Efeito do tabagismo no perfil de metilação de DNA no promotor de genes MHL1, hTERT e TP53 em células epiteliais da mucosa bucal

• Autor(a) principal: Oliveira, Sabrina Rocha Luna de
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFPB
• Texto Completo: https://repositorio.ufpb.br/jspui/handle/tede/6652
• topic: Metilação de DNA; epigenética; fumo; gene de reparo do DNA; gene da telomerase; TP53; mucosa bucal; DNA methylation; epigenetics; smoke; DNA repair gene; telomerase gene; TP53; buccal mucosa; CNPQ::CIENCIAS DA SAUDE::ODONTOLOGIA

DNA methylation, characterized by the addition of a methyl group in cytosines within CpG dinucelotides can modified gene transcription, leading to decrease or even silence a gene. The ability of the environmental factors to induce epigenetic changes has been investigated and many studies have shown a relationship between them. Studies show that pesticides, metal ions, drugs, diet, alcohol dependence and smoking are associated with epigenetic changes. Smoking is often associated with the risk of cancer in various tissues and cardiovascular diseases, being considered the leading cause of preventable death. The MLH1 gene is related to the repair of badly paired bases of DNA (DNA mismatch repair (MMR)). The hTERT gene comprises the catalytic subunit of telomerase enzyme, which is considered a biological clock, a marker indicating that the cellular senescence can be installed inevitably form. The TP53 is a tumor suppressor gene and its hypermethylation is related to the development of various cancers. The aim of this work was to investigate the smoking habit influence on DNA methylation status in the promoter of cancer-related genes, MLH1, hTERT and TP53 in oral epithelial cells of healthy subjects. Samples of oral epithelium of smokers, nonsmokers and former smokers were collected by rinsing and DNA was extracted. After, DNA Methylation analysis was performed by Methylation Sensitive Restriction Enzymes, using two restriction enzymes, the HpaII and HhaI, which cleave different sites. Following the enzymatic digestion, DNA was amplified by PCR, subjected to electrophoresis on a 6% polyacrylamide gel and stained with silver nitrate. Statistical analysis was performed by Chi-square test at a significance level of 5%. The investigated CpG dinucleotides located at HhaI and HpaII sites in the MLH1 gene promoter were observed to be fully methylated in DNA majority samples from the smoker group and statistical differences were found between nonsmokers and smokers and between smokers and former smokers (p<0.05). The same was observed in the hTERT gene promoter at HhaI site (p<0.05) and for HpaII site the unmethylated condition was more frequent in smoker in comparison to nonsmokers (p<0.05). For TP53 no differences were found among groups (p>0.05) which the fully methylated condition was found to be an usual event in healthy oral epithelial cells. We conclude that smoking may induce changes in DNA methylation status in cancer-related genes, such as MLH1 and hTERT of healthy oral epithelial cells and the cessation of smoking reversed the process.