EGFR expression in acquired middle ear cholesteatoma in children and adults

Osteopontin-driven partial epithelial-mesenchymal transition governs the development of middle ear cholesteatoma

Cholesteatoma is a common disease of the middle ear. Currently, surgical removal is the only treatment option and patients face a high risk of relapse. The molecular basis of cholesteatoma remains largely unknown. Here, we show that Osteopontin (OPN), a predominantly secreted protein, plays a crucial role in the development of middle ear cholesteatoma. Global transcriptome analysis revealed the loss of epithelial features and an enhanced immune response in human cholesteatoma tissues. Quantitative RT-PCR and immunohistochemical staining of middle ear cholesteatoma validated the reduced expression of epithelial markers, as well as the elevated expression of mesenchymal markers including Vimentin and Fibronectin, but not N-Cadherin, α-smooth muscle actin (α-SMA) or ferroptosis suppressor protein 1 (FSP1), indicating a partial epithelial-mesenchymal transition (EMT) state. Besides, the expression of OPN was significantly elevated in human cholesteatoma tissues. Treatment with OPN promoted cell proliferation, survival and migration and led to a partial EMT in immortalized human keratinocyte cells. Importantly, blockade of OPN signaling could remarkably improve the cholesteatoma-like symptoms in SD rats. Our mechanistic study demonstrated that the AKT-zinc finger E-box binding homeobox 2 (ZEB2) axis mediated the effects of OPN. Overall, these findings suggest that targeting the OPN signaling represents a promising strategy for the treatment of middle ear cholesteatoma.

Evaluation of significant gene expression changes in congenital and acquired cholesteatoma

Etiopathogenesis of acquired and congenital cholesteatoma is still unclear. The clinical behavior of adult acquired, pediatric acquired and congenital cholesteatomas show differences. The scope of the this study was to detect the matrix metalloproteinase (MMP), tissue inhibitors of metalloproteinase (TIMP) and epidermal growth factor receptor (EGFR) gene expression changes in cholesteatoma perimatrix and to compare these changes among congenital cholesteatoma, adult acquired cholesteatoma and pediatric acquired cholesteatoma. A total of 16 genes including MMPs, TIMPs and EGFR were analyzed in the samples of 32 cholesteatoma tissues. Real-time PCR was used for detection of the gene expression levels. Data analyses were achieved by ΔΔCT method (Light Cycler 480 Quantification Software) and Statistical Package for Social Sciences (SPSS) version 22.0. The expression levels of MMP-2, -9, -10, -11, -13, -14, -15, -16 and EGFR genes were significantly higher in acquired cholesteatoma than healthy tissue (p < 0.05). There was a statistically significant decrease (3.34 times more) in the mean TIMP-2 gene expression level in acquired cholesteatoma compared to healthy tissue (p < 0.05). There was a significant increase in the mean expression level of MMP-7 gene and a decrease in the mean expression level of TIMP-1 gene (3.12 times more) in congenital cholesteatoma compared to healthy tissue (p < 0.05). This study indicates that increased expression levels of some particular MMP genes and EGFR gene and decreased expression levels of TIMP genes may play an important role in the development of cholesteatoma. Further, MMP-9, MMP-13 and MMP-14 genes may have a remarkable role in the development of more aggressive cholesteatoma forms. The authors concluded that overexpression of MMP-9, MMP-13 and MMP-14 may cause stronger inflammation associated with cholesteatoma.

MicroRNA-21 promotes the proliferation and invasion of cholesteatoma keratinocytes

CONCLUSIONS

The present study revealed that miR-21 promotes the proliferation and invasion of cholesteatoma keratinocytes. These results provide a partial explanation for the more aggressive clinical behavior observed in cholesteatoma.

OBJECTIVE

This study aims to investigate the post-transcriptional regulatory effects that control proliferation, apoptosis, and invasion in cholesteatoma keratinocytes. In particular, the potential role of miR-21 was focused on in this study.

METHODS

Thirty cholesteatoma tissues were processed for RNA and cell culture. Cholesteatoma keratinocytes were transfected with miR-21 mimics, miR-21 inhibitors, or negative control miRNAs; and growth curves were drawn. RT-PCR was used to assess the expression levels of miR-21. EdU incorporation assay and TUNEL staining were used to assess the proliferation and apoptosis of cholesteatoma keratinocytes, respectively. The invasive abilities of cholesteatoma keratinocytes were examined using 6-well Transwell plates.

RESULTS

MiRNA-21 was upregulated when cholesteatoma keratinocytes were transfected with miR-21 mimics. Furthermore, the number of proliferative EdU + cells increased in cholesteatoma keratinocytes transfected with miR-21 mimics; and the number of TUNEL-positive cells also increased in cells transfected with miR-21 mimics. In addition, the number of migrated cells transfected with miR-21 mimics was higher, compared with migrated cells transfected miR-21 inhibitors or control miRNA.

MicroRNA let-7a suppresses the growth and invasion of cholesteatoma keratinocytes

Cholesteatomas are benign epidermally‑derived lesions of the temporal bone that are caused by migration of hyperproliferative keratinocytes into the middle ear and mastoid cavity. The molecular mechanisms that regulate the pathogenesis of cholesteatomas are currently not fully understood. The present study demonstrated the antigrowth and anti‑invasive effects of let‑7a microRNA (miRNA) on cholesteatoma keratinocytes. Let‑7a inhibited the growth of cholesteatoma keratinocytes through two different mechanisms: Restriction of the proliferation of keratinocytes by promoting cell cycle arrest in the G0/G1 phase, and the induction of apoptosis of the cells. In addition to its role in the inhibition of cell growth, let‑7a suppressed the migration and invasion of cholesteatoma keratinocytes. A mechanistic study showed that let‑7a downregulated the expression of miR‑21. Considering the function of miR‑21 in the regulation of proliferation and apoptosis, let‑7a may control cell proliferation and apoptosis by regulating miR‑21, and its targets, in cholesteatoma keratinocytes. In conclusion, the present study showed that let‑7a downregulates the expression of miR‑21, resulting in the suppression of proliferation and induction of apoptosis. The results of the present study reveal the crucial role of let‑7a miRNA in the inhibition of growth and invasion of cholesteatoma keratinocytes.

The role of EGFR/PI3K/Akt/cyclinD1 signaling pathway in acquired middle ear cholesteatoma

Cholesteatoma is a benign keratinizing and hyper proliferative squamous epithelial lesion of the temporal bone. Epidermal growth factor (EGF) is one of the most important cytokines which has been shown to play a critical role in cholesteatoma. In this investigation, we studied the effects of EGF on the proliferation of keratinocytes and EGF-mediated signaling pathways underlying the pathogenesis of cholesteatoma. We examined the expressions of phosphorylated EGF receptor (p-EGFR), phosphorylated Akt (p-Akt), cyclinD1, and proliferating cell nuclear antigen (PCNA) in 40 cholesteatoma samples and 20 samples of normal external auditory canal (EAC) epithelium by immunohistochemical method. Furthermore, in vitro studies were performed to investigate EGF-induced downstream signaling pathways in primary external auditory canal keratinocytes (EACKs). The expressions of p-EGFR, p-Akt, cyclinD1, and PCNA in cholesteatoma epithelium were significantly increased when compared with those of control subjects. We also demonstrated that EGF led to the activation of the EGFR/PI3K/Akt/cyclinD1 signaling pathway, which played a critical role in EGF-induced cell proliferation and cell cycle progression of EACKs. Both EGFR inhibitor AG1478 and PI3K inhibitor wortmannin inhibited the EGF-induced EGFR/PI3K/Akt/cyclinD1 signaling pathway concomitantly with inhibition of cell proliferation and cell cycle progression of EACKs. Taken together, our data suggest that the EGFR/PI3K/Akt/cyclinD1 signaling pathway is active in cholesteatoma and may play a crucial role in cholesteatoma epithelial hyper-proliferation. This study will facilitate the development of potential therapeutic targets for intratympanic drug therapy for cholesteatoma.

Acquired cholesteatoma: summary of the cascade of molecular events

BACKGROUND

Cholesteatoma is considered a benign, gradually expanding and destructive epithelial lesion of the temporal bone. The pathogenesis of different classifications of cholesteatoma is marked by similar underlying cellular and molecular processes. Stepwise explanations of the histopathogenesis have been described previously. The current paper focuses on expounding the molecular events of cholesteatoma.

METHOD AND RESULTS

Cholesteatoma pathogenesis encompasses a complex network of signalling pathways during: epidermal hyperplasia, perimatrix-matrix interactions and mucosal disease. This paper presents a review of the molecular events driven by inflammatory mediators and enzymes during: cholesteatoma growth (cell proliferation and apoptosis); maintenance and deterioration (angiogenesis and hypoxia, oxidative stress and toxicity); and complications (bone erosion and hearing loss). The cascade of molecular events applicable to atelectasis and cholesteatoma that coexist with chronic otitis media and bone erosion as sequelae is summarised.

CONCLUSION

The role of lipids in this disease is relatively unexplored, but there is evidence in support of fatty acid role-players that needs confirmation. Future directions in lipid research to delineate molecular mechanisms are proposed.