P14 methylation: an epigenetic signature of salivary gland mucoepidermoid carcinoma in the Serbian population

Molecular Aspects of Mucoepidermoid Carcinoma and Adenoid Cystic Carcinoma of the Salivary Gland

BACKGROUND

Salivary gland tumors (SGTs) are rare and highly heterogeneous lesions, making diagnosis a challenging activity. In addition, the small number of studies and samples evaluated difficults the determination of prognosis and diagnosis. Despite the solid advances achieved by research, there is still an intense need to investigate biomarkers for diagnosis, prognosis and that explain the evolution and progression of SGTs.

METHODS

We performed a comprehensive literature review of the molecular alterations focusing on the most frequent malignant SGTs: mucoepidermoid carcinoma and adenoid cystic carcinoma.

RESULTS

Due to the importance of biomarkers in the tumorigenenic process, this review aimed to address the mechanisms involved and to describe molecular and biomarker pathways to better understand some aspects of the pathophysiology of salivary gland tumorigenesis.

CONCLUSIONS

Molecular analysis is essential not only to improve the diagnosis and prognosis of the tumors but also to identify novel driver pathways in the precision medicine scenario.

Wakefield M. The role of aberrant DNA methylation in cancer initiation and clinical impacts

Epigenetic alterations, including aberrant DNA methylation, are now recognized as bone fide hallmarks of cancer, which can contribute to cancer initiation, progression, therapy responses and therapy resistance. Methylation of gene promoters can have a range of impacts on cancer risk, clinical stratification and therapeutic outcomes. We provide several important examples of genes, which can be silenced or activated by promoter methylation and highlight their clinical implications. These include the mismatch DNA repair genes MLH1 and MSH2, homologous recombination DNA repair genes BRCA1 and RAD51C, the TERT oncogene and genes within the P15/P16/RB1/E2F tumour suppressor axis. We also discuss how these methylation changes might occur in the first place - whether in the context of the CpG island methylator phenotype or constitutional DNA methylation. The choice of assay used to measure methylation can have a significant impact on interpretation of methylation states, and some examples where this can influence clinical decision-making are presented. Aberrant DNA methylation patterns in circulating tumour DNA (ctDNA) are also showing great promise in the context of non-invasive cancer detection and monitoring using liquid biopsies; however, caution must be taken in interpreting these results in cases where constitutional methylation may be present. Thus, this review aims to provide researchers and clinicians with a comprehensive summary of this broad, but important subject, illustrating the potentials and pitfalls of assessing aberrant DNA methylation in cancer.

Role of Histone Deacetylases in the Pathogenesis of Salivary Gland Tumors and Therapeutic Targeting Options

Salivary gland tumors (SGTs) comprise a rare and heterogenous category of benign/malignant neoplasms with progressively increasing knowledge of the molecular mechanisms underpinning their pathogenesis, poor prognosis, and therapeutic treatment efficacy. Emerging data are pointing toward an interplay of genetic and epigenetic factors contributing to their heterogeneity and diverse clinical phenotypes. Post-translational histone modifications such as histone acetylation/deacetylation have been shown to actively participate in the pathobiology of SGTs, further suggesting that histone deacetylating factors (HDACs), selective or pan-HDAC inhibitors (HDACis), might present effective treatment options for these neoplasms. Herein, we describe the molecular and epigenetic mechanisms underlying the pathology of the different types of SGTs, focusing on histone acetylation/deacetylation effects on gene expression as well as the progress of HDACis in SGT therapy and the current status of relevant clinical trials.

The Epigenesis of Salivary Glands Carcinoma: From Field Cancerization to Carcinogenesis

Salivary gland carcinomas (SGCs) are a diverse collection of malignant tumors with marked differences in biological activity, clinical presentation and microscopic appearance. Although the etiology is varied, secondary radiation, oncogenic viruses as well as chromosomal rearrangements have all been linked to the formation of SGCs. Epigenetic modifications may also contribute to the genesis and progression of SGCs. Epigenetic modifications are any heritable changes in gene expression that are not caused by changes in DNA sequence. It is now widely accepted that epigenetics plays an important role in SGCs development. A basic epigenetic process that has been linked to a variety of pathological as well as physiological conditions including cancer formation, is DNA methylation. Transcriptional repression is caused by CpG islands hypermethylation at gene promoters, whereas hypomethylation causes overexpression of a gene. Epigenetic changes in SGCs have been identified, and they have been linked to the genesis, progression as well as prognosis of these neoplasms. Thus, we conduct a thorough evaluation of the currently known evidence on the involvement of epigenetic processes in SGCs.

Analyses of P16INK4a gene promoter methylation relative to molecular, demographic and clinical parameters characteristics in non-small cell lung cancer patients: A pilot study

BACKGROUND

The aim of this study was to examine the methylation status of p16^INK4a promoter region in non small cell lung cancer (NSCLC) patients and their associations with single nucleotide polymorphisms (SNPs) of the epidermal growth factor receptor (EGFR) gene, as well as with demographic or clinical characteristics.

METHODS

Formalin-fixed and paraffin-embedded (FFPE) DNA samples extracted from 22 NSCLC patients were analyzed with methylation-specific polymerase chain reaction (PCR) method to obtain promoter methylation profile. The same cohort was genotyped for - 216G > T, -191 C > A, and 181,946 C > T EGFR SNPs.

RESULTS

There was a significant association between methylated p16^INK4a in patients prior therapy (p = 0.017) since a significantly higher frequency of methylated p16^INK4a was detected in these patients (40.9%) in comparison to frequency in patients after therapy (31.8%). Also, a higher frequency of methylated p16^INK4a was detected among patients with leucopenia (p = 0.056). No associations were observed between the methylation status of the p16^INK4a promoter region and EGFR SNPs or other clinical and demographic data in this cohort.

CONCLUSION

High frequency of methylation of the p16^INK4a gene promoter was observed in NSCLC patients prior therapy and with leucopenia that can indicate their significance related to advanced clinical stage.

Methylation of tumour suppressor genes in benign and malignant salivary gland tumours: a systematic review and meta-analysis

The aim of the present systematic review was to critically analyse the relationship between tumour suppressor genes (TSGs) promoter methylation, a potent mechanism of gene silencing, and the development of salivary gland tumours, as well as the possible effect on clinical/histological characteristics. Review protocol was registered in the International Prospective Register of Systematic Reviews (PROSPERO) database (registration ID CRD42020218511). A comprehensive search of Web of Science, Scopus, PubMed, and Cochrane Central Register of Controlled Trials was performed utilizing relevant key terms, supplemented by a search of grey literature. Newcastle-Ottawa Quality Assessment Scale (NOQAS) was used for the quality assessment of included studies. Sixteen cross-sectional and 12 case-control studies were included in the review, predominantly dealing with methylation in TSGs related to DNA repair, cell cycle, and cell growth regulation and differentiation. Quantitative synthesis could be performed on P16 (inhibitor of cyclin-dependent kinase 4a), RASSF1A (Ras association domain family 1 isoform A) and MGMT (O6-methylguanine DNA methyltransferase) genes only. It showed that P16 and RASSF1A genes were more frequently methylated in salivary gland tumours compared to controls (P = .0002 and P < .0001, respectively), while no significant difference was observed for MGMT. Additionally, P16 did not appear to be related to malignant transformation of pleomorphic adenomas (P = .330). In conclusion, TSG methylation is involved in salivary gland tumour pathogenesis and several genes might play a considerable role. Further studies are needed for a better understanding of complex epigenetic deregulation during salivary gland tumour development and progression.

Epigenetic alterations in ameloblastomas: A literature review

Background

Ameloblastoma is a locally aggressive tumor, originated from odontogenic epithelium, and affects the jawbones with an elevated recurrence rate. The molecular mechanisms involved with the pathogenesis of this tumor remain undetermined. This review aimed to describe the current data regarding epigenetic alterations in ameloblastoma.

Material and Methods

A systematized electronic search was performed in the English-language literature in three databases, combining the following keywords: ameloblastoma, epigenetic, methylation, noncoding RNA, histone acetylation.

Results

According to the gathered results of 11 studies in this review, epigenetic alterations could induce the development and progression of ameloblastoma. DNA methylation has been the most assessed mechanism in ameloblastomas.

Conclusions

Current literature data indicate that epigenetic events can be involved in the etiopathogenesis of ameloblastomas. Key words:Ameloblastoma, epigenetic, methylation, noncoding RNA, histone acetylation.

DNA methyltransferase expression is associated with cell proliferation in salivary mucoepidermoid carcinoma

OBJECTIVES

The present study investigated the correlation between the expression of DNA methyltransferase (DNMT)1, DNMT3A, and DNMT3B and the proliferation of mucoepidermoid carcinomas (MECs) using the molecular markers Ki-67 and cyclin D1. This study also demonstrates the effects of 5-aza-2-deoxycytidine (5AC) on the MEC tumor cell lines in relation to DNMT1 and DNMT3A expression, and cell-cycle arrest.

MATERIALS AND METHODS

The immunohistochemistry of DNMT1, DNMT3A, DNMT3B, Ki-67, and cyclin D1 was analyzed in 40 samples of MEC and 15 samples of healthy minor salivary glands. The effects of 5AC on DNMT1 and DNMT3B expression in MEC cell lines were analyzed by Western blot, and the effects of 5AC on the cell cycle were analyzed using flow cytometry.

RESULTS

The expression of DNMT1 and DNMT3B was more intense in MECs than in healthy salivary glands. A strong correlation was found between the expression of the DNMTs and the proliferation markers. This correlation was validated In Vitro, where treatment with 5AC reduced the expression of the DNMTs and the percentage of cells at the G2/M phase of the cell cycle.

CONCLUSION

The expression of DNMT1, DNMT3A, DNMT3B is correlated significantly with the expression of Ki-67 and cyclin D1. The treatment with 5AC reduces DNMT expression and decreases the percentage of cells at the G2/M phase of the cell cycle, while increasing the cells at the G0/G1 phase.

Epigenetic alterations in salivary gland tumors

Salivary gland tumors (SGTs) comprise a heterogeneous group of benign and malignant neoplasms that exhibit significant variability in their microscopic appearance, clinical presentation, and biological behavior. The etiologic factors are unknown; however, chromosomic translocation, secondary radiation, and chemotherapy can be associated with the development of SGT. It has been indicated that epigenetic alterations can be responsible for the development and progress of these neoplasms. The epigenetic mechanisms are defined as a set of DNA changes that do not alter the sequence of nucleotide bases but alter the expression of the proteins. These alterations have been studied in the SGT, and they were associated with the development and progress of these neoplasms and may influence on SGT prognosis. Hence, we critically review the currently available data on the participation of epigenetic events on salivary gland tumors.

Genetic and epigenetic alterations in the tumour, tumour margins, and normal buccal mucosa of patients with oral cancer

Despite adequate surgical resection, oral squamous cell carcinoma (OSCC) shows a high rate of recurrence and metastasis, which could be explained by the presence of molecular alterations in seemingly normal tumour margins and the entire oral mucosa. The aims of this study were (1) to assess the presence of gene amplification (c-Myc and HER2) and promoter methylation (p14 and p16) in the tumours, tumour margins, and unaffected oral mucosa of 40 OSCC patients, and (2) to evaluate the possibility of using these alterations as prognostic markers. c-Myc and HER2 genes were quantified by means of real-time PCR (qPCR), and p14 and p16 methylation status was determined by methylation-specific PCR (MSP PCR). All tissues examined exhibited molecular alterations in various proportions. Tumour tissues, as expected, showed the highest prevalence of alterations, while oral mucosa showed the lowest. Multiple alterations (co-alterations) in tumours and tumour margins were significantly more frequent than in unaffected oral mucosa (P<0.001 and P=0.027, respectively). HER2 amplification in margin tissue (P<0.001) and swabs (P=0.013), as well as the existence of three co-alterations in margins (P=0.001) and macroscopically unaffected oral mucosa (P<0.001) were correlated with shorter disease-specific survival.