CASP8 and cancer: By western blot analysis, we measured cleaved caspase-8 (extrinsic pathway) and cleaved caspase-9 (intrinsic pathway) and found out that only caspase-9 cleavage/activation was present in all three cancer cell lines (Fig 6A–6C) while caspase-8 cleavage/activation was not observed (Data not shown).