Screening And Activity Research For Anti-tumor Marine Natural Products Targeting Orphan Receptor Nur77

Nur77,orphan nuclear receptor,is one of the important members of nuclear receptor superfamily and critical target of anti-tumor drugs research.Natural products are substantial source of small modulator of Nur77.Marine natural products have unique chemical skeletons and broad bioactivity,but the mechanism and target of many marine natural products are still indefinite.In this study,anti-tumor ingredients targeting Nur77 were screened from marine natural products and further clarified its mechanism in order to discover novel small modulator of Nur77.In this study,ten marine natural compounds with potential anti-tumor activity were screeneded via MTT,and cembranoid type diterpenes compound sinularin targeting Nur77 was discovered through Fluorescence quench analysis.The structure-activity relationship about anti-tumor activity and Nur77 targeting effects of cembranoid diterpenoids were investigated.It was found that the lactone ring and the olefinic bond at a specific position are the key structural basis of activity.The possible binding sites and key amino acid residus of sinularin and Nur77-LBD were speculated through molecular modelling docking analysis.This result provided a basis for the structural modification and binding mode of this kind of components.Flow cytometry assay and western blotting analysis indicated sinularin could induce apoptosis of tumour cells in does-and time-dependent manner.Immunofluorescence analysis was used to investigate subcellular localization of Nur77 after treatment of sinularin.As a result,sinularin could induce nuclear export and mitochondrial targeting of Nur77.Meanwhile,siRNA approach demonstrated Nur77 was required for sinularin to trigger apoptosis.Besides,sinularin could enhance the transactivation activity of Nur77 by dual-luciferase reporter assays.These data suggested that sinularin may be a novel anti-tumor and Nur77-targeting compound with potential for further investigation,which revealed the anti-tumor mechanism of sinularin by targeting Nur77 for the first time.This study enriched the structure types of small molecule modulators of Nur77,and laid a foundation for further structural modification of these components and discovery of novel anti-tumor drugs targeting Nur77.