DNA methylation profile of genes related to immune response in generalized periodontitis.

BACKGROUND AND OBJECTIVE: Epigenetic events, as the DNA methylation, may be related to development of inflammatory diseases. Due to the important role of host's response in the pathogenesis of periodontitis, the purpose of the present study was to investigate the methylation profile of genes related to immune response in gingival tissues from patients with generalized periodontitis (GP) compared to healthy individuals. METHODS: Gingival tissues were collected from 20 individuals with GP and 20 healthy individuals. Genomic DNA was extracted and submitted to enzymatic digestions. An initial screening using a panel of genes involved with the response immune was performed in pools containing six samples of each group. Genes that presented different levels of methylation between the groups were selected for individual assays for validation. RESULTS: The array results showed an unmethylated profile in the majority of genes evaluated in both groups. MALT1, LTB, and STAT5 genes presented a profile of partial methylation in the control compared with GP group. Validation individual assays using a larger number of samples (n = 20, each group) confirmed the hypomethylation of STAT5 in the GP group compared with control group (P < .001). CONCLUSION: Generalized periodontitis is associated with hypomethylation of the STAT5 gene. Further studies are necessary to evaluate the functional impact these findings.

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.

Loss of heterozygosity of MIR15A/MIR16-1, negative regulators of the antiapoptotic gene BCL2, is not common in odontogenic keratocysts.

OBJECTIVES: The odontogenic keratocyst (OKC) is an aggressive odontogenic cyst that has a high recurrence rate. Apart from PTCH1 mutations, few molecular alterations are described in OKCs. Low expression of microRNAs (miRNAs) miR-15a and/or miR-16-1 in association with increased expression of their target, Bcl-2, have been previously found in OKC. In humans, MIR15A and MIR16-1 are clustered at chromosome position 13 q14, and loss of heterozygosity (LOH) at this locus occurs in different tumors. We aimed to determine whether deletion at 13 q14 is a potential mechanism leading to miR-15a/16-1 aberrant expression in OKC. METHODS: Genomic DNA was extracted from 15 formalin-fixed, paraffin-embedded microdissected OKC cases. The polymorphic DNA markers D13S272 and D13S273 on chromosome 13 q14.3, around MIR15A/MIR16-1, were amplified by polymerase chain reaction. LOH was examined by capillary electrophoresis DNA-fragment analysis. RESULTS: The D13S272 marker had no LOH in 12 informative cases, whereas 2 out of 9 informative cases (22%) had LOH at the D13S273 marker. CONCLUSIONS: An LOH event at MIR15A/MIR16-1 locus is not common in OKC. The mechanism underlying the regulation of miR-15a and miR-16-1 expression in OKC remains to be determined.