ESR1 and breast cancer: Since anastrozole can function as an ERα ligand, to investigate whether anastrozole regulates similar or different sets of genes compared with E2, we performed RNA sequencing (RNA-seq) using T47D breast cancer cells treated with anastrozole (10 nM) alone, E2 (0.1 nM) alone or anastrozole (10 nM) plus E2 (0.1 nM).