Analysis of amelogenin gene (AMGX, AMGY) expression in ameloblastoma

The Expression of Neuroendocrine Markers in a Small Subset of Ameloblastoma with Implications of Clusterin

Immunohistochemically, ameloblastomas often express CD56; however, novel neuroendocrine markers such as synaptophysin (SYP), insulinoma-associated protein 1 (INSM1), and chromogranin A (CgA) remain unexplored. We analyzed 36 ameloblastoma specimens for CD56, SYP, CgA, and clusterin (CLU) and examined limited samples for INSM1 expression by performing immunohistochemistry, transmission electron microscopy, and reverse transcriptase-polymerase chain reaction. Our findings indicate that the limited cells were positive for CD56, SYP, CgA, INSM1, and CLU expression in 72% (26/36), 14% (5/36), 0% (0/40), 80% (4/5), and 22% (8/36) of the cases, respectively. CD56 expression correlated with older age, but not with subtype, SYP, and CLU expression. However, SYP-positive cases were exclusively found in CD56- and CLU-positive cases, and SYP and CLU expression were significantly correlated. Selected cases had dense-core granules and NCAM1 and SYP mRNA expression. This study is the first to suggest neuroendocrine differentiation in ameloblastomas, as indicated by SYP and INSM1 immunoexpression and the presence of dense-core granules, which are consistent with the recent World Health Organization classification of Head and Neck Tumors guidelines. SYP-positive and CgA-negative phenotypes may characterize neuroendocrine differentiation in ameloblastoma. Although the underlying molecular mechanism remains unclear, CLU expression may be associated with neuroendocrine differentiation.

Amelogenin is a Potential Biomarker for the Aggressiveness in Odontogenic Tumors

Amelogenin (AMEL), the major structural protein of the enamel organic matrix, constitutes more than 90% of the enamel’s protein content, Aberrations of amelogenin are thought to be involved in the oncogenesis of odontogenic epithelium. The expression of amelogenin is possibly an indicator of differentiation of epithelial cells in the odontogenic tumors. Aim of the study: Investigating the expression of amelogenin in some odontogenic tumors, using an anti-amelogenin polyclonal antibody, and then compare it with AMEL expression in tooth buds as control. Materials and Methods: study sample consisted of 10 formalin-fixed, paraffin- embedded specimens of ameloblastoma, 10 Keratocystic odontogenic tumors, and 10 tooth buds were conventionally stained with hematoxylin-eosin and immunohistochemically with AMEL polyclonal antibody. Results: All of the odontogenic tumors expressed AMEL in the epithelial component, Intensity of expression in ameloblastoma and Keratocystic odontogenic tumor was lower, compared with tooth buds, Statistical analysis indicated a significant differences between the tumors and tooth buds. Conclusion: Amelogenin can be used as a marker for odontogenic epithelium, and the expression of amelogenin is possibly an indicator of epithelial cells differentiation in the odontogenic tumors, and therefore in prediction of the histological behavior of odontogenic tumors.

[The role of Wnt/β-catenin signaling pathway in ameloblastoma formation]

The aim of the study was to assess the role of the canonical Wnt/β-catenin signaling pathway in the formation and clinical course of various histological variants of ameloblastoma.

MATERIAL AND METHODS

76 cases of ameloblastoma were investigated, the average age of the patients was 46 years. There were 49 (64.5%) cases of recurrence of the disease. Tissue antigens were determined using monoclonal rabbit antibodies to Ki-67 and β-catenin.

RESULTS

it was found correlation between the proliferative activity of ameloblastoma cells and the intranuclear localization of β-catenin, indicating the activation of the Wnt/β-catenin-signaling pathway. It was shown that the nuclear localization of β-catenin is positively correlated with the recurrence.

CONCLUSION

The Wnt/β-catenin signaling pathway is involved in a formation and progression of ameloblastoma.

Amelogenin: A novel protein with diverse applications in genetic and molecular profiling

Tooth enamel is a unique entity among all mineralized tissues because of the presence of high mineral content. It is non collagenous and does not undergo resorption and remodelling. Its formation occurs through a transient collaborating network of enamel matrix proteins which controls hydroxyapatite crystal growth and orientation. Amelogenins constitute about 90% of the total enamel matrix proteins and play a major role in enamel bio mineralization. Amelogenin isoforms coalesce into nanospheres thus dictating the width and thickness of apatite crystals. The X and Y copies of amelogenins do not undergo homologous recombination, thus preferring it for sex determination in modern forensics. Recently, it was discovered that application of amelogenin to diseased periodontal tissue surfaces enhanced the regeneration of all the periodontal tissues. Additionally, low molecular mass amelogenin polypeptides have also been thought to possess osteogenic potential. Recent data regarding usage of immunohistochemical markers for mesenchymal stem cells suggested that amelogenin has the capacity to induce the recruitment of mesenchymal stem cells directly or indirectly during regeneration of the supporting periodontal tissues. Thus, our current concepts of dental enamel formation should be reviewed thoroughly so that this information could be applied to clinical circumstances where this understanding may be particularly relevant.

Review article: Current concepts of ameloblastoma pathogenesis

Ameloblastoma is a locally destructive and invasive tumour that can recur despite adequate surgical removal. Molecular studies have offered interesting findings regarding ameloblastoma pathogenesis. In the present review, the following topics are discussed regarding its molecular nature: clonality, cell cycle proliferation, apoptosis, tumour suppressor genes, ameloblastin and other enamel matrix proteins, osteoclastic mechanism and matrix metalloproteinases and other signalling molecules. It is clear from the literature reviewed that translational studies are necessary to identify prognostic markers of ameloblastoma behaviour and to establish new diagnostic tools to the differential diagnosis of unicystic from multicystic ameloblastoma. Finally, molecular biology studies are also important to develop more effective alternative approaches to the treatment of this aggressive odontogenic tumour.