ESR1 and breast cancer: ▪Increased intracellular reactive oxygen species (ROS)▪Induced apoptosis preferentially in BC cells▪Changed methylation status in some of the CpG islands in BC cells (DNAJC8, POTED, and EIF1YA) and estrogen receptor‐positive BC cells (ESFR1, PRR7, CD86, DHRS7B, FDX1, CREB3, BCL‐2, and BDNF)