Expressions of c-jun and p53 proteins in human middle ear cholesteatoma: relationship to keratinocyte proliferation, differentiation, and programmed cell death

The Science of Cholesteatoma

Cholesteatoma is a potential end-stage outcome of chronic ear infections that can result in the destruction of temporal bone structures with potential resultant hearing loss, vertigo, and intracranial infectious complications. There is currently no treatment apart from surgery for this condition, and despite years of study, the histopathogenesis of this disease remains poorly understood. This review is intended to summarize our accumulated knowledge of the mechanisms of cholesteatoma development and the underlying molecular biology. Attention will be directed particularly to recent developments, covering many potential pharmacologic targets that could be used to treat this disease in the future.

Review of potential medical treatments for middle ear cholesteatoma

Middle ear cholesteatoma (MEC), is a destructive, and locally invasive lesion in the middle ear driven by inflammation with an annual incidence of 10 per 100,000. Surgical extraction/excision remains the only treatment strategy available and recurrence is high (up to 40%), therefore developing the first pharmaceutical treatments for MEC is desperately required. This review was targeted at connecting the dysregulated inflammatory network of MEC to pathogenesis and identification of pharmaceutical targets. We summarized the numerous basic research endeavors undertaken over the last 30+ years to identify the key targets in the dysregulated inflammatory pathways and judged the level of evidence for a given target if it was generated by in vitro, in vivo or clinical experiments. MEC pathogenesis was found to be connected to cytokines characteristic for Th1, Th17 and M1 cells. In addition, we found that the inflammation created damage associated molecular patterns (DAMPs), which further promoted inflammation. Similar positive feedback loops have already been described for other Th1/Th17 driven inflammatory diseases (arthritis, Crohn’s disease or multiple sclerosis). A wide-ranging search for molecular targeted therapies (MTT) led to the discovery of over a hundred clinically approved drugs already applied in precision medicine. Based on exclusion criteria designed to enable fast translation as well as efficacy, we condensed the numerous MTTs down to 13 top drugs. The review should serve as groundwork for the primary goal, which is to provide potential pharmaceutical therapies to MEC patients for the first time in history.

Notch Signaling in Acquired Middle Ear Cholesteatoma

HYPOTHESIS

We hypothesized that an anomalous change of Notch signaling might be involved in the pathophysiology of cholesteatoma.

BACKGROUND

The Notch signaling pathway regulates integrated growth and differentiation control of keratinocytes. Its involvement in cholesteatoma proliferation has not been elucidated.

METHODS

We obtained cholesteatoma and external auditory canal (EAC) skin samples from patients with middle ear cholesteatoma who underwent tympanomastoid surgery. We performed polymerase chain reaction using the RT2 Profiler™ PCR Array Human Notch Signaling Pathway (Qiagen) in the cholesteatoma and EAC skin samples (n = 6 each). This was followed by immunohistochemical staining of Notch1, enhancer of split-1 (HES1), and p53 in 41 and 8 cholesteatoma and EAC skin samples, respectively.

RESULTS

The fold change of Notch1 gene expression was lowest in cholesteatoma, with a statistically significant difference (p = 0.0424). Moreover, the fold change of HES1 expression decreased (p = 0.272). The positive rates of Notch1 and HES1 protein expressions in the cholesteatoma (48.5 ± 32.4% and 44.9 ± 17.8%, respectively) were significantly lower than in the EAC skin (83.4 ± 17.5% and 55.7 ± 7.1%, respectively) (p < 0.001 and p < 0.01). In contrast, the positive rate of p53 expression in the cholesteatoma (8.5 ± 11.4%) was significantly higher than in the EAC skin (0.5 ± 0.7%) (p < 0.001).

CONCLUSION

The decreases in Notch1 and HES1 protein expression might play an important role in the hyperproliferative character of the keratinizing squamous epithelium in cholesteatoma. An increase in p53 might reflect the reaction to cellular hyperproliferation.

Comparative analysis of the expression of E-cadherin, β-catenin, and β1 integrin in congenital and acquired cholesteatoma

E-cadherin, β-catenin, and β1 integrin are important cell adhesion molecules to maintain epithelial structure and function. We investigated the expression of these cell adhesion molecules in cholesteatomas to understand the role of cell-cell and cell-extracellular matrix interaction in cholesteatomas. An immunohistochemical investigation was carried out on 35 cholesteatoma tissue samples (14 congenital, 21 acquired cholesteatomas) and 10 normal retroauricular skin (RAS) tissues which are obtained during middle ear surgery. The expression rate was measured to find out differences between retroauricular skin and cholesteatoma, as well as between congenital and acquired cholesteatoma. E-cadherin expression rate was significantly lower in the cholesteatoma (spinous layer 88.7 ± 17.9 %, granular layer 54.6 ± 22.6 %) than in the RAS (100 %, 74.4 ± 7.4 %) and in the acquired (83.3 ± 19.4 %, 48.1 ± 22.9 %) than in the congenital (96.7 ± 12.0 %, 64.4 ± 18.8 %). β-catenin expression rate was significantly lower in the cholesteatoma (spinous layer 84.1 ± 17.2 %, granular layer 28.7 ± 30.8 %) than in the RAS (100 %, 75.9 ± 6.1 %) and in the acquired (78.1 ± 17.0 %, 17.1 ± 22.3 %) than in the congenital (93.2 ± 13.5 %, 46.1 ± 34.2 %). The expression pattern of β-catenin is similar to that of E-cadherin. In β1 integrin, there was no significant difference of the expression rate between RAS and cholesteatoma, as well as between congenital and acquired cholesteatoma. In conclusion, the expression of E-cadherin and β-catenin is reduced in cholesteatoma, and the reduction is more pronounced in acquired cholesteatoma than in congenital cholesteatoma. Acquired cholesteatomas showed more aggressive characteristics than congenital cholesteatomas in terms of cell-cell adhesion.

Updates and knowledge gaps in cholesteatoma research

The existence of acquired cholesteatoma has been recognized for more than three centuries; however, the nature of the disorder has yet to be determined. Without timely detection and intervention, cholesteatomas can become dangerously large and invade intratemporal structures, resulting in numerous intra- and extracranial complications. Due to its aggressive growth, invasive nature, and the potentially fatal consequences of intracranial complications, acquired cholesteatoma remains a cause of morbidity and death for those who lack access to advanced medical care. Currently, no viable nonsurgical therapies are available. Developing an effective management strategy for this disorder will require a comprehensive understanding of past progress and recent advances. This paper presents a brief review of background issues related to acquired middle ear cholesteatoma and deals with practical considerations regarding the history and etymology of the disorder. We also consider issues related to the classification, epidemiology, histopathology, clinical presentation, and complications of acquired cholesteatoma and examine current diagnosis and management strategies in detail.

Induction of cytokine production in cholesteatoma keratinocytes by extracellular high-mobility group box chromosomal protein 1 combined with DNA released by apoptotic cholesteatoma keratinocytes

High-mobility group box chromosomal protein 1 (HMGB-1), a nuclear DNA binding protein, was recently rediscovered as a new proinflammatory cytokine. The purpose of this study was to determine HMGB-1 expression in vivo and to identify the effect of extracellular HMGB-1 in inflammatory process associated with bone destruction in cholesteatoma. We investigated the expression and location of HMGB-1 in the cholesteatoma and healthy skin using an immunofluorescence assay. We also detected apoptosis and DNA fragments in the cholesteatoma by TUNEL staining. HMGB-1 concentration in apoptotic supernatants from UV light-treated cells, culture supernatants and its translocation in cholesteatoma keratinocytes stimulated by supernatants from UV light-treated cells were measured by immunoblot analysis and immunofluorescence assay. Cultures of human cholesteatoma keratinocytes were exposed to CpG-DNA, HMGB-1, or CpG-DNA complexed to HMGB-1 for 24 h. Cytokines in the culture supernatant were measured by ELISA. In addition, levels of proinflammatory cytokines released by cholesteatoma keratinocytes stimulated by supernatants from UV light-treated cells with or without anti-HMGB-1 antibodies and supernatants from UV light-treated cells with DNase 1 were measured by enzyme-linked immunosorbent assay. The expression of HMGB-1 in cholesteatoma increased and it translocated both to the cytoplasm and extracellular space. Furthermore, the HMGB-1 concentration in supernatants increased significantly after addition of supernatants from UV light-treated cells. TNF-α and IL-1β can be induced by purified HMGB-1 combined with CpG-DNA in the cholesteatoma keratinocytes. In addition, supernatants of apoptotic cells containing HMGB-1-DNA were effective in inducing TNF-α and IL-1β secretion. This study suggested that persistent expression of extracellular HMGB-1 and DNA fragments in cholesteatoma leads to TNF-α and IL-1β production, causing bone resorption and destruction. Thus, we have implicated that HMGB-1-DNA complexes might act as a key molecule involved in bone resorption associated with cholesteatoma.

Etiopathogenesis of acquired cholesteatoma: prominent theories and recent advances in biomolecular research

OBJECTIVE

To review recent biomolecular advances in etiopathogenesis of acquired cholesteatoma.

DATA SOURCES

MEDLINE via OVID (to March 2014) and PubMed (to March 2014).

REVIEW METHODS

All articles referring to etiopathogenesis of acquired cholesteatoma were identified in the above databases, from which 89 articles were included in this review.

RESULTS

The mechanisms underlying the etiopathogenesis of acquired cholesteatoma remain a subject of competing hypotheses. Four theories dominate the debate, including theories of invagination, immigration, squamous metaplasia, and basal cell hyperplasia. However, no single theory has been able to explain the clinical characteristics of all cholesteatoma types: uncoordinated hyperproliferation, invasion, migration, altered differentiation, aggressiveness, and recidivism. Modern technologies have prompted a number of researchers to seek explanations at the molecular level. First, cholesteatomas could be considered an example of uncontrolled cell growth, capable of altering the balance toward cellular hyperproliferation and enhancing the capacity for invasion and osteolysis. Second, the dysregulation of cell growth control involves internal genomic or epigenetic alterations and external stimuli, which induce excessive host immune response to inflammatory and infectious processes. This comprises several complex and dynamic pathophysiologic changes that involve extracellular and intracellular signal transduction cascades.

CONCLUSIONS

This article summarizes the existing theories and provides conceptual insights into the etiopathogenesis of acquired cholesteatoma, with the aim of stimulating continued efforts to develop a nonsurgical means of treating the disorder.

Large-scale proteomics differentiates cholesteatoma from surrounding tissues and identifies novel proteins related to the pathogenesis

Cholesteatoma is the growth of keratinizing squamous epithelium in the middle ear. It is associated with severe complications and has a poorly understood etiopathogenesis. Here, we present the results from extensive bioinformatics analyses of the first large-scale proteomic investigation of cholesteatoma. The purpose of this study was to take an unbiased approach to identifying alterations in protein expression and in biological processes, in order to explain the characteristic phenotype of this skin-derived tumor. Five different human tissue types (cholesteatoma, neck of cholesteatoma, tympanic membrane, external auditory canal skin, and middle ear mucosa) were analyzed. More than 2,400 unique proteins were identified using nanoLC-MS/MS based proteomics (data deposited to the ProteomeXchange), and 295 proteins were found to be differentially regulated in cholesteatoma. Validation analyses were performed by SRM mass spectrometry. Proteins found to be up- or down-regulated in cholesteatoma were analyzed using Ingenuity Pathway Analysis and clustered into functional groups, for which activation state and associations to disease processes were predicted. Cholesteatoma contained high levels of pro-inflammatory S100 proteins, such as S100A7A and S100A7. Several proteases, such as ELANE, were up-regulated, whereas extracellular matrix proteins, such as COL18A1 and NID2, were under-represented. This may lead to alterations in integrity and differentiation of the tissue (as suggested by the up-regulation of KRT4 in the cholesteatoma). The presented data on the differential protein composition in cholesteatoma corroborate previous studies, highlight novel protein functionalities involved in the pathogenesis, and identify new areas for targeted research that hold therapeutic potential for the disease.

Differential gene expression in cholesteatoma by DNA chip analysis

OBJECTIVES/HYPOTHESIS

In contrast to normal epithelium, the desquamating stratified squamous epithelium of temporal bone cholesteatoma characteristically exhibits sustained hyperproliferative growth and a capacity for bone erosion. We conducted genome-wide microarray analyses to determine the molecular nature of cholesteatoma's biological processes and identify disease-associated, altered gene activity. We tested the hypothesis that genes contributing to the pathophysiology of cholesteatoma are differentially expressed compared to control tissue.

STUDY DESIGN

Prospective experimental analysis.

METHODS

Using new, enhanced microarray platforms and well-annotated human transcriptome probes, we measured global gene expression levels in surgical specimens of cholesteatoma and in the corresponding normal postauricular skin in four patients. Genes of interest were verified by quantitative real time reverse transcriptase polymerase chain reaction analyses using cholesteatoma and postauricular sample pairs (n = 13). External auditory canal skin from six additional patients was also evaluated as a normal control. Immunohistochemistry detected protein expression in tissue sections and the cells involved.

RESULTS

DNA chip analyses identified 282 differentially expressed genes in cholesteatoma compared to control samples. Of these, 104 genes were upregulated and 178 were downregulated. Ontological classifications indicate relationships to cellular processes including receptor binding, cell communication and motion, vitamin metabolism, and cytokine-mediated inflammation. Based on potential involvement in disease pathology, 10 genes were selected and independently verified by quantitative polymerase chain reaction. Immunohistochemical detection of transcobalamin-1 and CCL27 implicates cholesteatoma keratinocytes and dermal endothelial cells as contributors in disease processes.

CONCLUSIONS

We present a comprehensive, human genome-wide survey of disease-associated gene expression that extends the public database and provides new evidence for molecular mechanisms involved in cholesteatoma pathology. Laryngoscope, 123:S1-S21, 2013.

Mast cells positive for cluster of differentiation 117 protein: are they players or conductor in the orchestra of cholesteatoma?

BACKGROUND

The pathogenesis of cholesteatoma remains unclear, despite several theories. Alterations in the density of mast cells positive for cluster of differentiation 117 protein (also known as CD117) can be critical to cholesteatoma formation, due to the effect on keratinocyte growth factor production. This study aimed to investigate the potential role of these mast cells in cholesteatoma pathogenesis.

METHODS

The number and density of mast cells positive for cluster of differentiation 117 protein were immunohistochemically analysed in 52 patients: 22 with chronic otitis media alone (group one), 25 with chronic otitis media with cholesteatoma (group two) and five controls.

RESULTS

The number of these mast cells was much higher in group two (in cholesteatoma matrix tissue) than in group one (in chronic otitis media granulation tissue) or the controls (in normal post-auricular skin). The density of these mast cells was significantly greater in group two than in group one or the controls (p < 0.05). The number and density of these mast cells was much greater in group one than in controls (p < 0.01).

CONCLUSION

Mast cells positive for cluster of differentiation 117 protein could play a role in cholesteatoma formation. Further investigation of the role of these mast cells in cholesteatoma may suggest new ways of addressing this disorder, and may enable the development of targeted treatments.

Expression of EGFR and Microvessel Density in Middle Ear Cholesteatoma

Objectives

Cholesteatoma destructs bony tissue by the interactions between hyperproliferative epithelial cells and subepithelial inflammatory cells. The aim of this study was to evaluate the expression of epidermal growth factor receptor (EGFR) and microvessel density (MVD) in middle ear cholesteatoma tissue in an effort to determine the relationship between expression of EGFR and neovascularization.

Methods

We evaluated the expression of EGFR and MVD by immunohistochemical staining for CD31 and Factor VIII in 32 cholesteatoma tissue samples and 7 normal postauricular skin samples. We also analyzed the correlation between EGFR expression and MVD.

Results

The expression of EGFR was higher in cholesteatoma than in postauricular skin, but the difference was not statistically significant. EGFR was more highly expressed in the suprabasal layer than in the basal layer. Using CD31 and Factor VIII, we analyzed the MVD and found that it was significantly higher in cholesteatoma than in postauricular skin, and significantly correlated with the expression of EGFR.

Conclusion

Our results suggest that overexpression of EGFR and neovascularization are correlated with the growth of cholesteatoma.

Elevated level of tenascin and matrix metalloproteinase 9 correlates with the bone destruction capacity of cholesteatomas

OBJECTIVES

Bone destruction is a key step in the progression of cholesteatomas. Some of the lesions can grow without affecting the surrounding anatomic structures, whereas others can cause severe bone destruction despite their limited size. This study aims to identify factors that could play important role during the invasion of the disease.

METHODS

Cholesteatoma tissue samples were examined immunohistochemically. Tissue samples were arranged on the basis of bone destruction (destructive cholesteatomas [DC] and nondestructive cholesteatomas [NDC]). Double-immunofluorescent labeling was performed to detect simultaneously 1) tenascin (TN) and cytokeratin; 2) matrix metalloproteinase 9 (MMP-9) and TN; 3) TN and Ki-67. An in situ apoptosis detection kit was used to detect apoptotic cells. External auditory canal skin samples were used as control.

RESULTS

1) In DCs, more widespread stromal TN labeling was seen compared with NDCs or external auditory canal skin samples. 2) More enhanced MMP-9 staining was detected in DCs compared with NDCs. 3) The proportion of Ki-67-positive cells in DC samples was significantly higher than in NDCs. 4) The percentage of apoptotic cells was higher in NDC than in DC samples.

CONCLUSION

Our present study demonstrates that levels of TN, MMP-9, and proliferative activity are increased in cholesteatomas. It has also been shown that increased levels of TN, MMP-9-positive cells, and proliferative activity of the lesions, as well as decreased levels of apoptosis, can be linked to more aggressive clinical behavior of cholesteatomas. Our findings also indicate that TN and MMP-9 can be key molecules of bone destruction during cholesteatoma progression.

Chromosomal imbalances are associated with increased proliferation and might contribute to bone destruction in cholesteatoma

OBJECTIVES

Our aim was to evaluate the copy number alterations of chromosomes 3, 7, 8, and 17 in middle ear cholesteatomas and define the association between the rate of cell proliferation and chromosome number changes.

METHODS

Tissues were obtained from 16 patients. Fluorescence in situ hybridization was performed on tumor imprint preparations. Cell proliferation was characterized with Ki-67 monoclonal antibody on cholesteatoma samples and on postauricular skins as control.

RESULTS

Different degrees of aneusomy were found for all chromosomes except for chromosome 3. Chromosome copy number alterations were associated with elevated proliferative rate and related also with the aggressiveness of the lesions.

CONCLUSIONS

Based on our results, we assume that aneusomy of chromosomes 7, 8, and 17 might play an important role during invasion of the adjacent bony structures of cholesteatoma, as well as associate with increased cell proliferation activity, which might lead to the aggressive behavior of the tissue.

Expressions of caspase-14 in human middle ear cholesteatoma

OBJECTIVES

Cholesteatoma is characterized by an excessive proliferation and differentiation of keratinocytes with a progressive accumulation of keratin debris. Caspase-14 is a novel regulator of keratinocyte terminal differentiation. The purpose of this study was to investigate the expression patterns and localizations of caspase- 14 in cholesteatoma and in normal external auditory canal (EAC) epithelium.

METHODS

The expression levels of caspase-14 mRNA were evaluated through real-time polymerase chain reaction (PCR) and Western blotting. Cholesteatoma and normal EAC epithelium were immunostained with a monoclonal antibody to caspase-14. The localizations of immunoreactivity to the caspase-14 antibody were compared between cholesteatoma and normal EAC epithelium through immunohistochemical staining.

RESULTS

As shown by real-time reverse-transcription PCR, the expression level of caspase-14 mRNA in cholesteatoma epithelium was significantly higher than in normal EAC epithelium. Caspase-14 protein was detected in both normal EAC and cholesteatoma, but its expression was shown to be greater in cholesteatoma on Western blot analysis. As shown with immunohistochemical staining, caspase-14 protein was primarily expressed in the granular layer and the upper parts of the spinous layer in cholesteatoma epithelium and in the superficial layer of normal EAC epithelium. The expression of caspase-14 was more intense in cholesteatoma tissues than in normal EAC epithelium.

CONCLUSION

The increased level of caspase-14 expression in cholesteatoma tissues may play a role in terminal differentiation of epithelium and accumulation of keratin debris from external matrix.

Cell cycle inhibitory protein p27 in human middle ear cholesteatoma

AIM

To evaluate the immunohistochemical and molecular presentation of protein p27 in cholesteatoma.

METHODS

42 cholesteatoma samples and 6 external ear canal skin (EECS) specimens were investigated and analyzed taking into consideration congenital, acquired, recurrent cholesteatoma, and EECS.

RESULTS

The expression of p27 was found in 16 (38.1%) out of 42 specimens of cholesteatoma and in 5 (83.3%) out of 6 specimens of EECS. There was a significant difference in p27-positive staining rate between EECS and cholesteatoma epithelium (p < 0.008). The presence of p27 was detected in 10 cases of acquired cholesteatoma, 2 cases of congenital and 3 cases of recurrent cholesteatoma. There was no significant difference between the presence of p27 in cholesteatoma and EECS (p = 0.01).

CONCLUSION

The down-regulation of p27 is a key player in cell cycle control and plays an undefined role in the pathogenesis of all types of cholesteatoma.

Characterization of patterns of expression of protein kinase C-alpha, -delta, -eta, -gamma and -zeta and their correlations to p53, galectin-3, the retinoic acid receptor-beta and the macrophage migration inhibitory factor (MIF) in human cholesteatomas

Cholesteatoma is a benign disease characterized by the presence of an unrestrained growth and the accumulation of keratin in the middle ear cavity. Due to roles in cell proliferation, apoptosis and differentiation members of the protein kinase C (PKC) family could be involved in disease progression. This study focuses on the expression of protein kinase C-alpha, -delta, -eta, -gamma and -zeta in the epithelial tissues of 56 human cholesteatomas and their correlations with those of previously characterized distributions of p53, galectin-3, retinoic acid receptor-beta (RARbeta) and macrophage migration inhibitory factor (MIF). We have previously reported this marker set to be correlated with keratinocyte differentiation in human cholesteatomas. Our present data clearly show that the percentage of PKC-alpha (but not PKC-delta, -gamma, -eta and -zeta)-immunopositive cells in epithelial tissue fro recurrent cholesteatomas was significantly higher than in non-recurrent cases. Correlations between the PKC isoenzymes and the biological markers were non-uniform. PKC-alpha (but not PKC-delta, -gamma, -eta and -zeta) expression in epithelial cholesteatoma cells correlated significantly and positively with the percentages of p53-immunopositive cells. The patterns of PKC-alpha and -delta expression, but not of PKC-gamma, -eta and -zeta, correlated significantly and positively with galectin-3 expression. In addition, the correlation levels between the expression of PKC-alpha and -delta and that of galectin-3 varied depending on the infection and recurrence status. Presence of RARbeta correlated significantly (and positively) with the expression of PKC-gamma and -zeta and also in relation to the infection and recurrence status. MIF correlated presence significantly (and positively) with that of the five PKCs under study, depending on whether the cholesteatomas were non-infected or infected as well as non-recurrent or recurrent. In conclusion, the present study suggests that modifications occurring at the level of keratinocyte differentiation in human cholesteatomas involve distinct effectors, to which the activation of PKC-alpha, -delta, -eta, -gamma and -zeta can be added.

Expression of the gap junction proteins connexin 26 and connexin 43 in human middle ear cholesteatoma

CONCLUSION

The results of this study showed upregulated expression and a change in localization of both connexin 43 (Cx43) and Cx26 in human middle ear cholesteatoma compared to those in normal retroauricular skins (RASs) and ear canal skins (ECSs). This suggests that perturbations of intercellular communication through gap junctions may be associated with the pathology of human cholesteatomas.

OBJECTIVE

Cholesteatomas in the middle ear require intercellular signal exchange through gap junctions as well as intracellular signal pathways for the hyperproliferation and differentiation of epithelial cells. Cx is a gap junction protein involved in intercellular communication. The objective of this study was to analyze the expression and possible roles of Cx43 and Cx26 in human cholesteatoma compared to normal epithelium.

MATERIAL AND METHODS

Ten RASs, 10 ECSs and 10 cholesteatomas were obtained during middle ear operations. Immunohistochemical staining, Western blotting and reverse transcriptase polymerase chain reaction (RT-PCR) were used to detect Cx43 and Cx26. The expression patterns of Cx43 and Cx26 were also compared with that of the proliferation marker Ki67.

RESULTS

In human cholesteatomas, Cx43 was expressed in whole suprabasal layers, except in the basal layer, and Cx26 was usually expressed in the suprabasal and basal layers. However, normal RASs showed weak expression of Cx43 in the upper spinosal and granular layers (with no expression in the basal layers) and restricted localization of Cx26 in the basal layer. The expression of Cx43 and Cx26 in ECSs was weak but showed similar patterns to that of cholesteatoma. RT-PCR and Western blotting showed that the expression of Cx43 and Cx26 was higher in cholesteatoma than in RASs. Epithelial cells expressing Cx43 and Cx26 in cholesteatoma were not exactly identical to Ki67-expressing cells on immunohistochemical staining.

Caspase-3, Caspase-8, and Nuclear Factor-??B Expression in Human Cholesteatoma

BACKGROUND

Cholesteatoma is characterized by the accumulation of keratinizing epithelium resulting from the proliferation and differentiation of epithelium. Researchers are presently unraveling the role that apoptosis plays in the disease seen in cholesteatoma epithelium. Caspases play a key role in apoptosis. Caspase-8, which is activated by the induction of tumor necrosis factor-alpha, leads to activation of caspase-3, which activates apoptotic nucleases. Nuclear factor-kappaB is a transcription factor known to inhibit apoptosis induced by tumor necrosis factor-alpha.

HYPOTHESIS

In this study, we hypothesized that expression of caspase-3, caspase-8, and nuclear factor-kappaB is uniquely connected to the proliferation, differentiation, and programmed cell death of keratinocytes during the growth and development of cholesteatoma.

METHODS

We obtained 41 cholesteatoma specimens for this study. The presence of these proteins in cholesteatoma was examined using immunohistochemistry and a colorimetric assay system. We also examined the patterns of apoptosis by using terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling staining.

RESULTS

Using the immunoperoxidase staining method, caspase-3 was found to be densely localized in the spinous and granular layers of cholesteatoma epithelium; caspase-8 was also found in the granular layer. Nuclear factor-kappaB was localized densely in the perinuclear region of the epithelium. The results obtained with immunoperoxidase staining agreed with those obtained with terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling staining. In addition, the colorimetric assay method was used to measure the activity of caspase-3.

CONCLUSION

These findings suggest that caspase-3 and caspase-8 play important roles in programmed cell death, which results in the accumulation of keratin debris during the growth of cholesteatoma. Nuclear factor-kappaB was found in cholesteatoma epithelium, but the transcription factor appeared to be inactivated.

Up-Regulation of Peroxidase Proliferator-Activated Receptor?? in Cholesteatoma

OBJECTIVE

To evaluate the localization and expression of peroxidase proliferator-activated receptor (PPAR)gamma in cholesteatoma epithelium.

STUDY DESIGN

Experimental study.

METHODS

Reverse-transcription polymerase chain reaction was performed on cholesteatoma tissues from 10 adult patients undergoing tympanomastoid surgery for middle ear cholesteatoma and on 10 samples of normal external auditory canal skin tissue. The expression levels of PPARgamma to glyceraldehyde-3-phosphate dehydrogenase transcripts were semiquantified by densitometry. We also characterized the cellular localization of the PPARgamma protein immunohistochemically. Ki-67 was also localized to compare the proliferative activity of cells in cholesteatoma epithelium and in normal external auditory canal skin.

RESULTS

PPARgamma mRNA and protein were detected in normal external auditory canal skin and in cholesteatoma epithelium. The expression level of PPARgamma mRNA in cholesteatoma was significantly increased compared with that in normal external auditory canal skin. PPARgamma protein was expressed in cells mainly in the granular and prickle cell layers. However, the intensity of its expression was generally decreased in the parabasal layer of the cholesteatoma epithelium. Ki-67 was expressed in the nuclei of cells in the basal and parabasal layers, and a greater number of cells were Ki-67 immunopositive in cholesteatoma epithelium.

CONCLUSION

PPARgamma is up-regulated in the cholesteatoma epithelium compared with normal external auditory canal skin. These results suggest that PPARgamma may play an important role in the pathogenesis of cholesteatoma.

Apoptosis in the pathogenesis of cholesteatoma in adults

The aim of this study was to determine the distribution and apoptotic capacity in the various layers of cholesteatoma epithelium compared to the normal skin. Cholesteatomas were collected during surgical procedures of the ear. Normal skin specimens taken from the retroauricular area served as controls. Apoptosis was detected by using highly specific antibodies against APO2.7 antigen. The Membstain Apoptosis kit Direct based on in situ labeling of nuclear DNA fragmentation (Tolt-mediated dUTP nick and labeling TUNEL staining) was used. The distribution of apoptotic cells in the layer of the cholesteatoma epithelium and the epidermis was determined. The percentage of apoptotic cells was then counted per 100 cells of cholesteatoma epithelium and the normal epidermis in three different areas of each section and expressed in terms of mean +/- SD. An automatic analyzing system was used for counting. In normal epidermis, the apoptotic cells were observed in the granular layer of the epidermis. The percentage of these cells was 28.5 +/- 8.1%. A significantly greater number of apoptotic cells was observed in the suprabasal layers of the cholesteatoma epithelium (47.39 +/- 6.2%). A statistically significant difference was obtained for APO2.7-positive cells in the cholesteatoma epithelium as compared to the skin (P < 0.05) as determined by Student's t-test and the Mann-Whitney U test. Apoptotic activity is mainly observed in the suprabasal layer of cholesteatoma epithelium. It is not seen in the basal layer. Apoptosis plays an important role in the pathogenesis of cholesteatoma. It seems to be part of the differentiation and accumulation of keratin debris within the middle ear and expansion of cholesteatoma.

Algumas considerações sobre colesteatomas adquiridos pediátricos e adultos

Neste artigo, os autores dissertam sobre o tema colesteatoma, desde a primeira vez em que foi utilizada a palavra por Mueller (1838), até informações atuais. Fazem uma abordagem de sua definição, passam pela etiopatogênese e apresentam noções básicas sobre sua biologia. Ainda realizam uma ampla revisão sobre colesteatoma pediátrico, apresentam dados clínicos epidemiológicos e biológicos e mostram um paralelo com o colesteatoma em adultos. Para finalizar, descrevem alguns trabalhos sobre erosão da cadeia ossicular correlacionando-a com dados sobre a perimatriz, colágeno e colagenase.

Some considerations about acquired adult and pediatric cholesteatomas

Authors debate about cholesteatomas, from the first time this word was employed, by Muller, in 1838, until the recent updates. They dissert about its definition, etiology and pathology and present basic concepts about its biology. They also make a wide review about pediatric cholesteatoma, its epidemiology and biology, and compare it with adult cholesteatoma. Finally, they describe some articles about ossicle chain erosion and its correlation with cholesteatoma perimatrix, collagen and collagenase.

Reversibility of experimental cholesteatoma epithelium using Mongolian gerbils

CONCLUSION

The results of this study encourage our belief that some cholesteatomas can be managed using only conservative treatments.

OBJECTIVE

We hypothesized that once cholesteatoma is in a normal environment, its cellular or molecular pathology can revert to those characteristic of normal epidermis. The aim of this study was to determine whether or not common molecular characteristics of cholesteatoma were reversible after removal of inductive factors in experimental cholesteatoma induced in gerbils.

MATERIAL AND METHODS

We induced cholesteatoma using ear canal ligation in Mongolian gerbils. After ligation, the animals in the treated group were managed for 2 weeks. We examined differences between treated and untreated cholesteatomas using terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL) staining and an immunohistochemical technique using the proliferation markers proliferating cell nuclear antigen (PCNA) and cytokeratin (CK).

RESULTS

With PCNA and CK 13/16, the untreated group showed positive staining in the suprabasal and basal cells, but the treated group showed weakly positive staining only in the basal cell layer. With TUNEL staining, there were more positive cells in the untreated than the treated group.

Etiopathogenesis of cholesteatoma

Cholesteatoma is a destructive lesion of the temporal bone that gradually expands and causes complications by erosion of the adjacent bony structures. Bone resorption can result in destruction of the ossicular chain and otic capsule with consecutive hearing loss, vestibular dysfunction, facial paralysis and intracranial complications. Surgery is the only treatment of choice. The etiopathogenesis of cholesteatoma, however, is still controversial. This review was designed to understand the reasons for these disparities and to reduce or eliminate them. Future studies focused on developmental, epidemiological, hormonal and genetic factors as well as on treatment are likely to contribute to further understanding of cholesteatoma pathogenesis.

Differential expression of S100 calcium-binding proteins in epidermoid cysts, branchial cysts, craniopharyngiomas and cholesteatomas

AIMS

To investigate whether epidermoid cysts, branchial cysts, craniopharyngiomas and cholesteatomas express S100 proteins differentially by immunohistochemical assaying the presence of S100A1, S100A2, S100A3, S100A4, S100A5, S100A6 and S100B.

METHODS AND RESULTS

Immunopositivity/negativity was recorded for each S100 protein in a series of 52 cases consisting of 12 epidermoid cysts, 12 branchial cysts, 15 adamantinomatous craniopharyngiomas and 13 acquired cholesteatomas. Except in the case of the craniopharyngiomas, immunoreactivity was assessed independently in the basal membrane and the basal, the internal and the keratin layers. Our data show that in contrast to S100B, which was rarely expressed, S100A1, S100A2, S100A4 and S100A5 were often present in these four types of epithelial lesions. S100A3 and S100A6 and, to a lesser extent, S100A5 were the most differentially expressed proteins across the different histopathological groups analysed. These three proteins are expressed more often in craniopharyngiomas and cholesteatomas, the two more aggressive types of lesions.

CONCLUSIONS

This is the first study to report data on the expression of seven S100 proteins in different histopathological groups of epithelial head and neck lesions, whose precise embryological origins are still a matter of debate. S100 proteins could possibly be used as markers to target this embryonic origin, since our results show that S100A3 and S100A6 (and, to a lesser extent, S100A5) are expressed differentially across these different groups of epithelial lesions.

Characterization of the levels of expression of retinoic acid receptors, galectin-3, macrophage migration inhibiting factor, and p53 in 51 adamantinomatous craniopharyngiomas

OBJECT

Craniopharyngiomas are histopathologically defined as benign tumors that can behave very aggressively at the clinical level. They can originate from different types of embryonal epithelial tissue in which correct spatiotemporal regulation has been disrupted at the effector production level. The goal of this study was to determine the efficacy of using selected biological markers to distinguish between recurring and nonrecurring craniopharyngiomas.

METHODS

The authors used computer-assisted microscopy to determine quantitatively the immunohistochemical levels of expression of selected markers, including retinoic acid receptors (RARs), as response elements to retinoic acid in a series of 51 adamantinomatous craniopharyngiomas. These tumors may also originate as the result of physiological defects in the apoptosis-mediated elimination of embryological remnants of epithelial tissue. Galectin-3, p53, and the macrophage migration inhibiting factor (MIF) are known to play crucial roles in these processes. The authors quantitatively determined the levels of expression of these substances in this series of 51 craniopharyngiomas. The data show that all craniopharyngiomas were immunoreactive for RARalpha, whereas their immunoreactivity for RARbeta and RARgamma varied dramatically from one case to another. Craniopharyngiomas with low levels of RARbeta and high levels of RARgamma are more likely to recur than those with higher levels of RARbeta and lower levels of RARgamma. Rapidly recurring craniopharyngiomas also show significantly lower levels of expression of galectin-3 and MIF than nonrecurring or slowly recurring cases. Few tumors exhibited p53 immunopositivity.

CONCLUSIONS

The data indicate that even in the so-called adamantinomatous group of craniopharyngiomas, several subgroups with different clinical behavior patterns can be identified on the basis of differentiation markers relating mainly to the presence or absence of RARbeta and RARgamma.

Detection of macrophage migration inhibitory factor (MIF) in human cholesteatomas and functional implications of correlations to recurrence status and to expression of matrix metalloproteinases-3/9, retinoic acid receptor-beta, and anti-apoptotic galectin-3

OBJECTIVES

To investigate whether the expression of the macrophage migration inhibitory factor (MIF) 1) is detectable, 2) changes in relation to recurrence and infection status, and 3) relates to the levels of expression of growth regulators/differentiation markers, including galectin-1, -3, and -8, retinoid acid receptors (RAR)]-alpha, -beta, and -gamma, binding sites for sarcolectin, and invasion markers (cathepsins -B and -D, and matrix metalloproteinases [MMP]-2, -3, and -9) in human cholesteatomas.

STUDY DESIGN

An analysis of 56 cholesteatomas resected by the same surgeon using canal wall up and canal wall down surgical procedures.

METHODS

The immunohistochemical levels of expression of MIF and the proteases were quantitatively determined (using computer-assisted microscopy) on routine histologic slides by specific antibodies, and statistically correlated to parameters of the other markers determined previously in conjunction with data on apoptosis/proliferation.

RESULTS

MIF expression was detected. It was significantly higher in the epithelium (P =.002) and vessels (P =.04) of the connective tissues (but not in the connective tissue itself) of recurrent as opposed to non-recurrent cholesteatomas. The MIF expression is significantly correlated (P =.006) to the RAR beta expression in non-infected cholesteatomas, and to MMP-3 (P <.01) and anti-apoptotic galectin-3 (P =.01) in infected cholesteatomas. The level of MIF expression was also correlated significantly to MMP-9 (P = 0.003), RAR beta (P <.001), and galectin-8 (P =.003) expression in the cholesteatomas regardless of their infection status.

CONCLUSIONS

MIF expression in human cholesteatomas is related to the levels of biologic aggressiveness reflected in their recurrence status and MMP expression, and to the differentiation status reflected in their galactin and RAR beta expressions. Together with galectin-3, it could cooperate to form an anti-apoptotic feedback loop.

The levels of retinoid RARβ receptors correlate with galectin-1, -3 and -8 expression in human cholesteatomas

Cholesteatoma is a benign disease characterized by the presence of an unrestrained growth and the accumulation of keratin debris in the middle ear cavity. This often recurs, even when surgical resection is thought to be complete. In a previous study we showed that cholesteatomas with the highest apoptotic indices recurred more rapidly and also exhibited a high level of p53 immunopositive cells. In view of their relevance to the characterization of the cell differentiation status, the present study focuses on the expression of retinoid acid receptors (RARs) and galectins in human cholesteatomas. Retinoids control the differentiation processes in keratinocytes while galectins play strikingly modulatory roles at apoptosis and cell adhesion levels in a wide variety of tissue (embryonic, normal and neoplastic). To clarify the expression of these two protein families in human cholesteatomas we examined and quantified the levels of immunohistochemical expression of RARalpha, beta and gamma, and also galectin-1, -3 and -8 in a series of 70 human cholesteatomas. Our data show clearly that predominantly RARbeta and galectin-1 were expressed. The RARgamma concentration was significantly lower than that of the RARalpha; this was also observed for the galectin-8 concentration in comparison with the galectin-3 one. Furthermore, the level of RARbeta expression correlated highly (P=0.00001) with the level of galectin-8 expression, which also correlated significantly with the level of RARalpha and RARgamma expression. In addition, this parameter also correlated with the level of galectin-1 and galectin-3 expression. These data suggest that cholesteatomas may originate in an undifferentiated population of keratinocytes, and that a relation may exist between retinoid activity and galectins.

The levels of expression of galectin-3, but not of galectin-1 and galectin-8, correlate with apoptosis in human cholesteatomas

OBJECTIVES

To investigate whether galectins 1, 3, and 8 are expressed in human cholesteatomas and whether any such expression does correlate with the level of apoptosis, which is, as we have previously shown, predictive of recurrence.7

STUDY DESIGN

The analysis of 52 cholesteatomas resected by the same surgeon by means of canal wall up and canal wall down procedures.

METHODS

The immunohistochemical levels of expression of galectins 1, 3, and 8 were quantitatively determined (using computer-assisted microscopy) on conventional histological slides by means of specific anti-galectin-1, anti-galectin-3, and anti-galectin-8 antibodies. The level of apoptosis in each cholesteatoma under study had already been determined 7 by means of the in situ labeling of nuclear DNA fragmentation (Tolt-mediated dUTP nick end labeling [TUNEL] staining).

RESULTS

Galectin-1 was expressed markedly in both the epithelial and the connective tissue areas of all the cholesteatomas under study. The levels of expression of galectin-3 and galectin-8 were considerably lower than that of galectin-1. The level of expression of galectin-3 correlated both highly and positively with the level of apoptosis.

CONCLUSIONS

An upregulation of galectin-3 (known to have an antiapoptotic and antianoikis effect in certain model systems) expression, which is associated with pronounced apoptotic activity, could have a physiologically protective effect against the characteristically substantial apoptotic features occurring in recurrent cholesteatomas.

Cycline-dependent kinase inhibitor, p27 (KIP1), is associated with cholesteatoma

OBJECTIVE

Cyclin-dependent kinases (CDKis) can arrest the cell cycle, which in turn inhibits the cell proliferation. P27 (KIP1) is a CDKi and acts as a tumor suppressor gene. In this study, we aimed to investigate the role of p27 CDKi in cholesteatoma, a disease characterized by the presence of hyperproliferative squamous epithelium.

STUDY DESIGN

Immunohistochemical staining of 15 cholesteatoma and 18 control ear canal skin samples, which were taken intraoperatively, was performed for p27 positivity.

METHODS

The monoclonal antibodies to p27 were used for immunohistochemical staining of the sections. The streptavidin-biotin horseradish method was used. The number of cells staining positive for p27 was calculated, and the intensity of p27 positivity was graded.

RESULTS

P27 positivity was obtained in 9 (50%) of 18 skin tissues. In the cholesteatoma tissues, p27 positivity was found only in 2 (13.3%) tissue samples. The difference between the groups were statistically significant (P =.03). The mean numbers of p27 positivity were 11.8 +/- 15.5 and 1.4 +/- 3.8 (mean +/- standard deviation) in the skin and cholesteatoma samples, respectively. This difference was also statistically significant (P =.02). The p27 results of primary and secondary cholesteatoma samples were not significantly different (P =.3). The results of p27 were not related to the gender of the patients (P =.8).

CONCLUSION

P27 is involved directly or indirectly in the occurrence of cholesteatoma. Alterations of p27 levels in keratinocytes can influence the proliferative state of the keratinocytes. Altered p27 levels in cholesteatoma may suggest a molecular pathology in cholesteatoma. The search for significance of CDKis seems promising to better understand the pathogenesis of cholesteatoma.

Structural changes and protein expression in the mastoid bone adjacent to cholesteatoma

OBJECTIVE

Cholesteatoma of the mastoid and middle ear causes erosion of nearby bone. In this study we examined the mastoid bone adjacent to cholesteatoma and compared it with normal mastoid bone. In particular, noncollagenous proteins, which have a special structural and functional role in bone, were addressed.

STUDY DESIGN

Nine mastoid specimens with cholesteatoma and four normal specimens obtained at surgery were examined.

METHODS

Histological and immunohistochemical methods were employed to evaluate the nature of structure and noncollagenous protein content changes in the mastoid bone affected by cholesteatoma.

RESULTS

The bone associated with cholesteatoma had structural changes as a noncontinuous periosteum, empty lacunae, irregular cement lines, and, specifically, the appearance of eosinophilic vesicles at the interface between the bone and cholesteatoma Immunohistochemistry demonstrated that noncollagenous proteins were apparently absent in the affected mastoid bone. Bone remote from the cholesteatoma seemed normal.

CONCLUSIONS

These findings demonstrate for the first time the changes in the noncollagenous protein content in the mastoid bone affected directly by cholesteatoma These changes could be a result of a direct influence of cholesteatoma-derived products on the osteoblast.

Determination of the levels of expression of sarcolectin and calcyclin and of the percentages of apoptotic but not proliferating cells to enable distinction between recurrent and nonrecurrent cholesteatomas

OBJECTIVES

To investigate in a series of cholesteatomas 1. whether subgroups of cholesteatomas with specific proliferative/apoptotic features exhibit distinct differentiation markers and 2. whether these different subgroups identified at the biological level relate to specific groups of clinically identified cholesteatomas.

STUDY DESIGN

Analysis of 55 cholesteatomas resected by the same surgeon, by means of canal wall up and canal wall down surgical procedures.

METHODS

Two differentiation markers were used: biotinylated sarcolectin (to identify sarcolectin-binding sites) and a monoclonal antibody directed against calcyclin (which is the S100A6 protein). The growth pattern in cholesteatomas was characterized at three distinct levels: 1. the cell proliferation level determined by means of the MIB-1 antibody, which enables the Ki-67 cell-cycle-related antigen to be identified on archival material; 2. the apoptosis level determined by means of the in situ labeling of nuclear DNA fragmentation (TUNEL staining); and 3. the p53 tumor suppressor gene-related product determined by means of p53 immunohistochemistry.

RESULTS

The cholesteatomas that exhibited the highest proportion of apoptotic cells were those which exhibited the highest level of sarcolectin-binding sites (i.e., sialic acids). In contrast, the cholesteatomas exhibiting the lowest level of both proliferation and apoptosis showed the highest level of calcyclin. Recurrent cholesteatomas can be identified from nonrecurrent ones on the basis of three features, namely, the level of apoptotic cells, the way in which the apoptotic cells are distributed (i.e., homogeneously vs. heterogeneously), and the percentage of calcyclin-positive cells.

CONCLUSIONS

The present data emphasize the existence of distinct subgroups of cholesteatomas identifiable at both cell kinetic and differentiation levels. Some of the biological variables used here to identify distinct biological subgroups of cholesteatomas in turn enabled some biological variables to be identified, so making it possible to classify the cholesteatomas in terms of recurrence versus nonrecurrence.

Apoptosis in meatal skin, cholesteatoma and squamous cell carcinoma of the ear

Apoptosis in normal meatal skin, cholesteatoma and squamous cell carcinoma (SCC) of the ear was investigated by using morphological analysis and in-situ specific labelling of fragmented DNA. In meatal skin, apoptotic cells were localized mainly in the granular layers, but were not so restricted in cholesteatoma, while in SCC they were even more dispersed. The apoptotic index (AI) was low (1.59 +/- 0.10 SEM) in normal skin. It was increased in cholesteatoma (2.09 +/- 0.11), and was intermediate in SCC (1.72 +/- 0.14). By contrast, the mitotic index (MI) increased from 0.19 +/- 0.02 in normal skin, to 0.25 +/- 0.01 in cholesteatoma and to 0.25 +/- 0.02 in SCC. Our findings indicate that apoptosis is involved in the epithelial homeostasis of meatal skin, cholesteatoma and SCC of the ear. The hyperproliferation of epithelial cells in cholesteatoma is counteracted by an increased apoptosis rate, while in SCC the increased cell proliferation without a compensatory increase in apoptosis may be associated with the malignant transformation.

Transforming growth factor-alpha and rhinitis

OBJECTIVES

Transforming growth factor-alpha (TGF-alpha) has been implicated in diverse physiologic and pathophysiologic functions including immunological, inflammatory, and neoplastic processes. TGF-alpha has been localized in the hyperproliferative, inflammatory environment of chronic otitis media, cholesteatoma, and asthmatic airways. TGF-beta1, which must be present with TGF-alpha to transform fibroblasts, has been found in rhinitic mucosa and in asthma in prior studies. The authors sought to identify whether TGF-alpha also played a role in the inflammatory cascade and fibrosis of rhinitis.

STUDY DESIGN

A nonrandomized, prospective study was carried out in which samples of inferior turbinate and nasal polyps from rhinitic and nonrhinitic patients were subjected to immunohistochemistry and Western blotting to determine the presence of TGF-alpha.

METHODS

Twenty-seven subjects undergoing surgery for rhinitis, obstructive sleep apnea, nasal fracture, and rhinoplasty were recruited for this study, the latter three groups acting as controls. Immunohistochemical and Western blotting techniques were employed to identify the presence of TGF-alpha in inferior-turbinate and nasal-polyp samples of rhinitic subjects.

RESULTS

Immunohistochemistry demonstrated the selective staining of TGF-alpha in the basement membrane and extracellular matrix, including lymphatic, vascular, and glandular structures, in most turbinate samples and the absence of staining in corresponding controls. Further, TGF-alpha was isolated to a discrete 30-kD band in both inferior turbinate and polyp tissues by Western blotting without staining in the corresponding controls.

CONCLUSIONS

These results suggest that TGF-alpha may play a role in the inflammatory derangement of rhinitis.

Signal transduction pathway in human middle ear cholesteatoma

Phospholipase C-gamma1 plays a central role in signal transduction, and it is important in cellular growth, differentiation, and proliferation. Human cholesteatoma in the middle ear is characterized by the presence of a keratinizing epithelium that is believed to have hyperproliferative properties. The purpose of this study is to elucidate the distribution of phospholipase C-gamma1 in cholesteatoma matrix and deep meatal skin with Western blot analysis and immunohistochemistry. In conclusion, overexpression of phospholipase C-gamma1 in cholesteatoma matrix suggests a possible derangement of enhanced growth signal transduction in keratinocytes.

Expression of Fas/APO-1 and apoptosis of keratinocytes in human cholesteatoma

OBJECTIVES

The Fas/APO-1 is a cell surface receptor protein known to trigger apoptosis when conjugated with Fas ligand or specific agonistic antibodies. The present study investigated the expression of Fas/APO-1 and apoptotic cell death in both normal and cholesteatoma epithelia.

STUDY DESIGN

Ten cholesteatomas and retroauricular skins were taken during middle ear operations in the Ajou University Hospital for this study.

METHODS

In situ terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end-labeling (TUNEL) staining and agarose gel electrophoresis of genomic DNA were used for detection of apoptosis. The expression patterns of Fas/APO-1 protein were confirmed by immunoblot and immunohistochemical analysis.

RESULTS

In situ TUNEL staining revealed many positively stained nuclei in 9 of 10 suprabasal layers of cholesteatoma epithelium, whereas few positively stained cells were found on the granular layer of retroauricular skins. Typical "ladder pattern" was seen on the gel electrophoresis of the genomic DNA of cholesteatoma. Immunoblot analysis and immunohistochemical studies revealed that Fas/APO-1 protein was expressed in 8 of 10 cholesteatoma epithelia, whereas retroauricular skin showed negative reaction.

CONCLUSION

These results show the upregulated expression of Fas/APO-1 and increased apoptotic cell death in cholesteatoma epithelium. Because Fas/APO-1 is known as an apoptosis-triggering protein, it is suggested that the accumulation of keratin debris is due to increased apoptotic cell death related to Fas/APO-1 protein.

Mediation of signal transduction in keratinocytes of human middle ear cholesteatoma by ras protein

Immunolocalization was used to investigate the distribution of ras protein in both congenital and acquired cholesteatoma tissues. A pathological feature of middle ear cholesteatoma included accumulation of keratin debris due to active proliferation and differentiation of keratinocytes. Ras protein localized to the inner plasma membrane and cytoplasm of keratinocytes in all of the epithelial layers in both congenital and acquired cholesteatoma specimens. Keratinocytes in the basal layer were stained more intensely than their differentiated counterparts. Findings also demonstrated that receptors for epidermal growth factor, fibroblast growth factor, and plateletderived growth factor were present in the plasma membrane of keratinocytes. C-jun, a transcription factor was found in the nuclei of keratinocytes of the cholesteatoma epithelium. These findings indicate that ras protein plays a pivotal role in a signal transduction cascade between growth factor receptors in the plasma membrane and the transcription factor, c-jun, in the nuclei of keratinocytes during the growth of cholesteatoma.