[Effect of ursolic acid on proliferation and apoptosis of human osteosarcoma cell line U2-OS].

Objective: To investigate the effect of ursolic acid on the proliferation and apoptosis of human osteosarcoma cell line U2-OS and analyze its mechanism. Methods: Human osteosarcoma cell line U2-OS was divided into 4 groups, which was cultured with ursolic acid of 0, 10, 20, and 40 µmol/L, respectively. At 0, 24, 48, and 72 hours after being cultured, the cell proliferation ability was detected by cell counting kit 8 (CCK-8). At 48 hours, the effects of ursolic acid on cell cycle and apoptosis of U2-OS cells were measured by flow cytometry. Besides, the expressions of cyclin D1 and Caspase-3 were detected by real-time fluorescent quantitative PCR and Western blot. Results: CCK-8 tests showed that the absorbance ( A) value of each group was not significant at 0 and 24 hours ( P>0.05); but the differences between groups were significant at 48 and 72 hours ( P<0.05). Flow cytometry results showed that, with the ursolic acid concentration increasing, the G 1 phase of U2-OS cells increased, the S phase and G 2/M phase decreased, and cell apoptosis rate increased gradually. There were significant differences between groups ( P<0.05). Compared with the 0 µmol/L group, the relative expressions of cyclin D1 mRNA and protein in 10, 20, and 40 µmol/L groups significantly decreased ( P<0.05); whereas, there was no significant difference in relative expression of Caspase-3 mRNA between groups ( P>0.05). However, with the ursolic acid concentration increasing, the relative expressions of pro-Caspase-3 protein decreased and the relative expressions of activated Caspase-3 increased; there were significant differences between groups ( P<0.05). Conclusion: Ursolic acid can effectively inhibit the proliferation of osteosarcoma cell line U2-OS, induce the down-regulation of cyclin D1 expression leading to G 0/G 1 phase arrest, increase the activation of Caspase-3 and promote cell apoptosis.