Effects Of Melatonin Combined With Cisplatin Or Methotrexate On Osteosarcoma Cell Line SaOS-2

Objective:To observe the effects of Melatonin (Mel) combined with cis-platinum (DDP) or methotrexate (MTX) on the proliferation of osteosarcoma cell line SaOS-2, and to investigate whether Mel combined with DDP or MTX could play a synergistic antitumor effect.Methods:The SaOS-2 cells were treated by Mel alone or combination with DDP or MTX. (1) The cell activities were measured by cell counting kit-8 assay. And the combined effects were evaluated by the combination index (CI) value. CI<1 illustrates synergistic, CI=1 means additive, CI>1 suggests antagonistic effect. (2) The cell cycle distribution and (3) the cell apoptosis rate were analyzed by flow cytometry. The one-way ANOVA was used to analyze the experimental data and P<0.05 suggested a significant difference.Results:(1) After treatment with Mel (0.5,1,2,4,5 mmol/L), DDP (6.67, 16.67,33.33,66.66 umol/L) or MTX (0.1,0.5,1,2,4 mmol/L) alone, the cell activities were inhibited and the effects related the time and dose. The cell activities of the cells treatment with Mel (1 mmol/L) combined with DDP (6.67, 16.67,33.33,66.66 umol/L) were lower than that of DDP alone, and the CIs were more than 1 when it combined with the lower concentration of DDP (6.67, 16.67’,33.33 umol/L), suggesting that the combination effects were antagonistic, but when Mel (1 mmol/L) combined with DDP (66.66 umol/L), the CI was less than 1, suggesting that they played synergistic effects. The cell activities of the cells treatment with Mel (1 mmol/L) combined with MTX (0.1,0.5,1,2,4 mmol/L) were lower than MTX alone, the CIs were less than 1, suggesting they played synergistic effects. (2) When the cells were treated with Mel (1 mmol/L) alone or combined with MTX (0.5 mmol/L), the proportion of G1 stage cells increased and the proportion of S stage cells reduced; the proportion of S stage cells increased when the cells were treated with MTX (0.5 mmol/L); but the cell cycle distribution didn’t change when the cells were treated with DDP (16.67 umol/L) alone or combined with Mel (1 mmol/L). (3) The cells apoptosis rates were increased when the cells were treated with Mel (1 mmol/L) alone or combined with DDP (16.67 umol/L) or MTX (0.5 mmol/L), and they were more when the cells were treated with Mel combination with DDP or MTX than that of DDP or MTX alone.Conclusion:Mel could inhibit SaOS-2 cells activity, block the cell cycle at G1 stage, induce cell apoptosis. Mel combination with the lower concentration of DDP showed an antagonistic effect, but when it combined with MTX or the higher concentration of DDP, they played a synergistic effect.