Immunohistochemical expression of DNA methyltransferases 1, 3a and 3b in oral leukoplakias and squamous cell carcinomas

Over-expression of DNA methyltransferases DNMT1, DNMT3a and DNMT3b has been reported in various cancers and precancerous lesions. Objective: To investigate DNMT1, DNMT3a and DNMT3b enzymes in oral squamous cell carcinoma (SCC) and leukoplakia, and their relationship with histopathologic/clinical parameters. Study design: Immunohistochemistry was carried out to evaluate the three DNMTs in 60 samples of oral SCC and 37 samples of oral leukoplakia. Results: DNMT3a immunoreactivity in the three groups of oral SCC (39.8%) was significantly higher than in control (22.6%) (ANOVA, Student-Newman-Keuls test, P < 0.05), but not when compared to oral leukoplakia groups (28.2%). For DNMT1 and DNMT3b, there were no statistically significant differences between oral SCC groups (65% and 74.7%), oral leukoplakia groups (68.3% and 70.9%) and control (65.4% and 76.5%). There was a significantly higher mean percentage of DNMT1 immunoreactivity in non-smokers (ANOVA, P = 0.048), and a higher DNMT3a immunoreactivity in alcohol users (ANOVA, P = 0.01). Conclusions: Higher DNMT3a immunopositivity may be associated with oral SCC and alcohol use, whilst lower levels of DNMT1 may be related with smoking habit. However, there was a significantly higher mean percentage of DNMT1 immunoreactivity in non-smokers (ANOVA, P = 0.048), and a higher DNMT3a immunoreactivity in alcohol users (ANOVA, P = 0.010). (C) 2010 Elsevier Ltd. All rights reserved.