Oestrogen enhances the responsiveness of the MMTV-LTR to glucocorticoid in ZR-75-1 human breast cancer cells

Abstract

Treatment of ZR-75-1 human breast cancer cells with oestrogen has no direct effect on the expression of a transfected MMTV-LTR but enhances its inducibility in response to glucocorticoid treatment. This effect which can be produced with both oestradiol and diethylstilbestrol is specific to induction of the MMTV-LTR, no effect of the treatment on expression driven by the RSV-LTR being observed. The effect can be observed in cells pre-treated with oestrogen prior to removal of DNA and glucocorticoid addition but not in cells where oestrogen is added after removal of the DNA. The possible mechanisms of these effects and their relationship to the induction of oestrogen-responsive genes by this hormone are discussed.