Abstract
Objective: To investigate the effect and intrinsic mechanism of Honokiol (HNK) enhanced tumor necrosis factor-related apoptosis inducing ligand (TRAIL) on hepatocellular carcinoma HepG2 cells. Methods: HepG2 cells were routinely cultured. Firstly, a concentration gradient of HNK was given to observe its effect on the vitality of tumor cells. Western blot were used to detect change in the expression levels of c-jun N-terminal kinase (JNK), death receptor 4 (DR4), and DR5.Secondly, we observed the effect of combined drugs (HNK and TRAIL) on the vitality of tumor cells. Apoptosis-related protein expression levels were detected to determine the apoptosis condition. Thirdly, JNK inhibitor SP600125 was used to block the JNK pathway, and it was evaluated whether JNK signaling pathway mediated the DR4 and DR5 levels and finally, the subcutaneous tumor model of nude mice was constructed, and enhancement effect of HNK on TRAIL was confirmed in vivo. Results: Cell vitality was decreased (P < 0.05) in a dose-dependent manner after treatment with gradient HNK. Combined effect of TRAIL and HNK was superior to that of single drug administration (P < 0.05). Western blot analysis showed that pJNK level increased after HNK treatment and TRAIL receptor DR4 and DR5 expression were up-regulated. Combined application of HNK and TRAIL, B lymphocyte tumor factor 2 (BCL2) decreased significantly while Bcl2 related X protein (Bax) increased significantly. Blocking JNK pathway by SP600125, the expression of DR4 and DR5 decreased (P < 0.05), Bax expression decreased and Bcl2 expression increased compared with HNK+TRAIL group. In vivo results showed that TRAIL inhibited the growth of subcutaneous tumors, and enhanced inhibition effect in combination with TRAIL and HNK. Conclusion: HNK may enhance the inhibitory effect of TRAIL on HepG2 cells by activating JNK pathway and then upregulating the expression of DR4 and DR5.