In vitro and in vivo antitumor effects of acetylshikonin isolated from Arnebia euchroma (Royle) Johnst (Ruanzicao) cell suspension cultures Wenbi Xiong, Gang Luo, Liming Zhou, Yun Zeng and Wenji Yang
Abstract 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 μg/ml, 6.82 ± 1.5 μg/ml, 3.04 ± 0.44 μg/ml and 2.72 ± 0.38 μg/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.
Discussion Recent studies showed that shikonin derivatives acted on multiple tumor cells and triggered multiple cell death pathways. Therefore, shikonin derivatives are potentialcancer treatment agents. Acetylshikonin is a main shikonin derivative of Arnebia euchroma (Royle) Johnst. Other research on shikonin derivatives also demonstratedthat acetylshikonin inhibited K562 and HL-60 tumor growth [8]; however, acetylshikonin had not been studied in detail. The present study indicated that acetylshikoninhad in vitro and in vivo antitumor effects. Acetylshikonin possessed a high level of cytotoxic activity in vitro.
Conclusion Acetylshikonin isolated from Arnebia euchroma (Royle) Johnst cell suspension cultures exhibits specific in vivo and in vitro antitumor effects.