In order to elucidate the mechanisms responsible for increased apoptosis induction in MeWo and Mel-HO cells after Mcl-1 silencing and AdV-TRAIL infection, the activation of the initiator caspase-8, the intrinsic initiator caspase-9, and the main effector caspase-3 were examined by western blot analysis 24 h after application of AdV-TRAIL. The gene discussed is CASP9; the disease is infection.