SMAC mimetic birinapant inhibits hepatocellular carcinoma growth by activating the cIAP1/TRAF3 signaling pathway

The present study investigated the effects and molecular mechanism of the second mitochondria-derived activator of caspase (SMAC) mimetic birinapant on the proliferation and apoptotic rate of liver cancer cells. Western blotting and reverse transcription-quantitative PCR were used to detect the protein and mRNA expression levels of cellular inhibitor of apoptosis 1 (cIAP1) and tumor necrosis factor receptor-associated factor 3 (TRAF3) in the liver cancer cell lines Huh7, H22 and HepG2, and the hepatocyte line AML12. Annexin V-FITC and Transwell assays were used to assess the effect of birinapant pretreatment on the apoptotic rate and invasive ability of liver cancer cells. Lentivirus-mediated silencing of TRAF3 was performed in liver cancer cells. Western blotting was used to detect the lentivirus silencing efficiency. A subcutaneous hepatocellular carcinoma model was established in nude mice and 15 days after tumor induction the subcutaneous tumors were measured in each group. Immunohistochemistry assays were used to detect the protein expression levels of proliferating cell nuclear antigen and caspase-3. The results suggested that the expression levels of cIAP1 and TRAF3 were lower in Huh7, H22 and HepG2 cells compared with AML12 cells. Pretreatment with birinapant promoted apoptosis and inhibited invasion of liver cancer cells by activating the cIAP1/TRAF3 axis. Birinapant also promoted apoptosis and inhibited the growth of subcutaneous hepatocellular carcinoma tumors in nude mice. The present results suggested that the SMAC mimetic birinapant may promote apoptosis, and inhibit the proliferation and invasion of liver cancer cells. The molecular mechanism responsible for the effects of birinapant may be related to activation of the cIAP1/TRAF3 signaling pathway by birinapant in liver cancer cells.