Since the ERα promoter is mostly hypermethylated in ERα-negative breast cancer cells, we assessed the methylation status of the ERa promoter region from −66 to +356 covering 29 CpG dinucleotides and various overlapping transcription factor binding sites for 24 h, 48 h and 72 h (Fig. 4B). The gene discussed is ESR1; the disease is breast carcinoma.