Estrogen and antiestrogen action in reproductive tissues and tumors

It has long been known that several reproductive tissues undergo marked stimulation of growth and differentiation in response to sex steroid hormones. A major aim of research in this laboratory has been to try to elucidate the mechanisms by which estrogens and antiestrogens regulate the growth of reproductive tissues and of tumors that develop in reproductive tissues. This chapter describes selected aspects of the regulation of tissue responsiveness to estrogen, with particular focus on the status and function of the estrogen receptor as a determinant of tissue responsive capacity. The first part of the chapter describes studies in the uterus aimed at determining the factors influencing the estrogenic potency of compounds, and the latter part of the chapter will describe studies in hormone-dependent mammary tumors, as well as in uterus, aimed at defining the mechanisms by which antiestrogens are able to dramatically alter tissue sensitivity to estrogen.