Downregulation of MiR-203a Disinhibits Bmi1 and Promotes Growth and Proliferation of Keratinocytes in Cholesteatoma

Background: Keratinocytes are the predominant cell type in a cholesteatoma, and microRNA (miR)-203a has been shown to be essential for the growth and differentiation of keratinocytes. The regulatory mechanisms of miR-203a and Bmi1-the predicted target of miR-203a that is associated with cholesteatoma-have not been clarified. Methods: Real-time PCR and western blot were carried out for the detection of miRNAs, mRNAs, and proteins, including miR-203a, Bmi1, and phosphorylated (p-)Akt. Immunohistochemical staining was applied to observe the expression and distribution of Bmi1 and of p-Akt in cholesteatoma and in control retroauricular skin. The dual luciferase reporter assay was used to analyze the relationship between miR-203a and Bmi1. Ectopic miR-203a and Bmi1 were transfected into an immortalized line of human keratinocytes (HaCaT cells), and the roles of these molecules in cell proliferation, apoptosis, and migration were explored. Results: Cholesteatoma tissues were characterized by downregulation of miR-203a and concomitant upregulation of Bmi1. Results of the dual-luciferase reporter assay indicated that Bmi1 was a direct target gene of miR-203a. Silencing of miR-203a increased Bmi1 expression; promoted proliferation, colony formation, and migration of HaCaT cells; and inhibited apoptosis. Moreover, p-Akt was significantly increased in cholesteatoma tissues and was positively correlated with Bmi1. Suppression of Bmi1 reduced p-Akt expression in HaCaT cells; subsequent inhibition of miR-203a reversed this phenomenon. Conclusions: Our results reveal that miR-203a may regulate cholesteatoma growth and proliferation by targeting Bmi1. These findings provide insight for the development of novel nonsurgical options for cholesteatoma.