Shikonin Inhibits Tumor Growth in Mice by Suppressing Pyruvate Kinase M2-mediated Aerobic Glycolysis

Xiaoyue Zhao,Longwei Jiang,Ke Zen,Limin Li,Shaochang Jia,Yanan Zhu,Jianhua Hu

doi:10.1038/s41598-018-31615-y

Xiaoyue Zhao, Longwei Jiang + Show 5 more

Open Access

https://doi.org/10.1038/s41598-018-31615-y

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Abstract

Shift metabolism profile from mitochondrial oxidative phosphorylation to aerobic glycolysis (Warburg effect) is a key for tumor cell growth and metastasis. Therefore, suppressing the tumor aerobic glycolysis shows a great promise in anti-tumor therapy. In the present study, we study the role of shikonin, a naphthoquinone isolated from the traditional Chinese medicine Lithospermum, in inhibiting tumor aerobic glycolysis and thus tumor growth. We found that shikonin dose-dependently inhibited glucose uptake and lactate production in Lewis lung carcinoma (LLC) and B16 melanoma cells, confirming the inhibitory effect of shikonin on tumor aerobic glycolysis. Treatment of shikonin also decreased tumor cell ATP production. Furthermore, pyruvate kinase M2 (PKM2) inhibitor or activator respectively altered the effect of shikonin on tumor cell aerobic glycolysis, suggesting that suppression of cell aerobic glycolysis by shikonin is through decreasing PKM2 activity. Western blot analysis confirmed that shikonin treatment reduced tumor cell PKM2 phosphorylation though did not reduce total cellular PKM2 level. In vitro assay also showed that shikonin treatment significantly promoted tumor cell apoptosis compared to untreated control cells. Finally, when mice implanted with B16 cells were administered with shikonin or control vehicle, only shikonin treatment significantly decreased B16 tumor cell growth. In conclusion, this study demonstrates that shikonin inhibits tumor growth in mice by suppressing PKM2-mediated aerobic glycolysis.

Highlights

Shikonin is a natural product isolated from the roots of the Chinese herbs Lithospermum erythrorhizon, Arnebia euchroma and Onosma paniculata[9,10,11]
The results showed that control cells displayed a lower glucose uptake and lactate production following 10 μM shikonin treatment, whereas no significant effect of shikonin on tumor cell aerobic glycolysis was detected after modulating pyruvate kinase M2 (PKM2) activity with pTyr, FBP or Ser (Fig. 4C,D)
We demonstrate that shikonin can inhibit tumor proliferation in vitro and in vivo through decreasing PKM2-mediated aerobic glycolysis switch in tumor cells

Summary

Introduction

Shikonin is a natural product isolated from the roots of the Chinese herbs Lithospermum erythrorhizon, Arnebia euchroma and Onosma paniculata[9,10,11]. Other mechanisms involved in shikonin-induced cancer cell death include upregulation of p5319. The exact mechanism by which shikonin inhibits tumor cell proliferation, migration and invasion remains incompletely understood. It is not clear whether shikonin can be used as an effective anti-cancer reagent in vitro and in vivo. We tested the effect of shikonin on the proliferation and apoptosis of various cancer cells in vitro and in vivo. Our results show that shikonin dose-dependently inhibits tumor cell aerobic glycolysis and growth while promotes tumor cell apoptosis. The mechanistic study suggests that the mechanism underlying the anti-cancer effect of shikonin is to inhibit the phosphorylation of PKM2 and suppress PKM2-switched tumor cell aerobic glycolysis

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