GREB1 and tumor of uterus: In support of a proto-oncogenic function for GREB1, various fusion genes involving GREB1 have been identified in uterine tumors resembling ovarian sex-cord tumor (UTROSCT), including GREB1-NCOA1, GREB1-NCOA2, GREB1-NR4A3, GREB1-SS18, and ESR1-GREB1, although its role in tumorigenesis remains unclear (20–22).