Also, overexpression of the DNA methyltransferase, DNMT3B, was identified in lung and breast cancer cell lines (Beaulieu et al, 2002) and depletion of DNMT3B expression in breast cancer cell line was shown to activate the methylated RASSF1 (Wang et al, 2006); therefore, we analysed the expression of these factors by qRT-PCR. This evidence concerns the gene RASSF1 and breast cancer.