Background & objective: Staurosporine (STS), a non- specific protein kinase inhibitor, can extensively induce cell apoptosis. Orphan receptor TR3, an immediate-early response gene, belongs to the steroid/thyroid receptor superfamily. After stimulated by apoptosis-inducing agents, TR3 is expressed rapidly and translocates from nuclei to mitochondria,which finally induces cell apoptosis. This study was to investigate the mechanism by which STS induces apoptosis of gastric cancer cell line BGC-823,and its correlation with translocation of TR3 in BGC-823 cells.
Methods: Fluorescent microscopy was used to observe apoptotic morphology of BGC-823 cells after treated with STS for 3 and 24 h and stained by DAPI, and determine cell apoptotic rate. Laser scan confocal microscopy and Western blot were performed to investigate translocation of orphan receptor TR3 and the release of cytochrome c. Flow cytometry and confocal microscopy were used to examine mitochondrial membrane potential.
Results: After treated for 3 h,and 24 h,apoptosis rates of BGC-823 cells in STS-treatment groups were higher than those of cells in control groups (15.7% vs. 4.0%, and 39.4% vs. 4.7%). After BGC-823 cells exposed to STS for 3 h,TR3 translocated from nuclei to mitochondria, mitochondrial membrane potential was decreased, and cytochrome c released from mitochondria to the cytoplasm.
Conclusion: TR3, in response to STS, translocates from nuclei to cytoplasm, where it targets to mitochondria to induce cytochrome c release, finally results in apoptosis of gastric cancer cells.