Study Of The Abnormal Expression Of Tissue Enzymes And Oncogenes In The Middle Ear Cholesteatoma

The histopathological features of middle ear Cholesteatoma are characterized by hyperproliferative keratinizing squamous epithelium in the middle ear cavity, bone destruction of the surrounding tissues, and by apoptosis of keratinocyte. The biological properties of cholesteatoma, namely aggression, destructiveness, migration, uncoordinated proliferation, altered differentiation, and recidivism, are similar to those of a malignant tumor. Cholesteatoma is a bengin disease .The squamous epithelium of middle ear cholesteatoma shows hyperproliferative characteristics as evidenced by the expression of hyperproliferation-associated cytokeratin (CK16) and perproliferation-associated nuclear antigens Ki67 and PCNA. The overexpression of oncogene Bcl-xL and anti-oncogene p53 in cholesteatoma demonstrate that despite the hyperproliferation in the cholesteatoma epidermis, cells retain the capability to undergo apoptotic cell death. However, the precise mechanism responsible for the regulation of cholesteatoma growth and apoptosis is unclear. The current study had analyzed 32 cholesteatoma, 12 specimens of normal ear canal skin for altered expression of calpain with the methods of western-blot, RT-PCR and immunohistochemiscal analysis. Its aim was to study the role of calpain playing in apoptosis of cholesteatoma epidermis. The results showed that the protein expression of calpain in cholesteatoma tissue was obviously stronger than that in ear canal skin, and positive cells were observed in all epithelial layers of cholesteatoma except basal layer, especially in the granular layer and stratum corneum. Calpainâ… mRNA were detected in the normal ear canal skin and cholesteatoma, but the levels of cholesteatoma were higher than that of normal skin. No statistically significant differences were found between them(P>0.05). Calpainâ…¡mRNA were not detected or lower levels expression in the normal skin, while in contrast were markedly elevated in cholesteatoma compared to normal skin(P<0.0001). In conclusion, we have demonstrated that calpain has taken part in the process of apoptosis by direct proteolysis, and had a correlation with the apoptosis of middle ear cholesteatoma epidermis. These data suggest that the two major isoenzymes- Calpainâ… and Calpainâ…¡ in middle ear cholesteatoma were activated by Ca2+ and both of them degraded some cell protein , although , Calpainâ…¡played a more important role in the apoptosis mechanism of middle ear cholesteatoma. Oncogenes are cell growth genes, whose abnormal products will lead cell to proliferate continuously. It has been founded that the c-myc, c-jun, RAS and p53proteins present in cholesteatoma, involved in the regulation of both cell proliferation and apoptosis. The correlations of protooncogene MDM2, anti-oncogene PTEN with hyperproliferative behavior in middle ear cholesteatoma are unknown. Related reports have no presented. Also the expression of the MDM2 and PTEN were examined in the tissue of middle ear cholesteatoma by immunohistochemiscal S-P and RT-PCR method. It was shown that the expression of MDM2 in all epithelial layers of cholesteatoma was abundantly stained, especially in the granular layer and stratum corneum. Never detected MDM2 in the normal ear canal skin. PTEN mRNA and protein expression levels of cholesteatoma tissue were similar to the normal ear canal skin. So we suspect that the MDM2/p53 feedback loop were interrupted which resulted in abnormal proliferation and apoptosis of cholesteatoma epidermis. The role of PTEN in cholesteatoma trended to maintain normal physiological function of epithelial cells, and PTEN was not mutated to lead to uncontroled proliferation. Bone destruction is the important clinical feature of acquired cholesteatoma of the middle ear. In order to study the destructive mechanism of TIMPs, the expression of TIMP-1, TIMP-2 and IL-6 in cholesteatoma tissue were detected. The result showed that no significant difference in expression of TIMP-1 and TIMP-2 were founded between cholesteatoma and ear canal skin. Th...