Increased Amphiregulin Expression as a Biomarker of Cholesteatoma Activity

Objectives/Hypothesis: The purpose of this study was to evaluate human surgical specimens for cholesteatoma-associated changes in amphiregulin expression and determine potential relations to clinical disease variables. Amphiregulin, an epidermal growth factor receptor ligand, has functions in normal epithelial proliferation and aberrant neoplastic cell growth and is proinflammatory (e.g., rheumatoid arthritis, fibrosis) and active in hyperproliferative cutaneous conditions including psoriasis and wound healing. These known amphiregulin activities and the characteristic epithelial expansion and bone erosion of cholesteatoma pathophysiology prompted testing of the hypothesis that amphiregulin expression levels are altered in cholesteatoma and correlate to the disease state. Study Design: Prospective experimental study, cross-sectional analysis. Methods: Relative changes in amphiregulin gene expression were quantitated by real-time reverse-transcription polymerase chain reaction analyses of cholesteatoma epithelium compared to uninvolved control tissues from patients' postauricular and external auditory canal regions. Western immunoblot assays were performed for qualitative evaluation of amphiregulin protein expression. The t test and Fisher exact test were used for analysis. Results: A statistically significant increase in amphiregulin gene expression was associated with cholesteatoma specimens compared to uninvolved postauricular skin (PAS) and external auditory canal (EAC) skin, P = .004 and P = .002, respectively. From comparisons of 60 sets of skin pairs, the mean ratio of amphiregulin RNA expression for cholesteatoma/PAS is 4.94 (standard error of the mean [SEM] = 1.53, n = 30) and for cholesteatoma/EAC is 7.70 (SEM = 1.57, n = 30). Conclusions: Amphiregulin is overexpressed in epithelial tissues of human cholesteatoma. Significant relationships were identified between increased amphiregulin expression levels and the extent of cholesteatoma migration and bone erosion. Our study results indicate amphiregulin is a potential biomarker of early cholesteatoma disease processes.