Estrogen binding triggers a number of events resulting in activation of ER and induces conformational changes in the LBD, allowing the estrogen–ER complex to bind to specific DNA sequences [estrogen response elements (EREs)] while interacting with co-repressor and coactivator proteins to regulate the transcription of estrogen-responsive genes that are important in various physiological and pathological processes, including carcinogenesis and tumor progression (2, 4–6). This evidence concerns the gene ESR1 and neoplasm.