Fig 5 - available via license: CC BY
Content may be subject to copyright.
GLPT-mediated inhibition of mTORC1/2 is associated with activation of AMPK and inhibition of IGFR/PI3K/Rheb. a-d A549 cells (a-c) or A549 cells infected with Ad-AMPK-dn or Ad-GFP (control) (d) were treated with GLPT for 24 h at the indicated concentrations, and western blotting was then performed with the indicated antibodies. β-Tubulin served as a loading control
Source publication
Ganoderma lucidum (G. lucidum) extracts, as dietary supplements, have been found to exert potent anticancer activity, which is attributed to the presence of polysaccharides and triterpenes. However, the molecular mechanism underlying the anticancer action of G. lucidum extracts remains to be investigated. Here, we show that ReishiMax GLp, containin...
Contexts in source publication
Context 1
... IGFR-PI3K pathway and negatively regulated by PTEN, 36,42 to understand how GLPT inhibits mTORC1/2, we next investigated whether GLPT inhibits mTORC1/2 by altering the expression/ activity of these signaling proteins. As predicted, treatment with GLPT for 24 h dose-dependently reduced the levels of p-IGFRβ, p-PI3K (p85), and p-PDK1 in A549 cells (Fig. 5a). Additionally, GLPT dose-dependently downregulated the protein level of IGFRβ but did not reduce the protein levels of PI3K (p85) and PDK1 except at concentrations of 1 mg/ml and higher. Unexpectedly, GLPT treatment inhibited rather than activated PTEN, as indicated by the observation that GLPT decreased the protein level and increased ...
Context 2
... downregulated the protein level of IGFRβ but did not reduce the protein levels of PI3K (p85) and PDK1 except at concentrations of 1 mg/ml and higher. Unexpectedly, GLPT treatment inhibited rather than activated PTEN, as indicated by the observation that GLPT decreased the protein level and increased the phosphorylation level of PTEN (Fig. 5a). Thus, the results suggest that GLPT inhibition of mTORC1/2 is related to downregulation of the IGFR-PI3K pathway but not to upregulation of ...
Context 3
... mTORC1 is also negatively regulated by the AMPK-TSC2/ raptor network and positively regulated by Rheb, 38-41 we also examined whether GLPT suppresses mTORC1 by activating AMPK and inhibiting Rheb. As expected, 24-h treatment with GLPT dosedependently downregulated the protein level of Rheb (Fig. 5b), a direct activator of mTORC1. 39,40 In addition, GLPT treatment also activated the AMPK network, as evidenced by increased phosphorylation of AMPKα (T172) and the two substrates of AMPK, TSC2 (S1387) and raptor (S792), in A549 cells (Fig. 5c). Interestingly, ectopic expression of dominant-negative AMPKα (AMPKα-dn) by infection with ...
Context 4
... Rheb. As expected, 24-h treatment with GLPT dosedependently downregulated the protein level of Rheb (Fig. 5b), a direct activator of mTORC1. 39,40 In addition, GLPT treatment also activated the AMPK network, as evidenced by increased phosphorylation of AMPKα (T172) and the two substrates of AMPK, TSC2 (S1387) and raptor (S792), in A549 cells (Fig. 5c). Interestingly, ectopic expression of dominant-negative AMPKα (AMPKα-dn) by infection with Ad-AMPKα-dn partially prevented GLPT from inhibiting mTORC1-mediated S6K1 and 4E-BP1 phosphorylation (Fig. 5d), indicating that GLPT indeed inhibits mTORC1 partly through activation of AMPK. Collectively, these results suggest that GLPT inhibits ...
Context 5
... network, as evidenced by increased phosphorylation of AMPKα (T172) and the two substrates of AMPK, TSC2 (S1387) and raptor (S792), in A549 cells (Fig. 5c). Interestingly, ectopic expression of dominant-negative AMPKα (AMPKα-dn) by infection with Ad-AMPKα-dn partially prevented GLPT from inhibiting mTORC1-mediated S6K1 and 4E-BP1 phosphorylation (Fig. 5d), indicating that GLPT indeed inhibits mTORC1 partly through activation of AMPK. Collectively, these results suggest that GLPT inhibits mTORC1 in part by activating AMPK and inhibiting Rheb in addition to suppressing the IGFR-PI3K ...
Context 6
... 36,42 This study found that GLPT, similar to AZD8055, inhibited both mTORC1-mediated S6K1 and 4E-BP1 phosphorylation and mTORC2-mediated Akt (S473) phosphorylation (Fig. 4c). However, unlike AZD8055 or rapamycin, GLPT was able to induce AMPKα (T172) phosphorylation and subsequently induce AMPK-mediated TSC2 (S1387)/raptor (S792) phosphorylation (Fig. 5c). Expression of dn-AMPKα partially lessened the inhibitory effect of GLPT on mTORC1 (Fig. 5d), indicating that GLPT inhibits mTORC1 partly via activation of AMPK. In addition, GLPT also reduced the protein level of Rheb (Fig. 5b), a direct activator of mTORC1. 39,40 Moreover, GLPT was also able to suppress the IGFR-PI3K pathway in the ...
Context 7
... 4E-BP1 phosphorylation and mTORC2-mediated Akt (S473) phosphorylation (Fig. 4c). However, unlike AZD8055 or rapamycin, GLPT was able to induce AMPKα (T172) phosphorylation and subsequently induce AMPK-mediated TSC2 (S1387)/raptor (S792) phosphorylation (Fig. 5c). Expression of dn-AMPKα partially lessened the inhibitory effect of GLPT on mTORC1 (Fig. 5d), indicating that GLPT inhibits mTORC1 partly via activation of AMPK. In addition, GLPT also reduced the protein level of Rheb (Fig. 5b), a direct activator of mTORC1. 39,40 Moreover, GLPT was also able to suppress the IGFR-PI3K pathway in the cancer cells (Fig. 5a). Taken together, our data demonstrate that GLPTmediated inhibition of ...
Context 8
... to induce AMPKα (T172) phosphorylation and subsequently induce AMPK-mediated TSC2 (S1387)/raptor (S792) phosphorylation (Fig. 5c). Expression of dn-AMPKα partially lessened the inhibitory effect of GLPT on mTORC1 (Fig. 5d), indicating that GLPT inhibits mTORC1 partly via activation of AMPK. In addition, GLPT also reduced the protein level of Rheb (Fig. 5b), a direct activator of mTORC1. 39,40 Moreover, GLPT was also able to suppress the IGFR-PI3K pathway in the cancer cells (Fig. 5a). Taken together, our data demonstrate that GLPTmediated inhibition of mTORC1/2 is a consequence of inhibition of the IGFR-PI3K pathway, activation of the AMPK-TSC2/raptor network and downregulation of the ...
Context 9
... Expression of dn-AMPKα partially lessened the inhibitory effect of GLPT on mTORC1 (Fig. 5d), indicating that GLPT inhibits mTORC1 partly via activation of AMPK. In addition, GLPT also reduced the protein level of Rheb (Fig. 5b), a direct activator of mTORC1. 39,40 Moreover, GLPT was also able to suppress the IGFR-PI3K pathway in the cancer cells (Fig. 5a). Taken together, our data demonstrate that GLPTmediated inhibition of mTORC1/2 is a consequence of inhibition of the IGFR-PI3K pathway, activation of the AMPK-TSC2/raptor network and downregulation of the protein expression of Rheb. Therefore, our findings suggest that GLPT may be a novel mTOR inhibitor. How GLPT activates AMPK and ...
Similar publications
The mechanistic target of rapamycin (mTOR) kinase forms two multi-protein signaling complexes, mTORC1 and mTORC2, which are master regulators of cell growth, metabolism, survival and autophagy. Two of the subunits of these complexes are mLST8 and Raptor, β-propeller proteins that stabilize the mTOR kinase and recruit substrates, respectively. Here...
Herpes simplex virus type 1 (HSV-1) is a widespread contagious pathogen, mostly causing mild symptoms on the mucosal entry side. However, systemic distribution, in particular upon reactivation of the virus in immunocompromised patients, may trigger an innate immune response and induce damage of organs. In these conditions, HSV-1 may infect vascular...
Targeted deletion of Raptor, a component of mechanistic target of rapamycin complex 1 (mTORC1), reveals an essential role for mTORC1 in initiation/maintenance of leukemia in a CLL model, resulting from a failure for haemopoietic stem/progenitor cells (HSPCs) to commit to the B cell lineage. Induction of Raptor-deficiency in NSG mice transplanted wi...
The re-emergence of Zika virus (ZIKV) in 2015 as a significant human pathogen causing neurological diseases in infants as well as adults is a serious global health concern. A clear understanding of the mechanisms involved in ZIKV replication in infected host cells as well as the host responses to virus infection are keys to the development of thera...
The transcription factor TFEB is a master regulator of lysosomal biogenesis and autophagy. The phosphorylation of TFEB by the mechanistic target of rapamycin complex 1 (mTORC1) is unique in its mTORC1 substrate recruitment mechanism, which is strictly dependent on the amino-acid-mediated activation of the RagC GAP FLCN. TFEB lacks the TOR signaling...
Citations
... Additionally, GDNB decreased the size and weight of tumor in vivo through ERK signaling pathway which closely related to tumorigenesis and progression. GLPT suppressed the growth of A247 and A549 cells by inhibiting mTORC1/2 signaling through activation of AMPK and suppression of IGFR/PI3K/Rheb which provided a material basis for tumor cell growth [35]. EP-3-H from Enteromorpha prolifera had the ability to interact with FGF1 and FGF2, resulting in anti-lung cancer effects [36]. ...
... Li et al. proved that the APS can decrease the level of Bcl-xL in A549 cells [32]. Didem et al. showed that GLPT can increase caspase-dependent apoptosis via both mitochondrial and death receptor pathways [35]. GDNB promoted the expression of cleaved caspase-3 and Bax in A549 cells, and inhibited the expression of Bcl-2 [34]. ...
... Lu et al. demonstrated that SPS could trigger cell cycle arrest [51]. GLPT blocked the cell cycle in the G0/G1 phase by differentially inhibiting the expression of CDK and Cyclin proteins [35]. Water-soluble pectin polysaccharides HCA4S1 could block A549 cells in S phase by regulating the expression of Cyclin protein [52]. ...
... AMPK is activated in response to cellular energy depletion (i.e., increased intracellular AMP/ATP ratio) by LKB1-mediated phosphorylation of Thr172 in the AMPKα subunit, which can also be mediated by CAMKK2 when calcium flux occurs. AMPK activation has been shown to suppress the mammalian target of the rapamycin complex 1 (mTORC1) pathway by directly phosphorylating TSC2 and RAPTOR [7][8][9][10][11]. AMPK also activates p53 by phosphorylating Ser15 (in humans) in p53, thereby promoting arrest of the cell cycle [12,13]. ...
Citrus hassaku extract reportedly activates AMPK. Because this extract contains an abundance of auraptene, we investigated whether pure auraptene activates AMPK and inhibits proliferation using prostate cancer cell lines. Indeed, auraptene inhibited the proliferation and migration of LNCaP cells and induced phosphorylation of AMPK or its downstream ACC in LNCaP, PC3, and HEK-293 cells, but not in DU145 cells not expressing LKB1. In addition, the mTOR-S6K pathway, located downstream from activated AMPK, was also markedly suppressed by auraptene treatment. Importantly, it was shown that auraptene reduced androgen receptor (AR) and prostate-specific antigen (PSA) expressions at both the protein and the mRNA level. This auraptene-induced downregulation of PSA was partially but significantly reversed by treatment with AMPK siRNA or the AMPK inhibitor compound C, suggesting AMPK activation to, at least partially, be causative. Finally, in DU145 cells lacking the LKB1 gene, exogenously induced LKB1 expression restored AMPK phosphorylation by auraptene, indicating the essential role of LKB1. In summary, auraptene is a potent AMPK activator that acts by elevating the AMP/ATP ratio, thereby potentially suppressing prostate cancer progression, via at least three molecular mechanisms, including suppression of the mTOR-S6K pathway, reduced lipid synthesis, and AR downregulation caused by AMPK activation.
... This stimulated the release of cytokines including interleukin (IL)-1, IL-2, IL-6, IL-10, IL-12, tumor necrosis factor-alpha (TNF-α), interferongamma (IFN-γ), initiated an immune response and reduced the level of inflammation by activating MAPK/ERK-, NF-κB-, and AMPK pathways [19,20]. Most importantly, the activated immune response synergistic apoptotic pathways suppressed tumor growth in vitro and in vivo, hence, they indirectly reduced tumor progression [27][28][29]. Moreover, microorganisms colonizing the intestinal tract can ferment G. lucidum polysaccharides in vivo and produce metabolites such as short-chain fatty acids, increase the diversity and abundance of the intestinal community, as well as improve hypoglycemia, hypolipidemic, and antioxidant activities to promote overall health [30,31] (Fig. 1). ...
Ganoderma lucidum polysaccharides possess unique functional properties. Various processing technologies have been used to produce and modify G. lucidum polysaccharides to improve their yield and utilization. In this review, the structure and health benefits were summarized, and the factors that may affect the quality of G. lucidum polysaccharides were discussed, including the use of chemical modifications such as sulfation, carboxymethylation, and selenization. Those modifications improve the physicochemical characteristics and utilization of G. lucidum polysaccharides, and make them more stable that could be used as functional biomaterials to encapsulate active substances. Ultimate, G. lucidum polysaccharide-based nanoparticles were designed to deliver various functional ingredients to achieve better health-promoting effects. Overall, this review presents an in-depth summary of current modification strategies and offers new insights into the effective processing techniques to develop G. lucidum polysaccharide-rich functional foods or nutraceuticals.
... Fungal extracts or molecules of fungal origin can interact with these networks by modulating these factors in multiple ways ( Figure 4). Sohretoglu et al. [131], for example, demonstrated that a standardised G. lucidum extract, containing both polysaccharides and triterpenes, could activate AMPK and inhibit IGFR/PI3K bringing a cascading inhibition of cell proliferation and induce cell death by suppressing the mTORC2-mediated phosphorylation of Akt in human lung cancer cells (A549 and A427 cells). The extract from the mushroom Inonotus obliquus (Ach. ...
Since ancient times, mushrooms have been considered valuable allies of human well-being both from a dietary and medicinal point of view. Their essential role in several traditional medicines is explained today by the discovery of the plethora of biomolecules that have shown proven efficacy for treating various diseases, including cancer. Numerous studies have already been conducted to explore the antitumoural properties of mushroom extracts against cancer. Still, very few have reported the anticancer properties of mushroom polysaccharides and mycochemicals against the specific population of cancer stem cells (CSCs). In this context, β-glucans are relevant in modulating immunological surveillance against this subpopulation of cancer cells within tumours. Small molecules, less studied despite their spread and assortment, could exhibit the same importance. In this review, we discuss several pieces of evidence of the association between β-glucans and small mycochemicals in modulating biological mechanisms which are proven to be involved with CSCs development. Experimental evidence and an in silico approach are evaluated with the hope of contributing to future strategies aimed at the direct study of the action of these mycochemicals on this subpopulation of cancer cells.
... Moreover, BSGLWE suppressed tumor growth in vivo by regulating the expression of genes and proteins associated with the cell cycle and apoptosis (Fig. 3) [247]. G. lucidum exerts its anticancer activity for inhibiting proliferation and inducing cell death not only via caspase-dependent and cyclin-CDK2 pathways but also by regulating mTORC1/2-mediated signaling pathways by activating AMPK and inhibiting IGFR/PI3K/Rheb (Fig. 3) [250]. Water extract from G. lucidum also induced mitochondria-mediated apoptosis, arrested cell cycle at the S phase via the cyclin-CDK2 pathway, and inhibited cell migration associated with EMT in glioblastoma cells GBM8901 and U87 (Fig. 3) [251]. ...
... phase [221,222,225,250,249] but also arrested in the G2/M phase [224,247,253], S phase [251] and subG1 phase [248]. GLP conjugated with bismuth sulfide nanoparticles (GLP-BiNP) increased the sensitivity of radiotherapy to inhibit invasion, metastasis, and tumor growth, and alter the radiation-induced immunosuppression microenvironment [238]. ...
... Importantly, GLPT also caused phosphorylation of substrates of AMPK (TSC2 and RAPTOR) in A549 cancer cells. Furthermore, ectopically expressed dominant-negative form of AMPKα partially prevented GLPT mediated inhibitory effects on mTORC1induced phosphorylation of p70S6K and 4E-BP1 (Fig. 3) (Sohretoglu et al., 2019). ...
Background:
Fueled by rapidly evolving comprehension of multifaceted nature of cancers, recently emerging preclinical and clinical data have supported researchers in the resolution of knowledge gaps to deepen the understanding of the molecular mechanisms. The extra-ordinary and bewildering chemical diversity encompassed by biologically active natural products continues to be of relevance to drug discovery. Accumulating evidence has spurred a remarkable evolution of concepts related to pharmacological target of oncogenic signaling pathways by polysaccharides in different cancers.
Purpose:
The objective of the current review is to provide new insights into study progress on anticancer effects of bioactive herbal polysaccharides.
Methods:
PubMed, Scopus, Web of Science, Embase, and other databases were searched for articles related to anticancer effects of polysaccharides. Searches were conducted to locate relevant publications published up to October 2022.
Results:
Polysaccharides have been reported to pleiotropically modulate TGF/SMAD, BMP/SMAD, TLR4, mTOR, CXCR4 and VEGF/VEGFR cascades. We have also summarized how different polysaccharides regulated apoptosis and non-coding RNAs. Additionally, this mini-review describes increasingly sophisticated understanding related to polysaccharides mediated tumor suppressive and anti-metastatic effects in tumor-bearing mice. We have also provided an overview of the clinical trials related to chemopreventive role of polysaccharides.
Conclusion:
Genomic and proteomic findings from these studies will facilitate 'next-generation' clinical initiatives in the prevention/inhibition of cancer.
... The flow rate was adjusted to 1 ml/min, the eluent was collected at 10 ml/tube with an automatic collector, and the absorbance at 490 nm was measured with the phenol sulfuric acid method (Dubois et al., 1951). The elution fractions containing the same component were collected, concentrated to 1/8 of the original volume at 55°C; dialyzed with a dialysis bag with a molecular weight of 3,500 Da for 48 h, prefrozen at −40°C for 24 h, and then freeze-dried into powder (Zhang C. et al., 2019). Samples were placed on a SephadexG-100 dextran gel column and washed with ultrapure water, and the eluent was collected in a 5 ml tube. ...
... Many studies have shown that the low-toxicity natural polysaccharides extracted from Chinese herbal medicines inhibit the proliferation of tumour cells and selectively induce apoptosis (Sohretoglu et al., 2019). Different biological macromolecules can be extracted from different raw materials, and the types and structural characteristics of polysaccharides affect their biological activities (Zhao et al., 2017;Chen et al., 2020;Liu et al., 2020). ...
The Chinese medicinal herb Scutellaria barbata D. Don has antitumour effects and is used to treat liver cancer in the clinic. S. barbata polysaccharide (SBP), one of the main active components extracted from S. barbata D. Don, exhibits antitumour activity. However, there is still a lack of research on the extraction optimization, structural characterization, and anti-hepatoma activity of acidic polysaccharides from S. barbata D. Don. In this study, the optimal extraction conditions for SBP were determined by response surface methodology (RSM): the material-liquid ratio was 1:25, the extraction time was 2 h, and the extraction temperature was 90°C. Under these conditions, the average extraction efficiency was 3.85 ± 0.13%. Two water-soluble polysaccharides were isolated from S. barbata D. Don, namely, SBP-1A and SBP-2A, these homogeneous acidic polysaccharide components with average molecular weights of 1.15 × 10 ⁵ Da and 1.4 × 10 ⁵ Da, respectively, were obtained at high purity. The results showed that the monosaccharide constituents of the two components were fucose, galactosamine hydrochloride, rhamnose, arabinose, glucosamine hydrochloride, galactose, glucose, xylose, and mannose; the molar ratio of these constituents in SBP-1A was 0.6:0.3:0.6:30.6:3.3:38.4:16.1:8:1.4, and that in SBP-2A was 0.6:0.5:0.8:36.3:4.4:42.7:9.2:3.6:0.7. In addition, SBP-1A and SBP-2A contained uronic acid and β -glucan, and the residue on the polysaccharide was mainly pyranose. The in vitro results showed that the anti-hepatoma activity of SBP-2A was better than that of SBP-1A and SBP. In addition, SBP-2A significantly enhanced HepG2 cell death, as cell viability was decreased, and SBP-2A induced HepG2 cell apoptosis and blocked the G1 phase. This phenomenon was coupled with the upregulated expression of P53 and Bax/Bcl-2 ratio, as well as the downregulated expression of the cell cycle-regulating protein cyclinD1, CDK4, and Bcl-2 in this study. Further analysis showed that 50 mg/kg SBP-2A inhibited the tumour growth in H22 tumour-bearing mice, with an average inhibition rate of 40.33%. Taken together, SBP-2A, isolated and purified from S. barbata showed good antitumour activity in vivo and in vitro , and SBP-2A may be a candidate drug for further evaluation in cancer prevention. This study provides insight for further research on the molecular mechanism of the anti-hepatoma activity of S. barbata polysaccharide.
... 6 Accumulating illustrations have revealed that bioactive compounds and extracts from medicinal mushrooms inhibit the proliferation and induce apoptosis of adenocarcinoma human cells and can be owned as a chemotherapeutic agent. [7][8][9][10][11] Clinical practices have also assessed the anticarcinogenic property of medicinal mushrooms. 12 Assorted chemotherapeutic agents obtained from nontoxic natural products, have shown immense inhibition of cell viability and proliferation in cancerous cells through spurring cell-death signaling cascades. ...
Although comprehensive exertions have been made in late decades for treating advanced lung cancer with inclusive therapies but efficient anti-lung cancer therapeutics are statically inadequate in the clinics. Hence, compelling novel anti-lung cancer drugs are considerably desired. This backdrop enticed us to unveil anticancer efficacy of astrakurkurol, derivative of wild edible mushroom against lung cancer, whose effects have not yet been described. Mechanistic analysis disclosed that sensitizing effect of astrakurkurol is due to cell cycle arrest at G0/G1 phase, increased level of Fas, FADD, decreased ratio of Bax/Bcl-2, and increased cleaved form of caspase 9, 8, and 3. Apart from the induction of apoptosis, it was demonstrated for the first time that astrakurkurol induced an autophagic response as evidenced by the development of acidic vesicular organelles (AVOs) with up-regulation of beclin-1, Atg7, and downregulated p62. Apoptosis and autophagy can be sparked by the same stimuli, which was as evident from the astrakurkurol-induced inactivation of PI3K/AKT signaling. The thorough scanning of the mechanism of crosstalk between apoptosis and autophagy is requisite for prosperous anticancer remedy. Triterpenoid has evidently intensified cytotoxicity, induced apoptosis and autophagy on A549 cells. Besides astrakurkurol could also curb migration and regress the size of tumor in ex ovo xenograft model. All these findings put forth astrakurkurol as a convincing novel anti-cancer agent, for scrutinizing the lung cancer therapies and as a robust contender for future in vitro and in vivo analysis.
... 7 For example, they have been proven to play an effective role in cancer, neurodegenerative diseases, and diabetes, all of which are currently incurable diseases in humans. 8,9 G. lucidum is extremely attractive to researchers, and it provides an in-depth explanation of its therapeutic effects on various cancers. Similarly, Rupeshkumar et al affirmed the magical power of G. lucidum from different angles. ...
G. lucidum has a long history of thousands of years in China and is closely related with the lives of the Chinese people. It is reported to cure various diseases due to its high nutritional value and wide range of uses. The fascinating effects of G. lucidum have tethered a multitude of efforts to explore its effective ingredients and supplement functions. At present, many cancer research studies have reported the G. lucidum polysaccharides (GLPs) and G. lucidum triterpenes (GLTs) as the main active ingredients in G. lucidum, which have shown positive effects on radiotherapy and chemotherapy. GLPs or GLTs treatment synergizes with radiotherapy and chemotherapy through multiple pathways, including oxidative stress, apoptosis, immune microenvironment, etc. Therefore, this review aims to analyze and summarize these complex molecules from G. lucidum in order to create more treatment options for cancer patients in the future.
... Cell proliferation and viability were evaluated by cell counting and MTS assay, as described previously [36]. Treatment with DMSO (vehicle) served as a control. ...
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 AMPKa 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.
