S-phase kinase-associated protein 2 expression in laryngeal squamous cell carcinomas and its prognostic implications

The F-box protein S-phase kinase-associated protein 2 (Skp2) positively regulates the G1-S transition by controlling the stability of several G1 regulators, such as the cell cycle inhibitor p27(kipl). However, the clinical significance of Skp2 in patients with laryngeal squamous cell carcinoma (LSCC) remains unknown. In this study, a potential distribution of Skp2 in LSCC and its clinical implications was investigated by an immunohistochemical study. Overall, Skp2 overexpression was observed in 36.7% (37 of 102) patients and was significantly associated with lymph node metastasis (p = 0.002) and was inversely associated with p27 kip I expression (p = 0.026). Survival analysis using the Kaplan-Meier method showed that Skp2 overexpression was significantly associated with shorter disease-free and overall survival (p = 0.0051 and p = 0.0002, respectively). When Skp2 expression and p27(kipl) expression were combined, patients with both Skp2 overexpression and reduced expression of p27(kipl) revealed poorest disease-free and overall survival as compared to the other cases (p = 0.0017 and p < 0.0001, respectively). Additionally, in early stage (I, II) cases, Skp2 expression was also revealed to possess a significant prognostic factor in overall survival (p = 0.0234), but not in disease-free survival (p = 0.2055). By multivariate analysis using the Cox proportional hazards model, tumor grade, tumor size, clinical stage and Skp2 expression were independent prognostic factors both in disease-free and overall survival. These findings indicated that Skp2 expression was closely associated with tumor progression and represented an independent marker for prognosis of LSCC.