Antitumor efficacy of the c-met inhibitor tivantinib (ARQ–197) in liver cancer cells: effects on apoptosis and cell cycle

Background: c-met has become a promising therapeutic target in cancer therapy due to its prognostic significance and its important role in determining the metastatic properties of solid tumors. Tivantinib (ARQ–197) is a novel selective small molecule inhibitor of c-Met which is undergoing clinical investigation in several tumor entities.Aims and methods: we explored the effects of tivantinib on hepatocellular carcinoma cell lines to determine its mechanisms of action. Huh7 and HepG2 HCC cell lines were incubated with increasing concentrations of tivantinib or vehicle. For viability experiments pico-green assays were used. Apoptosis was evaluated by Hoechst staining, FACS analysis and by assessment of caspase 8 and 3 cleavage by western blot. Cell cycle changes were analyzed by FACS after propidium iodide staining.Results: As judged by pico-green analysis, viability of Huh7 and HepG2 cells incubated 5 days with tivantinib at the concentration of 0.39µM decreased to 2.0±1% and 2.6±1% respectively of the viability of vehicle-treated cells. As judged by FACS analysis after 24 hours incubation with tivantinib (4.8µM), apoptosis could be seen in 71.1±8.2% of HepG2 and 63.4±8.9% of Huh7 cells. Concomitantly, increased cleavage of caspase 3 and 8, and a G2-phase cell-cycle arrest could be detected (fraction of cells in G2 phase in Huh7 cells: 20.7±2% after incubation with DMSO vs. 59.7±2.6% in tivantinib-treated cells; p<0.01).Conclusion: Besides its known antimetastatic properties tivantinib exerts an antiproliferative effect in HCC cells by inducing apoptosis and causing a G2 cell cycle arrest at concentrations achievable in the clinical setting. Detection of both caspase–3 and caspase–8 cleavage at western blot suggests the recruitment of the extrinsic pathway to initiate apoptosis. Thus, a combination of tivantinib with agonistic antibodies targeting TRAIL receptors which have recently become available for the clinic should be further investigated.

HCC - c-met