Among these, the transcription factor ER is of particular interest, since previous studies have shown its functional connection with FOXO3: in breast cancer cells, ER is involved in the control of tumor aggressiveness through modulation of FOXO3 activity [105], while FOXO3 mRNA and protein were found to be upregulated by estradiol [106]; in prostate epithelial cells, a direct relationship between ERβ and FOXO3 expression has been described, resulting in cell differentiation and maintenance of cells in a quiescent state [107]. The gene discussed is ESR1; the disease is breast cancer.