Down-regulation of EMP1 is associated with epithelial metaplasia in nasal inverted papilloma

Epithelial membrane protein 1 (EMP1) is found to regulate epithelial cell proliferation and differentiation, and its down-regulation is reported in various squamous cell carcinomas. The aim of this study was to investigate if EMP1 plays an important role in the pathogenesis of nasal inverted papilloma (IP).Papilloma tissues were obtained from 40 IP patients. Biopsies of inferior turbinates mucosa from 20 healthy subjects were used as controls. Immunohistochemistry and quantitative PCR were performed to determine the expression levels of EMP1 in tissues from IP patients and healthy controls. Moderate epithelial metaplasia (17/35, 46%) showing irregular stratification with increased presence of transitional/squamous cells, was the most common epithelial alteration among the IP tissues. EMP1 staining was observed in all layers of the epithelial cells in healthy controls; whilst it was found only in the basal layer and ciliated cells (in mild metaplasia) in IP epithelium. Both EMP1 protein and mRNA levels were significantly decreased (3.0-fold and 2.6-fold, respectively), compared to the controls. Moreover, EMP1 expression level was significantly inversely-correlated with the severity of epithelial metaplasia in IPs. The down-regulation of EMP1 expression is associated with severe epithelial metaplasia in IP epithelium and thus, EMP1 could be used as a biomarker for aberrant epithelial remodeling in IP epithelium.