GNRH1 and breast cancer: Previous studies have also demonstrated that antagonists of GnRH-II, a version of GnRH with an alternative structural that is completely structurally conserved from fish to mammals, and different from GnRH in three amino acids, can induce apoptosis in endometrial cancer, breast cancer, and ovarian cancer cell lines through activating the intrinsic apoptosis pathway (33, 34).