LGK974 Potentiates the Lethality of TRAIL in Hepatocellular Carcinoma Cells by Inducing Apoptosis via Suppressing NF-κB Signaling Pathway

LGK974 is a potent Wingless-related integration site inhibitor at Phase II of a clinical trial. However, little is known about its role and the underlying mechanisms in human hepatocellular carcinoma. 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide and colony formation assays were used to determine the cytotoxicity of LGK974 on liver cancer cell lines. Flow cytometry assay was performed to examine the cell apoptosis induced by LGK974 alone or in combination with tumor necrosis factorrelated apoptosis-inducing ligand. Western blot assay was used to evaluate the protein expression profiling of caspases, poly adenosine diphosphate-ribose polymerase and B-cell lymphoma 2 family, as well as the activation of signaling pathways. At the present study, we demonstrated that LGK974 can suppress human hepatocellular carcinoma cell proliferation by inducing apoptosis and suppress colony formation. In addition, LGK974 effectively inhibited the protein expression of B-cell lymphoma 2, while elevated the protein expression of B-cell lymphoma 2 homologous antagonist/killer, B-cell lymphoma 2 associated agonist of cell death and B-cell lymphoma 2 like protein 11 in human hepatocellular carcinoma cells. More interestingly, it was observed that LGK974 obviously enhances the tumor necrosis factor-related apoptosis-inducing ligand induced apoptosis. Our data indicated that LGK974 not only inhibited the Wingless-related integration site/beta catenin signaling pathway, but also inactivated the nuclear factor kappa light chain enhancer of activated B cells signaling pathway. We also activated nuclear factor kappa light chain enhancer of activated B cells signaling pathway by using small interfering RNA against nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor alpha, which effectively attenuated the sensitization effects of LGK974 on tumor necrosis factor-related apoptosis-inducing ligand in human liver cancer cell line, HepG2 cells. Altogether, these data presented in this study illustrated that LGK974 potentiated the lethality of tumor necrosis factor-related apoptosis-inducing ligand in human hepatocellular carcinoma by inducing apoptosis via suppressing nuclear factor kappa light chain enhancer of activated B cells signaling pathway.