Abstract: Objective    To investigate whether epithelial membrane protein 1 (EMP1) plays an important role in the epithelial remodeling of sinonasal inverted papilloma (SNIP).  Methods    Papilloma tissues were obtained from 25 SNIP patients. Biopsies of inferior turbinates mucosa from 15 healthy subjects were used as controls. Immunohistochemistry and quantitative PCR were performed to compare the expression levels of EMP1 between tissues from SNIP patients and healthy controls.  Results    A moderate epithelial metaplasia (12/25, 48%) showing irregular stratification with the increase of transitional/squamous cells was the most common epithelial alteration occurred in the SNIP tissues. Both EMP1 protein and mRNA levels significantly decreased in SNIP tissues compared with the controls. Moreover, EMP1 expression level was significantly negatively correlated with the severity level of epithelial metaplasia in SNIPs.  Conclusion    Down-regulation of EMP1 is associated with severe level of epithelial metaplasia in SNIP epithelium, and it could be a biomarker for evaluating aberrant epithelial remodeling in SNIP epithelium.

Key words: Nasal epithelium, Epithelial membrane protein 1, Sinonasal inverted papilloma, Epithelial metaplasia