Of note, recent results by Suzuki demonstrated that 4-methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene (MBP), an active metabolite of bisphenol A, an environmental pollutant with estrogenic activity, significantly decreases ERα expression in ERα/β-positive human BC, yet stimulating cell proliferation through the activation of ERβ-mediated transcription [8], supporting the concept that exposure to EDs might alter the functional role of ERβ in BC cells from a suppressor to a promoter role. This evidence concerns the gene ESR1 and breast cancer.