ESR1 and breast cancer: We also explored the effects on the cells in terms of the methylation and transcription of ESR1 after treatment with a demethylating agent, decitabine (DAC), Furthermore, methylation levels across the ESR1 gene were assessed in 155 samples of human breast cancer, and in 89 samples of exfoliated breast epithelial cells from donated expressed breast milk (EBM) from healthy women.