Tamoxifen and raloxifene are examples of selective estrogen receptor modulators (SERMs) that exhibit tissue-specific activity of estrogens. When SERMs bind to the ER, conformation of the receptor changes in the special way and forms a new 3D structure that determines what coactivator is to be recruited to the promoter. The coregulator that is recruited to a particular promoter depends on the type of ER-dependent regulatory sequences that presented in that promoter. SERM activity also dpends on the ER?/ER? ratio in the tissues, particularly which ER form predominates. Therefore, a response to a specific SERM depends on various factors, such as chemical structure and the cellular and promoter context in which the SERM acts.