Over a third (38%) of ER coregulators identified in breast cancer are over-expressed (Lonard et al., 2007; Lonard and O'Malley, 2012; Cortez et al., 2014), such as SRC3 (AIB1) (List et al., 2001; Azorsa et al., 2001), SRC2 (Kurebayashi et al., 2000), and PELP1 (Habashy et al., 2010). Here, NCOA3 is linked to breast cancer.