Abstract: Objective To explore the expressions of Cyclin-dependent kinase 5 (CDK5) and Epithelial-Mesenchymal Transition (EMT) related proteins including N-cadherin, Vimentin and E-cadherin in head and neck squamous cell carcinoma (HNSCC), and to determine the relationship between the expression of CDK5 and prognosis. Methods The expression levels of CDK5 and EMT related proteins were evaluated by immunohistochemistry in 55 patients who were diagnosed as HN⁃ SCC. They were also analyzed in different clinical pathological factors. The correlation of CDK5 and EMT related proteins as well as the relationship between the expression of CDK5 and prognosis were also analyzed. Results The expression level of CDK5 was significantly higher in patients with lymph node metastasis than that in patients with non-lymph node metastasis (91.67% vs 30.23%, P < 0.05). It’s also higher in T3-T4 stages than that in T1-T2 stages (85% vs 20%, P < 0.05). The ex⁃ pression levels of N-cadherin and Vimentin were significantly higher in patients with lymph node metastasis than those in patients with non-lymph node metastasis (75.00% vs 6.98%; 91.67% vs 27.91%, all P < 0.05). However, the expression level of E-cadherin was significantly lower in patients with lymph node metastasis (8.33% vs 86.05%, P < 0.05) compared to that in patients without. CDK5 was positively correlated with N-cadherin and Vimentin, but negatively correlated with E-cad⁃ herin (rs=0.512, 0.443, -0.363, all P < 0.01). The 3-year survival rates were significantly lower in patients with high expres⁃ sion of CDK5 (37.5%) than that in patients with low expression of CDK5 (87%, Log-rank χ2=12.678, P < 0.01). Conclusion CDK5 and EMT related proteins were activated abnormally in HNSCC with lymph node metastasis. CDK5 may be a new bio⁃ logical marker for prognosis of HNSCC.

Key words: head and neck neoplasms, carcinoma, squamous cell, cyclin-dependent kinase 5, cadherins, vimentin, lymphatic metastasis