Moreover, analysis of public data profiling gene expression in breast cancer patients after blocking ERα using the aromatase inhibitor letrozole [41] found an increase in EGR1 transcript abundance (p = 1.775e-06, Wilcoxon rank sum test; Fig 5F), suggesting that the interaction between ERα and EGR1 is active in breast cancer tissue, though we observed no change in GDNF. This evidence concerns the gene CYP19A1 and breast cancer.