Dihydroartemisinin Inhibits mTORC1 Signaling by Activating the AMPK Pathway in Rhabdomyosarcoma Tumor Cells

Jun Luo,Bing Cheng,Lin Li,Wang Liu,Zhu Huang,Yang Wu,Chao Zhang,Shengyong Yang,Chaowei Shang,Shile Huang,Yan Luo,Xiaofeng Guo,Yoshinobu Odaka,Peter J Houghton

doi:10.3390/cells10061363

Abstract

Dihydroartemisinin (DHA), an anti-malarial drug, has been shown to possess potent anticancer activity, partly by inhibiting the mammalian target of rapamycin (mTOR) complex 1 (mTORC1) signaling. However, how DHA inhibits mTORC1 is still unknown. Here, using rhabdomyosarcoma (RMS) as a model, we found that DHA reduced cell proliferation and viability in RMS cells, but not those in normal cells, which was associated with inhibition of mTORC1. Mechanistically, DHA did not bind to mTOR or FK506 binding protein 12 (FKBP12). In addition, DHA neither inhibited insulin-like growth factor-1 receptor (IGF-1R), phosphoinositide 3-kinase (PI3K), and extracellular signal-regulated kinase ½ (Erk1/2), nor activated phosphatase and tensin homolog (PTEN) in the cells. Rather, DHA activated AMP-activated protein kinase (AMPK). Pharmacological inhibition of AMPK, ectopic expression dominant negative or kinase-dead AMPK, or knockdown of AMPKα attenuated the inhibitory effect of DHA on mTORC1 in the cells. Additionally, DHA was able to induce dissociation of regulatory-associated protein of mTOR (raptor) from mTOR and inhibit mTORC1 activity. Moreover, treatment with artesunate, a prodrug of DHA, dose-dependently inhibited tumor growth and concurrently activated AMPK and suppressed mTORC1 in RMS xenografts. The results indicated that DHA inhibits mTORC1 by activating AMPK in tumor cells. Our finding supports that DHA or artesunate has a great potential to be repositioned for treatment of RMS.

Highlights

Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma, which often occurs in the head, neck, bladder, vagina, uterus, arms, legs, and trunk [1]
Since many of those molecules (e.g., MYC, cyclin-dependent kinases (CDKs), vascular endothelial growth factor receptor (VEGF), focal adhesion kinase (FAK), and HIF-1α) targeted by DHA are directly or indirectly regulated by mTORC1 [5,6], we proposed that mTORC1 may be a major target of DHA for its anticancer activity, and DHA is a new inhibitor of mTORC1
Using RMS as a model, we focused on determining the molecular mechanism by which DHA inhibits mTORC1 in tumor cells

Summary

Introduction

Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma, which often occurs in the head, neck, bladder, vagina, uterus, arms, legs, and trunk [1]. RMS manifests in two major types, embryonal (ERMS) and alveolar (ARMS) [2]. The embryonic type resembles to the embryonic muscle cell precursor, whereas the alveolar type has clusters of round cells similar to lung alveoli [1,2]. 80% of ARMS tumors are characterized with the translocations or expression of the PAX3/7–FOXO1 fusion transcript, resulting in overexpression of receptor tyrosine kinases such as fibroblast growth factor receptor 4 (FGFR4), hepatocyte growth factor receptor (HGFR, named MET), and insulin-like growth factor 1 receptor (IGF-1R) [1,2].

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