Overexpression of FoxM1 in Sinonasal Inverted Papilloma and Associated Squamous Cell Carcinoma.

Abstract

BackgroundSinonasal inverted papilloma (IP) is a rare tumor of nasal cavity and paranasal sinuses. Its etiology and factors associated with tumor progression remains unclear. Forkhead Box M1 (FoxM1) has also been suggested to serve as an oncogene due to its pivotal roles in cell proliferation and cell cycle regulation. The aim of this study was to characterize the expression pattern of FoxM1 in IP and IP with associated squamous cell carcinoma (IPwSCC).MethodsThe study included 8 subjects with IPwSCC, 17 subjects with sinonasal IP, and 8 normal uncinate tissue (UT) mucosa. Real-time polymerase chain reaction (PCR) and immunohistochemistry were used to assess the expression and distribution of FoxM1, polo-like kinase 1 (PLK1), cyclin B1, and cyclin D1 in IP tissues and normal control. The expression of FoxM1, PLK1, cyclin B1, and cyclin D1 in IPwSCC was evaluated using immunohistochemistry.ResultsThe messenger RNA (mRNA) expression of FoxM1, PLK1, cyclin B1, and cyclin D1 was significantly upregulated in IP tissues versus normal UT by real-time PCR (all P values < .05). Using immunohistochemistry, the expression of FoxM1 was observed in the tumor cells of sinonasal IP and IPwSCC, but scarce positive cells in normal UT mucosa. The percentage of positive FoxM1-staining cells was statistically higher in IPwSCC than IP and normal UT mucosa (both P < .05). Both mRNA and protein expression of FoxM1 in IP with or without associated squamous cell carcinoma was correlated with tumor histological grades (both P < .05).ConclusionFoxM1, a proliferation specific transcription factor, was overexpressed in sinonasal IP and IPwSCC. FoxM1 might be a key molecule associated with growth of IP and malignant transformation of IP into IPwSCC.