The clinicopathological significances and biological functions of parafibromin expression in head and neck squamous cell carcinomas

Downregulated parafibromin expression is involved in the pathogenesis and progression of parathyroid, breast, gastric, colorectal, and lung cancers. To investigate the roles of parafibromin expression in tumorigenesis, progression, and prognostic evaluation of head and neck squamous cell carcinomas (HNSCCs), we transfected parafibromin-expressing plasmid into HNSCC cell and examined the phenotypes and their relevant molecules. Parafibromin expression was detected on tissue microarray containing squamous epithelium, dysplasia, and carcinoma of head and neck by immunohistochemistry. Parafibromin overexpression was found to suppress growth, migration, and invasion, and induce apoptosis, S arrest, and mesenchymal to epithelial transition (EMT), compared with the mock and control (P < 0.05). Both overexpression of Cyclin E1, Bax, and E-cadherin and hypoexpression of c-myc, Bcl-xL, and slug were detected in B88 transfectants, in comparison to mock and control by real-time PCR. Parafibromin expression was weaker in primary cancers than those in normal squamous tissue and dysplasia (P < 0.05), but stronger than the metastatic cancers in lymph node (P < 0.05). Parafibromin expression was negatively correlated with lymph node metastasis, tumor-node-metastasis (TNM) staging, but positively with human papillomavirus (HPV) positivity (P < 0.05). The HNSCCs in tongue showed more parafibromin expression than those in larynx (P < 0.05). There was stronger parafibromin expression in moderately-than poorly-differentiated carcinomas (P < 0.05). The significantly positive correlation was observed between parafibromin expression and relapse-free survival rate by Kaplan-Meier curves (P < 0.05). Cox’s proportional hazard model indicated that distant metastasis and parafibromin expression were independent prognostic factors for overall and relapse-free survival of HNSCC, respectively (P < 0.05). These findings suggest that downregulated expression of parafibromin protein plays an important role in the pathogenesis, differentiation, and metastasis of HNSCCs possibly by inducing apoptosis, suppressing proliferation, cell cycle progression, migration, invasion, and EMT. Parafibromin expression is an independent factor for relapse-free survival of HNSCCs.