Inhibitory effects of β,β-dimethylacrylshikonin on hepatocellular carcinoma in vitro and in vivo.

β,β-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 β,β-dimethylacrylshikonin on human hepatocellular carcinoma (HCC) cells both in vitro and in vivo. In vitro, the MTT assay showed that β,β-dimethylacrylshikonin inhibited the proliferation of SMMC-7721 cells in both dose- and time-dependent manners with its 50% inhibitory concentration (IC(50) ) at 48 h being 15.01 ± 0.76 µg/mL. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) and Hoechst staining detected the characteristics of cell apoptosis in β,β-dimethylacrylshikonin-treated cells and the apoptotic rates of treated groups were increased in a dose-dependent manner. Flow cytometric analysis revealed that β,β-dimethylacrylshikonin could block the cell cycle arrest at G2 phase. Furthermore, β,β-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 β,β-dimethylacrylshikonin significantly suppressed the growth of H(22) transplantable hepatoma, and induced the activation of caspase-3 determined by immunohistochemistry. The results indicate that β,β-dimethylacrylshikonin has significant antitumor effects on hepatocellular carcinoma both in vitro and in vivo.