PTCH-1 and MDM2 expression in ameloblastoma from a West African sub-population: implication for chemotherapeutics

Association of MDM2 Overexpression in Ameloblastomas with MDM2 Amplification and BRAFV600E Expression

Ameloblastoma is a rare tumor but represents the most common odontogenic neoplasm. It is localized in the jaws and, although it is a benign, slow-growing tumor, it has an aggressive local behavior and high recurrence rate. Therefore, alternative treatment options or complementary to surgery have been evaluated, with the most promising one among them being a targeted therapy with the v-Raf murine sarcoma viral oncogene homologue B (BRAF), as in ameloblastoma the activating mutation V600E in BRAF is common. Studies in other tumors have shown that the synchronous inhibition of BRAF and human murine double minute 2 homologue (MDM2 or HDM2) protein is more effective than BRAF monotherapy, particularly in the presence of wild type p53 (WTp53). To investigate the MDM2 protein expression and gene amplification in ameloblastoma, in association with BRAFV600E and p53 expression. Forty-four cases of ameloblastoma fixed in 10% buffered formalin and embedded in paraffin were examined for MDM2 overexpression and BRAFV600E and p53 expression by immunohistochemistry, and for MDM2 ploidy with fluorescence in situ hybridization. Sixteen of forty-four (36.36%) cases of ameloblastoma showed MDM2 overexpression. Seven of sixteen MDM2-positive ameloblastomas (43.75%) were BRAFV600E positive and fifteen of sixteen MDM2-positive ameloblastomas (93.75%) were p53 negative. All MDM2 overexpressing tumors did not show copy number alterations for MDM2. Overexpression of MDM2 in ameloblastomas is not associated with MDM2 amplification, but most probably with MAPK activation and WTp53 expression. Further verification of those findings could form the basis for the use of MDM2 expression as a marker of MAPK activation in ameloblastomas and the trial of dual BRAF/MDM2 inhibition in the management of MDM2-overexpressing/BRAFV600E-positive/WTp53 ameloblastomas.

Diagnostic significance of NM23 protein in ameloblastoma and ameloblastic carcinoma: An immunohistochemical study

BACKGROUND

Clinico-histopathologic assessment of patients with ameloblastoma and ameloblastic carcinoma remains the best diagnostic modality for the tumors. However, in cases where the criteria for arriving at a definitive diagnosis are not clearcut, the pathologist is faced with a dilemma and thus an imperative need for adjunct diagnostic methods.

OBJECTIVES

To evaluate/compare the immunohistochemical expression of NM23 in classical, borderline (atypical) ameloblastoma and ameloblastic carcinoma and to assess usefulness of NM23 in closing diagnostic gaps between ameloblastoma and ameloblastic carcinoma.

METHODS

Twenty-four (24) cases of ameloblastoma, 10 ameloblastoma with classical histopathologic features, 8 with nonclassical histopathology [atypical], and 6 cases of ameloblastic carcinoma were selected from cases seen at the Oral Pathology Laboratory of the Lagos State University College of Medicine, Nigeria. NM23 immunostaining protocol was done on the selected tissue blocks and evaluated using Sinicrope method. Analysis was done using R language.

RESULTS

Positive NM23 staining was observed in all cases of ameloblastoma and ameloblastic carcinoma, with more intense staining observed in the stellate reticulum-like areas than in the ameloblast-like areas. Ameloblastic carcinoma stained intensely with NM23 (100%) compared with atypical cases (37.5%) and ameloblastoma (20.0%; p = 0.04). The mean aggregate score was also significantly higher in AC (11 ± 2.4; p = 0.01). The mean aggregate score was also significant amongst growth pattern of ameloblastoma (p = 0 0.02).

CONCLUSIONS

The findings in this study reveal the usefulness of NM23 in differentiating ameloblastoma from ameloblastic carcinoma; a more comprehensive study with a larger sample size is recommended to corroborate or refute the findings in this study.

Expression of PTCH gene in ameloblastoma and odontogenic keratocyst: A comparative study

Aim

This is a cross-sectional comparative study, aimed to quantify the expression of patched (PTCH) gene in ameloblastoma, odontogenic keratocyst (OKC) and also the comparison of both the expressions.

Materials and Methods

Genomic deoxyribonucleic acid (DNA) was extracted and quantified, and the expression of the PTCH gene was done in 17 cases of ameloblastoma and 17 cases of OKC by quantitative real-time polymerase chain reaction (RT-qPCR).

Results

It was observed that there was an overexpression of the PTCH gene in both ameloblastoma and OKC with a good mean cycle threshold (CT) value of 32.71 ± 2.432 and 34.69 ± 1.875, respectively. When comparing the PTCH expression between the two, ameloblastoma showed higher expression than the OKC and the difference is statistically significant with P value of 0.025.

Conclusions

Our findings suggest that there is overexpression of PTCH in ameloblastoma and OKC, but it is highly expressed in ameloblastoma when compared to OKC. Overexpression of PTCH may constitute the activation of the Sonic Hedgehog pathway and may suggest the mechanism for the development of ameloblastoma and OKC. Hence it can be used as a valuable marker for early diagnosis and in the identification of therapeutic targets.