Dihydromyricetin Activates AMP-Activated Protein Kinase and P38 Exerting Antitumor Potential in Osteosarcoma

Numerous patientswithosteosarcoma either are not sensitive to chemotherapyor developdrug resistance to current chemotherapy regimens. Therefore, it is necessary to develop several potentially useful therapeutic agents. Dihydromyricetin is the major flavonoid component derived from Ampelopsis grossedentata, which has a long history of use in food and medicine. The present study examined the antitumor activity both in vitro and in vivowithout noticeable side effects and the underlyingmechanismof action of dihydromyricetin in osteosarcoma cells. We found that dihydromyricetin induced increased p21 expression and G2–M cellcycle arrest, caused DNA damage, activated ATM–CHK2–H2AX signaling pathways, and induced apoptosis in osteosarcoma cells as well as decreasing the sphere formation capability by downregulating Sox2 expression. Mechanistic analysis showed that the antitumor potential of dihydromyricetin may be due to the activation of AMPKa and p38, as the activating AMPKa led to the inactivation of GSK3b in osteosarcoma cells. Moreover, GSK3b deletion or GSK3b inhibition by LiCl treatment resulted in increased p21 expression and reduced Sox2 expression in osteosarcoma cells. Taken together, our results strongly indicate that the antitumor potential of dihydromyricetin is correlated with P38 and the AMPKa– GSK3b–Sox2 signaling pathway. Finally, immunohistochemical analysis indicated that some patients had a lower p-AMPK expression after chemotherapy, which supports that the combination of dihydromyricetin and chemotherapy drug will be beneficial for patients with osteosarcoma. In conclusion, our results are the first to suggest that dihydromyricetin may be a therapeutic candidate for the treatment of osteosarcoma. Cancer Prev Res; 1–12. 2014 AACR. Introduction Osteosarcoma is the most common primary malignant bone tumor in childhood and adolescence (1).The clinical outcome of patients with osteosarcoma can be improved with chemotherapy, and the 5-year survival rate has reached 60% to 70% (2). However, there is currently a need to identify effective agents for the treatment of this deadly disease and to develop new therapeutic strategies with less severe side effects, because numerous patients with osteosarcoma are either not sensitive to chemotherapyor develop drug resistance with current chemotherapy regimens. Ampelopsis grossedentata, a vine plant in South China, is a popular and multipurpose traditional Chinese medicinal herb and has a long history of being used as food and medicine (3). Dihydromyricetin, a 2,3-dihydroflavonol compound, is the main bioactive component extracted from Ampelopsis grossedentata, is one kind of flavonoids that has many biologic effects, including antialcohol intoxication, reducing blood pressure, antibacterial, antioxidant, and antitumor properties (4–6). Recently, it has been shown in some cancer cells that dihydromyricetin possesses antitumor effects, such as antiproliferation, cell-cycle arrest, induction of apoptosis, and increased sensitivity to chemotherapeutic drugs (7, 8). Moreover, dihydromyricetin has shown potential in ameliorating chemotherapy-induced side effects (9). However, very little is known about its effects on osteosarcoma, and the underlying mechanisms of dihydromyricetin’s anticancer effects are still under investigation. AMP-activated protein kinase (AMPK), a serine/threonine protein kinase and a member of the Snf1/AMPK protein kinase family, is a metabolic checkpoint protein downstream of the LKB1 tumor suppressor and integrates Authors' Affiliations: Department ofMusculoskeletalOncology, The First Affiliated Hospital of Sun Yat-Sen University; State Key Laboratory of Oncology in South China, Sun Yat-Sen University Cancer Center, Guangzhou; and The Institute of Biology, Guizhou Academy of Sciences, Guiyang, China Z. Zhao, J. Yin, and M. Wu contributed equally to this article. Corresponding Authors: Jingnan Shen, Department of Musculoskeletal Oncology, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, 510080, China. Phone: 86-020-87335039; Fax: 86-20-87332150; E-mail: [email protected]; and Qiang Jia, The Institute of Biology, Guizhou Academy of Sciences, Guiyang, 550001 China. Phone: 86-8513804942; Fax: 86-851-3838181; E-mail: [email protected] doi: 10.1158/1940-6207.CAPR-14-0067 2014 American Association for Cancer Research. Cancer Prevention Research www.aacrjournals.org OF1 for Cancer Research. on April 1, 2017. © 2014 American Association cancerpreventionresearch.aacrjournals.org Downloaded from Published OnlineFirst June 3, 2014; DOI: 10.1158/1940-6207.CAPR-14-0067