A role in ERα signalling for other NRs has recently been highlighted by the finding that retinoic acid receptor-α, an oestrogen-regulated gene in breast cancer (28,29), localizes to ERα binding sites to modulate the expression of oestrogen-regulated genes (30,31), providing crosstalk between oestrogen and retinoid signalling in breast cancer cells. This evidence concerns the gene ESR1 and breast cancer.