We investigated the relationship between head and neck squamous cell carcinoma (HNSCC) and the mRNA and protein expression levels of the circadian genes of the Period (Per) family, Per1, Per2 and Per3. Tissue sections of HNSCC and normal head and neck tissues from two patient cohorts from two different hospitals were collected to assess the mRNA and protein expressions of the three Per family genes using real-time quantitative PCR (RT-PCR) and immunohistochemistry (IHC). The clinicopathological features and disease prognosis for the latter cohort were analyzed through IHC and statistical methods. Protein positive expression levels of the three Per family genes in HNSCC tissues was found to be approximately two times lower than that in normal tissues (p < .01). Moreover, patients with locally advanced HNSCC showed significantly greater downregulation of Per1, Per2 and Per3 mRNA expression levels as compared to patients with early-stage cancer (p < .05). Immunohistochemical examination of HNSCC patient tissues revealed a positive correlation between the Per family protein expression and the clinical tumor staging (p < .05). In addition, the Per protein-positive expression group showed higher 3-year survival rates [overall survival (OS) and progression-free survival (PFS)] as assessed by Kaplan-Meier plots and statistical analysis (p < .05). Our findings confirm the positive correlation between Per family gene expression and survival outcomes and support their role as prognostic markers for HNSCC.
Keywords: Head and neck squamous cell carcinoma (HNSCC); Per1; Per2; Per3; circadian gene; immunohistochemistry; normal tissues of the head and neck; real-time quantitative PCR.