The protective effect of isoflavones against the development of prostate cancer has been reviewed and is considered to be mediated by hormone-like effects through estrogen receptor α and β (ER-α, ER-β) binding or by non-hormone-like effects, including the inhibition of tyrosine kinases, modulation of cell proliferation, regulation of the cell cycle, apoptosis and angiogenesis [17]. This evidence concerns the gene ESR1 and prostate cancer.