Expressão da H3K9ac e H4K12ac no Adenocarcinoma Polimorfo e Carcinoma Adenoide Cístico de Glândulas Salivares

Abstract

Epigenetic changes such as DNA methylation, microRNAs, and post-translational modifications (PTM) of histones have been the subject of major study for a variety of diseases, including cancer, since they are involved in the control of gene expression. Histone post-translational modifications control chromatin access to the most diverse transcription factors and thus modulate gene expression and silencing, therefore, changes in these modifications contribute to the appearance of tumors. The aim of this study was to obtain data on the presence of PTM, especially acetylation, in two of the most common malignant tumors of salivary glands that have morphohistogenetic similarities, but different behaviors: polymorphous adenocarcinoma (PAC) and adenoid cystic carcinoma (ACC). For this, we evaluated by immunohistochemistry the expression of H3K9ac and H4K12ac in 29 cases of PAC and 38 of ACC, with reference to its expression in admittedly normal non-neoplastic glandular tissue samples. For this, an index was constructed to translate absorbance intensity by nuclear area of the tumor parenchyma, called IOD. The analysis showed that IOD values for H3K9ac were significantly different between PAC (mean: 0.144; SD: ± 0.08) for the control and ACC (mean: 0.27, SD: ± 0.07) (p < 0.05). On the other hand, the values of IOD obtained for H4K12ac showed statistically significant differences for the PAC (mean: 0.114, SD: ± 0.06) and for the ACC (mean: 0.115, SD: ± 0.06) compared to controls (p < 0.05). When IOD values for H3K9ac and H4K12ac were analyzed according to predefined stratifications of clinicopathological variables, significant differences were observed for recurrent cases, which presented lower IOD values for H3K9ac than non-recurrent ones (p = 0.02). For H4K12ac, carriers of metastasis in the ACC group presented higher values than non-metastatic (p = 0.04). We found no correlation between H3K9ac and H4K12ac with cell proliferation (Ki67). It is concluded that variations in expression of these modifications may contribute to the appearance of these tumors. The results also point to the possibility that acetylation phenomena influence the behavior of the tumor. However, the results obtained require more consistency for its confirmation.