Potency and safety of DNA demethylating agents. (A) Comparison of the dose-dependent suppressive effects of 5-Aza, procainamide, IM25, and IM9 on the viability of MCF7 cells by MTT assays. Columns, mean (n = 3); error bars, S.D. (B) Parallel ELISA analysis of the suppressive effects on EGFP expression in the two-component reporter system. Columns, mean (n = 3); error bars, S.D. (C) Western blot analysis of the effects of procainamide, 5-Aza, IM9, and IM25, each at 7.5 μM, on EGFP expression.