The latter was established from an MMTV-Amplified in Breast Cancer 1 (AIB1) transgenic mouse mammary tumour (Torres-Arzayus et al, 2006; Torres-Arzayus et al, 2010); AIB1 is an ER co-activator (Li et al, 1997). The gene discussed is NCOA3; the disease is breast carcinoma.