Immunohistochemical demonstration of c-myc oncogene product in middle ear cholesteatoma

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.

Comparison of changes in mitochondrial bioenergetics between keratinocytes in human external auditory canal skin and cholesteatomas from normoxia to hypoxia

Cholesteatoma has attracted many studies seeking to uncover its nature and the pathogenesis of related diseases. However, no researchers have explored the mitochondrial bioenergetics of cholesteatoma. The aim of this study was to investigate the energy demand and differential mitochondrial respiration profiles between keratinocytes in external auditory canal (EAC) skin and cholesteatoma samples cultured in normoxic (20% O₂) and hypoxic (5% O₂) conditions. Enhanced cellular proliferation of both types of keratinocytes was found in hypoxia compared to normoxia. In 20% O₂ conditions, cholesteatoma keratinocytes exhibited less mitochondrial mass, lower ATP levels, and significantly lower basal oxygen consumption rate (OCR) and reserve capacity compared to normal skin keratinocytes. In contrast, in hypoxic conditions, cholesteatoma keratinocytes showed markedly higher levels in maximal OCR and reserve capacity, as well as lower proton leak OCRs, compared to normal skin keratinocytes. Hypoxia induced the reverse mitochondrial bioenergy profile from that in normoxia between these two types of keratinocytes, implying that an adaptive change of mitochondrial respiration to oxygen fluctuations may develop in cases of cholesteatoma. Such adaptation in response to hypoxic conditions may play a role in explaining the pathogenesis of acquired cholesteatoma.

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.

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.

The c-MYC protooncogene expression in cholesteatoma

Cholesteatoma is an epidermoid cyst, which is most frequently found in the middle ear. The matrix of cholesteatoma is histologically similar to the matrix of the epidermoid cyst of the skin (atheroma); their epithelium is characterized by hyperproliferation. The c-MYC protooncogene located on chromosome 8q24 encodes a transcription factor involved in the regulation of cell proliferation and differentiation. Previous studies have found aneuploidy of chromosome 8, copy number variation of c-MYC gene, and the presence of elevated level c-MYC protein in cholesteatoma. In this study we have compared the expression of c-MYC gene in samples taken from the matrix of 26 acquired cholesteatomas (15 children and 11 adults), 15 epidermoid cysts of the skin (atheromas; head and neck region) and 5 normal skin samples (retroauricular region) using RT-qPCR, providing the first precise measurement of the expression of c-MYC gene in cholesteatoma. We have found significantly elevated c-MYC gene expression in cholesteatoma compared to atheroma and to normal skin samples. There was no significant difference, however, in c-MYC gene expression between cholesteatoma samples of children and adults. The significant difference in c-MYC gene expression level in cholesteatoma compared to that of atheroma implies a more prominent hyperproliferative phenotype which may explain the clinical behavior typical of cholesteatoma.

Cholesteatoma triggering squamous cell carcinoma: case report and literature review of a rare tumor

BACKGROUND

The aim of this study was to report a case of squamous cell carcinoma of the petrous part of the temporal bone associated with a long history of secondary acquired cholesteatoma in a 71-year-old man.

PATIENTS AND METHODS

We present the case of a 71-year-old man diagnosed with secondary acquired cholesteatoma in 1950. Treatments consisted of repetitive surgery owing to several relapses. In 2004, he presented with progressive fetid otorrhea. Clinical and computed tomography findings were indicative for relapsing cholesteatoma and a subtotal petrosectomy was performed.

RESULTS

Histologic work-up demonstrated a moderately differentiated squamous cell carcinoma. The staging revealed stadium pT3 cN0 cM0. Postoperative treatment consisted of local radiation therapy with intensity-modulated beam geometry with a total of 64.2 Gy in 30 fractions using a simultaneous integrated boost.

CONCLUSION

Middle ear carcinoma can arise from acquired cholesteatoma. The pathogenesis of squamous cell carcinoma associated with cholesteatoma has not been elucidated satisfactorily. Due to the complex anatomic features, intensity-modulated radiation therapy is the technique of choice for postoperative radiotherapy.

Evaluation of c-MYC status in primary acquired cholesteatoma by using fluorescence in situ hybridization technique

OBJECTIVE

The object of study was to investigate the status of c-MYC oncogene in primary acquired cholesteatoma.

STUDY DESIGN

Descriptive study.

METHODS

Cholesteatoma samples were obtained from 15 patients with primary acquired cholesteatoma during surgical operation. Fluorescence in situ hybridization with a mixed DNA probe, which is specific for c-MYC located on 8q24 and chromosome 8 specific-alpha-satellite DNA probe (dual color), was used on the interphase nuclei.

RESULTS

Copy number of c-MYC oncogene and aneuploidy of chromosome 8 were 21.2% +/- 14.4% and 21.7% +/- 14.8%, respectively. There was no significant difference between copy number of c-MYC and frequency of chromosome 8 aneuploidy (p > 0.05). Ten of 15 cases showed different percentage of c-MYC and chromosome 8 aneuploidy, whereas 5 (33.3%) of 15 cases showed a normal distribution of c-MYC and chromosome 8 signals.

CONCLUSION

The copy number of c-MYC in 10 of 15 cases was found to be high as observed for chromosome 8 aneuploidy in primary acquired cholesteatoma. These findings suggest that the ability of hyperproliferation of primary acquired cholesteatoma might have been related to c-MYC copy number by deregulating c-MYC expression.

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.

Telomerase activity, telomere length, and apoptosis: a comparison between acquired cholesteatoma and squamous cell carcinoma

BACKGROUND

Cholesteatoma disease is characterized by accumulation of keratinizing epithelium. Several molecular markers of tumor formation have been found in cholesteatoma (e.g. upregulation of matrix metalloproteinases, c and activation of angiogenesis). Other molecular findings clearly distinguish between cholesteatoma and malignant tumors (e.g., lack of chromosomal instability, intact checkpoint responses). To further distinguish the molecular mechanisms in cholesteatoma from malignant tumors, the authors determined telomerase activity and telomere length in both tissue types.

METHODS

To evaluate the role of telomerase activation and telomere length in cholesteatoma, 29 cholesteatoma samples and 9 squamous cell carcinomas were analyzed for telomerase activity and telomere length. In addition, the rate of apoptosis was determined in both groups, using the TdT-mediated dUTP nick end labeling technique.

RESULTS

As previously described, a high proportion of squamous cell carcinoma exhibited telomerase activity (6/9, 66%). By contrast, a significantly lower rate of telomerase activity was found in cholesteatoma samples (1/29, 3.4%, p = 0.0002). Despite the differences in telomerase activity, the telomere length was similar in cholesteatoma (mean length 7.43 kb) and in squamous cell carcinoma (mean length 7.99 kb; difference not significant, p = 0.1364). The low rate of telomerase activity in cholesteatoma was accompanied by significantly higher rates of apoptosis in cholesteatoma (mean 30%) compared with squamous cell carcinoma tissue (mean 3%, p = 0.0031).

CONCLUSIONS

Taken together, these data show that telomerase activation is a rare event in cholesteatoma and that the absence of telomerase activity is accompanied by high rates of apoptosis in cholesteatoma. It is proposed that the absence of telomerase limits the proliferative capacity of cholesteatoma by induction of apoptosis, whereas the presence of telomerase allows immortal growth of squamous cell carcinoma.

Clinicopathological consultation. Ear cholesteatoma versus cholesterol granuloma

Cholesteatoma and cholesterol granuloma of the ear are two different pathologic conditions that have often been confused in the past, and even in the present, in the literature. The features differentiating the two lesions are presented.