Celastrol exerts synergistic effects with PHA-665752 and inhibits tumor growth of c-Met-deficient hepatocellular carcinoma in vivo

PHA665752 (PHA), a selective small molecule c-Met Inhibitor, potently inhibited HGF-stimulated and constitutive c-Met phosphorylation, as well as HGF and c-Met-driven phenotypes of a variety of tumor cells including hepatocellular carcinoma cells. However, these effects were impaired in c-Met-deficient cancer cells. In the present study, we investigated the potential anti-human c-Met-deficient hepatocellular carcinoma effects of Celastrol, a novel triterpene, and its combination with PHA. Human hepatocellular carcinoma cells BEL-7402 (c-Met-positive) and Huh7 (c-Met-deficient) were treated with different dose of PHA with or without equal dose of Celastrol, and cell growth, cell cycle and apoptosis were evaluated, respectively, by MTT assay, flow cytometry and Caspase3/7 activity. Nude mice bearing Huh7 xenografts were used to assess the in vivo anti-tumor activity. Our results showed that Celastrol at high concentration (>1.0 μM) induced G2/M arrest and apoptosis with the activation of Caspase3/7 in Huh7 cells whereas at low concentration (<1.0 μM) had no obvious effects. Low concentration Celastrol presented significant combined effects with PHA on Huh7 cells and Huh7 xenografts in terms of growth inhibition, migration inhibition and apoptosis induction. These results suggest that Celastrol and its combination with PHA present the therapeutic potential on c-Met-deficient hepatocellular carcinoma, and deserve further preclinical and clinical studies.