The estrogen receptor: a model for molecular medicine.

The identification of the estrogen receptor (ER) in the laboratory provided a mechanism to describe the target site specificity of estrogen action in uterus, vagina, pituitary gland, and breast cancer. Most importantly, a test was established to predict the outcome of antihormonal therapy in breast cancer, and a target was identified to develop new drugs for the treatment and prevention of breast cancer. The development of tamoxifen for the treatment of all stages of ER-positive breast cancers has resulted in the improved survival of breast cancer patients. However, the recognition of selective ER modulation, i.e., estrogen-like action in bones and lowering circulating cholesterol but antiestrogenic actions in breast and uterus, has resulted in the development of multifunctional medicines with the goal of preventing not only breast and uterine cancer but also osteoporosis and coronary heart disease.