Essential role of tuberous sclerosis genes TSC1 and TSC2 in NF-kappaB activation and cell survival

Polyvinyl Alcohol Capped Silver Nanostructures for Fortified Apoptotic Potential Against Human Laryngeal Carcinoma Cells Hep-2 Using Extremely-Low Frequency Electromagnetic Field

Purpose

: Polyvinyl alcohol-capped silver nanostructures (cAgNSs) were investigated in order to enhance the cytotoxicity, pro-apoptotic, and oxidant patterns of in human laryngeal carcinoma Hep-2 cells by employing a 50 mT electromagnetic field (LEMF) for 30 min.

Methods

Wet chemical reduction was used to synthesize the cAgNSs, and after they had been capped with polyvinyl alcohol, they were specifically examined for particle size analysis and structural morphology. To visualize how the silver may attach to the protein targets, a molecular docking study was conducted. Estimation of cytotoxicity, cell cycle progression supported by mRNA expression of three apoptotic-promoting genes and one apoptotic-resisting.

Results

Particle size analysis results were a mean particle size of 157.3±0.5 nm, zeta potential value of -29.6 mV±1.5 mV, and polydispersity index of 0.31±0.05. Significantly reduction of IC50 against Hep-2 cells by around 6-fold was concluded. Also, we obtained suppression of the proliferation of Hep-2 cells, especially in the G0/G1 and S phases. Significant enhanced mRNA expression revealed enhanced induced CASP3, p53, and Beclin-1 mediated pro-apoptosis and induced NF-κB mediated autophagy in Hep-2 cells. Augmented levels of GR, ROS and MDA as oxidative stress biomarkers were also obtained. HE staining of Hep-2 cells exposed to cAgNSs and LEMF confirmed the enhanced apoptotic potential comparatively.

Conclusion

By conclusion, the developed nano-sized structures with the aid of extremely-low frequency electromagnetic field were successful to fortify the anti-cancer profile of cAgNSs in Hep-2 cells.

Establishing and characterizing a novel doxorubicin-resistant acute myeloid leukaemia cell line

Drug resistance is a major setback in cancer treatment, thus models to study its mechanisms are needed. Our work aimed to establish and characterize a resistant cell line from a sensitive acute myeloid leukaemia (AML) cell line - HL60 - by treating the sensitive cells with increasing concentrations of doxorubicin. We confirmed (cell viability assays) that the established subline, HL60-CDR, was resistant to doxorubicin for at least 30 days without drug treatment. The HL60-CDR cells were also resistant to three other drugs (cisplatin, etoposide and daunorubicin), exhibiting a multidrug resistant (MDR) profile. We verified (Western Blotting) that the MDR cells do not express drug efflux pumps, nor present altered expression of apoptotic proteins, when compared with the parental cell line. HL60-CDR cells presented alterations in the cell cycle profile, and in the expression levels of proteins involved in DNA repair mechanisms and drug metabolism, when compared with their drug sensitive counterpart. Proteomic analysis revealed that HL60-CDR cells presented an upregulation of proteins involved in oncogenic pathways, such as TSC2, PDPK1, Annexin A2, among others. Overall, we established an AML MDR subline - HL60-CDR - which presents several resistance mechanisms, providing an in vitro model to test new compounds to circumvent MDR in AML.

Muscle stem cell adaptations to cellular and environmental stress

Background

Lifelong regeneration of the skeletal muscle is dependent on a rare population of resident skeletal muscle stem cells, also named ‘satellite cells’ for their anatomical position on the outside of the myofibre and underneath the basal lamina. Muscle stem cells maintain prolonged quiescence, but activate the myogenic programme and the cell cycle in response to injury to expand a population of myogenic progenitors required to regenerate muscle. The skeletal muscle does not regenerate in the absence of muscle stem cells.

Main body

The notion that lifelong regeneration of the muscle is dependent on a rare, non-redundant population of stem cells seems contradictory to accumulating evidence that muscle stem cells have activated multiple stress response pathways. For example, muscle stem cell quiescence is mediated in part by the eIF2α arm of the integrated stress response and by negative regulators of mTORC1, two translational control pathways that downregulate protein synthesis in response to stress. Muscle stem cells also activate pathways to protect against DNA damage, heat shock, and environmental stress. Here, we review accumulating evidence that muscle stem cells encounter stress during their prolonged quiescence and their activation. While stress response pathways are classically described to be bimodal whereby a threshold dictates cell survival versus cell death responses to stress, we review evidence that muscle stem cells additionally respond to stress by spontaneous activation and fusion to myofibres.

Conclusion

We propose a cellular stress test model whereby the prolonged state of quiescence and the microenvironment serve as selective pressures to maintain muscle stem cell fitness, to safeguard the lifelong regeneration of the muscle. Fit muscle stem cells that maintain robust stress responses are permitted to maintain the muscle stem cell pool. Unfit muscle stem cells are depleted from the pool first by spontaneous activation, or in the case of severe stress, by activating cell death or senescence pathways.

Yeast Crf1p: An activator in need is an activator indeed

Ribosome biogenesis is an energetically costly process, and tight regulation is required for stoichiometric balance between components. This requires coordination of RNA polymerases I, II, and III. Lack of nutrients or the presence of stress leads to downregulation of ribosome biogenesis, a process for which mechanistic target of rapamycin complex I (mTORC1) is key. mTORC1 activity is communicated by means of specific transcription factors, and in yeast, which is a primary model system in which transcriptional coordination has been delineated, transcription factors involved in regulation of ribosomal protein genes include Fhl1p and its cofactors, Ifh1p and Crf1p. Ifh1p is an activator, whereas Crf1p has been implicated in maintaining the repressed state upon mTORC1 inhibition. Computational analyses of evolutionary relationships have indicated that Ifh1p and Crf1p descend from a common ancestor. Here, we discuss recent evidence, which suggests that Crf1p also functions as an activator. We propose a model that consolidates available experimental evidence, which posits that Crf1p functions as an alternate activator to prevent the stronger activator Ifh1p from re-binding gene promoters upon mTORC1 inhibition. The correlation between retention of Crf1p in related yeast strains and duplication of ribosomal protein genes suggests that this backup activation may be important to ensure gene expression when Ifh1p is limiting. With ribosome biogenesis as a hallmark of cell growth, failure to control assembly of ribosomal components leads to several human pathologies. A comprehensive understanding of mechanisms underlying this process is therefore of the essence.

Green Synthesized Silver Nanoparticles-Mediated Cytotoxic Effect in Colorectal Cancer Cells: NF-κB Signal Induced Apoptosis Through Autophagy

Green synthesized silver nanoparticles (Ag-NPs) have demonstrated promising effects, including cytotoxicity and anticancer potential, in different cell lines. Therefore, in our previous study, Ag-NPs were synthesized from the reduction of AgNO₃ using Brassica rapa var. japonica (Bj) leaf extract as a reducing and stabilizing agent. The synthesized Ag-NPs were spherical in shape, with a size range of 15-30 nm. They had phase-centered cubic structure with strong growth inhibition potential against some bacteria. In continuation with our previous study, in the present study, we aimed to investigate the autophagy-regulated cytotoxic effect of Ag-NPs against human epithelial colorectal adenocarcinoma cells (Caco-2 cells). We found that the Bj leaf aqueous extract facilitated Brassica silver nanoparticles (Brassica Ag-NPs)-induced NF-κB mediated autophagy in Caco-2 cells. Results showed that Ag-NPs reduced cell viability of Caco-2 cells by inducing oxidative stress and DNA damage. Therefore, to understand the mechanism underlying the death-promoting activity of Ag-NPs in Caco-2 cells, western blotting was performed. Western blot analysis showed decreased expression of NFκB and increased expression of IκB, which is a sign of autophagy initiation. In addition, autophagosome formation was accelerated by the activity of p53 and light chain 3 (LC3) II. In addition, inhibition of Akt and mTOR also played a pivotal role in autophagy formation. Finally, excessive expansion of autophagy promoted apoptosis, which subsequently resulted in necrosis. These findings support a novel cell death-promoting function of autophagy by Ag-NPs in Caco-2 cells.

Deletion of mTOR in liver epithelial cells enhances hepatic metastasis of colon cancer

Activation of the mechanistic target of rapamycin (mTOR) pathway is frequently found in cancer, but mTOR inhibitors have thus far failed to demonstrate significant antiproliferative efficacy in the majority of cancer types. Besides cancer cell-intrinsic resistance mechanisms, it is conceivable that mTOR inhibitors impact on non-malignant host cells in a manner that ultimately supports resistance of cancer cells. Against this background, we sought to analyze the functional consequences of mTOR inhibition in hepatocytes for the growth of metastatic colon cancer. To this end, we established liver epithelial cell (LEC)-specific knockout (KO) of mTOR (mTOR^LEC ) mice. We used these mice to characterize the growth of colorectal liver metastases with or without partial hepatectomy to model different clinical settings. Although the LEC-specific loss of mTOR remained without effect on metastasis growth in intact liver, partial liver resection resulted in the formation of larger metastases in mTOR^LEC mice compared with wildtype controls. This was accompanied by significantly enhanced inflammatory activity in LEC-specific mTOR KO livers after partial liver resection. Analysis of NF-ĸB target gene expression and immunohistochemistry of p65 displayed a significant activation of NF-ĸB in mTOR^LEC mice, suggesting a functional importance of this pathway for the observed inflammatory phenotype. Taken together, we show an unexpected acceleration of liver metastases upon deletion of mTOR in LECs. Our results support the notion that non-malignant host cells can contribute to resistance against mTOR inhibitors and encourage testing whether anti-inflammatory drugs are able to improve the efficacy of mTOR inhibitors for cancer therapy. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Connectivity Map Analysis of a Single-Cell RNA-Sequencing -Derived Transcriptional Signature of mTOR Signaling

In the connectivity map (CMap) approach to drug repositioning and development, transcriptional signature of disease is constructed by differential gene expression analysis between the diseased tissue or cells and the control. The negative correlation between the transcriptional disease signature and the transcriptional signature of the drug, or a bioactive compound, is assumed to indicate its ability to “reverse” the disease process. A major limitation of traditional CMaP analysis is the use of signatures derived from bulk disease tissues. Since the key driver pathways are most likely dysregulated in only a subset of cells, the “averaged” transcriptional signatures resulting from bulk analysis lack the resolution to effectively identify effective therapeutic agents. The use of single-cell RNA-seq (scRNA-seq) transcriptomic assay facilitates construction of disease signatures that are specific to individual cell types, but methods for using scRNA-seq data in the context of CMaP analysis are lacking. Lymphangioleiomyomatosis (LAM) mutations in TSC1 or TSC2 genes result in the activation of the mTOR complex 1 (mTORC1). The mTORC1 inhibitor Sirolimus is the only FDA-approved drug to treat LAM. Novel therapies for LAM are urgently needed as the disease recurs with discontinuation of the treatment and some patients are insensitive to the drug. We developed methods for constructing disease transcriptional signatures and CMaP analysis using scRNA-seq profiling and applied them in the analysis of scRNA-seq data of lung tissue from naïve and sirolimus-treated LAM patients. New methods successfully implicated mTORC1 inhibitors, including Sirolimus, as capable of reverting the LAM transcriptional signatures. The CMaP analysis mimicking standard bulk-tissue approach failed to detect any connection between the LAM signature and mTORC1 signaling. This indicates that the precise signature derived from scRNA-seq data using our methods is the crucial difference between the success and the failure to identify effective therapeutic treatments in CMaP analysis.

Regulation of Nuclear Factor-KappaB (NF-κB) signaling pathway by non-coding RNAs in cancer: Inhibiting or promoting carcinogenesis?

The nuclear factor-kappaB (NF-κB) signaling pathway is considered as a potential therapeutic target in cancer therapy. It has been well established that transcription factor NF-κB is involved in regulating physiological and pathological events including inflammation, immune response and differentiation. Increasing evidences suggest that deregulated NF-κB signaling can enhance cancer cell proliferation, metastasis and also mediate radio-as well as chemo-resistance. On the contrary, non-coding RNAs (ncRNAs) have been found to modulate NF-κB signaling pathway under different settings. MicroRNAs (miRNAs) can dually inhibit/induce NF-κB signaling thereby affecting the growth and migration of cancer cells. Furthermore, the response of cancer cells to radiotherapy and chemotherapy may also be regulated by miRNAs. Regulation of NF-κB by miRNAs may be mediated via binding to 3^/-UTR region. Interestingly, anti-tumor compounds can increase the expression of tumor-suppressor miRNAs in inhibiting NF-κB activation and the progression of cancers. Long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) can also effectively modulate NF-κB signaling thus affecting tumorigenesis. It is noteworthy that several studies have demonstrated that lncRNAs and circRNAs can affect miRNAs in targeting NF-κB activation. They can act as competing endogenous RNA (ceRNA) thereby reducing miRNA expression to induce NF-κB activation that can in turn promote cancer progression and malignancy.

Upregulation of the pathogenic transcription factor SPI1/PU.1 in tuberous sclerosis complex and focal cortical dysplasia by oxidative stress

Tuberous sclerosis complex (TSC) is a congenital disorder characterized by cortical malformations and concomitant epilepsy caused by loss‐of‐function mutations in the mTOR suppressors TSC1 or TSC2. While the underlying molecular changes caused by mTOR activation in TSC have previously been investigated, the drivers of these transcriptional change have not been fully elucidated. A better understanding of the perturbed transcriptional regulation could lead to the identification of novel pathways for therapeutic intervention not only in TSC, but other genetic epilepsies in which mTOR activation plays a key role, such as focal cortical dysplasia 2b (FCD). Here, we analyzed RNA sequencing data from cortical tubers and a tsc2^−/− zebrafish. We identified differential expression of the transcription factors (TFs) SPI1/PU.1, IRF8, GBX2, and IKZF1 of which SPI1/PU.1 and IRF8 targets were enriched among the differentially expressed genes. Furthermore, for SPI1/PU.1 these findings were conserved in TSC zebrafish model. Next, we confirmed overexpression of SPI1/PU.1 on the RNA and protein level in a separate cohort of surgically resected TSC tubers and FCD tissue, in fetal TSC tissue, and a Tsc1^GFAP−/− mouse model of TSC. Subsequently, we validated the expression of SPI1/PU.1 in dysmorphic cells with mTOR activation in TSC tubers. In fetal TSC, we detected SPI1/PU.1 expression prenatally and elevated RNA Spi1 expression in Tsc1^GFAP−/− mice before the development of seizures. Finally, in vitro, we identified that in astrocytes and neurons SPI1 transcription was driven by H₂O₂‐induced oxidative stress, independent of mTOR. We identified SPI1/PU.1 as a novel TF involved in the pro‐inflammatory gene expression of malformed cells in TSC and FCD 2b. This transcriptional program is activated in response to oxidative stress and already present prenatally. Importantly, SPI1/PU.1 protein appears to be strictly limited to malformed cells, as we did not find SPI1/PU.1 protein expression in mice nor in our in vitro models.

Cell signaling pathways as molecular targets to eliminate AML stem cells

Acute myeloid leukemia (AML) remains the most lethal of leukemias and a small population of cells called leukemic stem cells (LSCs) has been associated with disease relapses. Some cell signaling pathways play an important role in AML survival, proliferation and self-renewal properties and are abnormally activated or suppressed in LSCs. This includes the NF-κB, Wnt/β-catenin, Hedgehog, Notch, EGFR, JAK/STAT, PI3K/AKT/mTOR, TGF/SMAD and PPAR pathways. This review aimed to discuss these pathways as molecular targets for eliminating AML LSCs. Herein, inhibitors/activators of these pathways were summarized as a potential new anti-AML therapy capable of eliminating LSCs to guide future researches. The clinical use of cell signaling pathways data can be useful to enhance the anti-AML therapy.

G3BPs tether the TSC complex to lysosomes and suppress mTORC1 signaling

Ras GTPase-activating protein-binding proteins 1 and 2 (G3BP1 and G3BP2, respectively) are widely recognized as core components of stress granules (SGs). We report that G3BPs reside at the cytoplasmic surface of lysosomes. They act in a non-redundant manner to anchor the tuberous sclerosis complex (TSC) protein complex to lysosomes and suppress activation of the metabolic master regulator mechanistic target of rapamycin complex 1 (mTORC1) by amino acids and insulin. Like the TSC complex, G3BP1 deficiency elicits phenotypes related to mTORC1 hyperactivity. In the context of tumors, low G3BP1 levels enhance mTORC1-driven breast cancer cell motility and correlate with adverse outcomes in patients. Furthermore, G3bp1 inhibition in zebrafish disturbs neuronal development and function, leading to white matter heterotopia and neuronal hyperactivity. Thus, G3BPs are not only core components of SGs but also a key element of lysosomal TSC-mTORC1 signaling.

Overexpression of miR-146a inhibits the apoptosis of hippocampal neurons of rats with cerebral hemorrhage by regulating autophagy

In this study, to investigate the effect of overexpression of miR-146a on autophagy of hippocampal neurons in rats with intracerebral hemorrhage (ICH), 72 Sprague-Dawley rats were randomly divided into the sham, ICH, miR-146a agomir, and miR-146a agomir control groups. The ICH model was constructed by injection of collagenase VII. The apoptosis of hippocampal neurons was measured by TUNEL assay. The levels of LC3 and Beclin 1 were analyzed by immunohistochemistry. Mitochondrial autophagy was examined by transmission electron microscopy. The levels of LC3A, LC3B, Beclin 1, Bax, Bcl-2, and cleaved caspase 3 were examined by Western blot. Western blot was also used to evaluate the expression of nuclear factor κB signaling pathway-related factors. To examine the effect of autophagy inhibitor (3-methyladenine (3-MA)) on miR-146a-regulated apoptotic protein expression, 30 rats were further divided into the sham, ICH, miR-146a agomir, 3-MA, and miR-146a + 3-MA groups. The levels of Bax, Bcl-2, and cleaved caspase 3 were examined by Western blot. Compared with the sham group, the nerve function scores, brain water content, the percentage of apoptotic cells, and the expression levels of LC3, Beclin 1, Bax, cleaved caspase 3, and p-P65 in the hippocampus of rats in the ICH group were all significantly increased (p < 0.05), whereas the expression levels of miR-146a, Bcl-2, and p-IκBα were markedly decreased (p < 0.05). Mitochondrial autophagy was also evident. Furthermore, compared with the ICH group, the results of the abovementioned tests in the miR-146a agomir group were reversed. The overexpression of miR-146a inhibited the autophagy of hippocampal neurons in rats with ICH.

The age-dependent effect of high-dose X-ray radiation on NFκB signaling, structure, and mechanical behavior of the intervertebral disc

Purpose: Ionizing radiation damages tissue and provokes inflammatory responses in multiple organ systems. We investigated the effects of high-dose X-ray radiation on the molecular inflammation and mechanical function of the intervertebral disc (IVD).Methods: Functional spine units (FSUs) containing the vertebrae-IVDs-vertebrae structure extracted from 1-month, 6-month, and 16-month-old NFκB-luciferase reporter mice and from 6-month-old myeloid differentiation factor 88 (MyD88)-null mice. After a preconditioning period in culture, the FSUs were subjected a single dose of ionizing X-ray radiation at 20 Gys, and then NFκB expression was monitored. The IVDs were then subjected to mechanical testing using dynamic compression, glycosaminoglycan (GAG) quantification, and histological analyses.Results: In the 1-month-old FSUs, the NFκB-driven luciferase activity was significantly elevated for 1 day following the exposure to radiation. The 6-month-old FSUs showed increased NFκB activity for 3 days, while the 16-month-old FSUs sustained elevated levels of NFκB activity throughout the 10-day culture period. All irradiated groups showed significant loss of disc height, GAG content, mechanical function and changes in structure. Ablation of MyD88 blunted the radiation-mediated NFκB signaling, and preserved GAG content, and the IVDs' structure and mechanical performance.Conclusions: These results suggest that high-dose radiation affects the IVDs' NFκB-dependent inflammatory processes that subsequently lead to functional deterioration. Blocking the transactivation potential of NFκB via MyD88 ablation preserved the structure and mechanical function of the FSUs. The long-term effects of radiation on IVD homeostasis should be considered in individuals susceptible to occupational and medical exposure.

Combination of targeting CD24 and inhibiting autophagy suppresses the proliferation and enhances the apoptosis of colorectal cancer cells

CD24 can regulate angiogenesis, drug sensitivity and the progression of colorectal cancer (CRC). However, whether CD24 regulates autophagy and apoptosis in CRC cells remains to be fully elucidated. The present study investigated the functional role of the altered expression of CD24 in the autophagy and apoptosis of HCT116 and HT29 human CRC cells. The results revealed lower expression levels of CD24 in HCT116 cells but higher levels in HT29 cells. Inducing the overexpression or the knockdown of CD24 did not affect the viability or spontaneous apoptosis of HCT116 and HT29 cells, respectively. Induction of the overexpression of CD24 significantly decreased the relative expression levels of Beclin‑1, autophagy‑related (Atg)3 and Atg5, and the numbers of microtubule‑associated protein‑1 light chain‑3 (LC3)‑positive puncta, but increased the expression of p62 in HCT116 cells. By contrast, CD24 silencing increased the expression of Beclin‑1, Atg3 and Atg5, and the numbers of LC3‑positive puncta, but decreased the expression of p62 in HT29 cells. Treatment with 3‑methyladenine, or the knockdown of Atg5 by specific small interfering RNA to attenuate autophagy significantly enhanced the viability of CD24‑overexpressing HCT116 cells, but reduced the viability of CD24‑silenced HT29 cells, relative to their controls. As a result, the attenuation of autophagy significantly decreased the frequency of apoptotic CD24‑overexpressing HCT116 cells, but increased the percentages of apoptotic CD24‑silenced HT29 cells. The overexpression of CD24 promoted the activation of nuclear factor (NF)‑κBp65, whereas CD24 silencing attenuated its activation in CRC cells. Inhibition of the activation of NF‑κB enhanced the CD24 overexpression‑induced decrease in autophagy, but attenuated the CD24 silencing‑induced increase in autophagy in CRC cells. Therefore, CD24 inhibited the autophagy of CRC cells, and the combination of targeting CD24 and inhibiting autophagy promoted the apoptosis of CRC cells. Conceivably, these findings may aid in the design of novel therapies for the intervention of CRC.

Krt5+/Krt15+ foregut basal progenitors give rise to cyclooxygenase-2-dependent tumours in response to gastric acid stress

The effective prevention of tumor initiation, especially for potentially inoperable tumors, will be beneficial to obtain an overall higher quality of our health and life. Hence, thorough understanding of the pathophysiological mechanisms of early tumor formation arising from identifiable cellular origins is required to develop efficient preventative and early treatment options for each tumor type. Here, using genetically engineered mouse models, we provide preclinical experimental evidence for a long-standing open question regarding the pathophysiological potential of a microenvironmental and physiological stressor in tumor development, gastric acid-mediated regional microscopic injury in foregut squamous epithelia. This study demonstrates the association of gastric acid stress with Cyclooxygenase-2-dependent tumor formation originating from tumor-competent Krt5⁺/Krt15⁺ foregut basal progenitor cells. Our findings suggest that clinical management of microenvironmental stressor-mediated microscopic injury may be important in delaying tumor initiation from foregut basal progenitor cells expressing pre-existing tumorigenic mutation(s) and genetic alteration(s).

Cellular extrinsic environmental factors contribute to tumour development. Here, the authors show that gastric acid stress stimulates tumour formation from a defined tumour-competent Krt5 + /Krt15 + foregut basal progenitor cell population.

Survival prediction of tuberous sclerosis complex gene variant in patients with advanced non-small-cell lung cancer treated with platinum doublet

Tuberous sclerosis complex (TSC) 1 and 2 function as tumor suppressors by inactivating the mammalian target of rapamycin (mTOR) pathway. Although the effect of platinum on TSC function has been studied, associations between TSC gene variants and survival of cancer patients treated with platinum-based chemotherapy were not evaluated. Genetic variants of TSC1 and TSC2 were identified by next-generation sequencing and selected for further clinical evaluation based on predetermined criteria. Associations of the gene variants with treatment outcomes (progression-free survival, PFS; overall survival, OS) were evaluated in testing and validation sets of patients with advanced non-small-cell lung cancer (NSCLC). Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated with the multivariable Cox model. The TSC1 Met322Thr (rs1073123) variant met the criteria for further analysis in testing and validation sets each containing 183 patients. The median PFS for the 366 patients was 4.9 months. Fifty-three patients (14.5%) had the TSC1 (Met322Thr or Thr322Thr) variant. TSC1 Met322Thr associated with longer PFS in the testing set (HR adjusted for age, gender, smoking habits, Eastern Cooperative Oncology Group performance status, histology, and stage [aHR] and 95% CI: 0.63 and 0.45–0.87, Cox P=0.009), and this was confirmed in the validation set (aHR and 95% CI: 0.58 and 0.36–0.93, Cox P=0.004). However, no association was found between the TSC1 gene variant and OS. These findings suggest that the TSC1 gene variant is an important predictive marker for platinum doublet chemotherapy outcomes in NSCLC patients.

Isoalantolactone inhibits IKKβ kinase activity to interrupt the NF-κB/COX-2-mediated signaling cascade and induces apoptosis regulated by the mitochondrial translocation of cofilin in glioblastoma

Isoalantolactone (IATL), a sesquiterpene lactone compound, possesses many pharmacological and biological activities, but its role in glioblastoma (GBM) treatment is still unknown. The aim of the current study was to investigate the antiglioma effects of IATL and to explore the underlying molecular mechanisms. In the current study, the biological functions of IATL were examined by MTT, cell migration, colony formation, and cell apoptosis assays. Confocal immunofluorescence techniques, chromatin immunoprecipitation, and pull‐down assays were used to explore the precise underlying molecular mechanisms. To examine IATL activity and the molecular mechanisms by which it inhibits glioma growth in vivo, we used a xenograft tumor mouse model. Furthermore, Western blotting was used to confirm the changes in protein expression after IATL treatment. According to the results, IATL inhibited IKKβ phosphorylation, thus inhibiting both the binding of NF‐κB to the cyclooxygenase 2 (COX‐2) promoter and the recruitment of p300 and eventually inhibiting COX‐2 expression. In addition, IATL induced glioma cell apoptosis by promoting the conversion of F‐actin to G‐actin, which in turn activates the cytochrome c (Cyt c) and caspase‐dependent apoptotic pathways. In the animal experiments, IATL reduced the size and weight of glioma tumors in xenograft mice and inhibited the expression of COX‐2 and phosphorylated NF‐κB p65 in the transplanted tumors. In conclusion, the current study indicated that IATL inhibited the expression of COX‐2 through the NF‐κB signaling pathway and induced the apoptosis of glioma cells by increasing actin transformation. These results suggested that IATL could be greatly effective in GBM treatment.

TORC1 regulates the DNA damage checkpoint via checkpoint protein levels

Target of rapamycin complex 1 (TORC1) protein kinase, a master controller of cell growth, is thought to be involved in genome integrity. However, the molecular mechanisms associated with this are unclear. Here, we show that TORC1 inactivation causes decreases in the levels of a wide range of proteins involved in the DNA damage checkpoint (DDC) signaling including Tel1, Mre11, Rad9, Mrc1, and Chk1 in budding yeast. Furthermore, TORC1 inactivation compromised DDC activation, DNA repair, and cell survival after DNA damage. TORC1 inactivation promoted proteasomal degradation of Rad9 and Mre11 in a manner dependent on Skp1-Cullin-F-box protein (SCF). Finally, CDK promoted the degradation of Rad9. This study revealed that TORC1 is essential for genome integrity via the maintenance of DDC signaling.

mTOR Senses Environmental Cues to Shape the Fibroblast-like Synoviocyte Response to Inflammation

Accumulating evidence suggests that metabolic master regulators, including mTOR, regulate adaptive and innate immune responses. Resident mesenchymal tissue components are increasingly recognized as key effector cells in inflammation. Whether mTOR also controls the inflammatory response in fibroblasts is insufficiently studied. Here, we show that TNF signaling co-opts the mTOR pathway to shift synovial fibroblast (FLS) inflammation toward an IFN response. mTOR pathway activation is associated with decreased NF-κB-mediated gene expression (e.g., PTGS2, IL-6, and IL-8) but increased STAT1-dependent gene expression (e.g., CXCL11 and TNFSF13B). We further demonstrate how metabolic inputs, such as amino acids, impinge on TNF-mTORC1 signaling to differentially regulate pro-inflammatory signaling circuits. Our results define a critical role for mTOR in the regulation of the pro-inflammatory response in FLSs and unfold its pathogenic involvement in TNF-driven diseases, such as rheumatoid arthritis (RA).

Downregulation of Pim-2 induces cell cycle arrest in the G0/G1 phase via the p53-non-dependent p21 signaling pathway

Pim-2 is a serine/threonine protein kinase that is highly expressed in various types of cancer, with essential roles in the regulation of signal transduction cascades, which promote cell survival and proliferation. The present study demonstrated that Pim-2 was expressed in cells lines derived from hematopoietic tumors and lung cancer. In vitro, downregulation of Pim-2 by short interfering RNA inhibited proliferation and delayed G₀/G₁ cell cycle progression in K562 leukemia, RPMI-8226 multiple myeloma, and H1299 and A549 non-small cell lung carcinoma cell lines. Furthermore, downregulation of Pim-2 resulted in upregulation of cyclin-dependent kinase (CDK) inhibitor p21, irrespective of the p53 status. In addition, the present study revealed that CDK2 and phosphorylated retinoblastoma (pRb) were significantly downregulated. This finding suggested that inhibition of CDK2 and pRb expression via upregulated p21 was involved in the downregulation of Pim-2-induced G₀/G₁ cell cycle arrest in lung cancer and hematopoietic malignancy cells. These results suggested that Pim-2 may serve a role in hematopoietic tumors, lung cancer proliferation and cell cycle progression by regulating the p21 signaling pathway. Downregulation of Pim-2 decreased cancer cell proliferation. Therefore, Pim-2 may be a potential therapy target in clinical cancer therapy.

Leucine alters immunoglobulin a secretion and inflammatory cytokine expression induced by lipopolysaccharide via the nuclear factor-κB pathway in intestine of chicken embryos

The mammalian target of rapamycin (mTOR) has been shown to be involved in lipopolysaccharide (LPS)-induced immune responses in many mammal cells. Here, we suggest that the mTOR pathway is involved in the intestinal inflammatory responses evoked by LPS treatment in chicken embryos. The intestinal tissue from Specific pathogen free chick embryos was cultured in the presence of LPS for 2 h. Secretory immunoglobulin A (sIgA) concentrations, messenger RNA (mRNA) expression of cytokines, and protein levels of nuclear factor-κB (NF-κB), mitogen-activated protein kinase (MAPK), mTOR and p70 ribosomal S6 kinase (p70S6K) were determined. The results showed that LPS treatment increased sIgA concentrations in a dose-dependent manner. The mRNA levels of interleukine (IL)-6, IL-8, IL-10, tumor necrosis factor-α and Toll-like receptor (TLR) 4 were upregulated by LPS treatment (P<0.05). Lipopolysaccharide increased the phosphorylation of Jun N-terminal kinase (JNK), p38 MAPK and NF-κB (P<0.05) while decreasing the phosphorylation level of mTOR (P<0.05). Supplementation of leucine at doses of 10, 20 and 40 mM dose-dependently decreased sIgA production. Leucine supplementation at 40 mM restored the phosphorylation level of mTOR and p70S6K while suppressing the phosphorylation levels of NF-κB (P<0.05) and partially down-regulating the phosphorylation of p38 MAPK and JNK. The transcription of IL-6 was significantly decreased by leucine supplementation. These results suggested that leucine could alleviate LPS-induced inflammatory responses by down-regulating NF-κB signaling pathway and evoking mTOR/p70S6K signaling pathway, which may involve in the regulation of the intestinal immune system in chicken embryos.

Adenosine Monophosphate-activated Protein Kinase (AMPK) Activators For the Prevention, Treatment and Potential Reversal of Pathological Pain

Pathological pain is an enormous medical problem that places a significant burden on patients and can result from an injury that has long since healed or be due to an unidentifiable cause. Although treatments exist, they often either lack efficacy or have intolerable side effects. More importantly, they do not reverse the changes in the nervous system mediating pathological pain, and thus symptoms often return when therapies are discontinued. Consequently, novel therapies are urgently needed that have both improved efficacy and disease-modifying properties. Here we highlight an emerging target for novel pain therapies, adenosine monophosphate-activated protein kinase (AMPK). AMPK is capable of regulating a variety of cellular processes including protein translation, activity of other kinases, and mitochondrial metabolism, many of which are thought to contribute to pathological pain. Consistent with these properties, preclinical studies show positive, and in some cases disease-modifying effects of either pharmacological activation or genetic regulation of AMPK in models of nerve injury, chemotherapy-induced peripheral neuropathy (CIPN), postsurgical pain, inflammatory pain, and diabetic neuropathy. Given the AMPK-activating ability of metformin, a widely prescribed and well-tolerated drug, these preclinical studies provide a strong rationale for both retrospective and prospective human pain trials with this drug. They also argue for the development of novel AMPK activators, whether orthosteric, allosteric, or modulators of events upstream of the kinase. Together, this review will present the case for AMPK as a novel therapeutic target for pain and will discuss future challenges in the path toward development of AMPK-based pain therapeutics.

mTORC1 Inhibits NF-κB/NFATc1 Signaling and Prevents Osteoclast Precursor Differentiation, In Vitro and In Mice

The mechanistic target of rapamycin complex 1 (mTORC1) is a critical sensor for bone homeostasis and bone formation; however, the role of mTORC1 in osteoclast development and the underlying mechanisms have not yet been fully established. Here, we found that mTORC1 activity declined during osteoclast precursors differentiation in vitro and in vivo. We further targeted deletion of Raptor (mTORC1 key component) or Tsc1 (mTORC1 negative regulator) to constitutively inhibit or activate mTORC1 in osteoclast precursors (monocytes/macrophages), using LyzM-cre mice. Osteoclastic formation was drastically increased in cultures of Raptor deficient bone marrow monocytes/macrophages (BMMs), and Raptor-deficient mice displayed osteopenia with enhanced osteoclastogenesis. Conversely, BMMs lacking Tsc1 exhibited a severe defect in osteoclast-like differentiation and absorptive function, both of which were restored following rapamycin treatment. Importantly, expression of nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) and nuclear factor of activated T cells, cytoplasmic 1 (NFATc1), transcription factors that are essential for osteoclast differentiation was negatively regulated by mTORC1 in osteoclast lineages. These results provide evidence that mTORC1 plays as a critical role as an osteoclastic differentiation-limiting signal and suggest a potential drawback in treating bone loss-related diseases with mTOR inhibitors clinically. © 2017 American Society for Bone and Mineral Research.

miR-130a upregulates mTOR pathway by targeting TSC1 and is transactivated by NF-κB in high-grade serous ovarian carcinoma

Activation of mammalian target of rapamycin (mTOR) signaling pathway is associated with poor prognosis of epithelial ovarian cancer. The TSC1-TSC2 complex is a critical negative regulator of mTOR signaling. Here, we demonstrated that TSC1 was frequently downregulated in high-grade serous ovarian carcinoma (HGSOC) and low TSC1 expression level is associated with advanced tumor stage. We next identified miR-130a to be a negative regulator of TSC1 by targeting its 3'UTR. miR-130a was overexpressed in HGSOC and could drive proliferation and invasion/metastasis of ovarian cancer cells. miR-130a could also attenuate rapamycin/starvation-induced autophagy. Ectopic TSC1 expression could block the effects of miR-130a on cell proliferation, migration and autophagy. Finally, we found that miR-130a expression could be upregulated by inflammatory factors and was transactivated by NF-κB. Therefore, our findings establish a crosstalk between inflammation and mTOR signaling that is mediated by miR-130a, which might have a pivotal role in the initiation and progression of HGSOC.

[Effect of TSC2 gene expression downregulation by lentivirus induced RNA interference on U937 cell line and its mechanism]

目的

研究下调TSC2基因表达对白血病U937细胞系的生物学作用及其对mTOR通路活性的影响。

方法

选择TSC2高表达的U937细胞系，通过慢病毒介导的RNA干扰技术下调TSC2基因表达；采用CCK-8比色法、细胞集落形成实验和流式细胞术检测其对细胞增殖、分化和凋亡的影响；采用Western blot法和实时荧光定量PCR（RQ-PCR）法检测TSC2表达下调对mTOR通路蛋白表达及活性的影响。

结果

TSC2基因表达降低能够促进U937细胞的增殖和集落形成（P<0.05）；能够使U937细胞G₁期[（52.53±3.75）%对（75.10±4.33）%，t=6.829，P=0.002]比例明显降低，G₂/M期[（22.43±1.00）%对（15.47±1.20）%，t=−5.581，P=0.019]、S期[（25.03±4.34）%对（14.33±0.91）%，t=−5.413，P=0.013]比例升高；对细胞分化和细胞凋亡没有明显影响（P>0.05）。TSC2基因表达下调后，mTOR活性升高，磷酸化的4EBP1和S6K1蛋白活性升高，而AKT蛋白活性没有明显变化；与细胞增殖相关的基因cyclin D1、c-myc表达升高，PTEN基因表达升高，P27KIP基因和凋亡相关基因BCL-XL的表达没有明显的改变。

结论

TSC2基因表达下调可以通过调节mTOR通路活性促进白血病细胞的增殖。

Bone Size and Quality Regulation: Concerted Actions of mTOR in Mesenchymal Stromal Cells and Osteoclasts

The bone size and quality, acquired during adolescent growth under the influence of anabolic hormones, growth factors, and nutrients, determine the height and bone stability and forecast osteoporosis risks in late life. Yet bone size and quality control mechanisms remain enigmatic. To study the roles of mammalian target of rapamycin (mTOR) signaling, sensor of growth factors and nutrients, in bone size and quality regulation, we ablated Tsc1, a suppressor of mTOR, in mesenchymal stromal cells (MSCs), monocytes, or their progenies osteoblasts and osteoclasts. mTOR activation in MSCs, but much less in osteoblasts, increased bone width and mass due to MSC hyperproliferation, but decreased bone length and mineral contents due to defective MSC differentiation. mTOR activation promotes bone mineral accretion by inhibiting osteoclast differentiation and activity directly or via coupling with MSCs. Tuberous sclerosis complex patient studies confirmed these findings. Thus, mTOR regulates bone size via MSCs and bone quality by suppressing catabolic activities of osteoclasts.

TNF-α stimulates endothelial palmitic acid transcytosis and promotes insulin resistance

Persistent elevation of plasma TNF-α is a marker of low grade systemic inflammation. Palmitic acid (PA) is the most abundant type of saturated fatty acid in human body. PA is bound with albumin in plasma and could not pass through endothelial barrier freely. Albumin-bound PA has to be transported across monolayer endothelial cells through intracellular transcytosis, but not intercellular diffusion. In the present study, we discovered that TNF-α might stimulate PA transcytosis across cardiac microvascular endothelial cells, which further impaired the insulin-stimulated glucose uptake by cardiomyocytes and promoted insulin resistance. In this process, TNF-α-stimulated endothelial autophagy and NF-κB signaling crosstalk with each other and orchestrate the whole event, ultimately result in increased expression of fatty acid transporter protein 4 (FATP4) in endothelial cells and mediate the increased PA transcytosis across microvascular endothelial cells. Hopefully the present study discovered a novel missing link between low grade systemic inflammation and insulin resistance.

Vascular hyperpermeability as a hallmark of phacomatoses: is the etiology angiogenesis related to or comparable with mechanisms seen in inflammatory pathways? Part II: angiogenesis- and inflammation-related molecular pathways, tumor-associated macrophages, and possible therapeutic implications: a comprehensive review

Phacomatoses are a special group of familial hamartomatous syndromes with unique neurocutaneous manifestations as well as characteristic tumors. Neurofibromatosis type 2 (NF2) and tuberous sclerosis complex (TSC) are representatives of this family. A vestibular schwannoma (VS) and subependymal giant cell tumor (SGCT) are two of the most common intracranial tumors associated with these syndromes, related to NF2 and TSC, respectively. These tumors can present with an obstructive hydrocephalus due to their location adjacent to or in the ventricles. Remarkably, both tumors are also known to have a unique association with elevated protein concentrations in the cerebrospinal fluid (CSF), sometimes in association with a non-obstructive (communicating) hydrocephalus. Of the two, SGCT has been shown to be associated with a predisposition to CSF clotting, causing a debilitating recurrent shunt obstruction. However, the exact relationship between high protein levels and clotting of CSF remains unclear, nor do we understand the precise mechanism of CSF clotting observed in SGCT. Elevated protein levels in the CSF are thought to be caused by increased vascular permeability and dysregulation of the blood-brain barrier. The two presumed underlying pathophysiological processes for that in the context of tumorigenesis are angiogenesis and inflammation. Both these processes are correlated to the phosphatidylinositol-3-kinase/Akt/mammalian target of rapamycin pathway which is tumorigenesis related in many neoplasms and nearly all phacomatoses. In this review, we discuss the influence of angiogenesis and inflammation pathways on vascular permeability in VSs and SGCTs at the phenotypic level as well as their possible genetic and molecular determinants. Part I described the historical perspectives and clinical aspects of the relationship between vascular permeability, abnormal CSF protein levels, clotting of the CSF, and communicating hydrocephalus. Part II hereafter describes the different cellular and molecular pathways involved in angiogenesis and inflammation observed in both tumors and explores the existing metabolic overlap between inflammation and coagulation. Interestingly, while increased angiogenesis can be observed in both tumors, inflammatory processes seem significantly more prominent in SGCT. Both SGCT and VS are characterized by different subgroups of tumor-associated macrophages (TAMs): the pro-inflammatory M1 type is predominating in SGCTs, while the pro-angiogenetic M2 type is predominating in VSs. We suggest that a lack of NF2 protein in VS and a lack of TSC1/TSC2 proteins in SGCT significantly influence this fundamental difference between the two tumor types by changing the dominant TAM type. Since inflammatory reactions and coagulation processes are tightly connected, the pro-inflammatory state of SGCT may also explain the associated tendency for CSF clotting. The underlying cellular and molecular differences observed can potentially serve as an access point for direct therapeutic interventions for tumors that are specific to certain phacomatoses or others that also carry such genetic changes.

Phycocyanin Inhibits Tumorigenic Potential of Pancreatic Cancer Cells: Role of Apoptosis and Autophagy

Pancreatic adenocarcinoma (PDA) is one of the most lethal human malignancies, and unresponsive to current chemotherapies. Here we investigate the therapeutic potential of phycocyanin as an anti-PDA agent in vivo and in vitro. Phycocyanin, a natural product purified from Spirulina, effectively inhibits the pancreatic cancer cell proliferation in vitro and xenograft tumor growth in vivo. Phycocyanin induces G2/M cell cycle arrest, apoptotic and autophagic cell death in PANC-1 cells. Inhibition of autophagy by targeting Beclin 1 using siRNA significantly suppresses cell growth inhibition and death induced by phycocyanin, whereas inhibition of both autophagy and apoptosis rescues phycocyanin-mediated cell death. Mechanistically, cell death induced by phycocyanin is the result of cross-talk among the MAPK, Akt/mTOR/p70S6K and NF-κB pathways. Phycocyanin is able to induce apoptosis of PANC-1 cell by activating p38 and JNK signaling pathways while inhibiting Erk pathway. On the other hand, phycocyanin promotes autophagic cell death by inhibiting PI3/Akt/mTOR signaling pathways. Furthermore, phycocyanin promotes the activation and nuclear translocation of NF-κB, which plays an important role in balancing phycocyanin-mediated apoptosis and autosis. In conclusion, our studies demonstrate that phycocyanin exerts anti-pancreatic cancer activity by inducing apoptotic and autophagic cell death, thereby identifying phycocyanin as a promising anti-pancreatic cancer agent.

Huaier aqueous extract inhibits proliferation and metastasis of tuberous sclerosis complex cell models through downregulation of JAK2/STAT3 and MAPK signaling pathways

Tuberous sclerosis complex (TSC) is a genetic disorder with formation of benign tumors in many different organs. It has attracted increasing attention from researchers to search for therapeutic drugs for TSC patients. Traditional Chinese medicine (TCM) has become an important source for finding antitumor drugs. Trametes robiniophila Μurr. (Huaier) is a kind of officinal fungi in China and has been applied in TCM for approximately 1,600 years. A large number of clinical applications have revealed that Huaier has good antitumor effect. In this study, we have investigated the effects of Huaier aqueous extract on two TSC cell models, including inhibition of proliferation, induction of apoptosis, cell cycle arrest, and anti-metastasis. We demonstrated that Huaier aqueous extract inhibited JAK2/STAT3 and MAPK signaling pathways in a dose-dependent manner. Therefore, based on the low toxicity and the multi-targets of Huaier treatment, Huaier may be a promising therapeutic drug for TSC.

Compensatory Increase of Transglutaminase 2 Is Responsible for Resistance to mTOR Inhibitor Treatment

The mechanistic target of rapamycin complex 1 (mTORC1) plays a crucial role in controlling cell growth and homeostasis. Deregulation of mTOR signaling is frequently observed in some cancers, making it an attractive drug target for cancer therapy. Although mTORC1 inhibitor rapalog-based therapy has shown positive results in various pre-clinical animal cancer studies, tumors rebound upon treatment discontinuation. Moreover, several recent clinical trials showed that the mTORC1 inhibitors rapamycin and rapalog only reduce the capacity for cell proliferation without promoting cell death, consistent with the concept that rapamycin is cytostatic and reduces disease progression but is not cytotoxic. It is imperative that rapamycin-regulated events and additional targets for more effective drug combinations be identified. Here, we report that rapamycin treatment promotes a compensatory increase in transglutaminase 2 (TGM2) levels in mTORC1-driven tumors. TGM2 inhibition potently sensitizes mTORC1-hyperactive cancer cells to rapamycin treatment, and a rapamycin-induced autophagy blockade inhibits the compensatory TGM2 upregulation. More importantly, tumor regression was observed in MCF-7-xenograft tumor-bearing mice treated with both mTORC1 and TGM2 inhibitors compared with those treated with either a single inhibitor or the vehicle control. These results demonstrate a critical role for the compensatory increase in transglutaminase 2 levels in promoting mTORC1 inhibitor resistance and suggest that rational combination therapy may potentially suppress cancer therapy resistance.

Targeting AMPK for the Alleviation of Pathological Pain

Chronic pain is a major clinical problem that is poorly treated with available therapeutics. Adenosine monophosphate-activated protein kinase (AMPK) has recently emerged as a novel target for the treatment of pain with the exciting potential for disease modification. AMPK activators inhibit signaling pathways that are known to promote changes in the function and phenotype of peripheral nociceptive neurons and promote chronic pain. AMPK activators also reduce the excitability of these cells suggesting that AMPK activators may be efficacious for the treatment of chronic pain disorders, like neuropathic pain, where changes in the excitability of nociceptors is thought to be an underlying cause. In agreement with this, AMPK activators have now been shown to alleviate pain in a broad variety of preclinical pain models indicating that this mechanism might be engaged for the treatment of many types of pain in the clinic. A key feature of the effect of AMPK activators in these models is that they can lead to a long-lasting reversal of pain hypersensitivity even long after treatment cessation, indicative of disease modification. Here, we review the evidence supporting AMPK as a novel pain target pointing out opportunities for further discovery that are likely to have an impact on drug discovery efforts centered around potent and specific allosteric activators of AMPK for chronic pain treatment.

Differential IKK/NF-κB Activity Is Mediated by TSC2 through mTORC1 in PTEN-Null Prostate Cancer and Tuberous Sclerosis Complex Tumor Cells

The serine/threonine protein kinase Akt plays a critical role in regulating proliferation, growth, and survival through phosphorylation of different downstream substrates. The mTOR is a key target for Akt to promote tumorigenesis. It has been reported that Akt activates mTOR through phosphorylation and inhibition of the tuberous sclerosis complex (TSC) protein TSC2. Previously, it was demonstrated that mTOR activates IKK/NF-κB signaling by promoting IκB kinase (IKK) activity downstream of Akt in conditions deficient of PTEN. In this study, the mechanistic role of the tumor-suppressor TSC2 was investigated in the regulation of IKK/NF-κB activity in PTEN-null prostate cancer and in TSC2-mutated tumor cells. The results demonstrate that TSC2 inhibits IKK/NF-κB activity downstream of Akt and upstream of mTORC1 in a PTEN-deficient environment. However, TSC2 promotes IKK/NF-κB activity upstream of Akt and mTORC1 in TSC2 mutated tumor cells. These data indicate that TSC2 negatively or positively regulates IKK/NF-κB activity in a context-dependent manner depending on the genetic background.

IMPLICATIONS

This study provides fundamental insight for understanding the molecular details by which TSC2/mTOR regulates NF-κB signaling in different tumors.

The second-generation mTOR kinase inhibitor INK128 exhibits anti-inflammatory activity in lipopolysaccharide-activated RAW 264.7 cells

Cross-talk between the mTOR (mechanistic target of rapamycin) and NF-κB (nuclear factor kappa-B) pathways has been reported to regulate macrophage responses to lipopolysaccharide (LPS). In this study, we aimed to explore the effect of INK128, a second-generation inhibitor of mTOR, on the inflammatory cytokine production in LPS-stimulated RAW 264.7 cells. Our data showed that INK128 strikingly inhibited the phosphorylation of p70S6K, 4E-BP1 and AKTSer473 in both unstimulated and LPS-stimulated cells. Although it increased the phosphorylation levels of inhibitor kappa-B (IκB) in LPS-stimulated cells, INK128 did not significantly change the levels of NF-κB phosphorylation. In addition, LPS-induced expression of IL-1β and IL-6 was markedly suppressed by INK128 at both mRNA and protein levels. However, the expression of Tumor necrosis factor-alpha (TNF-α protein), but not its mRNA level, was suppressed by this reagent. Our results suggest that the mTOR inhibitor INK128 not only regulates the NF-κB signaling but also influences the inflammatory cytokine expression at both transcriptional and translational levels.

TSC1 controls IL-1β expression in macrophages via mTORC1-dependent C/EBPβ pathway

The tuberous sclerosis complex 1 (TSC1) is a tumor suppressor that inhibits the mammalian target of rapamycin (mTOR), which serves as a key regulator of inflammatory responses after bacterial stimulation in monocytes, macrophages, and primary dendritic cells. Previous studies have shown that TSC1 knockout (KO) macrophages produced increased inflammatory responses including tumor necrosis factor-α (TNF-α) and IL-12 to pro-inflammatory stimuli, but whether and how TSC1 regulates pro-IL-1β expression remains unclear. Here using a mouse model in which myeloid lineage-specific deletion of TSC1 leads to constitutive mTORC1 activation, we found that TSC1 deficiency resulted in impaired expression of pro-IL-1β in macrophages following lipopolysaccharide stimulation. Such decreased pro-IL-1β expression in TSC1 KO macrophages was rescued by reducing mTORC1 activity with rapamycin or deletion of mTOR. Rictor deficiency has no detectable effect on pro-IL-1β synthesis, suggesting that TSC1 positively controls pro-IL-1β expression through mTORC1 pathway. Moreover, mechanism studies suggest that mTORC1-mediated downregulation of the CCAAT enhancer-binding protein (C/EBPβ) critically contributes to the defective pro-IL-1β expression. Overall, these findings highlight a critical role of TSC1 in regulating innate immunity by control of the mTOR1-C/EBPβ pathway.

Aberrant nuclear factor-kappa B activity in acute myeloid leukemia: from molecular pathogenesis to therapeutic target

The overall survival of patients with acute myeloid leukemia (AML) has not been improved significantly over the last decade. Molecularly targeted agents hold promise to change the therapeutic landscape in AML. The nuclear factor kappa B (NF-κB) controls a plethora of biological process through switching on and off its long list of target genes. In AML, constitutive NF-κB has been detected in 40% of cases and its aberrant activity enable leukemia cells to evade apoptosis and stimulate proliferation. These facts suggest that NF-κB signaling pathway plays a fundamental role in the development of AML and it represents an attractive target for the intervention of AML. This review summarizes our current knowledge of NF-κB signaling transduction including canonical and non-canonical NF-κB pathways. Then we specifically highlight what factors contribute to the aberrant activation of NF-κB activity in AML, followed by an overview of 8 important clinical trials of the first FDA approved proteasome inhibitor, Bortezomib (Velcade), which is a NF-κB inhibitor too, in combination with other therapeutic agents in patients with AML. Finally, this review discusses the future directions of NF-κB inhibitor in treatment of AML, especially in targeting leukemia stem cells (LSCs).

Mechanism of autophagic regulation in carcinogenesis and cancer therapeutics

Autophagy in cancer is an intensely debated concept in the field of translational research. The dual nature of autophagy implies that it can potentially modulate the pro-survival and pro-death mechanisms in tumor initiation and progression. There is a prospective molecular relationship between defective autophagy and tumorigenesis that involves the accumulation of damaged mitochondria and protein aggregates, which leads to the production of reactive oxygen species (ROS) and ultimately causes DNA damage that can lead to genomic instability. Moreover, autophagy regulates necrosis and is followed by inflammation, which limits tumor metastasis. On the other hand, autophagy provides a survival advantage to detached, dormant metastatic cells through nutrient fueling by tumor-associated stromal cells. Manipulating autophagy for induction of cell death, inhibition of protective autophagy at tissue-and context-dependent for apoptosis modulation has therapeutic implications. This review presents a comprehensive overview of the present state of knowledge regarding autophagy as a new approach to treat cancer.

Targeting aPKC disables oncogenic signaling by both the EGFR and the proinflammatory cytokine TNFα in glioblastoma

Grade IV glioblastoma is characterized by increased kinase activity of epidermal growth factor receptor (EGFR); however, EGFR kinase inhibitors have failed to improve survival in individuals with this cancer because resistance to these drugs often develops. We showed that tumor necrosis factor-α (TNFα) produced in the glioblastoma microenvironment activated atypical protein kinase C (aPKC), thereby producing resistance to EGFR kinase inhibitors. Additionally, we identified that aPKC was required both for paracrine TNFα-dependent activation of the transcription factor nuclear factor κB (NF-κB) and for tumor cell-intrinsic receptor tyrosine kinase signaling. Targeting aPKC decreased tumor growth in mouse models of glioblastoma, including models of EGFR kinase inhibitor-resistant glioblastoma. Furthermore, aPKC abundance and activity were increased in human glioblastoma tumor cells, and high aPKC abundance correlated with poor prognosis. Thus, targeting aPKC might provide an improved molecular approach for glioblastoma therapy.

Therapeutic targeting of autophagy in cancer. Part I: molecular pathways controlling autophagy

Autophagy is a process in which cells can generate energy and building materials, by degradation of redundant and/or damaged organelles and proteins. Especially during conditions of stress, autophagy helps to maintain homeostasis. In addition, autophagy has been shown to influence malignant transformation and cancer progression. The precise molecular events in autophagy are complex and the core autophagic machinery described to date consists of nearly thirty proteins. Apart from these factors that execute the process of autophagy, several signalling pathways are involved in converting internal and external stimuli into an autophagic response. In this review we provide an overview of the signalling pathways that influence autophagy, particularly in cancer cells. We will illustrate that interference with multiple of these signalling pathways can have significant effects on cancer cell survival.

TBK1 regulates prostate cancer dormancy through mTOR inhibition

The mechanisms that regulate hematopoietic stem cell (HSC) dormancy and self-renewal are well established and are largely dependent on signals emanating from the HSC niche. Recently, we found that prostate cancer (PCa) cells target the HSC niche in mouse bone marrow (BM) during metastasis. Little is known, however, as to how the HSC niche may regulate dormancy in cancer cells. In this study, we investigated the effects of TANK binding kinase 1 (TBK1) on PCa dormancy in the BM niche. We found that binding with niche osteoblasts induces the expression of TBK1 in PCa cells PC3 and C4-2B. Interestingly, TBK1 interacts with mammalian target of rapamycin (mTOR) and inhibits its function. Rapamycin, an mTOR inhibitor, induces cell cycle arrest of PCa cells and enhances chemotherapeutic resistance of PCa cells. As a result, the knockdown of TBK1 decreases PCa stem-like cells and drug resistance in vitro and in vivo. Taken together, these results strongly indicate that TBK1 plays an important role in the dormancy and drug resistance of PCa.

Role of AMP-activated protein kinase in cancer therapy

Recent advances in AMP-activated protein kinase (AMPK) as a target in cancer waxed and waned over the past decade of cancer research. AMPK is a cellular energy sensor, present in almost all eukaryotic cells. An elevated AMP/ATP ratio activates the AMPK, which in turn inhibits energy-consuming processes and induces catabolic events that generate ATP to restore the energy homeostasis inside the cell. Several reports have indicated that AMPK regulates several metabolic pathways and may be a potential therapeutic target for the treatment of cancer. Cancer cells have specific metabolic changes that differ from normal cells, and AMPK prevents the deregulated processes in cancer. AMPK may also act to inhibit tumor formation through modulation of cell growth, cell proliferation, autophagy, stress responses, and cell polarity. AMPK has been shown to inhibit mammalian target of rapamycin (mTOR) through tuberous sclerosis complex 2 (TSC2) phosphorylation and phosphatase and tensin homolog (PTEN), considered as central cell growth controller signals in diseases. In response to glucose deprivation, AMPK phosphorylates and activates p53, which induces cell cycle arrest in the G1/S phase of the cell cycle. AMPK has also been reported to block cyclin-dependent kinases through phosphorylation of p27(kip1) , promoting its stabilization and allowing cells to survive metabolic stress via induction of autophagy. Additionally, AMPK induces autophagy by phosphorylation and activation of eEF-2 kinase, and prevents the formation of new proteins. AMPK activators are also used for the treatment of type II diabetes and cancer. This review focuses on AMPK activation and its possible therapeutic role in the treatment of cancer.

Contrasting effects of chronic, systemic treatment with mTOR inhibitors rapamycin and metformin on adult neural progenitors in mice

The chronic and systemic administration of rapamycin extends life span in mammals. Rapamycin is a pharmacological inhibitor of mTOR. Metformin also inhibits mTOR signaling but by activating the upstream kinase AMPK. Here we report the effects of chronic and systemic administration of the two mTOR inhibitors, rapamycin and metformin, on adult neural stem cells of the subventricular region and the dendate gyrus of the mouse hippocampus. While rapamycin decreased the number of neural progenitors, metformin-mediated inhibition of mTOR had no such effect. Adult-born neurons are considered important for cognitive and behavioral health, and may contribute to improved health span. Our results demonstrate that distinct approaches of inhibiting mTOR signaling can have significantly different effects on organ function. These results underscore the importance of screening individual mTOR inhibitors on different organs and physiological processes for potential adverse effects that may compromise health span.

MTOR inhibition attenuates DNA damage and apoptosis through autophagy-mediated suppression of CREB1

Hyperactivation of mechanistic target of rapamycin (MTOR) is a common feature of human cancers, and MTOR inhibitors, such as rapamycin, are thus becoming therapeutics in targeting certain cancers. However, rapamycin has also been found to compromise the efficacy of chemotherapeutics to cells with hyperactive MTOR. Here, we show that loss of TSC2 or PTEN enhanced etoposide-induced DNA damage and apoptosis, which was blunted by suppression of MTOR with either rapamycin or RNA interference. cAMP response element-binding protein 1 (CREB1), a nuclear transcription factor that regulates genes involved in survival and death, was positively regulated by MTOR in mouse embryonic fibroblasts (MEFs) and cancer cell lines. Silencing Creb1 expression with siRNA protected MTOR-hyperactive cells from DNA damage-induced apoptosis. Furthermore, loss of TSC2 or PTEN impaired either etoposide or nutrient starvation-induced autophagy, which in turn, leads to CREB1 hyperactivation. We further elucidated an inverse correlation between autophagy activity and CREB1 activity in the kidney tumor tissue obtained from a TSC patient and the mouse livers with hepatocyte-specific knockout of PTEN. CREB1 induced DNA damage and subsequent apoptosis in response to etoposide in autophagy-defective cells. Reactivation of CREB1 or inhibition of autophagy not only improved the efficacy of rapamycin but also alleviated MTOR inhibition-mediated chemoresistance. Therefore, autophagy suppression of CREB1 may underlie the MTOR inhibition-mediated chemoresistance. We suggest that inhibition of MTOR in combination with CREB1 activation may be used in the treatment of cancer caused by an abnormal PI3K-PTEN-AKT-TSC1/2-MTOR signaling pathway. CREB1 activators should potentiate the efficacy of chemotherapeutics in treatment of these cancers.

AMPK: An emerging target for modification of injury-induced pain plasticity

Chronic pain is a critical medical problem afflicting hundreds of millions of people worldwide with costly effects on society and health care systems. Novel therapeutic avenues for the treatment of pain are needed that are directly targeted to the molecular mechanisms that promote and maintain chronic pain states. Recent evidence suggests that peripheral pain plasticity is promoted and potentially maintained via changes in translation control that are mediated by mTORC1 and MAPK pathways. While these pathways can be targeted individually, stimulating the AMPK pathway with direct or indirect activators achieves inhibition of these pathways via engagement of a single kinase. Here we review the form, function and pharmacology of AMPK with special attention to its emerging role as a potential target for pain therapeutics. We present the existing evidence supporting a role of AMPK activation in alleviating symptoms of peripheral nerve injury- and incision-induced pain plasticity and the blockade of the development of chronic pain following surgery. We argue that these preclinical findings support a strong rationale for clinical trials of currently available AMPK activators and further development of novel pharmacological strategies for more potent and efficacious manipulation of AMPK in the clinical setting. Finally, we posit that AMPK represents a unique opportunity for drug development in the kinase area for pain because it is pharmacologically manipulated via activation rather than inhibition potentially offering a wider therapeutic window with interesting additional pharmacological opportunities. Altogether, the physiology, pharmacology and therapeutic opportunities surrounding AMPK make it an attractive target for novel intervention for chronic pain and its prevention.