Abstract
Hepatocellular carcinoma (HCC) cells are intrinsically resistant to tumour necrosis factor-related apoptosis ligand (Apo2L/TRAIL), in part, due to the compensatory activation of nuclear factor-kappaB (NF-kappa B). To broaden the clinical utilization of Apo2L/TRAIL in HCC, OSU-A9, a potent indole-3-carbinol-derived Akt/NF-kappa B signalling inhibitor was used to overcome the intrinsic resistance. The antitumour effects of OSU-A9, Apo2L/TRAIL and the therapeutic combination were assessed by MTT assay, caspase activation and PARP cleavage, and the synergistic interactions were determined by Calcusyn analysis. NF-kappa B reporter gene and RT-PCR were tested for the activation of NF-kappa B and the expression of death receptors (DR)4 and 5. OSU-A9 could sensitize HCC cells to Apo2L/TRAIL with high potency through down-regulation of Akt/NF-kappa B signalling. OSU-A9 dose-dependently reduced Akt phosphorylation and the expression and nuclear localization of RelA/p65, accompanied by parallel decreases in the expression of NF-kappa B target products, including Bcl-xL, Mcl-1, cIAP1, cIAP2 and survivin. Moreover, OSU-A9 increased DR5 expression through a reactive oxygen species (ROS)-dependent mechanism. Concertedly, these mechanisms underlie the synergistic interaction between OSU-A9 and Apo2L/TRAIL in mediating apoptotic death in HCC cells. The ability of OSU-A9 to accentuate Apo2L/TRAIL-induced apoptosis by inactivating Akt/NF-kappa B signalling might foster a promising therapeutic strategy for HCC.