Discovery of novel molecular characteristics and cellular biological properties in ameloblastoma

Targeting BRD4 attenuates the stemness and aggressiveness of ameloblastoma

BACKGROUND

BRD4, belonging to the bromodomain extra-terminal (BET) protein family, plays a unique role in tumor progression. However, the potential impact of BRD4 in ameloblastoma (AM) remains largely unknown. Herein, we aimed to assess the expression and functional role of BRD4 in AM.

METHODS

The expression level of BRD4 was assessed by immunohistochemistry. The proliferation, migration, invasion, and tumorigenic abilities of AM cells were assessed by a series of assays. To explore the molecular expression profile of BRD4-depleted AM cells, RNA sequencing (RNA-seq) was performed. Bioinformatic analysis was performed on AM expression matrices obtained from the Gene Expression Omnibus (GEO). The therapeutic efficacy of BET-inhibitors (BETi) was assessed with AM patient-derived organoids.

RESULTS

Upregulation of BRD4 was observed in conventional AMs, recurrent AMs, and ameloblastic carcinomas. Depletion of BRD4 inhibited proliferation, invasion, migration, and tumorigenesis in AM. Administration of BETi attenuated the aggressiveness of AM and the growth of AM patient-derived organoids. Bioinformatic analysis indicated that BRD4 may promote AM progression by regulating the Wnt pathway and stemness-associated pathways.

CONCLUSION

BRD4 increases the aggressiveness and promotes the recurrence of ameloblastoma by regulating the Wnt pathway and stemness-associated pathways. These findings highlight BRD4 as a promising therapeutic target in AM management.

Identification of Molecular Mechanisms of Ameloblastoma and Drug Repositioning by Integration of Bioinformatics Analysis and Molecular Docking Simulation

Background

Ameloblastoma (AM) is a benign tumor locally originated from odontogenic epithelium that is commonly found in the jaw. This tumor makes aggressive invasions and has a high recurrence rate. This study aimed to investigate the differentially expressed genes (DEGs), biological function alterations, disease targets, and existing drugs for AM using bioinformatics analysis.

Methods

The data set of AM was retrieved from the GEO database (GSE132474) and identified the DEGs using bioinformatics analysis. The biological alteration analysis was applied to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Protein-protein interaction (PPI) network analysis and hub gene identification were screened through NetworkAnalyst. The transcription factor-protein network was constructed via OmicsNet. We also identified candidate compounds from L1000CDS2 database. The target of AM and candidate compounds were verified using docking simulation.

Results

Totally, 611 DEGs were identified. The biological function enrichment analysis revealed glycosaminoglycan and GABA (γ-aminobutyric acid) signaling were most significantly up-regulated and down-regulated in AM, respectively. Subsequently, hub genes and transcription factors were screened via the network and showed FOS protein was found in both networks. Furthermore, we evaluated FOS protein to be a therapeutic target in AMs. Candidate compounds were screened and verified using docking simulation. Tanespimycin showed the greatest affinity binding value to bind FOS protein.

Conclusions

This study presented the underlying molecular mechanisms of disease pathogenesis, biological alteration, and important pathways of AMs and provided a candidate compound, Tanespimycin, targeting FOS protein for the treatment of AMs.

Extracellular matrix of ameloblastoma-derived negatively regulates osteogenic differentiation

OBJECTIVE

To investigate the effects of key pathogenic genes involved in the development of jaw ameloblastoma (AB) and its associated extracellular matrix (ECM) on osteogenic differentiation in order to provide a theoretical foundation for future research into bone aggressiveness of AB.

METHODS

The essential genes were identified by five AB patients for whole-exome sequencing and the microarray datasets GES38494 and GES132472. Moreover, the expression of key genes and their encoded proteins in AB tissues was explored. In addition, AB-derived the decellularized ECM (ABdECM) tissues were generated by the decellularization technique. Furthermore, the osteogenic development of periodontal ligament stem cells (PDLSCs) was mimicked by simulating the effects of the AB tumor microenvironment (TME).

RESULTS

The AB essential genes including COL1A2, COL4A2, FBN1, and HPSE were discovered. Among them, the expression of HPSE was down-regulated, while that of COL1A2, COL4A2, and FBN1 was noticeably upregulated in AB compared with normal gingival tissues of the jaws. In vitro osteogenic differentiation of PDLSCs was suppressed by the ABdECM.

CONCLUSIONS

Abnormal ECM proteins encoded by COL4A2, COL1A2, FBN1, and HPSE genes can cause disturbance in the ECM environment of AB and promote bone resorption.

Molecular pathogenesis of ameloblastoma

Ameloblastoma (AM) is a benign, although aggressive, epithelial odontogenic tumour originating from tooth-forming tissues or remnants. Its aetiopathogenesis remains unclear; however, molecular analysis techniques have allowed researchers to progress in understanding its genetic basis. The high frequency of BRAF p.V600E as a main driver mutation in AM is well established; nevertheless, it is insufficient to explain its tumourigenesis. In this review, we aimed to integrate the current knowledge about the biology of AM and to describe the main genetic alterations reported, focusing on the findings of large-scale sequencing and gene expression profiling techniques. Current evidence shows that besides BRAF mutation and activation of the MAPK pathway, alterations in Hedgehog and Wnt/β-catenin pathway-related genes are also involved in AM pathogenesis. Recently, a tumour suppressor gene, KMT2D, has been reported as mutated by different research groups. The biological impact of these mutations in the pathogenesis of AM has yet to be elucidated. Further studies are needed to clarify the impact of these findings in the identification of novel biomarkers that could be useful for diagnosing, classifying, and molecular targeting this neoplasm.

BRAF p.V600E Mutational Status Does Not Correlate with Biological Behavior in Conventional Ameloblastomas: A Disease-Free Survival Analysis

BACKGROUND

Dysregulation of the MAPK pathway appears to exert a pivotal role in the pathogenesis of ameloblastomas, since BRAF p.V600E has been reported in over 65% of the tumors. Therefore, the purpose of this study was to investigate whether the BRAF p.V600E is related to biological behavior and disease-free survival in patients with conventional ameloblastomas.

METHODS

This is a retrospective cohort study based on the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) recommendations. The study population consisted of individuals treated for conventional ameloblastomas. Clinical, imaging, histomorphological, immunohistochemical (Ki67 and CD138/syndecan-1), and molecular BRAF p.V600E mutation analyses were performed. Bivariate statistical analysis was performed through chi-square and Fisher's exact tests. Kaplan-Meier analysis with log-rank test and Cox proportional hazards regression were used to identify predictors of disease-free survival, with a significance level of 5%.

RESULTS

Forty-one individuals were included, with a male-to-female ratio of 1.15:1. BRAF p.V600E mutation was identified in 75.6% of the tumors. No association between the BRAF mutational status and other clinical, imaging, histomorphological, and immunohistochemical variables was observed. Only the initial treatment modality was significantly associated with a better prognosis in univariate (p = 0.008) and multivariate (p = 0.030) analyses, with a hazard ratio of 9.60 (95%IC = 1.24-73.89), favoring radical treatment.

CONCLUSION

BRAF p.V600E mutation emerges as a prevalent molecular aberration in ameloblastomas. Nevertheless, it does not seem to significantly affect the tumor proliferative activity, CD138/syndecan-1-mediated cell adhesion, or disease-free survival outcomes.

PDZ-binding kinase inhibitor OTS514 suppresses the proliferation of oral squamous carcinoma cells

OBJECTIVE

PDZ-binding kinase (PBK) has been reported as a poor prognostic factor and is a promising molecular target for anticancer therapeutics. Here, we aimed to investigate the effect of specific PBK inhibitor OTS514 on the survival of OSCC cells.

METHODS

Four OSCC cell lines (HSC-2, HSC-3, SAS, and OSC-19) were used to examine the effect of OTS514 on cell survival and apoptosis. DNA microarray analysis was conducted to investigate the effect of OTS514 on gene expression in OSCC cells. Gene set enrichment analysis was performed to identify molecular signatures related to the antiproliferative effect of OTS514.

RESULTS

OTS514 decreased the cell survival of OSCC cells dose-dependently, and administration of OTS514 readily suppressed the HSC-2-derived tumor growth in immunodeficient mice. Treatment with OTS514 significantly increased the number of apoptotic cells and caspase-3/7 activity. Importantly, OTS514 suppressed the expression of E2F target genes with a marked decrease in protein levels of E2F1, a transcriptional factor. Moreover, TP53 knockdown attenuated OTS514-induced apoptosis.

CONCLUSION

OTS514 suppressed the proliferation of OSCC cells by downregulating the expression of E2F target genes and induced apoptosis by mediating the p53 signaling pathway. These results highlight the clinical application of PBK inhibitors in the development of molecular-targeted therapeutics against OSCC.

Single-cell transcriptomics reveals cell atlas and identifies cycling tumor cells responsible for recurrence in ameloblastoma

Ameloblastoma is a benign tumor characterized by locally invasive phenotypes, leading to facial bone destruction and a high recurrence rate. However, the mechanisms governing tumor initiation and recurrence are poorly understood. Here, we uncovered cellular landscapes and mechanisms that underlie tumor recurrence in ameloblastoma at single-cell resolution. Our results revealed that ameloblastoma exhibits five tumor subpopulations varying with respect to immune response (IR), bone remodeling (BR), tooth development (TD), epithelial development (ED), and cell cycle (CC) signatures. Of note, we found that CC ameloblastoma cells were endowed with stemness and contributed to tumor recurrence, which was dominated by the EZH2-mediated program. Targeting EZH2 effectively eliminated CC ameloblastoma cells and inhibited tumor growth in ameloblastoma patient-derived organoids. These data described the tumor subpopulation and clarified the identity, function, and regulatory mechanism of CC ameloblastoma cells, providing a potential therapeutic target for ameloblastoma.

Does BRAF V600E mutation affect recurrence rate of ameloblastomas? Systematic review and meta-analysis

OBJECTIVE

The objective of this systematic review with meta-analysis was to critically evaluate the available data on the association of the BRAF V600E mutation and recurrence rate of ameloblastomas.

MATERIALS AND METHODS

This systematic review was registered in Prospero (CRD42020183645) and performed based on the PRISMA statement. A comprehensive search in PubMed, Web of Science, Scopus and Cochrane Library databases was performed in order to answer the question "Does BRAF V600E mutation affect recurrence rate of ameloblastomas?" Methodological quality and risk of bias of the selected studies were assessed with JBI Critical Appraise Tool. Meta-analysis of quantitative data was conducted with RevMan 5.3 and Jamovi 2.3.

RESULTS

The initial search identified 302 articles, and 21 met the inclusion criteria. A total of 855 subjects with ameloblastoma were included in the analysis. The pooled measures for frequency of BRAF V600E mutation was 65.30% (95% CI: 0.56-0.75; p < .001; I2  = 90.85%; τ = 0.205; p < .001), and the pooled recurrence rate was 25.30% (95% CI: 0.19-0.31; p < .001; I2  = 79.44%; τ = 0.118; p < .001). No differences in recurrence rate were observed between the BRAF V600E and wild type BRAF ameloblastomas, with a pooled Odds Ratio of 0.93 (95% CI: 0.56-1.54; p = .78; I2  = 31%; p = .09).

CONCLUSIONS

BRAF V600E mutation is a frequent event in ameloblastomas, but does not increase nor reduce its recurrence rate, and thus have a limited value in predicting its prognosis.

Inhibition of VEGFR2 and EGFR signaling cooperatively suppresses the proliferation of oral squamous cell carcinoma

BACKGROUND

Epidermal growth factor receptor (EGFR) is frequently overexpressed in oral squamous cell carcinoma (OSCC), and EGFR-targeting therapeutics have been widely employed to treat patients with a variety of carcinomas including OSCC. Here, we aimed to investigate alternative signaling for OSCC survival under the disruption of EGFR signaling.

METHODS

OSCC cell lines, namely HSC-3 and SAS, were utilized to investigate how EGFR disruption affects cell proliferation. Gene set enrichment analysis was performed to examine how EGFR disruption affects oncogenic signaling in OSCC cells. Disruption of KDR gene was performed using CRISPR/Cas9 techniques. A VEGFR inhibitor, vatalanib was used to research the impact of VEGFR inhibition on OSCC survival.

RESULTS

EGFR disruption significantly decreased the proliferation and oncogenic signaling including Myc and PI3K-Akt, in OSCC cells. Chemical library screening assays revealed that VEGFR inhibitors continued to inhibit the proliferation of EGFR-deficient OSCC cells. In addition, CRISPR-mediated disruption of KDR/VEGFR2 retarded OSCC cell proliferation. Furthermore, combined erlotinib-vatalanib treatment exhibited a more potent anti-proliferative effect on OSCC cells, compared to either monotherapy. The combined therapy effectively suppressed the phosphorylation levels of Akt but not p44/42.

CONCLUSION

VEGFR-mediated signaling would be an alternative signaling pathway for the survival of OSCC cells under the disruption of EGFR signaling. These results highlight the clinical application of VEGFR inhibitors in the development of multi-molecular-targeted therapeutics against OSCC.

CAMK2D: a novel molecular target for BAP1-deficient malignant mesothelioma

Malignant mesothelioma (MMe) is a rare but aggressive malignancy. Although the molecular genetics of MMe is known, including BRCA1-associated protein-1 (BAP1) gene alterations, the prognosis of MMe patients remains poor. Here, we generated BAP1 knockout (BAP1-KO) human mesothelial cell clones to develop molecular-targeted therapeutics based on genetic alterations in MMe. cDNA microarray and quantitative RT-PCR (qRT-PCR) analyses revealed high expression of a calcium/calmodulin-dependent protein kinase type II subunit delta (CAMK2D) gene in the BAP1-KO cells. CAMK2D was highly expressed in 70% of the human MMe tissues (56/80) and correlated with the loss of BAP1 expression, making it a potential diagnostic and therapeutic target for BAP1-deficient MMe. We screened an anticancer drugs library using BAP1-KO cells and successfully identified a CaMKII inhibitor, KN-93, which displayed a more potent and selective antiproliferative effect against BAP1-deficient cells than cisplatin or pemetrexed. KN-93 significantly suppressed the tumor growth in mice xenografted with BAP1-deficient MMe cells. This study is the first to provide a potential molecular-targeted therapeutic approach for BAP1-deficient MMe.

Desmoplastic Adamantinoma-like Thymic Carcinoma: Clinicopathologic, Immunohistochemical, and Molecular Study of 5 Cases

Five cases of a heretofore unreported rare variant of thymic carcinoma characterized by a striking resemblance to adamantinoma of the mandible are described. The tumors occurred in 4 women and 1 man aged 58 to 76 years (mean: 67.8 y); they arose in the anterior mediastinum and measured from 5.3 to 12.0 cm in greatest diameter (mean: 8.9 cm). Presenting symptoms included chest pain, shortness of breath, and in 2 patients, pleural effusion. One tumor was asymptomatic and discovered incidentally. Histologically, the tumors were extensively desmoplastic, and the cellular proliferation was characterized by multiple islands of squamous epithelium with striking peripheral palisading of nuclei and central areas containing clear cells resembling a stellate reticulum. Areas of preexisting spindle cell thymoma were identified in 2 cases; these areas gradually merged with the higher-grade component of the lesion. Cystic changes were noted in 3 cases. Immunohistochemical studies in 3 cases showed the tumor cells were positive for cytokeratins, p40 and p63, and all showed a high proliferation rate (>50% nuclear positivity) with Ki-67. Next-generation sequencing was performed in 2 cases that showed amplification of the AKT1 gene (copy numbers 6 and 13). Clinical follow-up in 3 patients showed recurrence and metastasis after 1 and 2 years; 1 patient passed away 2 years after diagnosis due to the tumor. Desmoplastic adamantinoma-like thymic carcinoma represents an unusual histologic variant of thymic carcinoma that needs to be distinguished from metastases from similar tumors to the mediastinum.

BRAF V600E Mutation in Ameloblastoma: A Systematic Review and Meta-Analysis

The discovery that ameloblastoma has a high mutation incidence of BRAF V600E may enable a better investigation of pathophysiology. However, there is inconsistent evidence regarding this mutation occurrence and its association with clinical information. This systematic review and meta-analysis aim to pool the overall mutation prevalence of BRAF V600E in reported ameloblastoma cases and to determine its association with patient demographic and clinicopathological features. Following the PRISMA guidelines, a comprehensive article search was conducted through four databases (Scopus, Google Scholar, PubMed, and Web of Science). Seventeen articles between 2014 and 2022 met the inclusion criteria with 833 ameloblastoma cases. For each included study, the significance of BRAF V600E on the outcome parameters was determined using odd ratios and 95% confidence intervals. Meta-analysis prevalence of BRAF V600E in ameloblastoma was 70.49%, and a significant meta-analysis association was reported for those younger than 54 years old and in the mandible. On the contrary, other factors, such as sex, histological variants, and recurrence, were insignificant. As a result of the significant outcome of BRAF V600E mutation in ameloblastoma pathogenesis, targeted therapy formulation can be developed with this handful of evidence.

Analyses of Transcriptomics Cell Signalling for Pre-Screening Applications in the Integrated Approach for Testing and Assessment of Non-Genotoxic Carcinogens

With recent rapid advancement of methodological tools, mechanistic understanding of biological processes leading to carcinogenesis is expanding. New approach methodologies such as transcriptomics can inform on non-genotoxic mechanisms of chemical carcinogens and can be developed for regulatory applications. The Organisation for the Economic Cooperation and Development (OECD) expert group developing an Integrated Approach to the Testing and Assessment (IATA) of Non-Genotoxic Carcinogens (NGTxC) is reviewing the possible assays to be integrated therein. In this context, we review the application of transcriptomics approaches suitable for pre-screening gene expression changes associated with phenotypic alterations that underlie the carcinogenic processes for subsequent prioritisation of downstream test methods appropriate to specific key events of non-genotoxic carcinogenesis. Using case studies, we evaluate the potential of gene expression analyses especially in relation to breast cancer, to identify the most relevant approaches that could be utilised as (pre-) screening tools, for example Gene Set Enrichment Analysis (GSEA). We also consider how to address the challenges to integrate gene panels and transcriptomic assays into the IATA, highlighting the pivotal omics markers identified for assay measurement in the IATA key events of inflammation, immune response, mitogenic signalling and cell injury.

Potential Biomarkers and Signaling Pathways Associated with the Pathogenesis of Primary Ameloblastoma: A Systems Biology Approach

Objective

Ameloblastoma is a benign odontogenic tumor that may lead to ameloblastic carcinoma. This study aimed to determine potential signaling pathways and biological processes, critical genes and their regulating transcription factors (TFs), and miRNAs, as well as protein kinases involved in the etiology of primary ameloblastoma.

Methods

The dataset GSE132472 was obtained from the GEO database, and multivariate statistical analyses were applied to identify differentially expressed genes (DEGs) in primary ameloblastoma tissues compared to the corresponding normal gingiva samples. A protein-protein interaction (PPI) map was built using the STRING database. The Cytoscape software identified significant modules and the hub genes within the PPI network. Gene Ontology annotation and signaling pathway analyses were executed by employing the DAVID and Reactome databases, respectively. Significant TFs and miRNAs acting on the hub genes were identified using the iRegulon plugin and MiRWalk 2.0 database, respectively. A protein kinase enrichment analysis was conducted using the online Kinase Enrichment Analysis 2 (KEA2) web server. The approved drugs acting on the hub genes were also found.

Results

A total of 1,629 genes were differentially expressed in primary ameloblastoma (P value <0.01 and |Log2FC| > 1). HRAS, CDK1, MAPK3, ERBB2, COL1A1, CYCS, and BRCA1 demonstrated high degree and betweenness centralities in the PPI network. E2F4 was the most significant TF acting on the hub genes. BTK was the protein kinase significantly enriched by the TFs. Cholesterol biosynthesis was considerably involved in primary ameloblastoma.

Conclusions

This study provides an intuition into the potential mechanisms involved in the etiology of ameloblastoma.

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.

Identification of key biomarkers related to epithelial-mesenchymal transition and immune infiltration in ameloblastoma using integrated bioinformatics analysis

OBJECTIVE

This study aimed to elucidate the underlying mechanisms of ameloblastoma (AM) through integrated bioinformatics analysis.

METHODS

We downloaded two microarrays of AMs from the GEO database and identified differentially expressed genes (DEGs) by integrated bioinformatics analysis. The enrichment analysis of DEGs was conducted to characterize GO and KEGG pathways. Protein-protein interaction (PPI) network and hub genes were screened via STRING and Cytoscape. CIBERSORT algorithm was utilized to analyze immune infiltration in AMs. We also verified the diagnostic and therapeutic value of hub genes.

RESULTS

Overall, 776 DEGs were identified in AMs through bioinformatics analysis. The function enrichment analysis shed light on pathways involved in AMs. Subsequently, we screened six hub genes via PPI network. Furthermore, we evaluated immune infiltration in AMs and found that macrophages may be participating in the progression of AMs. The upregulated expression of FN1 was related to the macrophages M2 polarization. Finally, ROC analysis indicated that six hub genes had high diagnostic value for AMs and 11 drugs interacted with upregulated hub genes were identified by screening the DGIdb database.

CONCLUSION

This study revealed the underlying mechanisms of pathogenesis and biological behavior of AMs and provided candidate targets for the diagnosis and treatment of AMs.

Comparative transcriptional profiling of canine acanthomatous ameloblastoma and homology with human ameloblastoma

Ameloblastomas are odontogenic tumors that are rare in people but have a relatively high prevalence in dogs. Because canine acanthomatous ameloblastomas (CAA) have clinicopathologic and molecular features in common with human ameloblastomas (AM), spontaneous CAA can serve as a useful translational model of disease. However, the molecular basis of CAA and how it compares to AM are incompletely understood. In this study, we compared the global genomic expression profile of CAA with AM and evaluated its dental origin by using a bulk RNA-seq approach. For these studies, healthy gingiva and canine oral squamous cell carcinoma served as controls. We found that aberrant RAS signaling, and activation of the epithelial-to-mesenchymal transition cellular program are involved in the pathogenesis of CAA, and that CAA is enriched with genes known to be upregulated in AM including those expressed during the early stages of tooth development, suggesting a high level of molecular homology. These results support the model that domestic dogs with spontaneous CAA have potential for pre-clinical assessment of targeted therapeutic modalities against AM.

Correlation of BRAF mutational status with clinical characteristics and survival outcomes of patients with ameloblastoma: the experience of 11 Italian centres

AIMS

Ameloblastoma is a rare odontogenic tumour with an aggressive local behaviour. Mutations in the mitogen-activated protein kinase pathway, namely BRAF V600E mutations, are a common finding. To date, there is no clear correlation between BRAF V600 mutation and clinical outcome.

METHODS

We retrospectively reviewed the medical records of patients who underwent surgery for ameloblastoma between May 1998 and June 2018, at 11 participating Italian centres. BRAF mutational status was evaluated by quantitative PCR/pyrosequencing. The primary end points were to determine BRAF mutational status in primitive and recurrent ameloblastoma, and to assess the relapse-free interval (RFI); the secondary end point was to investigate the correlation of BRAF mutational status with the clinical features of the tumour and survival outcomes.

RESULTS

Overall, 74 patients were included: 33 (44.5%) were BRAF wild type and 41 (55.4%) BRAF V600 mutated. BRAF V600 mutated ameloblastomas occurred more frequently in younger patients (p=0.0031), were located at the mandible (p=0.0009) and presented with unicystic variant. After a median follow-up of 60 months, 21 (28.3%) patients relapsed (30.3% and 26.8% in the BRAF wild type and BRAF mutated group, respectively). At univariable Cox models, none of the investigated variables, including microscopic margin involvement, was associated with RFI.

CONCLUSIONS

Local recurrence occurs in 30% of patients with ameloblastoma. BRAFV600 mutation is associated with younger age, mandibular localisation and with unicystic ameloblastoma. Neither BRAF mutation nor microscopically positive surgical margins were associated with RFI. Further studies are needed to elucidate outcomes of this rare disease according to clinical, histopathological and comprehensive molecular features.

Identification of circ_0089153/miR-608/EGFR p53 axis in ameloblastoma via MAPK signaling pathway

OBJECTIVES

This study investigated the role of circular RNAs (circRNAs) in the pathogenesis of ameloblastoma (AB), identifying potential novel targets for future targeted therapy.

MATERIALS AND METHODS

CircRNA and microRNA (miRNA) profiling in AB were built with microarrays. Six novel circRNAs were validated, circ-miRNA networks were delineated. Hsa-miR-608 was filtered over cross-comparison between database screening, miRNA microarray and validated. Circ-miRNA binding sponge was validated via luciferase reporter assay. Downstream mRNAs were screened. Regulation between miRNAs and mRNAs was confirmed in vitro. Gene interaction networks and circRNA-miRNA-mRNA interaction pathway enrichment analyses were established.

RESULTS

Six differentially expressed circRNAs were selected and validated. According to miRNAs and pathways predicted, six correlated miRNAs were selected, hsa-miR-608 was filtered and validated. The hsa_circ_0089153/hsa-miR-608 binding sponge was validated. Downstream gene interaction networks showed that EGFR and p53 had the strongest co-expression. In vitro transfection results confirmed the suppressive function of miR-608 and EGFR p53. Hsa_circ_0089153/hsa-miR-608/EGFR p53 interaction pathway enrichment analysis confirmed functions mainly enriched in MAPK and related signaling pathways regulating AB progression.

CONCLUSIONS

Six novel circRNAs were identified. Hsa_circ_0089153/hsa-miR-608 sponging was validated, hsa-miR-608 downregulated EGFR and p53, which might further regulate cell proliferation, differentiation, apoptosis, and cell cycle processes via the MAPK signaling pathway.

Genetic factors in the pathogenesis of ameloblastoma, dentigerous cyst and odontogenic keratocyst

Ameloblastoma (AB), dentigerous cyst (DC) and Odontogenic keratocyst (OKC) are odontogenic lesions with propensity to malignant transformation or local invasion. The molecular mechanisms of development of these lesions are not fully understood. However, some researches have reported dysregulation of tumor suppressor genes or oncogenes in these lesions. Down-regulation of P53 gene has been reported in AB, DC and OKC. Moreover, several long non-coding RNAs such as ENST00000512916 and KIAA0125 have been dysregulated in AB tissues. Single nucleotide polymorphisms within a variety of genes have been associated with certain types of odontogenic lesions. In the current review, we summarize the current data about the expression pattern of genes in these lesions and the observed association between genetic polymorphisms and development of these lesions.

Wnt5a regulates Ameloblastoma Cell Migration by modulating Mitochondrial and Cytoskeletal Dynamics

Objective: Abnormal expression of Wnt5a has been detected in various tumors, including ameloblastoma (AB). Yet, there is no specific mechanistic evidence for the functional role of Wnt5a in AB. In this study, we aimed to conduct a mechanistic examination of the importance of Wnt5a in AB development. Methods: The expressions of Wnt5a and Coro1A were examined by Western blot and immunohistochemistry both in AB tissues and AM-1 cells. The number and size of mitochondria were detected by electronic transmission microscope and confocal microscope. Gain-of-function and loss-of-function assays were used to explore the biological roles of Wnt5a and Coro1A in organelle dynamics changes and cell migration. Cell migration was detected by wound healing and transwell assay. Results: We found that in AM-1 cells, up-regulation of Wnt5a led to enhanced mitochondrial energy production and altered calcium homeostasis, with elevated calcium levels directly leading to altered mitochondrial dynamics and interactions between the cytoskeleton and the mitochondria. When Wnt5a or its downstream cytoskeleton-associated protein Coro1A was knocked down, the migration capacity of AM-1 cells was markedly impaired. Conclusion: Together, these results suggest that Wnt5a plays mitochondria and cytoskeleton specific roles in regulating the development of human AB, with its down-regulation leading to impaired tumor development, thus highlighting Wnt5a or Coro1A as potentially viable therapeutic targets for the treatment of AB.

Discovery of novel molecular characteristics and cellular biological properties in ameloblastoma

Ameloblastoma is a rare odontogenic benign tumor accounting for less than 1% of head and neck tumors. Advanced next generation sequencing (NGS) analyses identified high frequency of BRAF V600E and SMO L412F mutations in ameloblastoma. Despite the existence of whole genomic sequence information from patients with ameloblastoma, entire molecular signature of and the characteristics of ameloblastoma cells are still obscure. In this study, we sought to uncover the molecular basis of ameloblastoma and to determine the cellular phenotype of ameloblastoma cells with BRAF mutations. Our comparative cDNA microarray analysis and gene set enrichment analysis (GSEA) showed that ameloblastoma exhibited a distinct gene expression pattern from the normal tissues: KRAS-responsive gene set is significantly activated in ameloblastoma. Importantly, insulin like growth factor 2 (IGF2), a member of KRAS-responsive genes, enhances the proliferation of an ameloblastoma cell line AMU-AM1 with BRAF mutation. In addition, Toll-like receptor 2 (TLR2) knockdown readily inactivated KRAS-responsive gene sets as well as increases caspase activities, suggesting that TLR2 signaling may mediate cell survival signaling in ameloblastoma cells. Collectively, the findings may help to further clarify the pathophysiology of ameloblastoma and lead to the development of precision medicine for patients with ameloblastoma.