Inhibitory Effects of β,β-Dimethylacrylshikonin on Hepatocellular Carcinoma In Vitro and In Vivo

beta,beta-Dimethylacrylshikonin is one of the most abundant naphthoquinones in the root extracts of Lithospermum erythrorhizon Sieb. et Zucc. (Boraginaceae), which have been reported to have antitumor effects. This study evaluated the antiproliferative activity of beta,beta-dimethylacrylshikonin on human hepatocellular carcinoma (HCC) cells both in vitro and in vivo. In vitro, the MTT assay showed that beta,beta-dimethylacrylshikonin inhibited the proliferation of SMMC-7721 cells in both dose- and time-dependent manners with its 50% inhibitory concentration (IC50) at 48?h being 15.01?+/-?0.76?mu g/mL. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) and Hoechst staining detected the characteristics of cell apoptosis in beta,beta-dimethylacrylshikonin-treated cells and the apoptotic rates of treated groups were increased in a dose-dependent manner. Flow cytometric analysis revealed that beta,beta-dimethylacrylshikonin could block the cell cycle arrest at G2 phase. Furthermore, beta,beta-dimethylacrylshikonin down-regulated the mRNA and protein expression of Bcl-2 but up-regulated that of Bax. The cleaved caspase-3 protein was also detected in treated cells. The experiment in vivo showed that beta,beta-dimethylacrylshikonin significantly suppressed the growth of H22 transplantable hepatoma, and induced the activation of caspase-3 determined by immunohistochemistry. The results indicate that beta,beta-dimethylacrylshikonin has significant antitumor effects on hepatocellular carcinoma both in vitro and in vivo. Copyright (c) 2011 John Wiley & Sons, Ltd.