Prognostic significance of p16, p53, Bcl-2, and Bax in oral and oropharyngeal squamous cell carcinoma

Background: The proteins p16, p53, Bcl-2, and Bax are important cell cycle and apoptotic regulators involved in carcinogenesis and found to have prognostic significance in various cancers. However, the data for squamous cell carcinoma of oral cavity (OSCC) and of oropharynx (OPSCC) are conflicting.

Objective: We sought to determine if expression of p16, p53, Bcl-2, and Bax expression are associated with 5-year overall survival (OS) of patients with OSCC and OPSCC.

Methods: One-hundred thirty-seven cases of OSCC and 140 cases of OPSCC diagnosed from January 2002 to December 2004 at Songklanagrind Hospital, Songkhla, Thailand, were analyzed using a Cox proportional hazards model for 5-year OS in relation to immunohistochemical detection of Bcl-2, Bax, p53, and p16 proteins.

Results: The frequencies of p16, p53, Bcl-2, and Bax expression in OSCC were 13%, 45%, 4%, and 66%, and in OPSCC were 18%, 53%, 22%, and 75%, respectively. In univariate analysis, clinical variables including T stage, N stage and treatment were significantly associated with survival. In multivariate Cox regression, Bax overexpression was significantly associated with poor survival both in OSCC (HR 1.77, 95% CI 1.04-3.01) and in OPSCC (HR 2.21, 95% CI 1.00-4.85). We found no significant association of p16, Bcl-2, and p53 expression with survival.

Conclusion: The expression pattern of p16, p53, Bcl-2, and Bax are similar in OSCC and OPSCC. Only Bax expression has prognostic significance for both tumor sites.