PrP exposure could activate estrogen-related pathways, for example, 20 nM (3.6 μg/L) PrP stimulated both the mRNA (24 h exposure) and protein (48 h exposure) expression of the progesterone receptor (PGR), estrogen receptor ERα and Erβ in MCF-7 breast cancer cells [33]. This evidence concerns the gene ESR1 and breast cancer.