Evaluation of a subset of tumor suppressor gene for copy number and epigenitic changes in pleomorphic adenoma and carcinoma ex-pleomorphic adenoma carcinogenesis

MicroRNA copy number alterations in the malignant transformation of pleomorphic adenoma to carcinoma ex pleomorphic adenoma

OBJECTIVE

This study used array comparative genomic hybridization to assess copy number alterations (CNAs) involving miRNA genes in pleomorphic adenoma (PA), recurrent pleomorphic adenoma (RPA), residual PA, and carcinoma ex pleomorphic adenoma (CXPA).

MATERIALS AND METHODS

We analyzed 13 PA, 4 RPA, 29 CXPA, and 14 residual PA using Nexus Copy Number Discovery software. The miRNAs genes affected by CNAs were evaluated based on their expression patterns and subjected to pathway enrichment analysis.

RESULTS

Across the groups, we found 216 CNAs affecting 2261 miRNA genes, with 117 in PA, 59 in RPA, 846 in residual PA, and 2555 in CXPA. The chromosome 8 showed higher involvement in altered miRNAs in PAs and CXPA patients. Six miRNA genes were shared among all groups. Additionally, miR-21, miR-455-3p, miR-140, miR-320a, miR-383, miR-598, and miR-486 were prominent CNAs found and is implicated in carcinogenesis of several malignant tumors. These miRNAs regulate critical signaling pathways such as aerobic glycolysis, fatty acid biosynthesis, and cancer-related pathways.

CONCLUSION

This study was the first to explore CNAs in miRNA-encoding genes in the PA-CXPA sequence. The findings suggest the involvement of numerous miRNA genes in CXPA development and progression by regulating oncogenic signaling pathways.

Carcinoma Ex Pleomorphic Adenomas: An Institutional Experience and Literature Review

OBJECTIVES

To provide an institutional experience with cases diagnosed as carcinoma ex pleomorphic adenoma (CXPA), including the cytologic and histologic findings and clinical follow-up, followed by a comparison to the experience documented in the literature.

METHODS

We identified cases of CXPA diagnosed at our institution from 2011 to 2021 and reviewed the cytologic and histologic diagnoses, as well as the treatment and clinical outcomes. Additionally, a literature review of the English literature was performed on CXPAs from 2011 to 2021.

RESULTS

Forty-one cases of CXPA were identified, with the majority subclassified as adenocarcinoma, not otherwise specified. Five tumors underwent cytogenetic studies and five underwent molecular studies. To date, 36 patients are alive, 8 of whom experienced locoregional recurrence or distant metastasis.

CONCLUSIONS

Our institutional experience was comparable to that reported in the literature. Further studies are required to inquire about the role of molecular profiles of CXPAs in clinical risk assessment.

Pleomorphic adenoma of the cheek: a case presentation

Background

Pleomorphic adenoma, also known as a benign mixed tumor, is the most common salivary gland tumor. The parotid gland accounts for 90% of the total, with the minor salivary glands accounting for 10%. Buccal minor salivary glands pleomorphic adenoma is extremely rare. It manifests as a painless, firm, slow-growing mass in most cases.

Case presentation

A pleomorphic adenoma in the buccal minor salivary glands was discovered in an adult 43-year-old female patient treated with wide surgical resection. A literature review of the PA of the cheek is stated.

Conclusion

In the differential diagnosis of cheek masses, pleomorphic adenoma should be scrutinized. The remedy of choice is wide local excision with at least a 5-year follow-up.

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.

Retinoic acid receptor beta promoter methylation and risk of cervical cancer

Cervical cancer is one of the leading causes of death in women worldwide, particularly in developing countries. Human papillomavirus has been reported as one of the key etiologic factors in cervical carcinoma. Likewise, epigenetic aberrations have ability to regulate cancer pathogenesis and progression. Recent research suggested that methylation has been detected already at precancerous stages, which methylation markers may have significant value in cervical cancer screening. The retinoic acid receptor beta (RARβ) gene, a potential tumor suppressor gene, is usually expressed in normal epithelial tissue. Methylation of CpG islands in the promoter region of the RARβ gene has been found to be associated with the development of cervical cancer. To investigate whether RARβ methylation is a potential biomarker that predicts the progression of invasive cancer, we reviewed 14 previously published articles related to RARβ methylation. The majority of them demonstrated that the frequency of RARβ promoter methylation was significantly correlated with the severity of cervical epithelium abnormalities. However, methylation of a single gene may not represent the best approach for predicting disease prognosis. Analyzing combinations of aberrant methylation of multiple genes may increase the sensitivity, and thus this approach may serve as a better tool for predicting disease prognosis.

DNA methylation polymerase chain reaction (PCR) array of apoptosis-related genes in pleomorphic adenomas of the salivary glands

OBJECTIVE

The aim of this study was to evaluate the DNA methylation profile in 22 apoptosis-related genes in pleomorphic adenomas (PAs) of the salivary glands, in comparison with normal salivary glands (NSGs), and to address the differences in methylation patterns between smaller and larger tumors. Additionally, we investigated if the hypermethylation of differentially methylated genes between NSGs and PAs impacted the messenger RNA (mRNA) transcription.

DESIGN

Twenty-three fresh PA samples and 12 NSG samples were included. The PA samples were divided into 2 groups: PAs with clinical size larger than 2 cm (n = 12) and PAs with clinical size 2 cm or smaller (n = 11). DNA methylation at the promoter region of a panel of 22 genes involved in apoptosis was profiled by using a human apoptosis DNA methylation polymerase chain reaction array, and the transcriptional levels of genes showing differential methylation profiles between PAs and NSGs were assessed.

RESULTS

TNFRSF25 and BCL2 L11 were highly methylated in PAs, in comparison with NSGs, irrespective of tumor size. However, no difference could be observed in the mRNA transcription between PAs and NSGs.

CONCLUSIONS

Hypermethylation of the proapoptotic genes BCL2 L11 and TNFRSF25 is observed in PA. However, this phenomenon did not impact mRNA transcription.