Identification of androgen response elements in mouse mammary tumour virus and the rat prostate C3 gene

The effect of steroid hormones on mouse mammary tumour virus (MMTV) promoter activity has been analysed in the breast cancer cell lines ZR-75-1 and T-47D 11. Both androgens and progestins were stimulatory in both cell lines, whereas glucocorticoids were stimulatory in only ZR-75 cells. A glucocorticoid response was restored to T-47D cells by the transient expression of a glucocorticoid receptor expression vector, suggesting that endogenous receptors were limiting. The effect of androgen was mediated by a region of MMTV previously shown to be essential for glucocorticoid and progestin responses between nucleotides -201 and -69 upstream of the cap site. Similarly, the effect of androgens on the rat prostate C3(1) gene promoter was analysed in the rat prostate cell line T5. Although these cells had functional androgen receptors which could stimulate MMTV-promoter activity, they were incapable of interacting with androgen response elements to stimulate transcription from the C3(1) promoter.