Figure 4.

Bortezomib upregulates p21^cip1/waf1. (A) SNU-216 cells were treated with TRAIL and/or bortezomib for 24 h and 48 h. The expression of indicated proteins including p21^cip1/waf1 were visualized by western blot analysis. (B) SNU-216 cells were transduced with scramble or p21^cip1/waf1 shRNA expressing lentiviruses, then were selected by puromycin (2.5 µg/ml) for one week. The p21^cip1/waf1 knockdown cells were treated with TRAIL in the presence or absence of bortezomib for 24 h and 48 h. Cell viability of SNU-216 after 24 h and 48 h treatment was measured by MTT assay and relative cell viability was calculated against untreated control. MTT results shown are the means ± SE of three independent experiments. 'ns' for P>0.05 in Student's t-test. (C) Expression of p21^cip1/waf1 and activation of caspases in the p21^cip1/waf1 knockdown cells were visualized by western blot analysis. All cells (A~C) were treated with TRAIL at 12.5 ng/ml and/or bortezomib (22.75 nM) for indicated time period. The images shown are representatives of triple experiments (A and C).