Triptolide induces mitochondrial apoptosis through modulating dual specificity phosphatase 1/mitogen-activated protein kinases cascade in osteosarcoma cells.

Due to chemoresistance and metastasis, the overall prognosis of osteosarcoma (OS) has not improved over the last two decades. Exploring novel therapeutic agents that can circumvent theses malignant phenotypes of OS would be essential to improve the survival of OS patients. Triptolide is a unique diterpene triepoxide that possesses potent antitumor activities.However, the effects and mechanism of triptolide on OS cells remain unknown. The effects of triptolide on viability, apoptosis, cell cycle distribution and migratory ability of OS cells were measured using MTT, flow cytometry and wound healing and transwell invasion assays. And an OS tumor xenograft mouse model was produced to further study the in vivo antitumor effects of triptolide. The expression of DUSP1 at the protein and mRNA level in OS cells was detected by western blot and qPCR. We report that triptolide exhibits multidimensional antitumor activities in OS cells, including the induction of apoptosis and G1 phase accumulation, inhibition of cell viability, migration, and invasion. We further demonstrate that triptolide inhibits the expression of dual-specificity protein phosphatase1 (DUSP1) through inhibiting its promoter activity, which causes sustained activation of three subfamilies of mitogen-activated protein kinase (MAPK). And the modulation of DUSP1/MAPK cascade is associated with the apoptosis of OS cells, since the ectopic expression of DUSP1 or the inhibition of MAPK using specific inhibitors can counteract triptolide-induced apoptosis. In addition, triptolide enhances doxorubicin-induced apoptosis. In summary, our study suggests that DUSP1 is an important cellular target of triptolide, and triptolide may be a promising treatment option for OS as a single agent or combined with other chemotherapeutics.