Figure 10.

Etoposide downregulates Cdc20 and securin expression in H460 cells. Inhibition of the Cdc20-APC/C pathway sensitizes H460 cells to etoposide-induced cell death. A, H460 cells were treated with increasing concentrations of etoposide (1.56 μM, 3.125 μM, 6.25 μM, 12.5 μM, 25 μM, 50 μM, and 100 μM) for 48 h. Cells were then collected and cell lysates were subjected to immunoblotting analysis using antibody probes specific for Cdc20 and securin. Ponceau S staining shows equal total protein loading. Quantification of protein band intensity is shown at the bottom of each blot. B, H460 cells were transfected with either control (Ctl) or Cdc20 siRNA (10 pmol) and cultured in the presence of either DMSO or different concentrations of etoposide (1.56 μM, 3.125 μM, 6.25 μM, 12.5 μM, 25 μM, 50 μM, and 100 μM) for 24 h. Cell survival was quantified by MTT assay. C, H460 cells were treated with Apcin (50 μM) and pro-TAME (40 μM) in the presence of either DMSO or different concentrations of etoposide (1.56 μM, 3.125 μM, 6.25 μM, 12.5 μM, 25 μM, 50 μM, and 100 μM) for 24 h. Cell survival was quantified by MTT assay. Values in (B) and (C) represent means ± SEM; statistical comparisons were made using the student’s t test. ∗p < 0.001. DMSO, dimethyl sulfoxide.