Steroid hormone receptors and oncogenes.

Steroid hormones exert diverse effects on normal growth and development through the action of specific intracellular receptor molecules. These receptors are thought to function as trans-acting regulatory proteins by interacting with chromatin and modulating the transcription of specific genes in target cells. Another class of molecules, the viral oncogenes (v-oncs) encode proteins which are associated with the transformation of normal cells to cancer cells. The cellular oncogenes (proto-oncogenes), from which the viral oncogenes were derived, may have important roles in the growth and differentiation of normal cells. Steroid hormones, directly or in conjunction with altered oncogene products, also appear to be important in the growth and differentiation of cancer cells. Recently it has been determined that the amino acid sequences of the steroid receptors are similar to the erb-A oncogene product, which subsequently has been found to be a thyroid hormone receptor. These results have led to the hypothesis that the steroid receptors and the erb-A product are members of a superfamily of transcription factors which regulate normal and malignant growth and differentiation. Similarities and functional interactions between steroid receptors and oncogene products will be the focus of this review. The results to date imply that these two classes of molecules have interesting and important inter-relationships.