Nur77 (aka TR3 or NGFI-B) is an orphan nuclear receptor and plays important roles in carcinogenesis,inflammation,metabolism,and energy homeostasis.However,there is no physiological ligand identified up to date,which impedes the in-depth investigation on switching the Nur77 multi-functionality.The first clue on the regulatory mechanism of Nur77 was derived from our identification of cytosporone B (Csn-B) isolated from an endophytic fungus,Dotiorella sp.HTF3.