Suzuki et al. demonstrated that RNAi-Mediated knockdown of DNMT1 expression led to demethylation of tumor suppressor gene (RASSF1A, p16 ink4A, and CDH1) promoters in lung and breast cancer cell lines (NCI-H1299 and HCC1954), which restored the expression of RASSF1A and SEMA3B genes [29]. This evidence concerns the gene DNMT1 and breast cancer.