Steroid antagonists as nuclear receptor blockers

Molecular analysis of sex steroid receptors, together with the availability of a range of ligands for these receptors that affect differentially the physiological actions of the ligand-receptor complex in the cell nucleus, is providing new insights into the processes that control transcriptional activation leading to cell growth. These studies serve to focus attention on the importance of other cell specific factors that are important in determining the transcriptional efficiency of the hormone-receptor complex. Elucidation of the nature and role of such factors may lead ultimately to hormonal or anti-hormonal agents targeted to modulate selected hormone mediated events in specific cells or organs. The sex steroid receptors are prototypes of a much larger family of proteins that control transcription, including proteins that bind to ligands known to be important physiologically, such as thyroid hormones and retinoids, as well as "orphan" receptors for which no ligands have been described. The established value of steroid antagonists in cancer therapy suggests that further developments in the understanding of new members of the steroid receptor superfamily may lead to the development of novel anti-cancer agents. The developing understanding of "cross talk" between steroid-receptor and growth factor-receptor mediated tumour growth stimulatory pathways may also provide previously unrecognized opportunities for tumour therapy.