Figure 4.

Effects of DNA methyltransferase antisense treatment on drug-induced hypermethylation and chemotherapy resistance. a) MCF-7/Adr cells had no expression of dnmts transcripts after 72 h of antisense treatments; b) transfected cells with the antisense oligonucleotides had a 5-mC content between 2 and 4%, as compared with 5.6% in untreated MCF-7Adr cells, and c) MTT assays demonstrate that cells transfected with mismatch (MM) oligonucleotides showed no reduced cell viability and only a small reduction when challenged with adriamycin. The sole transfection with oligonucleotides against dnmts led to a reduction in viability between 30 and 40%, and when treated with adriamycin strong cytotoxicity was observed being higher for dnmt1 followed by -3a and -b.