Immunohistochemical investigation of epidermal growth factor receptor expression in ameloblastomas

Significance of EGFR investigation in odontogenic keratocyst: a narrative review

BACKGROUND

The recent classification of odontogenic keratocysts (OKSs) recognized them as benign neoplasms, although previous findings have revealed their aggressive nature. Immunohistochemical and molecular analyses have investigated OKSs, but the role of epidermal growth factor receptor (EGFR) has not been fully investigated, despite the importance of this oncogene in the process of carcinogenesis in tumors of epithelial origin. The EGFR protein is usually overexpressed, and the EGFR gene is mutated or amplified.

AIMS OF STUDY

This brief review aims to emphasize the importance of EGFR detection in these types of cysts.

METHODS AND RESULTS

It was revealed that the majority of the studies examined EGFR protein expression using immunohistochemical methods; however, considering EGFR gene variants, mutations were less explored in the previous period from 1992 to 2023. Although EGFR gene polymorphisms are clinically important, they were not identified in the present study.

CONCLUSIONS

In light of the current significance of EGFR variants, it would be beneficial to examine them in odontogenic lesions. This would enable resolving of discrepancies about their nature, and potentially enhance classifications OKCs in the future.

Nuclear localization of epidermal growth factor receptor (EGFR) in ameloblastomas

BACKGROUND

Ameloblastoma is a locally invasive neoplasm often associated with morbidity and facial deformities, showing increased Epidermal Growth Factor Receptor (EGFR) expression. Inhibition of EGFR was suggested as a treatment option for a subset of ameloblastomas. However, there are resistance mechanisms that impair anti-EGFR therapies. One important resistance mechanism for EGFR-inhibition is the EGFR nuclear localization, which activates genes responsible for its mitogenic effects, such as Cyclin D1.

METHODS

We assessed EGFR nuclear localization in encapsulated (unicystic, n = 3) and infiltrative (multicystic, n = 11) ameloblastomas and its colocalization with Cyclin D1 by using anti-EGFR and anti-lamin B1 double labeling immunofluorescence analyzed by confocal microscopy. Oral inflammatory fibrous hyperplasia and oral squamous cell carcinoma samples were used for comparison.

RESULTS

Twelve cases of ameloblastoma exhibited nuclear EGFR colocalization with lamin B1. This positive staining was mainly observed in the ameloblast-like cells. The EGFR nuclear localization was also observed in control samples. In addition, nuclear EGFR colocalized with Cyclin D1 in ameloblastomas.

CONCLUSIONS

Nuclear EGFR occurs in ameloblastomas in association with Cyclin D1 expression, which is important in terms of tumor biology clarification and raises a concern about anti-EGFR treatment resistance in ameloblastomas.

Quantitative and qualitative analysis of epidermal growth factor receptor expression in pericoronal follicles in predicting proliferative potential

OBJECTIVE

The odontogenic epithelium in pericoronal follicles (PFs) are known to proliferate to form cysts and tumors. This epithelium is mostly composed of the reduced enamel epithelium (REE) and odontogenic rests (OR). The objective of the present study was to evaluate the epidermal growth factor receptor (EGFR) immunoexpression in these PFs to assess their proliferative potential.

STUDY DESIGN

The immunoexpression of EGFR in 30 PFs were assessed by two independent observers for intensity, percentage and the location of the EGFR staining.

RESULTS

EGFR immunoexpression was noted in 100% of the follicles. A greater proportion of the follicles showed strong intensity (70%). It was noted that nearly 54% of the follicles demonstrated more than 50% of cells with EGFR immunolabelling. EGFR showed combined cytoplasm and membrane staining (40%) and cytoplasm only staining (37%). The analysis of the REE and OR individually for the above-mentioned parameters did not show statistical significance.

CONCLUSION

The increased intensity and overall positivity of the epithelium in follicles shows that odontogenic epithelium is responsive to EGFR mediated growth factors. The predominant combined staining pattern is suggestive of increased potential for the epithelium to undergo cystic or neoplastic proliferation.

High frequency of BRAF V600E mutations in ameloblastoma

Ameloblastoma is a benign but locally infiltrative odontogenic neoplasm. Although ameloblastomas rarely metastasise, recurrences together with radical surgery often result in facial deformity and significant morbidity. Development of non-invasive therapies has been precluded by a lack of understanding of the molecular background of ameloblastoma pathogenesis. When addressing the role of ERBB receptors as potential new targets for ameloblastoma, we discovered significant EGFR over-expression in clinical samples using real-time RT-PCR, but observed variable sensitivity of novel primary ameloblastoma cells to EGFR-targeted drugs in vitro. In the quest for mutations downstream of EGFR that could explain this apparent discrepancy, Sanger sequencing revealed an oncogenic BRAF V600E mutation in the cell line resistant to EGFR inhibition. Further analysis of the clinical samples by Sanger sequencing and BRAF V600E-specific immunohistochemistry demonstrated a high frequency of BRAF V600E mutations (15 of 24 samples, 63%). These data provide novel insight into the poorly understood molecular pathogenesis of ameloblastoma and offer a rationale to test drugs targeting EGFR or mutant BRAF as novel therapies for ameloblastoma.

EGFR, CD10 and proliferation marker Ki67 expression in ameloblastoma: possible role in local recurrence

Background

Ameloblastoma is an odontogenic neoplasm characterized by local invasiveness and tendency towards recurrence.

Aims

Studying the role played by EGFR, CD10 and Ki67 in the recurrence of ameloblastoma.

Methods

This study was carried out on 22 retrospective cases of mandibular ameloblastoma from the period from Jan 2002 to Jan 2008 with follow up period until Jan 2011 (3 to 8 years follow up peroid). Archival materials were obtained from pathology department, Mansoura university. Paraffin sections of tumor tissue from all cases were submitted for routine H&E stains and immunohistochemistry using EGFR, CD10 and Ki67 monoclonal antibodies. Statistical analysis using of clinical data for all patients, tumor type, EGFR, CD10 and Ki67 expression in relation to recurrence were evaluated.

Results

Among the 22 cases, 10 cases were males and 12 were females with sex ratio 1:1.2. Age ranged from 34 to 59 years old with a mean age 44.18 year. Five cases showed local recurrence within studied period and proved by biopsy. No statistically significant relation was found between local recurrence and patient age, tumor size, tumor type, EGFR expression. There was a significant relation between CD10 expression as well as Ki67 labelling index and recurrence (P value = 0.003, 0.000 respectively).

Conclusion

Evaluation of CD10 and Ki67 status together with conventional histological evaluation can help in providing more information about the biologic behavior of the tumor, while EGFR could be a target of an expanding class of anticancer therapies.

Since ameloblastomas are EGFR-positive tumors, anti-EGFR agents could be considered to reduce the size of large tumors and to treat unresectable tumors that are in close proximity to vital structures.

Virtual Slides

The virtual slide(s) for this article can be found here:

http://www.diagnosticpathology.diagnomx.eu/vs/1902106905645651

Quantitative analysis of argyrophilic nucleolar organizer regions and epidermal growth factor receptor in ameloblastomas

OBJECTIVE

The aim of this study was to evaluate the proliferation activity by means of the quantification of the argyrophilic nucleolar organizer regions (AgNORs) and the patterns of expression of the epidermal growth factor receptor (EGFR) in ameloblastomas.

METHOD

The methods of evaluation included the H/E stain for the morphologic analysis, the silver impregnation technique for quantification of the AgNORs and the immunohistochemical stain with anti-EGFR antibody in 11 cases of ameloblastoma.

RESULTS

The results did not show a significant statistical difference as per quantification of the AgNORs. The expression of the EGFR on the epithelial islands of ameloblastoma was not uniform, and the location of the expression was also variable. The predominant expression was that of cytoplasm and the islands with an expression of membrane only were rare and generally smaller in size.

CONCLUSION

The tumor presents an irregular growth. Smaller islands are associated with a higher proliferation activity and therefore could be responsible for tumor infiltration.

Molecular pathology of odontogenic tumors

Odontogenic tumors are lesions derived from the elements of the tooth-forming apparatus and are found exclusively within the jawbones. This review represents a contemporary outline of our current understanding of the molecular and genetic alterations associated with the development and progression of odontogenic tumors, including oncogenes, tumor-suppressor genes, oncoviruses, growth factors, telomerase, cell cycle regulators, apoptosis-related factors, regulators of tooth development, hard tissue-related proteins, cell adhesion molecules, matrix-degrading proteinases, angiogenic factors, and osteolytic cytokines. It is hoped that better understanding of related molecular mechanisms will help to predict the course of odontogenic tumors and lead to the development of new therapeutic concepts for their management.

Epidermal growth factor receptor expression in ameloblastoma

Ameloblastoma is a locally aggressive tumor with possible lethal potential. Currently extensive surgery is the most acceptable treatment modality.

AIM

To investigate the presence of EGFR in ameloblastoma in order to consider using newly developed anti-EGFR therapeutic agents in cases of unresectable tumors. The study consisted of 58 formalin-fixed, paraffin-embedded specimens of ameloblastoma that were immunohistochemically stained with a monoclonal anti-EGFR antibody (clone 31G7). Positive and negative controls determined specificity of the antibody. A staining score based on the staining intensity and the proportion of stained cells was established, ranging between 0 and 2. All specimens were EGFR positive; 8 (14%) exhibited the maximum score of 2 and 19 (33%) scored between 1 and 2. Since ameloblastomas are EGFR-positive tumors, anti-EGFR agents could be considered to reduce the size of large tumors and to treat unresectable tumors that are in close proximity to vital structures.

Aberrant gene expression in epithelial cells of mixed odontogenic tumors

Comparative investigations of odontogenic cells in normally forming teeth and tumors may provide insights into the mechanisms of the differentiation process. The present study is devoted to late phenotypic markers of ameloblast and odontoblast cells, i.e., proteins involved in biomineralization. The in situ expression of amelogenins, keratins, collagens type III and IV, vimentin, fibronectin, osteonectin, and osteocalcin was performed on normal and tumor odontogenic human cells. The pattern of protein expression showed some similarities between ameloblasts and odontoblasts present in normally developing human teeth and cells present in neoplastic tissues of ameloblastic fibroma, ameloblastic fibro-odontomas, and complex odontomas. Amelogenins (for ameloblasts) and osteocalcin (for odontoblasts) were detected in cells with well-organized enamel and dentin, respectively. In contrast, "mixed" cells located in epithelial zones of mixed odontogenic tumors co-expressed amelogenins and osteocalcin, as shown by immunostaining. The presence of osteocalcin transcripts was also demonstrated by in situ hybridization in these cells. Keratins and vimentin were detected in the same epithelial zones. Tumor epithelial cells were associated with various amounts of polymorphic matrix (amelogenin- and osteocalcin-immunoreactive), depending on the types of mixed tumors. No osteocalcin labeling was found in epithelial tumors. This study confirms that the differentiation of normal and tumor odontogenic cells is accompanied by the expression of some common molecules. Furthermore, the gene products present in normal mesenchymal cells were also shown in odontogenic tumor epithelium. These data may be related to a tumor-specific overexpression of the corresponding genes transcribed at an undetectable level during normal development and/or to an epithelial-mesenchymal transition proposed to occur during normal root formation. A plausible explanation for the results is that the odontogenic tumor epithelial cells are recapitulating genetic programs expressed during normal odontogenesis, but the tumor cells demonstrate abnormal expression patterns for these genes.