Background: Gallbladder cancer is the most frequent malignancy of the bile duct with high aggressive and extremely\r\npoor prognosis. The main objective of the paper was to investigate the inhibitory effects of oridonin, a diterpenoid\r\nisolated from Rabdosia rubescens, on gallbladder cancer both in vitro and in vivo and to explore the mechanisms\r\nunderlying oridonin-induced apoptosis and cell cycle arrest.\r\nMethods: The anti-tumor activity of oridonin on SGC996 and NOZ cells was assessed by the MTT and colony forming\r\nassays. Cell cycle changes were detected by flow cytometric analysis. Apoptosis was detected by annexin V/PI\r\ndouble-staining and Hoechst 33342 staining assays. Loss of mitochondrial membrane potential was observed by\r\nRhodamine 123 staining. The in vivo efficacy of oridonin was evaluated using a NOZ xenograft model in athymic\r\nnude mice. The expression of cell cycle- and apoptosis-related proteins in vitro and in vivo was analyzed by western blot\r\nanalysis. Activation of caspases (caspase-3, -8 and -9) was measured by caspases activity assay.\r\nResults: Oridonin induced potent growth inhibition, S-phase arrest, apoptosis, and colony-forming inhibition in SGC996\r\nand NOZ cells in a dose-dependent manner. Intraperitoneal injection of oridonin (5, 10, or 15 mg/kg) for 3 weeks\r\nsignificantly inhibited the growth of NOZ xenografts in athymic nude mice. We demonstrated that oridonin\r\nregulated cell cycle-related proteins in response to S-phase arrest by western blot analysis. In contrast, we\r\nobserved inhibition of NF-?B nuclear translocation and an increase Bax/Bcl-2 ratio accompanied by activated\r\ncaspase-3, caspase-9 and PARP-1 cleavage after treatment with oridonin, which indicate that the mitochondrial\r\npathway is involved in oridonin-mediated apoptosis.\r\nConclusions: Oridonin possesses potent anti-gallbladder cancer activities that correlate with regulation of the\r\nmitochondrial pathway, which is critical for apoptosis and S-phase arrest. Therefore, oridonin has potential as a\r\nnovel anti-tumor therapy for the treatment of gallbladder cancer.
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