In prostate cancer cell lines, the anti-proliferative activity of ER-β has been shown by the downregulation of key oncoproteins including phosphoinositide 3-kinase (PI3K), c-Myc, and Cyclin E and the upregulation of tumor suppressor genes such as phosphatase and tensin homolog (PTEN) and forhead box O3 (FOXO3), supporting the idea that ER-β agonists might be considered for inhibiting the malignant processes [44]. This evidence concerns the gene FOXO3 and prostate cancer.