Figure 5
HDACi synergize with TRAIL. (a) FLIP expression, cleavage of PARP and processing of procaspase-3 in H460 and A549 cells were determined by western blotting. Cells were pre-treated with 5 μM vorinostat for 6 h prior to treatment with TRAIL for a further 18 h. (b) Colony formation was assessed 2 weeks following treatment of H460 and A549 cells with vorinostat alone, TRAIL alone or co-treatment with both agents at the concentrations indicated. After 24 h of treatment, the media was removed, cells washed in PBS, and fresh media added. (c) Viability of H460 and A549 cells was assessed 72 h after co-treatment with TRAIL and vorinostat. The cell viability data was used to assess synergy using the CI method. (d) Western blot analysis of FLIP expression, procaspase-8 processing and PARP cleavage in control (EV) and FLIPS overexpressing H460 cells treated as indicated for 24 h. (e) Sub-G1 analysis of apoptosis in H460 and A549 cells treated with vorinostat alone, TRAIL alone or co-treated with both agents (combo). Cells were transfected with 20 nM procaspase-8-targeted siRNA (siCaspase-8) or control siRNA (SC) for 48 h before TRAIL/vorinostat treatment. Significance was determined using Student’s t-test: *P<0.05; **P<0.01
