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Immunolocalization of DNMT1 and DNMT3a in Salivary Gland Neoplasms

Objective: Salivary gland neoplasms pathogenesis has not been well established. DNA methylation occurs when methyl groups are added to cytosine nucleotides in specific areas of the gene by the enzyme DNA methyltransferase (DNMT). This chemical modification can alter gene expression without altering DNA sequence. While DNMT3a is mostly involved in de novo methylation, DNMT1 acts as a maintenance methyltransferase. We aimed to investigate the immunoexpression of DNMT3a and DNMT1 in minor salivary gland neoplasms, comparing it with normal tissue. Material: Forty-four formalin-fixed and paraffin-embedded samples of pleomorphic adenoma, adenoid cystic carcinoma, mucoepidermoid carcinoma and polymorphous low-grade adenocarcinoma were included in the study. The DNMT1 and DNMT3a proteins were identified by using a highly sensitive polymer-based system. Results: Positive nuclear and cytoplasmic labeling for DNMT1 was observed in all samples, including the controls. Positive nuclear labeling for DNMT3a was found only in few neoplasms: 1 pleomorphic adenoma (9.0%), 2 adenoid cystic carcinoma (16.6%) and 1 mucoepidermoid (9.0%) cases. Conclusion: Our results were not able to demonstrate a clear correlation between DNMT1 and DNMT3a immunoexpression and salivary gland neoplasms development.