Cyclin D1 overexpression and poor clinical outcomes in Taiwanese oral cavity squamous cell carcinoma

Cyclin D1 gene regulates cell cycle and plays an important role in the tumorigenesis of human cancers. The association between cyclin D1, clinicopathologic parameters and prognosis in oral cavity squamous cell carcinoma (OSCC) is inconclusive. A total of 264 male OSCCs were examined for cyclin D1 protein expression using immunohistochemistry (IHC). The expression levels of cyclin D1 were defined as overexpression when more than 10% of tumor cells displayed nuclear staining with moderate to strong intensity. Overexpression of cyclin D1 was found in 97 (36.7%) OSCCs. Cyclin D1 protein overexpression was significantly associated with lymph node metastasis (P = 0.002), tumor cell differentiation (P = 0.031) and tumor stage (P = 0.051), but not associated with age onset, cigarette smoking, alcohol drinking, or areca quid chewing. Overexpression of cyclin D1 was also significantly associated with poor clinical outcomes in terms of disease-free survival (DFS, P = 0.002) and overall survival (OS, P < 0.001). The effects of cyclin D1 protein overexpression on DFS (hazard ratio (HR) = 1.540; 95% confidence interval (CI), 1.068 - 2.222) and OS (HR = 1.702; 95% CI, 1.168 - 2.480) were still existed after adjusting for clinicopathological parameters (such as age, primary tumor status, tumor cell differentiation, and lymph node metastasis) using logistic multivariate analysis. Cyclin D1 protein worked as an independent prognostic factor and can be as a biomarker for the aggressiveness of OSCC.