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  • Title: Roles of cytokines and cell cycle regulating substances in proliferation of cholesteatoma epithelium.
    Author: Tanaka Y, Kojima H, Miyazaki H, Koga T, Moriyama H.
    Journal: Laryngoscope; 1999 Jul; 109(7 Pt 1):1102-7. PubMed ID: 10401849.
    Abstract:
    OBJECTIVES: It can be surmised that the cell cycle must be involved in cell proliferation of the epithelium of middle ear cholesteatoma. Thus a comparative study was conducted of the levels of expression of cyclin-dependent kinase 2 (cdk2) and cyclin-dependent kinase 4 (cdk4)-substances known to be involved in the cell cycle-in cholesteatoma epithelium and the normal epithelium of the bony region of the external ear canal. In addition, it has been reported that the expression of cytokines in the epithelium is accelerated in response to subepithelial inflammation. This suggests that an interaction between the epithelium and subepithelium, which is subject to paracrine regulation, is deeply involved in epithelial proliferation. Accordingly, attention was focused on interleukin-1alpha (IL-1alpha) and keratinocyte growth factor (KGF), cytokines which are found in the subepithelium, and experiments were conducted to elucidate their effects on the expression of the substances known to be involved in the cell cycle. METHODS: The expressions of cdk2 and cdk4 in the cholesteatoma epithelium and external ear canal epithelium were investigated by an immunohistochemical technique. In addition, cultured human keratinocytes were grown in medium containing IL-1alpha or KGF at concentrations of 0, 20, and 100 ng/mL, and the differences in the expression of cdk2 and cdk4 were investigated and compared by Western blot analysis. RESULTS: In the cholesteatoma epithelium specimens, cdk2 and cdk4 were observed to be expressed in the basal and parabasal layers and in the upper layer (prickle layer and granular layer). Their expression tended to be increased compared with their expression in the normal external ear canal epithelium, and this tendency was marked in subepithelial sites showing severe inflammation. In addition, exposure of cultured human keratinocytes to IL-la or KGF resulted in accelerated expression of both cdk2 and cdk4, and this was especially striking in the case of addition of KGF. CONCLUSION: It can be surmised that, in cholesteatoma, accelerated expression of IL-1alpha and KGF by inflammatory cells at subepithelial sites of inflammation leads to upregulation of cdk2 and cdk4 in epithelial cells and to cell proliferation. It was concluded that this is at least one sequence of events involved in the mechanism causing epithelial proliferation in cholesteatoma.
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