Steroid hormone-induced expression of oncogene encoded nuclear proteins

In this article we have attempted to review the literature on the regulation of nuclear protooncogene expression by steroid hormones and other small molecules that interact with receptors of the steroid/thyroid superfamily. Until about 5 years ago, there were relatively few reports of steroidal regulation of cellular oncogenes, but hundreds of papers on this topic have appeared since then. This demonstrates the intense interest in this area that has developed recently. It now been demonstrated that all the major classes of steroid hormones control expression of nuclear protooncogenes in one or more systems. Given the actions of these proteins as transcription factors and their central role in cellular communications systems, it seems likely that they play a key role in mediating the biological effects of steroids on processes such as proliferation and differentiation. To date, most of the work in this general area has focused primarily on the regulation of three genes: c-fos, c-jun, and c-myc. However, a quick glance at the table of nuclear protooncogenes in the introduction of this article indicates that over 40 nuclear protooncogenes are now recognized. For the large majority of these regulatory effects of steroids and related molecules have not yet been reported. Hence, we predict that reports in this general area of research will continue to appear at a very rapid rate over the next few years. In addition, we have tried to provide enough background information for readers to get an overview of the regulation of nuclear protooncogene expression by nonsteroidal factors. We felt this information was important to emphasize that steroid hormones represent only one of the many classes of regulatory molecules that control expression of nuclear protooncogenes. Thus, an important area for future research will be to understand how these multiple regulatory systems interact to control expression of this important class of cellular oncogenes and the biological processes that they mediate.