To further interpret the epigenetic mechanisms on ERα regulation by EGCG and SFN treatment, we assessed gene expression and enzymatic activities of two important epigenetic-modulatory enzymes including HDAC1 involved in regulation of histone acetylation and DNA methyltransferase1 (DNMT1) involved in regulation of DNA methylation processes in breast cancer MDA-MB-231 and MDA-MB-157 cells. Here, DNMT1 is linked to breast cancer.