GREB1 is an early response gene in the estrogen receptor-regulated pathway. It is thought to play an important role in hormone-responsive tissues and cancer. GREB1 is expressed in proliferating prostate tissue & prostate cancer and is thought to act as a regulator of hormone-dependent cancer growth in breast and prostate cancers. Its promoter contains putative androgen receptor response elements. Three alternatively spliced transcript variants encoding distinct isoforms have been found for this gene.