Up-regulation of neutrophil gelatinase-associated lipocalin in cholesteatoma

Conclusion. Neutrophil gelatinase-associated lipocalin (NGAL) and Ki-67 expression were up-regulated in cholesteatoma and the expression pattern of NGAL in the epithelial layer was inversely related to the expression of Ki-67. Therefore, NGAL may be related to dysregulated differentiation in the keratinocytes during the development of a cholesteatoma. Objectives. We investigated the differential expression and localization of NGAL in middle ear cholesteatoma and compared the results to normal external auditory canal (EAC) skin. We also compared the expression and localization of NGAL with the expression and localization of Ki-67 in middle ear cholesteatoma. Subjects and methods. Tissue samples from middle ear cholesteatomas and normal EAC skin were obtained from 20 patients undergoing middle ear surgery. NGAL mRNA expression was determined by the reverse transcriptase-polymerase chain reaction (RT-PCR). The expression of NGAL protein was analyzed by Western blot. NGAL and Ki-67 were localized by immunohistochemical staining. Results. A significantly greater expression of the NGAL mRNA was observed in cholesteatoma epithelium than in normal EAC skin (p < 0.05). NGAL was detected in the granular layer of cholesteatoma. However, NGAL was scarcely expressed in normal EAC skin. Ki-67 was detected predominantly in the basal and parabasal layers of cholesteatoma epithelium.