Synergistic apoptotic effect of the combination of diosgenin and TRAIL on non-small-cell lung cancer cell line A549 evaluated with the Chou-Talalay method

This study is to investigate the apoptotic induction effect of the combination of diosgenin and TNF-related apoptosis-inducing ligand (TRAIL) on non-small-cell lung cancer cell line A549 by using the Chou- Talalay method, and observe the mechanism of the combination.  The apoptotic effect of diosgenin or TRAIL alone and their combination on A549 and normal cell line 293T proliferation was measured by MTT assay.  Chou-Talalay method was used to evaluate the combination effect.  Apoptosis was examined by Hoechst 33342 staining and flow cytometry assay.  Western blotting detects the expression of apoptosis-associated proteins.  Diosgenin or TRAIL alone can inhibit proliferation of A549 in a concentration-dependent manner.  According to the Chou-Talalay method, when f_a = 0.1, CI > 1, when f_a > 0.1, CI < 1.  Combined with TRAIL, the IC₅₀ of diosgenin decreases from 21.864 to 14.810 μmol·L⁻¹ (P < 0.05) on A549 cells.  But for 293T cells, IC₅₀ of diosgenin does not change significantly.  As with Hoechst 33342 staining and flow cytometry assay, the apoptosis ratios also increased in the combination group.  At protein expression level, combination-treated group displays increased Caspase-8, Caspase-9, Bid, Caspase-3 activation and PARP cleavage, significantly decreased Bcl-2 and increased Bax expression, and MAPK pathways were activated.  The combination of diosgenin and TRAIL has synergistic effect on A549 cells.