Evaluation of the acetylation status of H3 histone and its contribution to genomic instability in oral leukoplakia and proliferative verrucous leukoplakia

Author(s)

Camila De Oliveira Barbeiro

• Document type: Master's Dissertation
• Press: Araraquara. 2020-04-02.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Odontologia. Araraquara
• Defense date: 2020-02-19
• Advisor: Andreia Bufalino

Abstract

Oral potentially malignant disorders (OPMDs) are clinical presentations that present an increased risk of cancer development in the oral cavity, whether in a clinically definable precursor lesion or clinically normal oral mucosa. Among the main OPMDs, oral leukoplakia (OL) presents itself as a non-scratchable white plaque of questionable risk, which can be homogeneous or non-homogeneous, whose malignant transformation rate varies from 0.2% to 17.5%. In addition, OL has the same risk factors that are observed in the development of oral squamous cell carcinoma (OSCC), which is the main malignant neoplasm affecting the oral cavity. Another important OPMD is proliferative verrucous leukoplakia (PVL), which also presents itself as a white, non-scratchable, but multifocal plaque and has a persistent and progressive behavior for malignancy, with a malignant transformation rate of 70% to 100% of the cases. Unlike OL, risk factors such as tobacco, alcohol and areca nut do not appear to be associated with the development of PVL. Additionally, PVL has a poor response to all treatment modalities, suffers rapid dissemination through oral sites and often shows recurrence. The degree of epithelial dysplasia identified in OPMDs is currently used as a risk predictor for malignant transformation, however several studies have shown that it is not a reliable predictor. Recent studies also suggest that the inflammatory infiltrate associated with OPMD may be due to its etiology and clinical comportment. Furthermore, recently, epigenetic changes involving histones and DNA methylation in different types of cancer have been studied, as well as in some OPMDs in order to discover targets for effective therapeutic measures. Among the several factors inducing epigenetic changes, chronic inflammation has been identified as one of these factors. Thus, the present study had specific objectives: (1) to compare the levels of histone H3 acetylation, the accumulation of DNA damage and the levels of global DNA methylation between OL and PVL; (2) to evaluate whether the levels of histone H3 acetylation in dysplastic and tumor cell lines are altered by the contact with peripheral blood mononuclear cells (PBMCs); and (3) assess whether such changes are accompanied by changes in cell proliferation and epithelial-mesenchymal transition (EMT). To achieve these goals, the levels of histone H3 acetylation, DNA damage and methylation were assessed by immunofluorescence. In addition, cell co-culture assays with PBMCs and oral keratinocyte lines (NOK-SI, DOK, SCC-25 and Detroit 562) were performed to assess the influence of PBMCs on the acquisition of advantages for tumor progression. The results of the immunofluorescence showed that both OPMDs were hypoacetylated compared to the control. However, when comparing only OL and PVL, we observed that the PVL group was more hyperacetylated than OL. It was also observed that the levels of DNA damage and methylation were increased in the OL group in relation to PVL. The experiments with cell culture revealed that the contact of dysplastic and normal oral keratinocytes with PBMCs was able to favor EMT. Our results revealed two main points: 1) both OPMDs have different epigenetic profiles; 2) the direct contact of PMBCs with normal, dysplastic and tumoral oral keratinocytes seems to be important in early events of tumorigenesis such as EMT. (AU)

• FAPESP's process: 18/04954-2 - Evaluation of the acetylation status of H3 histone and its contribution to genomic instability in oral leukoplakia and Proliferative Verrucous Leukoplakia
• Grantee: Camila de Oliveira Barbeiro
• Support Opportunities: Scholarships in Brazil - Master