HHT-induced Mcl-1 down-regulation was largely because of proteasome degradation. (A) HHT-induced Mcl-1 down-regulation was not a result of caspase-3 cleavage. CLL cells were incubated with 0.1 or 1μM HHT for 24 hours with or without the addition of 100μM Z-VAD-FMK. PARP and Mcl-1 proteins were analyzed by immunoblotting. (B) Apoptosis was detected by annexin V–PI staining. Each data point represents the mean ± SEM of 4 patient samples; □ indicates HHT only; ■, HHT with 100μM Z-VAD-FMK. (C) HHT-induced Mcl-1 down-regulation was largely because of proteasome degradation. CLL cells were incubated with 0.1 or 1μM HHT for 24 hours with or without the addition of 10μM MG-132. PARP and Mcl-1 proteins were analyzed by immunoblotting.