title: Ciclopirox olamine inhibits mTORC1 signaling by activation of AMPK.
abstract: Ciclopirox olamine (CPX), an off-patent antifungal agent, has recently been identified as a potential anticancer agent. The mammalian target of rapamycin (mTOR) is a central controller of cell growth, proliferation and survival. Little is known about whether and how CPX executes its anticancer action by inhibiting mTOR. Here we show that CPX inhibited the phosphorylation of p70 S6 kinase 1 (S6K1) and eukaryotic initiation factor 4E binding protein 1 (4E-BP1), two downstream effector molecules of mTOR complex 1 (mTORC1), in a spectrum of human tumor cells, indicating that CPX inhibits mTORC1 signaling. Using rhabdomyosarcoma cells as an experimental model, we found that expression of constitutively active mTOR (E2419K) conferred resistance to CPX inhibition of cell proliferation, suggesting that CPX inhibition of mTORC1 contributed to its anticancer effect. In line with this, treatment with CPX inhibited tumor growth and concurrently suppressed mTORC1 signaling in RD xenografts. Mechanistically, CPX inhibition of mTORC1 was neither via inhibition of IGF-I receptor or phosphoinositide 3-kinase (PI3K), nor by activation of phosphatase and tensin homolog (PTEN). Instead, CPX inhibition of mTORC1 was attributed to activation of AMP-activated protein kinase (AMPK)-tuberous sclerosis complexes (TSC)/raptor pathways. This is supported by the findings that CPX activated AMPK; inhibition of AMPK with Compound C or ectopic expression of dominant negative AMPKα partially prevented CPX from inhibiting mTORC1; silencing TSC2 attenuated CPX inhibition of mTORC1; and CPX also increased AMPK-mediated phosphorylation of raptor (S792). Therefore, the results indicate that CPX exerts the anticancer effect by activating AMPK, resulting in inhibition of mTORC1 signaling.
authors.affiliation: State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China; Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA; Yunnan Key Laboratory of Natural Medicinal Chemistry, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China.
authors.forename: Hongyu
authors.initials: H
authors.lastname: Zhou
authors.affiliation: Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA; Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA.
authors.forename: Chaowei
authors.initials: C
authors.lastname: Shang
authors.affiliation: State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China; Yunnan Key Laboratory of Natural Medicinal Chemistry, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China.
authors.forename: Min
authors.initials: M
authors.lastname: Wang
authors.affiliation: Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA; Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA.
authors.forename: Tao
authors.initials: T
authors.lastname: Shen
authors.affiliation: State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China; Yunnan Key Laboratory of Natural Medicinal Chemistry, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China.
authors.forename: Lingmei
authors.initials: L
authors.lastname: Kong
authors.affiliation: State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China; University of the Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Chunlei
authors.initials: C
authors.lastname: Yu
authors.affiliation: State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China.
authors.forename: Zhennan
authors.initials: Z
authors.lastname: Ye
authors.affiliation: Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA.
authors.forename: Yan
authors.initials: Y
authors.lastname: Luo
authors.affiliation: Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA.
authors.forename: Lei
authors.initials: L
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China; Yunnan Key Laboratory of Natural Medicinal Chemistry, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China. Electronic address: liyanb@mail.kib.ac.cn.
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA; Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA. Electronic address: shuan1@lsuhsc.edu.
authors.forename: Shile
authors.initials: S
authors.lastname: Huang
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D000970:Antineoplastic Agents / Q000009:adverse effects / Q000494:pharmacology / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D000077768:Ciclopirox; D019008:Drug Resistance, Neoplasm; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D006801:Humans; D000076222:Mechanistic Target of Rapamycin Complex 1; D008819:Mice, Nude; D046912:Multiprotein Complexes / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D009363:Neoplasm Proteins / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D011728:Pyridones / Q000009:adverse effects / Q000494:pharmacology / Q000627:therapeutic use*; D011897:Random Allocation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012208:Rhabdomyosarcoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D015398:Signal Transduction / Q000187:drug effects*; D013047:Specific Pathogen-Free Organisms; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D047368:Tumor Burden / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D046912:Multiprotein Complexes; D009363:Neoplasm Proteins; D011728:Pyridones; D011994:Recombinant Proteins; D000077768:Ciclopirox; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases
keywords: AMPK; Ciclopirox; Raptor; TSC2; mTOR