Discovery of novel S6K1 inhibitors by an ensemble-based virtual screening method and molecular dynamics simulation.

Ribosomal protein S6 kinase beta-1 (S6K1) is considered a potential target for the treatment of various diseases, such as obesity, type II diabetes, and cancer. Development of novel S6K1 inhibitors is an urgent and important task for the medicinal chemists. In this research, an effective ensemble-based virtual screening method, including common feature pharmacophore model, 3D-QSAR pharmacophore model, naïve Bayes classifier model, and molecular docking, was applied to discover potential S6K1 inhibitors from BioDiversity database with 29,158 compounds. Finally, 7 hits displayed considerable properties and considered as potential inhibitors against S6K1. Further, carefully analyzing the interactions between these 7 hits and key residues in the S6K1 active site, and comparing them with the reference compound PF-4708671, it was found that 2 hits exhibited better binding patterns. In order to further investigate the mechanism of the interactions between 2 hits and S6K1 at simulated physiological conditions, the molecular dynamics simulation was performed. The ΔGbind energies for S6K1-Hit1 and S6K1-Hit2 were - 111.47 ± 1.29 and - 54.29 ± 1.19 kJ mol-1, respectively. Furthermore, deep analysis of these results revealed that Hit1 was the most stable complex, which can stably bind to S6K1 active site, interact with all of the key residues, and induce H1, H2, and M-loop regions changes. Therefore, the identified Hit1 may be a promising lead compound for developing new S6K1 inhibitor for various metabolic diseases treatment.

TAKTIC: A prospective, multicentre, uncontrolled, phase IB/II study of LY2780301, a p70S6K/AKT inhibitor, in combination with weekly paclitaxel in HER2-negative advanced breast cancer patients.

BACKGROUND: Hormone-resistant HER2-negative or triple-negative advanced breast cancers (ABC) are routinely treated with paclitaxel chemotherapy. LY2780301 is a dual inhibitor of p70 ribosomal protein S6 kinase and AKT. The TAKTIC study aimed at exploring the combination of paclitaxel and LY2780301 in this population. METHODS: In this multicentric phase Ib/II trial, we enrolled patients with HER2-negative ABC, with (phase IB) or without (phase II) prior to cytotoxic treatment for advanced disease. Oral LY2780301 was administered once daily in combination with intravenous weekly paclitaxel. Primary endpoints were to determine the recommended phase II dose (RP2D) of the combination of LY2780301 with weekly paclitaxel (phase Ib), and to estimate a 6 months objective response rate (ORR) (phase II) in patients with HER2-negative ABC, both in the overall patient population and in cases with activation of the PI3K/AKT pathway (PI3KAKT+). RESULTS: A total of 51 patients were enrolled; RP2D was LY2780301 500 mg QD+ paclitaxel 80 mg/m2. Main drug-related adverse events noted in phase Ib included neuropathy (75% of patients, grade 3-4 in 8%), asthenia (58% of patients, no grade 3-4), and ungual toxicity (50% of patients, grade 3-4 in 25%). They were similar in the phase II part, except that 14% of patients experienced pneumonia (grade 3-4 in 6%). In the phase II part, 6-month ORR in the overall population and in PI3KAKT+ subgroup were, respectively, 63.9% [48.8-76.8] and 55% [35-73.7]. CONCLUSION: Combining LY2780301 and weekly paclitaxel in patients with HER2-negative ABC was feasible with preliminary evidence of efficacy in both the overall population and the PI3KAKT+ subgroup. TRIAL REGISTRATION ID: NCT01980277.

Identification of Clinical Candidate M2698, a Dual p70S6K and Akt Inhibitor, for Treatment of PAM Pathway-Altered Cancers.

Herein, we report the discovery of a novel class of quinazoline carboxamides as dual p70S6k/Akt inhibitors for the treatment of tumors driven by alterations to the PI3K/Akt/mTOR (PAM) pathway. Through the screening of in-house proprietary kinase library, 4-benzylamino-quinazoline-8-carboxylic acid amide 1 stood out, with sub-micromolar p70S6k biochemical activity, as the starting point for a structurally enabled p70S6K/Akt dual inhibitor program that led to the discovery of M2698, a dual p70S6k/Akt inhibitor. M2698 is kinase selective, possesses favorable physical, chemical, and DMPK profiles, is orally available and well tolerated, and displayed tumor control in multiple in vivo studies of PAM pathway-driven tumors.

Discovery of 4-aminopyrimidine analogs as highly potent dual P70S6K/Akt inhibitors.

Activation of the PI3K/Akt/mTOR kinase pathway is associated with human cancers. A dual p70S6K/Akt inhibitor is sufficient to inhibit strong tumor growth and to block negative impact of the compensatory Akt feedback loop activation. A scaffold docking strategy based on an existing quinazoline carboxamide series identified 4-aminopyrimidine analog 6, which showed a single-digit nanomolar and a micromolar potencies in p70S6K and Akt enzymatic assays. SAR optimization improved Akt enzymatic and p70S6K cellular potencies, reduced hERG liability, and ultimately discovered the promising candidate 37, which exhibited with a single digit nanomolar value in both p70S6K and Akt biochemical assays, and hERG activities (IC50 = 17.4 µM). This agent demonstrated dose-dependent efficacy in inhibiting mice breast cancer tumor growth and covered more than 90% pS6 inhibition up to 24 h at a dose of 200 mg/kg po.

TLR-4 Agonist Induces IFN-γ Production Selectively in Proinflammatory Human M1 Macrophages through the PI3K-mTOR- and JNK-MAPK-Activated p70S6K Pathway.

IFN-γ, a proinflammatory cytokine produced primarily by T cells and NK cells, activates macrophages and engages mechanisms to control pathogens. Although there is evidence of IFN-γ production by murine macrophages, IFN-γ production by normal human macrophages and their subsets remains unknown. Herein, we show that human M1 macrophages generated by IFN-γ and IL-12- and IL-18-stimulated monocyte-derived macrophages (M0) produce significant levels of IFN-γ. Further stimulation of IL-12/IL-18-primed macrophages or M1 macrophages with agonists for TLR-2, TLR-3, or TLR-4 significantly enhanced IFN-γ production in contrast to the similarly stimulated M0, M2a, M2b, and M2c macrophages. Similarly, M1 macrophages generated from COVID-19-infected patients' macrophages produced IFN-γ that was enhanced following LPS stimulation. The inhibition of M1 differentiation by Jak inhibitors reversed LPS-induced IFN-γ production, suggesting that differentiation with IFN-γ plays a key role in IFN-γ induction. We subsequently investigated the signaling pathway(s) responsible for TLR-4-induced IFN-γ production in M1 macrophages. Our results show that TLR-4-induced IFN-γ production is regulated by the ribosomal protein S6 kinase (p70S6K) through the activation of PI3K, the mammalian target of rapamycin complex 1/2 (mTORC1/2), and the JNK MAPK pathways. These results suggest that M1-derived IFN-γ may play a key role in inflammation that may be augmented following bacterial/viral infections. Moreover, blocking the mTORC1/2, PI3K, and JNK MAPKs in macrophages may be of potential translational significance in preventing macrophage-mediated inflammatory diseases.

Phase 1 study of M2698, a p70S6K/AKT dual inhibitor, in patients with advanced cancer.

BACKGROUND: The PI3K/AKT/mTOR (PAM) pathway is a key regulator of tumor therapy resistance. We investigated M2698, an oral p70S6K/AKT dual inhibitor, in patients with advanced cancer who failed standard therapies. METHODS: M2698 was administered as monotherapy (escalation, 15-380 mg daily; food effect cohort, 240-320 mg daily) and combined with trastuzumab or tamoxifen. RESULTS: Overall, 101 patients were treated (M2698, n = 62; M2698/trastuzumab, n = 13; M2698/tamoxifen, n = 26). Patients were predominantly aged < 65 years, were female, had performance status 1 and were heavily pretreated. There was a dose- and concentration-dependent inhibition of pS6 levels in peripheral blood mononuclear cells and tumor tissue. M2698 was well tolerated; the most common treatment-emergent adverse events were gastrointestinal, abnormal dreams and fatigue (serious, attributed to M2698: monotherapy, 8.1%; M2698/trastuzumab, 7.7%; M2698/tamoxifen, 11.5% of patients). The recommended phase 2 doses of M2698 were 240 mg QD (monotherapy), 160 mg QD (M2698/trastuzumab) and 160 mg QD/240 mg intermittent regimen (M2698/tamoxifen). In the monotherapy cohort, 27.4% of patients had stable disease at 12 weeks; no objective response was noted. The median progression-free survival (PFS) durations in patients with PAM pathway alterations with and without confounding markers (KRAS, EGFR, AKT2) were 1.4 months and 2.8 months, respectively. Two patients with breast cancer (M2698/trastuzumab, n = 1; M2698/tamoxifen, n = 1) had partial response; their PFS durations were 31 months and 2.7 months, respectively. CONCLUSIONS: M2698 was well tolerated. Combined with trastuzumab or tamoxifen, M2698 demonstrated antitumor activity in patients with advanced breast cancer resistant to multiple standard therapies, suggesting that it could overcome treatment resistance. Trial registration ClinicalTrials.gov, NCT01971515. Registered October 23, 2013.

Prophylactic treatment with BX795 blocks activation of AKT and its downstream targets to protect vaginal keratinocytes and vaginal epithelium from HSV-2 infection.

Genital herpes infections in humans are usually caused by herpes simplex virus type-2 (HSV-2), which result in recurrent lesions in the anogenital region. Past studies have shown that a viral protein translation inhibitor, BX795 is capable of mitigating HSV-2 infection both in vitro and in vivo when dosed therapeutically. However, any preventative benefits of this compound against HSV-2 infection remain poorly understood. In this study, we show that BX795 when added prophylactically to human vaginal keratinocytes generates strong preventative effects against a future HSV-2 infection. As a possible mechanism for this action, we found that BX795 efficiently reduces phosphorylation of AKT and its downstream targets p70S6K and 4EBP1. Our in-silico protein docking studies support our immunoblotting results and provide further credence to the proposed mechanism. Using a murine model of vaginal infection, we show that prior treatment with BX795 is also protective in vivo and leads to lower viral replication in the vaginal tissue.

LY­294002 enhances the chemosensitivity of liver cancer to oxaliplatin by blocking the PI3K/AKT/HIF­1α pathway.

Liver cancer remains one of the leading causes of cancer deaths worldwide. The therapeutic effect of oxaliplatin on liver cancer is often limited by acquired resistance of the cancer cells. Abnormal activation of the PI3K/AKT pathway plays an important role in the acquired resistance of oxaliplatin. The present study investigated the effects of the PI3K inhibitor LY­294002 and AKT inhibitor MK2206 on the chemosensitivity of oxaliplatin­resistant liver cancer cells and the molecular mechanism involved. An oxaliplatin­resistant liver cancer cell line HepG2R was developed. MTT assay, clone formation experiments, flow cytometry and Annexin V­FITC/PI staining were used to determine the proliferation, cycle and apoptosis of HepG2R cells when oxaliplatin was combined with LY­294002 or MK2206 treatment. The effects of LY­294002 and MK­2206 on the abnormal activation of PI3K/AKT pathway and hypoxia inducible factor (HIF)­1α protein level in HepG2R cells were detected using western blotting. The results indicated that the PI3K/AKT pathway is stably activated in HepG2R cells. Compared with the AKT inhibitor MK2206, the PI3K inhibitor LY­294002 more effectively downregulated the phosphorylation levels of p85, p110α, p110ß, p110γ and AKT in the PI3K/AKT pathway in HepG2R cells, and more effectively inhibited the proliferation of the cells. LY­294002 enhanced the chemotherapy sensitivity of HepG2R cells to oxaliplatin by inducing G0/G1 phase arrest and increasing the proportion of apoptotic cells. In addition, LY­294002 reduced the level of HIF­1α, which is highly expressed in HepG2R cells. It was concluded that LY­294002 enhanced the chemosensitivity of liver cancer cells to oxaliplatin by inhibiting the PI3K/AKT signaling pathway, which may be related to the inhibition of HIF­1α expression. These findings may have clinical significance for the treatment of oxaliplatin­resistant liver cancer.

Inhibition of p70 isoforms of S6K1 induces anoikis to prevent transformed human hepatocyte growth.

AIMS: The mTOR/S6K1 signaling axis, known for cell growth regulation, is hyper-activated in multiple cancers. In this study, we have examined the mechanisms for ribosomal protein p70-S6 kinase 1 (S6K1) associated transformed human hepatocyte (THH) growth regulation. MAIN METHODS: THH were treated with p70-S6K1 inhibitor and analyzed for cell viability, cell cycle distribution, specific marker protein expression by western blot, and tumor inhibition in a xenograft mouse model. We validated our results by knockdown of p70-S6K1 using specific siRNA. KEY FINDINGS: p70-S6K1 inhibitor treatment caused impairment of in vitro hepatocyte growth, and arrested cell cycle progression at the G1 phase. Further, p70-S6K1 inhibitor treatment exhibited a decrease in FAK and Erk activation, followed by altered integrin-ß1 expression, caspase 8, and PARP cleavage appeared to be anoikis like growth inhibition. p70-S6K1 inhibitor also depolymerized actin microfilaments and diminished active Rac1/Cdc42 complex formation for loss of cellular attachment. Similar results were obtained with other transformed human hepatocyte cell lines. p70-S6K1 inhibition also resulted in a reduced phospho-EGFR, Slug and Twist; implicating an inhibition of epithelial-mesenchymal transition (EMT) state. A xenograft tumor model, generated from implanted THH in nude mice, following intraperitoneal injection of S6K1 inhibitor prevented further tumor growth. SIGNIFICANCE: Our results suggested that p70-S6K1 inhibition alters orchestration of cell cycle progression, induces cell detachment, and sensitizes hepatocyte growth impairment. Targeting p70 isoform of S6K1 by inhibitor may prove to be a promising approach together with other therapies for hepatocellular carcinoma (HCC) treatment.

Astaxanthin Inhibits p70 S6 Kinase 1 Activity to Sensitize Insulin Signaling.

Astaxanthin (AST) is a carotenoid with therapeutic values on hyperglycemia and diabetic complications. The mechanisms of action of AST remain incompletely understood. p70 S6 kinase 1 (S6K1) is a serine/threonine kinase that phosphorylates insulin receptor substrate 1 (IRS-1)S1101 and desensitizes the insulin receptor (IR). Our present study aims to determine if AST improves glucose metabolisms by targeting S6K1. Western blot analysis revealed that AST inhibited the phosphorylation of two S6K1 substrates, S6S235/236 and IRS-1S1101, but enhanced the phosphorylation of AKTT308, AKTS473, and S6K1T389 by feedback activation of the phosphatidylinositol-3 (PI-3) kinase in 3T3-L1 adipocytes and L6 myotubes. In vitro kinase assays revealed that AST inhibited S6K1 activity with an IC50 value of approximately 13.8 µM. AST increased insulin-induced IR tyrosine phosphorylation and IRS-1 binding to the p85 subunit of PI-3 kinase. Confocal microscopy revealed that AST increased the translocation of the glucose transporter 4 (GLUT4) to the plasma membrane in L6 cells. Glucose uptake assays using a fluorescent dye, 2-NBDG (2-N-(Nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose), revealed that AST increased glucose uptake in 3T3-L1 adipocytes and L6 myotubes under insulin resistance conditions. Our study identifies S6K1 as a previously unrecognized molecular target of AST and provides novel insights into the mechanisms of action of AST on IR sensitization.

S6K1 blockade overcomes acquired resistance to EGFR-TKIs in non-small cell lung cancer.

The development of resistance to EGFR Tyrosine kinase inhibitors (TKIs) in NSCLC with activating EGFR mutations is a critical limitation of this therapy. In addition to genetic alterations such as EGFR secondary mutation causing EGFR-TKI resistance, compensatory activation of signaling pathways without interruption of genome integrity remains to be defined. In this study, we identified S6K1/MDM2 signaling axis as a novel bypass mechanism for the development of EGFR-TKI resistance. The observation of S6K1 as a candidate mechanism for resistance to EGFR TKI therapy was investigated by interrogation of public databases and a clinical cohort to establish S6K1 expression as a prognostic/predictive biomarker. The role of S6K1 in TKI resistance was determined in in vitro gain-and-loss of function studies and confirmed in subcutaneous and orthotopic mouse lung cancer models. Blockade of S6K1 by a specific inhibitor PF-4708671 synergistically enhanced the efficacy of TKI without showing toxicity. The mechanistic study showed the inhibition of EGFR caused nuclear translocation of S6K1 for binding with MDM2 in resistant cells. MDM2 is a downstream effector of S6K1-mediated TKI resistance. Taken together, we present evidence for the reversal of resistance to EGFR TKI by the addition of small molecule S6K1/MDM2 antagonists that could have clinical benefit.

In Vitro and In Vivo Antiviral Activity of Gingerenone A on Influenza A Virus Is Mediated by Targeting Janus Kinase 2.

Janus kinase (JAK) inhibitors have been developed as novel immunomodulatory drugs and primarily used for treating rheumatoid arthritis and other inflammatory diseases. Recent studies have suggested that this category of anti-inflammatory drugs could be potentially useful for the control of inflammation "storms" in respiratory virus infections. In addition to their role in regulating immune cell functions, JAK1 and JAK2 have been recently identified as crucial cellular factors involved in influenza A virus (IAV) replication and could be potentially targeted for antiviral therapy. Gingerenone A (Gin A) is a compound derived from ginger roots and a dual inhibitor of JAK2 and p70 S6 kinase (S6K1). Our present study aimed to determine the antiviral activity of Gin A on influenza A virus (IAV) and to understand its mechanisms of action. Here, we reported that Gin A suppressed the replication of three IAV subtypes (H1N1, H5N1, H9N2) in four cell lines. IAV replication was also inhibited by Ruxolitinib (Rux), a JAK inhibitor, but not by PF-4708671, an S6K1 inhibitor. JAK2 overexpression enhanced H5N1 virus replication and attenuated Gin A-mediated antiviral activity. In vivo experiments revealed that Gin A treatment suppressed IAV replication in the lungs of H5N1 virus-infected mice, alleviated their body weight loss, and prolonged their survival. Our study suggests that Gin A restricts IAV replication by inhibiting JAK2 activity; Gin A could be potentially useful for the control of influenza virus infections.

The mTORC1 inhibitor rapamycin and the mTORC1/2 inhibitor AZD2014 impair the consolidation and persistence of contextual fear memory.

RATIONALE: The mechanistic target of rapamycin (mTOR) kinase mediates various long-lasting forms of synaptic and behavioural plasticity. However, there is little information concerning the temporal pattern of mTOR activation and susceptibility to pharmacological intervention during consolidation of contextual fear memory. Moreover, the contribution of both mTOR complex 1 and 2 together or the mTOR complex 1 downstream effector p70S6K (S6K1) to consolidation of contextual fear memory is unknown. OBJECTIVE: Here, we tested whether different timepoints of vulnerability to rapamycin, a first generation mTOR complex 1 inhibitor, exist for contextual fear memory consolidation and persistence. We also sought to characterize the effects of dually inhibiting mTORC1/2 as well as S6K1 on fear memory formation and persistence. METHODS: Rapamycin was injected systemically to mice immediately, 3 h, or 12 h after contextual fear conditioning, and retention was measured at different timepoints thereafter. To determine the effects of a single injection of the dual mTROC1/2 inhibitor AZD2014 after learning on memory consolidation and persistence, a dose-response experiment was carried out. Memory formation and persistence was also assessed in response to the S6K1 inhibitor PF-4708671. RESULTS: A single systemic injection of rapamycin immediately or 3 h, but not 12 h, after learning impaired the formation and persistence of contextual fear memory. AZD2014 was found, with limitations, to dose-dependently attenuate memory consolidation and persistence at the highest dose tested (50 mg/kg). In contrast, PF-4708671 had no effect on consolidation or persistence. CONCLUSION: Our results indicate the need to further understand the role of mTORC1/2 kinase activity in the molecular mechanisms underlying memory processing and also demonstrate that the effects of mTORC1 inhibition at different timepoints well after learning on memory consolidation and persistence.

Regulation of Mumps Virus Replication and Transcription by Kinase RPS6KB1.

Mumps virus (MuV) caused the most viral meningitis before mass immunization. Unfortunately, MuV has reemerged in the United States in the past several years. MuV is a member of the genus Rubulavirus, in the family Paramyxoviridae, and has a nonsegmented negative-strand RNA genome. The viral RNA-dependent RNA polymerase (vRdRp) of MuV consists of the large protein (L) and the phosphoprotein (P), while the nucleocapsid protein (NP) encapsulates the viral RNA genome. These proteins make up the replication and transcription machinery of MuV. The P protein is phosphorylated by host kinases, and its phosphorylation is important for its function. In this study, we performed a large-scale small interfering RNA (siRNA) screen targeting host kinases that regulated MuV replication. The human kinase ribosomal protein S6 kinase beta-1 (RPS6KB1) was shown to play a role in MuV replication and transcription. We have validated the role of RPS6KB1 in regulating MuV using siRNA knockdown, an inhibitor, and RPS6KB1 knockout cells. We found that MuV grows better in cells lacking RPS6KB1, indicating that it downregulates viral growth. Furthermore, we detected an interaction between the MuV P protein and RPS6KB1, suggesting that RPS6KB1 directly regulates MuV replication and transcription.IMPORTANCE Mumps virus is an important human pathogen. In recent years, MuV has reemerged in the United State, with outbreaks occurring in young adults who have been vaccinated. Our work provides insight into a previously unknown mumps virus-host interaction. RPS6KB1 negatively regulates MuV replication, likely through its interaction with the P protein. Understanding virus-host interactions can lead to novel antiviral drugs and enhanced vaccine production.

Caffeine Potentiates Ethanol-Induced Neurotoxicity Through mTOR/p70S6K/4E-BP1 Inhibition in SH-SY5Y Cells.

Caffeine is a popular psychostimulant, which is frequently consumed with ethanol. However, the effects of caffeine on neuronal cells constantly exposed to ethanol have not been investigated. Apoptosis and oxidative stress occurring in ethanol-induced neurotoxicity were previously associated with decreased phosphorylation of the mTOR/p70S6K/4E-BP1 signaling proteins. Evidence also suggested that caffeine inhibits the mTOR pathway. In this study, human SH-SY5Y neuroblastoma cells were exposed to caffeine after pretreatment for 24 hours with ethanol. Results indicated that both ethanol and caffeine caused neuronal cell death in a dose- and time-dependent manner. Exposure to 20-mM caffeine for 24 hours magnified reduced cell viability and enhanced apoptotic cell death induced by 200 mM of ethanol pretreatment. The phosphorylation of mTOR, p70S6K, and 4E-BP1 markedly decreased in cells exposed to caffeine after ethanol pretreatment, associated with a decrease of the mitochondrial membrane potential (ΔΨm). These findings suggested that caffeine treatment after neuronal cells were exposed to ethanol resulted in marked cell damages, mediated through enhanced inhibition of mTOR/p70S6K/4E-BP1 signaling leading to impaired ΔΨm and, eventually, apoptotic cell death.

1,8-Cineole promotes G0/G1 cell cycle arrest and oxidative stress-induced senescence in HepG2 cells and sensitizes cells to anti-senescence drugs.

AIMS: 1,8-Cineole is a plant-derived monoterpene and a major constituent of Eucalyptus essential oil. Previously, we demonstrated that 1,8-cineole inhibited hepatocellular carcinoma (HCC) HepG2 cell growth. However, the underlying mechanisms remain unknown. Here, we evaluated the mechanisms of action of 1,8-cineole and the potential benefits of its combination with anticancer compounds harboring "anti-senescence" properties in HepG2 cells. MAIN METHODS: Cell viability was determined by the MTT assay. Cell cycle was assessed through flow cytometry (FC) and western blot (WB). Senescence was determined by the SA-ß-galactosidase assay, and apoptosis by caspase-3 activity, WB, and TUNEL. MAPKs (ERK, JNK, and p38), AMPK, and Akt/mTOR were analyzed by WB. Reactive oxygen species (ROS) and mitochondrial membrane potential (ΔΨm) were evaluated by FC and fluorescence microscopy. KEY FINDINGS: 1,8-Cineole inhibited cell proliferation by promoting G0/G1 arrest. While 1,8-cineole was unable to trigger apoptosis, it induced cellular senescence. 1,8-Cineole promoted ROS production, ΔΨm depolarization, AMPK, ERK, and p38 activation and mTOR inhibition. Antioxidants, like N-acetyl-L-cysteine and vitamins, prevented HepG2 cell growth inhibition and senescence induced by 1,8-cineole. Pre-incubation with 1,8-cineole sensitized HepG2 cells to the anti-senescence compounds, quercetin, simvastatin, U0126, and SB202190. Combinations of 1,8-cineole and each compound synergistically inhibited cell viability, and combined treatment with 1,8-cineole and simvastatin induced apoptosis. SIGNIFICANCE: 1,8-Cineole induces G0/G1 arrest and senescence in HepG2 cells through oxidative stress and MAPK, AMPK, and Akt/mTOR pathways, and sensitizes cells to anti-senescence drugs, suggesting that 1,8-cineole has potential as an antineoplastic and adjuvant compound in combination with anti-senescence drugs in HCC therapy.

Inhibition of mTORC1/P70S6K pathway by Metformin synergistically sensitizes Acute Myeloid Leukemia to Ara-C.

AIMS: Chemo-resistance still was the main obstacle for AML patients, more effective and less toxic forms of therapies were desperately needed. Metformin, a classic hypoglycemic drug for diabetes recently delivered us a new identity that it exerted anti-tumor activity through suppressing mTOR in various tumors. But the anti-tumor effect of metformin in AML was not clear. METHODS: In this study, we used CCK8 assay and apoptosis assay to determine the anti-leukemia activity of metformin combined with AraC, and explore the mechanism of the joint role of Ara-C/metformin in AML. We finally used xenograft experiment in mice to determine the anti-leukemia effect of Ara-C/metformin in vivo. KEY FINDINGS: We found that metformin could synergistically sensitize AML cells to Ara-C via inhibiting mTORC1/P70S6K pathway. In vivo experiment also verified metformin in aid of Ara-C caused an obviously synergistic anti-tumor effect. SIGNIFICANCE: We firstly found the synergistic anti-tumor effect of Ara-C/metformin in AML through inhibiting mTORC1/P70S6K pathway.

The 3F Library: Fluorinated Fsp3 -Rich Fragments for Expeditious 19 F†NMR Based Screening.

Fragment-based drug discovery (FBDD) is a popular method in academia and the pharmaceutical industry for the discovery of early lead candidates. Despite its wide-spread use, the approach still suffers from laborious screening workflows and a limited diversity in the fragments applied. Presented here is the design, synthesis, and biological evaluation of the first fragment library specifically tailored to tackle both these challenges. The 3F library of 115 fluorinated, Fsp3 -rich fragments is shape diverse and natural-product-like with desirable physicochemical properties. The library is perfectly suited for rapid and efficient screening by NMR spectroscopy in a two-stage workflow of 19 F NMR and subsequent 1 H NMR methods. Hits against four diverse protein targets are widely distributed among the fragment scaffolds in the 3F library and a 67 % validation rate was achieved using secondary assays. This collection is the first synthetic fragment library tailor-made for 19 F NMR screening and the results demonstrate that the approach should find broad application in the FBDD community.

Identification of a novel S6K1 inhibitor, rosmarinic acid methyl ester, for treating cisplatin-resistant cervical cancer.

BACKGROUND: The mTOR/S6K1 signaling pathway is often activated in cervical cancer, and thus considered a molecular target for cervical cancer therapies. Inhibiting mTOR is cytotoxic to cervical cancer cells and creates a synergistic anti-tumor effect with conventional chemotherapy agents. In this study, we identified a novel S6K1 inhibitor, rosmarinic acid methyl ester (RAME) for the use of therapeutic agent against cervical cancer. METHODS: Combined structure- and ligand-based virtual screening was employed to identify novel S6K1 inhibitors among the in house natural product library. In vitro kinase assay and immunoblot assay was used to examine the effects of RAME on S6K1 signaling pathway. Lipidation of LC3 and mRNA levels of ATG genes were observed to investigate RAME-mediated autophagy. PARP cleavage, mRNA levels of apoptotic genes, and cell survival was measured to examine RAME-mediated apoptosis. RESULTS: RAME was identified as a novel S6K1 inhibitor through the virtual screening. RAME, not rosmarinic acid, effectively reduced mTOR-mediated S6K1 activation and the kinase activity of S6K1 by blocking the interaction between S6K1 and mTOR. Treatment of cervical cancer cells with RAME promoted autophagy and apoptosis, decreasing cell survival rate. Furthermore, we observed that combination treatment with RAME and cisplatin greatly enhanced the anti-tumor effect in cisplatin-resistant cervical cancer cells, which was likely due to mTOR/S6K1 inhibition-mediated autophagy and apoptosis. CONCLUSIONS: Our findings suggest that inhibition of S6K1 by RAME can induce autophagy and apoptosis in cervical cancer cells, and provide a potential option for cervical cancer treatment, particularly when combined with cisplatin.

Cardamonin inhibits breast cancer growth by repressing HIF-1α-dependent metabolic reprogramming.

BACKGROUND: Cardamonin, a chalcone isolated from Alpiniae katsumadai, has anti-inflammatory and anti-tumor activities. However, the molecular mechanism by which cardamonin inhibits breast cancer progression largely remains to be determined. METHODS: CCK-8 and Hoechst 33258 staining were used to detect cell growth and apoptosis, respectively. HIF-1α driven transcription was measured by luciferase reporter assay. Glucose uptake and lactate content were detected with 2-NBDG and L-Lactate Assay Kit. Cell metabolism assays were performed on Agilent's Seahorse Bioscience XF96 Extracellular Flux Analyzer. Mitochondrial membrane potential was measured with JC-1 probe. DCFH-DA was used to measure ROS level. Protein expression was detected by western blotting assay. Immunohistochemistry was performed to measure the expression of HIF-1α, LDHA and CD31 in tumor tissues. RESULTS: Cardamonin inhibited growth of the triple negative breast cancer cell line MDA-MB-231 in vitro and in vivo by suppressing HIF-1α mediated cell metabolism. Cardamonin inhibited the expression of HIF-1α at mRNA and protein levels by repressing the mTOR/p70S6K pathway, and subsequently enhanced mitochondrial oxidative phosphorylation and induced reactive oxygen species (ROS) accumulation. We also found that cardamonin inhibited the Nrf2-dependent ROS scavenging system which further increased intracellular ROS levels. Eventually, accumulation of the intracellular ROS induced apoptosis in breast cancer cells. In addition, cardamonin treatment reduced glucose uptake as well as lactic acid production and efflux, suggesting its function in repressing the glycolysis process. CONCLUSIONS: These results reveal novel function of cardamonin in modulating cancer cell metabolism and suppressing breast cancer progression, and suggest its potential for breast cancer treatment.