Expression of cell cycle regulatory proteins and analysis of apoptosis in normal nasal mucosa and in nasal polyps

Background: The etiopathogenesis of nasal polyps still is to be clarified. Although hyperplasia is a typical feature of these pathological processes, little attention has been paid to specific aspects of cellular growth in polyps. We have evaluated the expression and localization of some of the regulatory proteins that direct the cell through the specific sequence of events culminating in mitosis or apoptosis in nasal polyps. Methods: Twenty samples of nasal polyps and 20 samples of normal nasal mucosa have been analyzed for apoptotic index by detecting the DNA 3\u2032 OH ends deriving from DNA fragmentation. Moreover, they have been evaluated by immunohistochemical staining for expression of Ki-67, cyclins A and B1, p53, p21, p27, murine double minute clone 2, and Bcl-2. Results: We have identified a greater proportion of proliferating cells in the lining epithelial cells of the polyps when compared with the normal mucosa as stained with anti-Ki-67 antibodies. An overexpression of p53, MDM2, and Bcl-2 and an increased apoptosis were observed in nasal polyps compared with the normal mucosa, whereas no variation of p27 expression was observed. The p21 and eyclins A and B1 were rarely expressed in both pathological and normal tissue. Conclusion: The p53-based control system of cell cycle progression appears to be altered in nasal polyps, potentially leading to an abrogation of the DNA damage checkpoint. Evaluation of the expression of the regulatory proteins that direct the cells throughout their cycle in nasal polyps may allow a better understanding of the biological behavior and clinical outcome of these benign pathological entities