Expression and Localization of mRNA for Epidermal Growth Factor and Epidermal Growth Factor Receptor in Human Cholesteatoma

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Abstract
The roles of epidermal growth factor (EGF) and epidermal growth factor receptor (EGF-R) in the proliferation and progression of the epithelium of middle ear cholesteatoma were studied. An attempt was made to elucidate the site and degree of localization of the EGF mRNA and EGF-R mRNA in the epithelium of the cholesteatoma by means of the non-radioactive in situ hybridization method. Ten cholesteatoma specimens excised during operations and six normal skin specimens (control) collected from the external ear canal were used in this study. The signal of the EGF mRNA was slightly expressed in part of the basal cells in only one of the six control specimens, while the signal was strongly expressed along the basal cells of the cholesteatoma epithelium in five of the ten specimens. The signal of the EGF-R mRNA was observed along the basal cell layer in five of the six control specimens, while the signal was strongly expressed in all layers of the cholesteatoma epithelium in all ten specimens. The expression was especially marked in the basal cell layer. These findings suggest the possibilities that abnormal expression of the EGF-R mRNA in nearly entire epithelial layers of cholesteatoma is due to overexpression of EGF-R gene, and that there is a mechanism of epithelial basal cell proliferation through an autocrine regulatory system via EGF and EGF-R.