CpG islands were hypomethylated in ERα‐positive cell lines like MCF‐7, ZR75‐1, and T47D, whereas they were hypermethylated in ERα‐negative BC cells such as MDA‐MB‐231, MDA‐MB‐435, MDA‐MB‐468, and Hs578t.8 Here, ESR1 is linked to breast cancer.