Immunohistochemical detection of phosphorylated Akt, PI3K, and PTEN in ameloblastic tumors

Identification of ferroptosis-related proteins in ameloblastoma based on proteomics analysis

PURPOSE

We used proteomic sequencing and experimental verification to identify the potential ferroptosis-related proteins in ameloblastoma.

METHODS

Samples of ameloblastoma (n = 14) and normal gingival tissues (n = 5) were collected for proteomic sequencing to identify differentially expressed proteins (DEPs) in ameloblastoma. Ferroptosis-related genes were downloaded from FerrDb V2, which were then compared with DEPs to obtain ferroptosis-related DEPs (FR-DEPs). A functional enrichment analysis was performed, and a protein-protein interaction network was built. The hub proteins were screened using the Cytoscape software, and potential drugs targeting them were retrieved from the DrugBank database. A hub protein was selected for immunohistochemical validation, and its expression was assessed in ameloblastomas, odontogenic keratocysts, dentigerous cysts, and normal gingival tissues. The primary ameloblastoma cells were cultured to explore the effect of the protein on the migratory properties of the tumour cells.

RESULTS

A total of 58 FR-DEPs were screened, and six hub proteins were identified: mTOR, NFE2L2, PRKCA, STAT3, EGFR, and CDH1. Immunohistochemical analysis showed that mTOR expression was upregulated in ameloblastomas compared with that in odontogenic keratocysts, dentigerous cysts, and normal gingival tissues. p-mTOR was highly expressed in ameloblastomas, with a positivity rate of 83.3%. In addition, rapamycin, an inhibitor of mTOR, can inhibit the migratory capacity of primary cultured ameloblastoma cells.

CONCLUSION

Our results revealed the ferroptosis-related proteins in ameloblastomas and their underlying biological processes. Additionally, mTOR was overexpressed and was found to be associated with the aggressiveness of ameloblastomas, which may be a potential target for future treatments.

Identification of BRAF V600E mutation in odontogenic tumors by high-performance MALDI-TOF analysis

Odontogenic tumors are rare lesions with unknown etiopathogenesis. Most of them are benign, but local aggressiveness, infiltrative potential, and high recurrence rate characterize some entities. The MAP-kinase pathway activation can represent a primary critical event in odontogenic tumorigenesis. Especially, the BRAF V600E mutation has been involved in 80–90% of ameloblastic lesions, offering a biological rationale for developing new targeted therapies. The study aims to evaluate the BRAF V600E mutation in odontogenic lesions, comparing three different detection methods and focusing on the Sequenom MassARRAY System. 81 surgical samples of odontogenic lesions were subjected to immunohistochemical analysis, Sanger Sequencing, and Matrix-Assisted Laser Desorption/Ionization-Time of Flight mass spectrometry (Sequenom). The BRAF V600E mutation was revealed only in ameloblastoma samples. Moreover, the presence of BRAF V600E was significantly associated with the mandibular site (ρ = 0.627; P value <0.001) and the unicystic histotype (ρ = 0.299, P value <0.001). However, any significant difference of 10-years disease-free survival time was not revealed. Finally, Sequenom showed to be a 100% sensitive and 98.1% specific, suggesting its high-performance diagnostic accuracy. These results suggest the MAP-kinase pathway could contribute to ameloblastic tumorigenesis. Moreover, they could indicate the anatomical specificity of the driving mutations of mandibular ameloblastomas, providing a biological rational for developing new targeted therapies. Finally, the high diagnostic accuracy of Sequenom was confirmed.

BDNF/TrkB/Akt Signaling Pathway Epithelial Odontogenic Tumors and Keratocyst: An Immunohistochemical Study Comparative With Dental Germs

Odontogenic lesions (OL) are an important group of oral and maxillofacial diseases represented by odontogenic cysts, benign, and malignant tumors. The brain-derived neurotrophic factor (BDNF)/ tropomyosin receptor kinase B (TrkB) signaling pathway has multiple biological actions and has been identified as an important pathway in the proliferation, invasion, and survival of different epithelial tumors. Its role in the development of OL, however, has so far been unexplored. Our aim was to evaluate the BDNF/TrkB/Akt/p-RPS6 signaling pathway in OL of epithelial origin. This cross-sectional study comprised 3 cases of tooth germs, 25 cases of odontogenic keratocyst (OK), 29 cases of ameloblastoma (Am), and 6 cases of ameloblastic carcinoma. Immunohistochemical staining for BDNF, TrkB, p-Akt, and p-RPS6 was performed. OLs were evaluated according to the pattern of immunohistochemical expression in epithelial cells and by semiquantitative scores that considered the intensity of staining and percentage of positive cells. BDNF stromal expression was also assessed. No significant differences were observed with respect to the percentage of positive cases for all markers. Regarding the immunoreactive scores, BDNF and p-RPS6 expressions were similar in the odontogenic epithelium of all OL. However, TrkB and p-Akt were overexpressed in OK compared with ameloblastic carcinoma. In Am, epithelial BDNF was significantly higher compared with stromal expression. In conclusion, BDNF seems to participate in the development of cystic, benign, and malignant odontogenic epithelium to similar degrees. The acquisition of the invasive or malignant phenotype in odontogenic neoplasms is not associated with alterations in the BDNF/TrkB/Akt/RPS6 axis, which could be implicated in the differentiation process.

Immunohistochemical analysis of Nuclear Factor-kappa B (NF-κB) between follicular and plexiform ameloblastomas: A pilot study

Background:

Ameloblastoma among benign tumors holds a unique position by its locally destructive and invasive nature. Tumors that originate from the odontogenic apparatus or its remnants in the jaws show diverse clinical presentations, behavior and histologic patterns. The differed biological behavior behind follicular and plexiform ameloblastomas has never attained completeness because of the lack of rhythmic correlation regarding the exact mechanism. Nuclear factor-kappa B (NF-κB) pathways play a crucial role in survival, death and differentiation during physiologic and pathologic conditions. With this background, the study has been aimed to investigate the expression of NF-κB in follicular and plexiform ameloblastomas.

Objective:

The objective of this study was to analyze the immunohistochemical expression pattern of NF-κB in ameloblastoma and to compare the immunohistochemical expression pattern of NF-κB among the histological types of ameloblastoma, follicular and plexiform patterns.

Methodology:

Total 20 ameloblastomas (10 follicular, 10 plexiform) were immunostained with antihuman NF-κB p65 mouse IgG monoclonal antibody, and the pattern of staining is statistically analyzed using Chi-square test with the level of significance (P < 0.05).

Results:

Twelve (3 follicular, 9 plexiform) out of 20 ameloblastomas showed immunoreactivity to NF-κB p65. In ameloblastoma, only the peripheral preameloblast-like tall columnar cells showed reactivity, whereas the stellate reticulum-like cells are immunonegative. The staining pattern was membranous in the immunoreactive cells. The results were studied with the associated and inducing pathways from the literature, and a possible mechanism has been proposed.

Conclusion:

The expression pattern of NF-κB was found to be higher in plexiform ameloblastoma than follicular ameloblastoma.

Role of phosphatase and tensin homolog in pathogenesis of ameloblastoma: An immunohistochemical study

Background

Altered molecular signaling pathways in ameloblastoma have been identified to play a pivotal role in the mechanism of oncogenesis, differentiation, and tumor progression. Phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin pathway is one of the signaling pathways that are associated with the pathogenesis of ameloblastoma. Phosphatase and tensin homolog (PTEN) controls cell migration and proliferation. It monitors the level of the Akt and maintains cellular integrity. The present study was aimed to study the immunoexpression of PTEN in ameloblastoma to understand its role in the pathogenesis of ameloblastoma.

Materials and Methods

Twenty cases of ameloblastoma and ten cases of normal tooth germ were subjected to immunohistochemical staining against PTEN.

Results

Strong PTEN immunopositivity was seen in the tooth germs, while weak positivity was seen in the ameloblastoma. The immunoscore for PTEN was calculated by adding the percentage score and the intensity score. Seventeen cases showed the reduced PTEN expression in the epithelial component of ameloblastoma. The unpaired t-test showed a statistically significant difference in the mean PTEN immunoscore in tooth germ and ameloblastoma.

Conclusion

The study showed reduced PTEN immunoreactivity, which plays a role in the pathogenesis of ameloblastoma, through Akt pathway.

Immunohistochemical Detection of Nerve Growth Factor (NGF) in Follicular and Plexiform Ameloblastoma - A Novel Study

Background:

Ameloblastoma is the second most common odontogenic tumor that holds a unique position among benign tumors due to its locally destructive and invasive nature. The differed tumor biology behind follicular and plexiform ameloblastoma is always an enigma. Nerve growth factor (NGF), a neurotrophin that plays a major role during odontogenesis, could also possibly play a role in the pathogenesis of odontogenic tumors such as ameloblastoma. With this background, the study was aimed to investigate the expression of NGF in follicular and plexiform ameloblastoma.

Objectives:

The objectives of this study were to analyze the immunohistochemical expression pattern of NGF in ameloblastoma and to compare the immunohistochemical expression pattern of NGF among the follicular and plexiform histological types of ameloblastoma.

Materials and Methods:

Forty histological sections of ameloblastomas (20 follicular and 20 plexiform) were stained immunohistochemically with anti-human NGF mouse IgG monoclonal antibody and the staining was analyzed statistically.

Results:

Almost all the 40 ameloblastoma samples (20 follicular and 20 plexiform) showed positive immunoreactivity to NGF. Both peripheral pre-ameloblast-like tall columnar cells and central stellate-reticulum-like cells showed positive reactivity. The pattern of staining was membranous in the immunoreactive cells. The χ² value for the immunoexpression between follicular and plexiform ameloblastoma was statistically significant with a P value <0.002. A possible mechanism has been proposed after studying the results with the downstream pathways obtained from literature.

Conclusion:

The pattern of expression of NGF is seen in both follicular and plexiform ameloblastoma. But the intensity is more in plexiform than that of follicular ameloblastoma.

Investigation of PTEN promoter methylation in ameloblastoma

Background

Phosphatase and tensin homolog (PTEN) acts as a tumor suppressor gene. Inactivation of PTEN has been reported in various types of cancers. PTEN promoter methylation possibly underlies PTEN inactivation, which results in tumorigenesis. The aim of this study was to investigate whether PTEN promoter methylation contributes to PTEN inactivation in ameloblastoma and its associated protein expression.

Material and Methods

In total, 20 fresh-frozen ameloblastoma samples were evaluated for PTEN promoter methylation using methylation-specific polymerase chain reaction (MS-PCR). A subset of 10 paraffin-embedded ameloblastoma samples was examined for PTEN expression through immunohistochemistry. Four primary cultured ameloblastoma cells were investigated for PTEN promoter methylation and PTEN transcriptional expression via reverse transcription PCR.

Results

PTEN promoter methylation was detected in 65% (13/20) of the ameloblastoma samples. Of 10 ameloblastoma samples, 4 exhibited reduced PTEN expression. Of 5 samples with methylated PTEN, 3 (60%) were associated with loss of PTEN expression. However, PTEN expression was detected in 4 (80%) of 5 samples with unmethylated PTEN. In addition, 3 (75%) of 4 primary ameloblastoma cell cultures exhibited an inverse correlation between PTEN promoter methylation and PTEN transcription level.

Conclusions

PTEN promoter methylation is found in a number of ameloblastomas but not significantly correlated with loss of PTEN expression. Genetic or epigenetic mechanisms other than PTEN promoter methylation may contribute to PTEN inactivation in ameloblastoma tumor cells.

Key words:PTEN, promoter methylation, ameloblastoma.

Immunohistochemical detection of Tyrosine Kinase receptor (TrK) in follicular and plexiform ameloblastoma - A novel study

Objectives:

The objective is to analyze the immunohistochemical expression pattern of tyrosine kinase receptor (TrK) in ameloblastoma and to compare the immunohistochemical expression pattern of TrK among the histological types of ameloblastoma, follicular and plexiform patterns.

Materials and Methods:

Forty ameloblastomas (20 follicular and 20 plexiform) were immunostained with anti-human TrK mouse IgG monoclonal antibody, and the pattern of staining is statistically analyzed.

Results:

Total 20 (4 follicular and 16 plexiform) out of 40 ameloblastomas showed immunoreactivity to TrK. Only the peripheral preameloblast like tall columnar cells showed reactivity, whereas the stellate reticulum like cells is immunonegative. The staining pattern was membranous in the immunoreactive cells. The Chi-square value for the immunoexpression between follicular and plexiform ameloblastoma was statistically significant with a P < 0.005. The results were studied with the downstream pathways from the literature, and a possible mechanism has been proposed.

Conclusion:

The expression pattern of TrK is found to be more in plexiform ameloblastoma than follicular ameloblastoma.

Genetic alteration of Exon 5 of the PTEN gene in Indian patients with ameloblastoma

OBJECTIVE

The PI3K/Akt/mTOR pathway is one of the signaling pathways associated with the pathogenesis of ameloblastoma. The phosphatase and tensin (PTEN) homologue controls cell migration and proliferation. It monitors the level of Akt and maintains cellular integrity. The aim of the present study was to study the genetic alteration of Exon 5 of the PTEN gene in Indian patients with ameloblastoma.

STUDY DESIGN

Total DNA was extracted from formalin-fixed paraffin-embedded tissue samples from 20 cases with solid multicystic ameloblastoma (SMA) and from 10 cases with normal tooth germ. Exon 5 of the PTEN gene, was assessed for its role in the pathogenesis of ameloblastoma.

RESULTS

Five of 20 cases of SMA showed genetic alteration. Of these cases 3 (15%) showed silent mutation, 1 (5%) showed change in amino acid sequence from valine to glutamic acid, and 1 (5%) showed nonsense-mediated mRNA decay.

CONCLUSIONS

The present study showed 25% somatic mutational frequency in exonic region 5 of the PTEN gene. This may indicate its role in the pathogenesis of ameloblastoma.

Cancer genes mutation profiling in calcifying epithelial odontogenic tumour

Aims

To identify calcifying epithelial odontogenic tumour (CEOT) mutations in oncogenes and tumour suppressor genes.

Methods

A panel of 50 genes commonly mutated in cancer was sequenced in CEOT by next-generation sequencing. Sanger sequencing was used to cover the region of the frameshift deletion identified in one sample.

Results

Missense single nucleotide variants (SNVs) with minor allele frequency (MAF) <1% were detected in PTEN, MET and JAK3. A frameshift deletion in CDKN2A occurred in association with a missense mutation in the same gene region, suggesting a second hit in the inactivation of this gene. APC, KDR, KIT, PIK3CA and TP53 missense SNVs were identified; however, these are common SNVs, showing MAF >1%.

Conclusion

CEOT harbours mutations in the tumour suppressor PTEN and CDKN2A and in the oncogenes JAK3 and MET. As these mutations occurred in only one case each, they are probably not driver mutations for these tumours.

Immunohistochemical biomarkers in ameloblastomas

Ameloblastoma is an aggressive odontogenic tumour, which is locally invasive and highly recurrent. Studies show that ameloblastoma is a benign odontogenic neoplasia, being relatively rare and occasionally presenting behaviour of malignant lesions. In addition to these particularities, the histological diagnosis of ameloblastoma can be challenging when the tumour shows high rates of mitosis, absence of nuclear pleomorphism, basilar hyperplasia and neural invasion. In order to help in the diagnosis, prognosis and treatment of this neoplasia, some immunohistochemical markers were shown to be associated with tumoural epithelium. The identification of these markers as well as of their association with clinical signs can be useful to elaborate more efficient treatment strategies and to control this pathology, including improvement of the quality of life of patients affected by this neoplasia. This article aims to review some markers associated with specific molecular pathways, bone remodelling, cell proliferation, apoptosis, cell signalling and tumour suppression.

Immunohistochemical Detection of p75 Neurotrophin Receptor (p75-NTR) in Follicular and Plexiform Ameloblastoma

INTRODUCTION

Ameloblastoma holds a unique position among benign tumours by its locally destructive and invasive nature. Recently improvised molecular techniques helped researchers to unravel the myth behind such biologic behaviour. Though interesting findings have been delivered, the rhythmic correlation regarding the exact mechanism still remains lacking. Neurotrophins and their receptor mediated pathways play a crucial role in survival, death and differentiation of many neuroectoderm derived cells. With this background, the study has been aimed to investigate the expression of p75-NTR (Neurotrophin Receptor) in follicular and plexiform ameloblastoma.

AIM

To analyze the immunohistochemical expression pattern of p75-NTR in ameloblastoma and to compare the immunohistochemical expression pattern of p75-NTR among the histological types of ameloblastoma, follicular and plexiform patterns.

MATERIALS AND METHODS

Total 22 ameloblastomas (12 follicular, 10 plexiform) were immuno-stained with anti-human p75-NTR mouse IgG monoclonal antibody and the pattern of staining is statistically analyzed.

RESULTS

Only 11 (10 follicular, 1 plexiform) out of 22 ameloblastomas showed immuno-reactivity to p75-NTR. In ameloblastoma, only the peripheral pre-ameloblast like tall columnar cells showed reactivity whereas the stellate reticulum-like cells were immuno-negative. The staining pattern was membranous in the immuno-reactive cells. The results were studied with the downstream pathways from the literature and a possible mechanism has been proposed.

CONCLUSION

The expression pattern of p75-NTR was found to be more in follicular ameloblastoma than plexiform.

Molecular Signaling in Benign Odontogenic Neoplasia Pathogenesis

Several molecular pathways have been shown to play critical roles in the pathogenesis of odontogenic tumors. These neoplasms arise from the epithelial or mesenchymal cells of the dental apparatus in the jaw or oral mucosa. Next generation genomic sequencing has identified gene mutations or single nucleotide polymorphisms associated with many of these tumors. In this review, we focus on two of the most common odontogenic tumor subtypes: ameloblastoma and keratocystic odontogenic tumors. We highlight gene expression and protein immunohistological findings and known genetic alterations in the hedgehog, BRAF/Ras/MAPK, epidermal growth factor receptor, Wnt and Akt signaling pathways relevant to these tumors. These various pathways are explored to potentially target odontogenic tumors cells and prevent growth and recurrence of disease. Through an understanding of these signaling pathways and their crosstalk, molecular diagnostics may emerge as well as the ability to exploit identified molecular differences to develop novel molecular therapeutics for the treatment of odontogenic tumors.

Thymosin beta 4 is associated with RUNX2 expression through the Smad and Akt signaling pathways in mouse dental epithelial cells

In previous studies by our group, we reported that thymosin beta 4 (Tb4) is closely associated with the initiation and development of the tooth germ, and can induce the expression of runt-related transcription factor 2 (RUNX2) during the development of the tooth germ. RUNX2 regulates the expression of odontogenesis-related genes, such as amelogenin, X-linked (Amelx), ameloblastin (Ambn) and enamelin (Enam), as well as the differentiation of osteoblasts during bone formation. However, the mechanisms through which Tb4 induces the expression of RUNX2 remain unknown. In the present study, we employed a mouse dental epithelial cell line, mDE6, with the aim to elucidate these mechanisms. The mDE6 cells expressed odontogenesis-related genes, such as Runx2, Amelx, Ambn and Enam, and formed calcified matrices upon the induction of calcification, thus showing characteristics of odontogenic epithelial cells. The expression of odontogenesis-related genes, and the calcification of the mDE6 cells were reduced by the inhibition of phosphorylated Smad1/5 (p-Smad1/5) and phosphorylated Akt (p-Akt) proteins. Furthermore, we used siRNA against Tb4 to determine whether RUNX2 expression and calcification are associated with Tb4 expression in the mDE6 cells. The protein expression of p-Smad1/5 and p-Akt in the mDE6 cells was reduced by treatment with Tb4-siRNA. These results suggest that Tb4 is associated with RUNX2 expression through the Smad and PI3K-Akt signaling pathways, and with calcification through RUNX2 expression in the mDE6 cells. This study provides putative information concerning the signaling pathway through which Tb4 induces RUNX2 expression, which may help to understand the regulation of tooth development and tooth regeneration.

Molecular concepts in the pathogenesis of ameloblastoma: implications for therapeutics

Ameloblastoma is a benign odontogenic neoplasm that may exhibit aggressive biological behavior as evidenced by its rapid growth and significance recurrence rates following initial surgical resection. Currently, the only therapy for ameloblastoma is surgical, and adjunctive treatment modalities are needed to mitigate tumor growth and to reduce the need for extensive and disfiguring surgeries. Many studies have identified markers expressed by ameloblastoma and these lend insight to our understanding of tumor progression. This review provides a summary of the specific molecular pathways implicated in tumor pathogenesis, including those involved in bone remodeling, apoptosis, cell signaling, and tumor suppression. Based on these data, we identify several prognostic or therapeutic markers that have been used successfully in the treatment of other neoplastic processes that may also have diagnostic and prognostic utility for ameloblastoma. Thus, it is important to determine which markers hold the greatest promise for clinical management of this benign neoplasm in order to improve treatment options, particularly in patients with aggressive forms of ameloblastoma.

Activation of the Akt/mTOR pathway in dentigerous cysts, odontogenic keratocysts, and ameloblastomas

OBJECTIVE

The aim of this study was to investigate the Akt/mTOR pathway in dentigerous cysts (DCs), odontogenic keratocysts (OKCs), and ameloblastomas.

STUDY DESIGN

A total of 90 cases were studied (30 DCs, 30 OKCs, and 30 ameloblastomas). Patient records on age, sex, lesion location, symptoms, and radiographic and histopathologic features were collected. The phosphorylation of components of the Akt/mTOR pathway [p-Akt (Ser473), p-Akt (Thr308), and phosphorylated-ribosomal protein S6 (p-RPS6)] was studied using immunohistochemistry. Correlations with clinical features were analyzed using the Spearman rank test.

RESULTS

Over 90% of OKCs and ameloblastomas and 60% of DCs stained positive for p-Akt (Ser473). Phospho-Akt (Thr308) was positive in 73% of ameloblastomas, 40% of OKCs, and 20% of DCs. Phospho-RPS6 was detected most frequently in OKCs (83%), followed by ameloblastomas (76%) and DCs (53%). No correlations were noted between the immunohistochemical findings and the clinicopathologic parameters.

CONCLUSIONS

The Akt/mTOR pathway is upregulated in DCs, OKCs, and ameloblastomas. This pathway may be involved in the development of these lesions.

Acute sensitivity of the oral mucosa to oncogenic K-ras

Mouse models of cancer represent powerful tools for analysing the role of genetic alterations in carcinogenesis. Using a mouse model that allows tamoxifen-inducible somatic activation (by Cre-mediated recombination) of oncogenic K-ras^G12D in a wide range of tissues, we observed hyperplasia of squamous epithelium located in moist or frequently abraded mucosa, with the most dramatic effects in the oral mucosa. This epithelium showed a sequence of squamous hyperplasia followed by squamous papilloma with dysplasia, in which some areas progressed to early invasive squamous cell carcinoma, within 14 days of widespread oncogenic K-ras activation. The marked proliferative response of the oral mucosa to K-ras^G12D was most evident in the basal layers of the squamous epithelium of the outer lip with hair follicles and wet mucosal surface, with these cells staining positively for pAKT and cyclin D1, showing Ras/AKT pathway activation and increased proliferation with Ki-67 and EdU positivity. The stromal cells also showed gene activation by recombination and immunopositivity for pERK indicating K-Ras/ERK pathway activation, but without Ki-67 positivity or increase in stromal proliferation. The oral neoplasms showed changes in the expression pattern of cytokeratins (CK6 and CK13), similar to those observed in human oral tumours. Sporadic activation of the K-ras^G12D allele (due to background spontaneous recombination in occasional cells) resulted in the development of benign oral squamous papillomas only showing a mild degree of dysplasia with no invasion. In summary, we show that oral mucosa is acutely sensitive to oncogenic K-ras, as widespread expression of activated K-ras in the murine oral mucosal squamous epithelium and underlying stroma can drive the oral squamous papilloma–carcinoma sequence. Copyright © 2011 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

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.