. Results: （1） The overall positive expression rate of COX-2， PCNA and p53 in nasopharyngeal carcinoma was 90%, 75% and 68% respectively, higher than that in the normal nasopharynx. （2） Intensity of expression of COX-2, PCNA and p53 in nasopharyngeal carcinoma was related to tumor stage, tumor differentiation and lymph node metastasis (P＜0.05). （3） Expressions of COX-2, PCNA and p53 were correlated with each other in nasopharyngeal carcinoma. （4） Positive COX-2 and PCNA were associated with a lower 5-year survival and they were significant prognostic variables for recurrence(P＜0.05). Conclusion: COX-2, PCNA and p53 may play vital roles in the tumorigenesis and development of the cancer via different methods. Unfavorable prognosis was associated with expression of COX-2 and PCNA while not with p53. Immunohistochemical assessment of COX-2 and PCNA might be a useful molecular marker for predicting prognosis in nasopharyngeal cancer.

Key words: Cyclooxygenase-2, Proliferating cell nuclear antigen, Protein, p53, Nasopharyngeal carcinoma, Immunohistochemistry, Prognosis