Combination of WIN55,212-2 and auranofin synergistically suppresses human hepatocellular carcinoma HepG2 cell proliferation and tumorigenesis and induces cellular senescence and apoptosis via Wnt/ β-catenin signaling

WIN55,212-2(WIN) is a cannabinoid receptor agonist. We previously found that WIN may induce cell cycle arrest and inhibit the proliferation and migration of hepatocellular carcinoma (HCC) BEL7402 cells. Auranofin (AUR) is an FDA-approved drug against rheumatoid arthritis that is currently enrolled in clinical trials as an anti-tumor agent. However, the precise functions of WIN and/or AUR on HCC carcinogenesis remain unexplored. In the present study, we aimed to study the synergistic antitumor effects and the associated underlying mechanisms of AUR/WIN combination therapy on HCC. We showed that WIN/AUR cotreatment synergistically suppressed HepG2 cell proliferation, migration and invasion. Western blot assay found that WIN/AUR cotreatment synergistically downregulated the expression of Bcl-2, cyclin D1, β-catenin, c-myc, and MMP-9 and increased the expression of Bip and ATF4, further activating Caspase3, Caspase 8, Caspase 9 and PARP cleavage. Cotreatment of AUR/WIN also arrested cell cycle at the G1 phase and induced senescence and apoptosis, evidenced by an increase in the number of SA-β-gal + senescent cells and loss of mitochondrial membrane potential (MMP) in AUR/WIN-cotreated cells. Luciferase reporter assay found that the activation of Wnt/β-catenin signaling was significantly suppressed upon WIN/AUR cotreatment in comparison with other groups. Moreover, WIN/AUR cotreatment synergistically inhibited tumor growth in subcutaneous xenograft mice models. In conclusion, our results demonstrated WIN/AUR-mediated apoptosis and suppressive effects on cell growth, migration and invasion were associated with Bcl-2 downregulation, endoplasmic reticulum (ER) stress and caspase activation, leading to downregulation of Wnt/β-catenin signaling. Therefore, WIN/AUR cotreatment may present promising combination therapy for the treatment of HCC.