GREB1 and prostate cancer: In this regard, an early estrogen-responsive gene, GREB1, was identified which responds to both estrogen and androgen levels and is able to act as a pan-steroid responsive gene, stimulating the proliferation of breast, ovarian and prostate cancer cells (27); GREB1 may serve as clinical marker to monitor the response to endocrine therapy but also as a potential therapeutic target (28).