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. 2016 Jan 25;6:18953. doi: 10.1038/srep18953

Figure 5. Chemical inhibitors and shRNA against caspases 8 and 9 reveal that inhibition of caspase 9 prevents activation of caspase 8 in cells treated with proteasome inhibitors.

Figure 5

(a) DNA fragmentation in LN18 cells pre-treated 30 min with caspase 8 inhibitor (25 μM z-IETD-fmk) or caspase 9 inhibitor (25 μM z-LEHD-fmk), followed by 48 h of treatment with proteasome inhibitors. (b) Western blot of caspases 8 and 9 in LN18 cells pre-treated with specific inhibitors of caspase 8 or 9, followed by 16 h treatment with 100 nM MRZ or BTZ. (c,d) Western blot densitometry from (b) showing the ratio of cleaved to whole caspase 8 in cells pre-treated with the caspase 9 inhibitor (c), or the ratio of cleaved to whole caspase 9 in cells pre-treated with the caspase 8 inhibitor (d). (e,f) DNA fragmentation in LN18 cells stably expressing shCTRL, shCASP 8, or shCASP9 treated for 24 h (e) or 48 h (f) with proteasome inhibitors. (g) Western blot of caspase 8 and 9 cleavage in shCTRL, shCASP8, and shCASP9 LN18 cells treated 16 h with 100 nM proteasome inhibitors. (h,i) Densitometry from (g) showing the ratio of cleaved to whole caspase 8 in cells with or without caspase 9 (h), or the ratio of cleaved to whole caspase 9 in cells with or without caspase 8 (i). *p < 0.05. All error bars represent the standard error of the mean for N = 3 independent experiments.