Expression of epigenetic modifiers is not significantly altered by exposure to secondhand smoke

Quantification of the expression of genes encoding DNA methyltransferases (Dnmt1, Dnmt3a, Dnmt3b and Dnmt3l), methyl binding domain proteins (Mecp2, Mbd2 and Mbd3) and histone deacetylases (Hdac1 and Hdac2) by quantitative reverse-transcription polymerase chain reaction analysis showed modest but not statistically significant differences in the relative transcription of these key epigenetic regulators between SHS-exposed mice and age-matched controls. The non-significant changes in the expression of main epigenetic modifiers in SHS-exposed mice imply that SHS may predominantly induce genotoxic effects, particularly at non-tumorigenic doses, whereas epigenetic effects may only be secondary and manifest en route to tumor formation.