NR4A1 and breast cancer: To determine whether pharmacological activation of NR4A1 inhibits the growth of BC cells, we treated cells with a small-molecule agonist, cytosporone B (Csn-B), which specifically binds to the ligand-binding domain of NR4A1 and stimulates NR4A1-dependent transcription of target genes, including NR4A1 itself51.