Hyperproliferation-associated keratin expression in human middle ear cholesteatoma.

Cholesteatoma is characterized by the presence of a squamous epithelium invading the middle ear altering its growth properties. This epithelium is believed to have hyperproliferative properties. Keratin 16 is accepted as a molecular marker for hyperproliferative epithelia. Two monoclonal antibodies K8.12 (directed against keratin 13) and KS.1A3 (directed against keratin 13 and 16) were used in an alkaline phosphatase anti-alkaline-phosphatase (APAAP)-technique to compare the expression of both keratin 13 and keratin 16 in normal human skin and aural cholesteatoma. Furthermore, the cytokeratin expression was compared to that of normal skin and palatine tonsil using one-dimensional gel electrophoresis. For both monoclonal antibodies, normal ear skin was stained only in the basal layer. In contrast, in the cholesteatoma samples the immunostaining of the antibody KS-1A3 was done not only in the basal cell layer but also in the suprabasal cells of the stratum spinosum and stratum granulosum. Using gel-electrophoresis, the presence of cytokeratin 16 was demonstrated in the cholesteatoma samples only. These results support the hyperproliferative character of cholesteatoma epithelium.