DNA methylation analysis of cancer-related genes in oral epithelial cells of healthy smokers

Aim: The aim of this study was to investigate the smoking habit influence on DNA methylation status in the promoters of the cancer related-genes MLH1, hTERT and TP53 in oral epithelial cells of healthy subjects. Materials and methods: DNA methylation analysis was performed using methylation-sensitive restriction enzymes (MSRE) in oral epithelial cells from non-smokers, smokers and ex-smokers. Results: The investigated CpG dinucleotides located at HhaI and HpaII sites in the MLH1 gene promoter were observed to be fully methylated in the majority of DNA samples from the smoker group and statistical differences were found between non-smokers and smokers and between smokers and ex-smokers (p < 0.05). The same was observed in the hTERT gene promoter at HhaI sites (p <0.05) and for HpaII sites the unmethylated condition was more frequent in smokers in comparison: to non-smokers (p < 0.05). For TP53, no differences were found among groups (p > 0.05), with the fully methylated condition found to be a common event in healthy oral epithelial cells. Conclusion: We conclude that smoking may induce changes in DNA methylation status in cancer-related genes of oral epithelial cells and that the cessation of smoking is capable of reversing this process. Based on our data, we suggest that DNA methylation status of the hTERT and MLH1 gene promoters are promising markers for screening a set of smoking-related alterations in oral cells. (C) 2015 Elsevier Ltd. All rights reserved.