The recent discovery of a second estrogen receptor, ER&B;, shows that the mechanisms behind the effects of estrogen are far more complicated than previously assumed, and gives unique opportunities to gain a better understanding of these phenomena. ER&B; is expressed in many important target tissues for estrogen, and a better insight into the respective mechanisms of action of ERalpha and ER&B; might give clues concerning the etiology and pathogenesis of for example prostate or ovarian cancer. Development of ERalpha and ER&B; specific ligands may furthermore open up interesting new possibilities for treatment of e.g. postmenopausal symptoms and breast cancer. In this review, we will try to summarize what is known sofar about estrogen receptor &B;, with some emphasis on the human receptor and its expression. We will furthermore try so summarize what is known about different isoforms of the receptor, in view of what is known about isoforms and variants of other receptors, in particular estrogen receptor alpha (ERalpha) and the progesterone receptor (PR).
This study was supported by a grant from the Swedish Cancer Society.