Tanaka Y, Kojima H, Miyazaki H, Koga T, Moriyama H
Department of Otorhinolaryngology, The Jikei University School of Medicine, Tokyo, Japan.
Laryngoscope. 1999 Jul;109(7 Pt 1):1102-7. doi: 10.1097/00005537-199907000-00017.
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.
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.
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.
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.
可以推测细胞周期必定参与中耳胆脂瘤上皮细胞的增殖过程。因此，开展了一项对比研究，比较细胞周期蛋白依赖性激酶2（cdk2）和细胞周期蛋白依赖性激酶4（cdk4）（已知参与细胞周期的物质）在胆脂瘤上皮和外耳道骨部正常上皮中的表达水平。此外，有报道称上皮细胞中细胞因子的表达会因上皮下炎症而加速。这表明受旁分泌调节的上皮与上皮下之间的相互作用与上皮增殖密切相关。因此，研究聚焦于上皮下发现的细胞因子白细胞介素-1α（IL-1α）和角质形成细胞生长因子（KGF），并开展实验以阐明它们对已知参与细胞周期的物质表达的影响。
采用免疫组织化学技术研究cdk2和cdk4在胆脂瘤上皮和外耳道上皮中的表达。此外，将培养的人角质形成细胞在含有浓度为0、20和100 ng/mL的IL-1α或KGF的培养基中培养，通过蛋白质印迹分析研究并比较cdk2和cdk4表达的差异。
在胆脂瘤上皮标本中，观察到cdk-2和cdk4在基底层、副基底层以及上层（棘层和颗粒层）均有表达。与正常外耳道上皮中的表达相比，它们的表达有增加趋势，且在显示严重炎症的上皮下部位这种趋势更为明显。此外，将培养的人角质形成细胞暴露于IL-1α或KGF会导致cdk2和cdk4的表达加速，添加KGF时尤其显著。
可以推测，在胆脂瘤中，炎症部位上皮下的炎症细胞使IL-1α和KGF的表达加速，导致上皮细胞中cdk2和cdk4上调并引起细胞增殖。得出的结论是，这至少是胆脂瘤上皮增殖机制中涉及的一系列事件之一。
