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BACKGROUND: PEA3 transcription factor has been identified as a downstream target of the MAPK and PI3K pathways, and PEA3 overexpression has been observed in a variety of tumor types. We aimed to evaluate PEA3 expression in odontogenic cysts and tumors and compare the expression among odontogenic lesions. In addition, the correlations between PEA3 expression and clinicopathological characteristics of conventional ameloblastoma and unicystic ameloblastoma were investigated. METHODS: This study was performed on 165 samples of odontogenic cysts and tumors including 20 dentigerous cysts, 20 odontogenic keratocysts, 16 adenomatoid odontogenic tumors, 5 ameloblastic fibromas, 45 unicystic ameloblastomas, and 59 conventional ameloblastomas. The sections were immunohistochemically stained with mouse monoclonal anti-PEA3 antibody and PEA3 expression was evaluated as the immunoreactive score. RESULTS: PEA3 expression was absent in all dentigerous cysts (DCs) and odontogenic keratocysts, while all adenomatoid odontogenic tumors showed either no (75%) or low (25%) expression of PEA3. Most of the ameloblastic fibromas (60%) displayed no PEA3 expression. A high expression of PEA3 was observed in a substantial number of unicystic ameloblastomas (48.9%) and conventional ameloblastomas (49.2%) in our study. PEA3 expression in DCs, odontogenic keratocysts and adenomatoid odontogenic tumors were significantly different from that in conventional ameloblastomas and that in unicystic ameloblastomas (p < 0.05). The expression of PEA3 was significantly different in the age groups of unicystic ameloblastomas and histological subtypes of conventional ameloblastomas (p < 0.05). CONCLUSION: PEA3 overexpression is predominant in unicystic ameloblastomas and conventional ameloblastomas compared to other odontogenic lesions, indicating a pivotal role of PEA3 as a downstream effector of MAPK pathway in these two odontogenic lesions.

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OBJECTIVE: Dental hard tissue is among the hardest tissue of humans because it contains high amounts of inorganic substances. This leads to difficulty in preparing histological sections for histopathological examination. Acid and chelating agents are generally used to decalcify teeth. We aimed to compare the histological quality of teeth decalcified with various calcifying agents including 5% nitric acid, 50% formic acid with 20% sodium citrate (Anna Morse solution), 10% formic acid, commercial solution, and 14.4% neutral EDTA. MATERIALS AND METHODS: Freshly extracted premolar teeth were fixed and submitted for decalcification using different agents. Histological examination was qualitatively evaluated for tissue integrity and staining quality. RESULTS: Dentin integrity of teeth decalcified with all decalcifying agents did not show any statistical differences except that with the formic acid, whereas cementum integrity decalcified with neutral EDTA showed a superior score compared with other agents. Tissue integrity and staining quality of dental pulp cells were the best decalcified with neutral EDTA or Anna Morse solution. CONCLUSION: Our findings demonstrated that EDTA and Anna Morse solution gave a similar efficiency in the preservation of tissue integrity while Anna Morse solution may be recommended as a decalcification agent in routine use due to the more satisfying decalcification time than EDTA.

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OBJECTIVE: Oral verrucous squamous cell carcinoma or oral verrucous carcinoma (OVC) is a rare verrucous variant of oral squamous cell carcinoma (OSCC), which accounts for 2 to 12% of all oral carcinomas. Oral verrucous hyperplasia (OVH) is clinically similar to OVC and has been proposed to be a precursor lesion of OVC. Etiopathogenesis of both lesions is still inconspicuous. Oncogenic viruses such as human papillomavirus (HPV) and Epstein-Barr virus (EBV) have been reported to be associated with some cases of OSCC, and we hypothesized that it may act as a causative agent of these verrucous lesions. This study aimed to investigate frequency of HPV and EBV infections in OVC and OVH. MATERIAL AND METHODS: Using polymerase chain reaction (PCR), a total of 35 formalin-fixed paraffin-embedded (FFPE) tissue samples, including 27 OVC samples and 8 OVH samples, were investigated for HPV and EBV infection. HeLa and B95-8 cell lines were used as positive controls of HPV and EBV PCR, respectively. RESULTS: All OVC and OVH samples show a positivity to GAPDH, whereas neither HPV nor EBV PCR products was detected in both OVC and OVH samples. CONCLUSIONS: In summary, our study demonstrated that HPV and EBV are not involved in pathogenesis of OVC and OVH. Other etiologic factors contributing to OVC and OVH need to be further clarified.

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Enhancer of zeste homolog 2 (EZH2), a component of the polycomb repressive complex 2 that catalyzes trimethylation of H3K27 (H3K27me3), has been shown to promote tumor development and progression. Expression of EZH2 is associated with cell cycle regulation and cell proliferation in various neoplasms. Oral verrucous hyperplasia (OVH) and Oral verrucous carcinoma (OVC) are rare entities and share several clinical and histopathologic features. Problems distinguishing these lesions are added by a lack of adjacent normal tissue of the biopsy samples and poorly oriented tissue sections. The aim of this study was to investigate the expression of EZH2 and H3K27me3 in OVH and OVC and comparing the expression with normal oral mucosa and oral squamous cell carcinoma (OSCC). Seventy-eight samples, including 25 cases of OVC, 8 cases of OVH, 35 cases of OSCC and 10 cases of normal oral mucosa, were retrieved and submitted for immunohistochemical staining. The results demonstrated that the mean labeling indices (LIs) of EZH2 and H3K27me3 expression were highest in OSCC, followed by the OVC, OVH, and normal mucosa. Statistical differences in EZH2 LI were observed among these lesions whereas H3K27me3 LI was significantly different among OSCC, OVH and normal mucosa. EZH2 LI was found to have a sensitivity of 72.00% and specificity of 87.50% in distinguishing OVH from OVC, and a sensitivity of 57.14% and specificity of 84.00% in distinguishing OVC from OSCC. A positive correlation between EZH2 and H3K27me3 expression was significantly found in OVC but not in OVH and OSCC. These findings highlight the involvement of epigenetic regulation by EZH2-mediated H3K27me3 in the pathogenesis of OVH and OVC, and EZH2 expression indicates disease progression of these verrucous lesions. Diagnostic test analysis further suggests that EZH2 may be used as an additional test for differentiating OVH from OVC in questionable cases.

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