Glucocorticoid induced loss of oestrogen receptor alpha gene methylation and restoration of sensitivity to fulvestrant in triple negative breast cancer

•Glucocorticoids alter epigenetic patterns in breast cancer cell lines.•Glucocorticoids lead to the loss of methylation on the promoter region of ESR1 in triple negative breast cancer xenografts.•Triple negative breast cancer cells respond to fulvestrant following long term exposure to cortisol.