Increased expression of hepatic DNA methyltransferase in smokers

The DNA methyltransferase enzyme (DNA MTase) catalyzes DNA methylation at c ytosines in CpG dinucleotides. 5-Methylcytosine modification of DNA is impo rtant in gene regulation, DNA replication, chromatin organization and disea se. Increased levels of DNA MTase have been associated with the initiation and promotion of cancer. This study was conducted to assess whether cigaret te smoking and other factors, such as age and gender, influence DNA MTase e xpression in nontumorous tissue. DNA MTase was significantly (p < 0.05) hig her in samples from cigarette smokers; the mean level of DNA MTase mRNA was almost 2-fold higher in these samples than in those from nonsmokers. Level s of DNA MTase mRNA were higher in samples from females than in those from males, but the difference was not statistically significant. Age was not as sociated with DNA MTase levels. Increased levels of DNA MTase in individual s who smoke may indicate a greater susceptibility to the risk of cancer sin ce increased levels of this enzyme are found in cancer cell lines and human tumors. The results of this study suggest that further investigations of i ncreased expression of this enzyme as a predisposing factor for cancer susc eptibility are needed.