Background: Shikonin derivatives have cytotoxic and antitumor effects. This study aims to investigate the antitumor effects of acetylshikonin isolated from a Chinese medicinal herb Arnebia euchroma (Royle) Johnst.
Methods: The 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to determine the in vitro antitumor effects of acetylshikonin on human lung adenocarcinoma cell line A549, human hepatocellular carcinoma cell line Bel-7402, human breast adenocarcinoma cell line MCF-7 and mouse Lewis lung carcinoma (LLC) cell line. C57BL/6 mice with LLC model were used to study the in vivo antitumor effects of acetylshikonin. The expression of bax, bcl-2 and caspase-3 proteins in LLC tissue was determined with immunohistochemical staining.
Results: In A549, Bel-7402, MCF-7 and LLC cell lines, acetylshikonin inhibited cell growth in a dose-dependent manner. IC50 (means +/- SD) were 5.6 +/- 0.86 microg/ml, 6.82 +/- 1.5 microg/ml, 3.04 +/- 0.44 microg/ml and 2.72 +/- 0.38 microg/ml respectively. Acetylshikonin suppressed tumor growth in C57BL/6 mice with LLC. The inhibition rate of acetylshikonin (2 mg/kg) was 42.85%. Immunohistochemical staining revealed that in the acetylshikonin groups the expression of bax and caspase-3 increased, whereas the expression of bcl-2 decreased, suggesting that acetylshikonin induced tumor cell apoptosis through activating the pro-apoptotic bcl-2 family and caspase-3.
Conclusion: Acetylshikonin isolated from Arnebia euchroma (Royle) Johnst cell suspension cultures exhibits specific in vivo and in vitro antitumor effects.