Research Article

Human Embryonic Stem Cells Acquire Responsiveness to TRAIL upon Exposure to Cisplatin

Figure 4

Downregulation of caspase 8 abolishes apoptosis induced by cisplatin and TRAIL. (a) Morphology of hESC upon siRNA-mediated knockdown of caspases 8 and 10, respectively, followed by combined cisplatin and TRAIL treatment, as observed by light microscopy (10x, bar 50 μm). (b) Activation of the caspase cascade upon the given treatments are demonstrated by western blot visualization of the following inactive (full length) caspases: procaspase 3 (~35 kDa), procaspase 8 (~55 kDa), and procaspase 10 (~60 kDa). Their active forms include the following: cleaved caspase 3 (~17/12 kDa), cleaved caspase 8 (~18 kDa), and cleaved caspase 10 (~20 kDa). Staining with 0.1% amidoblack was used to evaluate the protein loading. Both CCTL12 and CCTL14 lines of hESC were used (); a representative picture is shown. To demonstrate caspase 8 activation under control (scrambled) conditions, a longer exposure of the membrane with the visible ~18 kDa fragment is shown in Supplementary Figure 3. (c) Western blot analysis of caspase 3 activation in hESC upon treatment with cisplatin, TRAIL, and caspase 10 inhibitor Z-AEVD-fmk (20 μM). The CCTL14 line of hESC was used ().