Expression of Fas/APO‐1 and Apoptosis of Keratinocytes in Human Cholesteatoma

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Abstract
The Fas/APO-1 is a cell surface receptor protein known to trigger apoptosis when conjugated with Fas ligand or specific agonistic antibodies. The present study investigated the expression of Fas/APO-1 and apoptotic cell death in both normal and cholesteatoma epithelia. Ten cholesteatomas and retroauricular skins were taken during middle ear operations in the Ajou University Hospital for this study. In situ terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end-labeling (TUNEL) staining and agarose gel electrophoresis of genomic DNA were used for detection of apoptosis. The expression patterns of Fas/APO-1 protein were confirmed by immunoblot and immunohistochemical analysis. In situ TUNEL staining revealed many positively stained nuclei in 9 of 10 suprabasal layers of cholesteatoma epithelium, whereas few positively stained cells were found on the granular layer of retroauricular skins. Typical "ladder pattern" was seen on the gel electrophoresis of the genomic DNA of cholesteatoma. Immunoblot analysis and immunohistochemical studies revealed that Fas/APO-1 protein was expressed in 8 of 10 cholesteatoma epithelia, whereas retroauricular skin showed negative reaction. These results show the upregulated expression of Fas/APO-1 and increased apoptotic cell death in cholesteatoma epithelium. Because Fas/APO-1 is known as an apoptosis-triggering protein, it is suggested that the accumulation of keratin debris is due to increased apoptotic cell death related to Fas/APO-1 protein.