Cytosporone B

Cytosporone B is the first naturally occurring agonist for nuclear orphan receptor Nur77. The molecule binds with high affinity (IC50=0.278 nM) to the ligand-binding domain of Nur77 and stimulates Nur77-dependent activities. Nur77 is also involved in glucose homeostasis, where it induces genes involved in gluconeogenesis. Csn-B physically binds to Nur77 and activates its transactivational activity and translocation to mitochondria to induce apoptosis. It inhibits cancer cell proliferation and tumor growth.(In Vitro):Cytosporone B targets the ligand binding domain of Nur77, which selectively stimulates the transactivational activity of Nur77. Cytosporone B induces luciferase activity in cells that are cotransfected with GAL4- Nur77 or GAL4-LBD. The EC50 of cytosporone B for Nur77 is 0.278 nM. Cytosporone B displays robust pro-apoptotic activity in gastric cancer cells BGC-823. 63.5% of the cells are apoptotic when treated with cytosporone B for 48 h. Cytosporone B shows selective effect on cancerous cells. Cytosporone B inhibits proliferation of human gastric cancer BGC-823 cells and human colon cancer SW620 cells by 470%, but it has a modest effect on human lung cancer H1299 cells and human hepatoma HepG2 cells.(In Vivo):In the hepatocytes of wild-type mice, the transcriptional activity of the reporter is induced five-fold with cytosporone B treatment. In wild-type mice, cytosporone B treatment significantly increases glucose levels from 3.2 to 11.4 mM within the first 30 min, and thereafter blood glucose gradually decreased before reaching the initial level after 300 min.