High frequency of BRAF V600E mutation in Iranian population ameloblastomas

Programmed death-ligand 1 regulates ameloblastoma growth and recurrence

Tumor cell-intrinsic programmed death-ligand 1 (PD-L1) signals mediate tumor initiation, progression and metastasis, but their effects in ameloblastoma (AM) have not been reported. In this comprehensive study, we observed marked upregulation of PD-L1 in AM tissues and revealed the robust correlation between elevated PD-L1 expression and increased tumor growth and recurrence rates. Notably, we found that PD-L1 overexpression markedly increased self-renewal capacity and promoted tumorigenic processes and invasion in hTERT+-AM cells, whereas genetic ablation of PD-L1 exerted opposing inhibitory effects. By performing high-resolution single-cell profiling and thorough immunohistochemical analyses in AM patients, we delineated the intricate cellular landscape and elucidated the mechanisms underlying the aggressive phenotype and unfavorable prognosis of these tumors. Our findings revealed that hTERT+-AM cells with upregulated PD-L1 expression exhibit increased proliferative potential and stem-like attributes and undergo partial epithelial‒mesenchymal transition. This phenotypic shift is induced by the activation of the PI3K-AKT-mTOR signaling axis; thus, this study revealed a crucial regulatory mechanism that fuels tumor growth and recurrence. Importantly, targeted inhibition of the PD-L1-PI3K-AKT-mTOR signaling axis significantly suppressed the growth of AM patient-derived tumor organoids, highlighting the potential of PD-L1 blockade as a promising therapeutic approach for AM.

Frequency of BRAF V600E immunoexpression in ameloblastomas: a multi-institutional analysis of 86 cases in Latin America and comprehensive review of the literature

BACKGROUND

The initiation of odontogenic tumorigenesis often involves the activation of the MAP-kinase pathway, with a pivotal role played by the BRAF V600E mutation. This study aimed to investigate the frequency of BRAF V600E immunoexpresion in ameloblastomas diagnosed in four Latin American centers and correlate this finding with the histological types and subtypes of the analyzed cases.

MATERIAL AND METHODS

A total of 86 samples of ameloblastomas were examined for immunohistochemistry using anti-BRAF V600E antibody. The histopathological features of each case were analyzed.

RESULTS

Positivity for anti-BRAF V600E antibody was detected in 65/86 cases (75.6%). BRAF V600E was positive in 38/56 cases (67.9%) of conventional ameloblastomas and in 27/30 cases (90.0%) of unicystic ameloblastomas. A statistically significant difference in BRAF V600E positivity was observed when comparing unicystic ameloblastomas to conventional ameloblastomas (p=0.03). No statistically significant difference in BRAF V600E positivity was observed when comparing histological variants, both for conventional ameloblastomas and unicystic ameloblastomas.

CONCLUSIONS

This study highlights a high frequency of BRAF V600E immunoreactivity in ameloblastomas among Latin American cases. The prevalence of the BRAF V600E immunoexpresion may suggest the feasibility of utilizing BRAF-targeted therapy for ameloblastomas with this mutation.

Differential Profile of Primary and Recurrent Ameloblastomas Among Afro-descendants and Non-Afro-descendants-a Systematic Review

Ameloblastoma is an aggressively growing jaw tumor with high recurrent properties. Reports on global and racial distribution of ameloblastoma are variable and inconclusive. The role of race and ethnicity on ameloblastoma growth characteristics, genetic mutational profile, and recurrence is also still unclear. The primary aim of this systematic review was to assess genetic, racial, and ethnic distribution of primary and recurrent ameloblastoma from published literature. The secondary aim was to assess potential correlations between ethnicity, genetic mutation, and disparities in ameloblastoma treatment outcomes in Afro-descendants and non-Afro-descendants. Twenty-three eligible articles were selected based on preferred reporting items for systematic review and meta-analysis (PRISMA), and a total of 169 ameloblastoma cases were evaluated. Data on patient demographics, ameloblastoma growth characteristics, and genetic status were collected for quantitative analysis. Among a total of 169 ameloblastoma cases, Afro-descendant patients had higher primary and recurrent ameloblastomas at 15.5% and 4.7% respectively compared to non-Afro-descendant at 10.7% and 1.8% respectively. Additionally, BRAF V600E was positively associated with 48.8% of all ameloblastomas and strong predilection for Afro-descendants. Despite the paucity of information on genetic profile of ameloblastomas in the Afro-descendant patient cohort, this ethnic group still accounted for 2.95% of all BRAF V600E-positive tumors. These suggest that Afro-descendants are understudied regarding ameloblastoma characteristics, genetic profile, and recurrence profile. Mutational analysis of ameloblastoma tumors in Afro-descendants should be promoted.

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.

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.

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.

The Molecular Pathology of Odontogenic Tumors: Expanding the Spectrum of MAPK Pathway Driven Tumors

Odontogenic tumors comprise a heterogeneous group of lesions that arise from the odontogenic apparatus and their remnants. Although the etiopathogenesis of most odontogenic tumors remains unclear, there have been some advances, recently, in the understanding of the genetic basis of specific odontogenic tumors. The mitogen-activated protein kinases/extracellular signal-regulated kinases (MAPK/ERK) pathway is intimately involved in the regulation of important cellular functions, and it is commonly deregulated in several human neoplasms. Molecular analysis performed by different techniques, including direct sequencing, next-generation sequencing, and allele-specific qPCR, have uncovered mutations in genes related to the oncogenic MAPK/ERK signaling pathway in odontogenic tumors. Genetic mutations in this pathway genes have been reported in epithelial and mixed odontogenic tumors, in addition to odontogenic carcinomas and sarcomas. Notably, B-Raf proto-oncogene serine/threonine kinase (BRAF) and KRAS proto-oncogene GTPase (KRAS) pathogenic mutations have been reported in a high proportion of ameloblastomas and adenomatoid odontogenic tumors, respectively. In line with the reports about other neoplasms that harbor a malignant counterpart, the frequency of BRAF p.V600E mutation is higher in ameloblastoma (64% in conventional, 81% in unicystic, and 63% in peripheral) than in ameloblastic carcinoma (35%). The objective of this study was to review MAPK/ERK genetic mutations in benign and malignant odontogenic tumors. Additionally, such genetic alterations were discussed in the context of tumorigenesis, clinical behavior, classification, and future perspectives regarding therapeutic approaches.

Genetic Profile of Adenomatoid Odontogenic Tumor and Ameloblastoma. A Systematic Review

Purpose: To perform a comprehensive and systematic critical appraisal of the genetic alterations reported to be present in adenomatoid odontogenic tumor (AOT) compared to ameloblastoma (AM), to aid in the understanding in their development and different behavior.

Methods: An electronic search was conducted in PubMed, Scopus, and Web of Science during March 2021. Eligibility criteria included publications on humans which included genetic analysis of AOT or AM.

Results: A total of 43 articles reporting 59 AOTs and 680 AMs were included. Different genomic techniques were used, including whole-exome sequencing, direct sequencing, targeted next-generation sequencing panels and TaqMan allele-specific qPCR. Somatic mutations affecting KRAS were identified in 75.9% of all AOTs, mainly G12V; whereas a 71% of the AMs harbored BRAF mutations, mainly V600E.

Conclusions: The available genetic data reports that AOTs and AM harbor somatic mutations in well-known oncogenes, being KRAS G12V/R and BRAFV600E mutations the most common, respectively. The relatively high frequency of ameloblastoma compared to other odontogenic tumors, such as AOT, has facilitated the performance of different sequencing techniques, allowing the discovery of different mutational signatures. On the contrary, the low frequency of AOTs is an important limitation for this. The number of studies that have a assessed the genetic landscape of AOT is still very limited, not providing enough evidence to draw a conclusion regarding the relationship between the genomic alterations and its clinical behavior. Thus, the presence of other mutational signatures with clinical impact, co-occurring with background KRAS mutations or in wild-type KRAS cases, cannot be ruled out. Since BRAF and RAS are in the same MAPK pathway, it is interesting that ameloblastomas, frequently associated with BRAFV600E mutation have aggressive clinical behavior, but in contrast, AOTs, frequently associated with RAS mutations have indolent behavior. Functional studies might be required to solve this question.

Genetic Study of BRAF V600E and SMO L412F Mutations in Japanese Patients with Ameloblastoma

Background and aim: Ameloblastoma is a benign, intraosseous, progressively growing, epithelial, odontogenic neoplasm. BRAF and SMO mutations have been reported in ameloblastoma. In this study, we evaluated BRAF V600E and SMO L412F mutations; and assessed the relationship between BRAF V600E mutant expression and the clinicopathological features in Japanese patients with ameloblastoma. Methods: We examined 24 formalin-fixed paraffin-embedded samples. All specimens were from patients with mandibular ameloblastoma: 20 were conventional ameloblastoma and 4 were unicystic ameloblastoma. The BRAF V600E mutation was assessed by Sanger sequencing and immunohistochemistry, and the SMO L412F mutation was assessed only by Sanger sequencing. Results: Twenty of the 24 (83%) ameloblastoma samples carried the BRAF V600E mutation; 22 of the 24 (92%) samples were immunohistochemically positive for BRAF V600E. However, the SMO L412F mutation was not detected in any of them. The BRAF V600E mutation status did not correlate with the clinicopathological features, such as age, sex, location, method, recurrence, and subtype. Conclusion: BRAF inhibitors could be a potential treatment option for Japanese patients with ameloblastoma, harboring the BRAF V600E mutation.

Analysis of BRAF V600E expression and disease-free survival in patients with ameloblastoma

The correlation between BRAF mutation and the aggressiveness of ameloblastoma remains controversial. The aim of this study was to investigate the association of BRAF V600E expression with clinicopathological features and disease-free survival (DFS) in patients with ameloblastoma. Seventy-four conventional ameloblastoma samples were collected. Immunohistochemistry using anti-BRAF V600E antibody was performed on formalin-fixed, paraffin-embedded tissue sections. Clinicopathological characteristics and treatment outcomes were retrieved from the patient medical records. BRAF V600E immunoreactivity was detected in 50/74 cases (67.6%); 39 were strongly positive and 11 weakly. There was a significant difference in BRAF V600E expression between ameloblastoma and dental follicle (P = 0.034). However, there was no significant association of BRAF V600E expression with any clinicopathological features, including sex, age, location, duration, tumour size, radiographic appearance, cortical perforation, recurrence, and histological subtype. DFS analysis revealed that patients with BRAF-mutated ameloblastoma had a shorter median survival time (84 months vs 168 months) and lower 5-year survival rate (59% vs 67%) compared to the BRAF wild-type group; however, this was not statistically significant (P = 0.169). Moreover, logistic regression analysis revealed that treatment with enucleation was an independent risk factor for tumour recurrence (odds ratio 9.236; P = 0.028). This study demonstrated that the BRAF V600E mutation was not associated with any clinicopathological features of ameloblastoma. A trend towards earlier recurrence in tumours with BRAF mutation was observed, but this requires further investigation. Furthermore, the findings suggest that the treatment modality is an important factor in determining recurrence in ameloblastoma despite genetic alterations.

Evaluation of squamous cell carcinoma antigen 1 expression in oral squamous cell carcinoma (tumor cells and peritumoral T-lymphocytes) and verrucous carcinoma and comparison with normal oral mucosa

Background:

Squamous cell carcinoma antigen (SCCA) is used as a prognostic marker for recurrence of squamous cell carcinoma in various sites, including head and neck. Studies suggest that its high serum levels are correlated to some clinical features, such as nodal metastasis. However, it is still unknown if high SCCA in patients with SCCA tissue expression in tumor cells are related to peripheral T-lymphocytes. Therefore, we did this study to evaluate SCCA expression in squamous cell carcinoma and verrucous carcinoma and to compare it with normal oral mucosa, also investigating the correlation between serum-based and tissue-based antigen levels.

Methodology:

In this study, the immunohistochemistry (IHC) technique was used to determine the SCCA1 expression pattern in 81 specimens divided into 3 groups, including oral squamous cell carcinoma, verrucous carcinoma, and normal oral mucosa. Serum-based and tissue-based antigen levels of 20 oral squamous cell carcinoma cases were compared by the western blot assay. SCCA expression was also evaluated and compared in both tumor cells and peripheral T-lymphocytes by the immunofluorescence assay.

Results:

Our results showed that the SCCA levels in SCC specimens were significantly lower than in verrucous carcinoma and normal and hyperplastic oral mucosa specimens. We found no correlation between the IHC expression of SCCA and serum levels. SCCA was well expressed in both tumor cells and peripheral T-lymphocytes.

Conclusion:

Decreasing SCCA in SCC specimens suggested that SCC tumor cells may affect more than the serum levels of SCCA in some patients. In addition, expression of SCCA in peripheral T-lymphocytes showed that both tumor cells and T-lymphocytes may cause serum SCCA.

Comparison of Immunohistochemistry and DNA Sequencing for BRAF V600E Mutation Detection in Mandibular Ameloblastomas

This study aimed to investigate the presence of BRAF V600E mutation in mandibular ameloblastoma by comparing the results of molecular detection and immunohistochemical analysis. A 128 cases of mandibular ameloblastoma and 30 cases of dentigerous cyst (control group) were selected for analysis. Detection of BRAF V600E mutation was performed with immunohistochemistry (IHC) and polymerase chain reaction techniques. Clinico-pathologic data were collected in order to investigate possible associations with the mutation. Of the 128 cases submitted to IHC, 81.2% (108 cases) showed positivity for anti-BRAF V600E antibody, whereas 24 were negative (18.8%). Molecular analysis of the BRAF V600E mutation by polymerase chain reaction was possible in 116 cases due to DNA quality. Of these cases, 96 were positive (82.8%) and 20 negative (17.2%). All cases of dentigerous cyst were negative for BRAF V600E mutation in both techniques. Considering the sequencing as a gold standard method, the receiver operating characteristics curve analysis showed sensitivity of 0.99 and specificity of 1 (area under the curve=0.995, standard error=0.006; P<0.001; 95% confidence interval=0.983 to 1). We also tested the agreement between the techniques by using the Cohen's κ coefficient, with κ being 0.97 (P<0.001). IHC is a reliable test for identifying the BRAF V600E mutation in ameloblastomas, presenting advantages such as being more frequently used in surgical pathology laboratories and requiring fewer critical steps for paraffin-embedded tissue compared with molecular biology techniques.

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.