Characteristics of nasal inverted papilloma and its malignant transformation: a study of cell proliferation and programmed cell death

BACKGROUND: In nasal inverted papilloma (IP) and its malignant transformation process, abnormal cell growth has been regarded as a altered proliferation of the epithelial cells, while the role of programmed cell death in this process remains to be determined. METHODS: An apoptotic index was calculated, and the proliferation ability by using Ki67 as a marker was evaluated in the study subjects, which consisted of 15 cases of nasal chronic sinusitis, 23 cases of nasal IP, 9 cases of nasal IP with dysplasia, 8 cases of nasal IP with squamous cell carcinoma (SCC), and 21 cases of primary SCC. In addition, expressions of apoptosis-related molecules p53, Bcl-2, Bax, and Fas were investigated also. RESULTS: The result showed that the Ki67 index increased in IP and IP with dysplasia. The Ki67 value was further enhanced in SCC within IP and primary SCC. The apoptotic index was low in IP with dysplasia, IP with SCC, and primary SCC. Concerning the expression of apoptosis-related proteins, p53 protein accumulated in IP with dysplasia, IP with SCC, and primary SCC. The p53 overexpression was directly correlated with the Ki67 index in IP and primary SCC diseases. No remarkable differences were found regarding expression of Bcl-2 and Fas productions among these diseases, and Bax protein was decreased only in primary SCC. CONCLUSION: We concluded that inhibition of apoptosis could be an early sign of IP undergoing malignant transformation. A high proliferative rate was a characteristic of IP-associated malignant diseases.