The aim of this study is to investigate the apoptotic inhibition and its molecular mechanism of dexamethasone (DEX) acting on cisplatin (CDDP)-induced apoptosis of human lung adenocarcinoma cell SPC-A1. SPC-A1 cells were pre-cultured in vitro for 24 hours with DEX in different concentrations and then CDDP was added in different concentrations for culturing for further 48 hours. The survival rates of the cells were determined by MTT. The expression of serum/glucocorticoid-induced kinase (SGK-1) and mitogen-activated protein kinase phosphatase-1 (MKP-1) in SPC-A1 cells after being cultured by 1 μmol/L DEX at different time was detected by semi-quantitative RT-PCR technology. The expression of glucocorticoid receptor (GR) in SPC-A1 cells was measured by immunohistochemistry (IHC) with biotin-labeled anti-GR. The results of MTT showed that SPC-A1 cells had resistance to CDDP-induced apoptosis with pre-cultured DEX and the resistance intensity presented DEX concentration-dependent. The expressing quantity of SGK-1 in SPC-A1 cells stimulated by DEX could be elevated and increased with intention of time, but the express of MKP-1 was not detected. Up-regulated expression of GR in SPC-A1 cells stimulated by DEX was detected by IHC. The number of cells expressing GR in SPC-A1 cells was significantly higher than that in the control group. The results showed that DEX inhibited apoptosis of SPC-A1 cells induced by CDDP. The possible molecular mechanism is that elevated expression of GR induced by DEX up-regulates the expression of SGK-1 which locates at the downstream of anti-apoptosis pathway. The apoptosis resistance of SPC-A1 cells may account for all above the factors.
ObjectiveTo investigate the effects of cinobufagin on the apoptosis in U-2OS osteosarcomas cells (U-2OS cells) and explore its potential mechanism. MethodsThe cytostatic effects of cinobufagin (10, 20, 50, 100, 200, and 400 nmol/L) on U-2OS cells were evaluated by MTT assay at 24, 48, and 72 hours after culture; simple U-2OS cells served as control group. The impact of cinobufagin (100 nmol/L) on the apoptosis in U-2OS cells was determined by flow cytometry at 48 hours after culture, which were treated with cinobufagin (experimental group) or with cinobufagin plus Z-VAD-FMK (control group), and simple U-2OS cells served as blank control group. The Caspase-3 activity was measured by Caspase-3 activity assay kit at 48 hours after culture, which were treated with cinobufagin (20, 50, and 100 nmol/L), and simple U-2OS cells served as control group.The expression of apoptosis signal pathway related proteins in U-2OS cells treated with cinobufagin were detected by Western blot at 48 hours after culture, which were treated with cinobufagin (20, 50, and 100 nmol/L), and simple U-2OS cells served as control group. ResultsThe results of MTT assay showed that cinobufagin inhibited the proliferation of U-2OS cells in a dose- and time-dependent manners. At each time point, the growth rate of U-2OS cells was significantly reduced with the increasing cinobufagin concentration, and as time prolonged, the growth rate of U-2OS cells behaved the same way in the same group. There were significant differences among different time points and groups (P<0.05). The apoptotic rate of experimental group (46.87%±11.23%) was significantly higher than that of the control group (2.34%±0.98%) and blank control group (1.04%±0.25%) (P<0.05). The Caspase-3 activity in 20, 50, and 100 nmol/L groups were 1.14±0.32, 1.31±0.41, and 1.92±0.54, respectively, which were significantly higher than that in control group (P<0.05). Compared with 20 and 50 nmol/L groups, 100 nmol/L group significantly increased the Caspase-3 activity in U-2OS cells (P<0.05). Compared with the control group, the expressions of cleaved Caspase-3, cleaved Caspase-9, and Bax were obviously up-regulated; the Bcl-2 expression was down-regulated; and the ratio of Bax/Bcl-2 was increased in different cinobufagin-treated groups (P<0.05). The same tendency was seen in different cinobufagin-treated goups, showing significant differences among groups (P<0.05). ConclusionCinobufagin can inhibite the proliferation of U-2OS cells, and induce cell apoptosis. The potential mechanism of cinobufagin-induced apoptosis may be related to the mitochondria-mediated pathway.