ESR1 and breast cancer: Previous studies from our lab show that HOTAIR is required for the viability of breast cancer cells and its expression is transcriptionally regulated by estradiol via coordination of estrogen receptors (ERs) and ER-coregulators such as MLL (mixed lineage leukemia)-family of histone methyltransferases and CBP/p300 in breast cancer cells55,56,60,128.