Riding up the escaLEC-TOR for valvular health.

Endothelial-lined valves assure unidirectional flow in the lymphatic system. In this issue, Saygili Demir et al. (2023. J. Cell Biol.https://doi.org/10.1083/jcb.202207049) demonstrate how continuous repair of these valves occur, beginning with mTOR-activated cell replication in valve sinuses, and followed by cell migration to cover the valve surface.

CD4 T cell-intrinsic STING signaling controls the differentiation and effector functions of TH1 and TH9 cells.

BACKGROUND: While stimulator of interferon genes (STING) activation in innate immune cells of the tumor microenvironment can result in CD8 T cell-dependent antitumor immunity, whether STING signaling affects CD4 T-cell responses remains elusive. METHODS: Here, we tested whether STING activation modulated the effector functions of CD4 T cells in vivo by analyzing tumor-infiltrating CD4 T cells and evaluating the contribution of the CD4 T cell-derived cytokines in the antitumor activity of the STING ligand 2'3'-cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) in two mouse tumor models. We performed ex vivo experiments to assess the impact of STING activation on CD4 T-cell differentiation and investigate the underlying molecular mechanisms. Finally, we tested whether STING activation enhances TH9 cell antitumor activity against mouse melanoma upon adoptive transfer. RESULTS: We found that activation of STING signaling cell-intrinsically enhances the differentiation and antitumor functions of TH1 and TH9 cells by increasing their respective production of interferon gamma (IFN-γ) and interleukin-9. IRF3 and type I interferon receptors (IFNARs) are required for the STING-driven enhancement of TH1 cell differentiation. However, STING activation favors TH9 cell differentiation independently of the IFNARs/IRF3 pathway but through mammalian target of rapamycin (mTOR) signaling, underscoring that STING activation differentially affects the fate of distinct CD4 T-cell subsets. The therapeutic effect of STING activation relies on TH1 and TH9-derived cytokines, and STING activation enhances the antitumor activity of TH9 cells upon adoptive transfer. CONCLUSION: Our results reveal the STING signaling pathway as a therapeutic target to boost CD4 T-cell effector functions and antitumor immunity.

Loss of ARID1A activates mTOR signaling and SOX9 in gastric adenocarcinoma-rationale for targeting ARID1A deficiency.

BACKGROUND: Gastric adenocarcinoma (GAC) is a lethal disease with limited therapeutic options. Genetic alterations in chromatin remodelling gene AT-rich interactive domain 1A (ARID1A) and mTOR pathway activation occur frequently in GAC. Targeting the mechanistic target of rapamycin (mTOR) pathway in unselected patients has failed to show survival benefit. A deeper understanding of GAC might identify a subset that can benefit from mTOR inhibition. METHODS: Genomic alterations in ARID1A were analysed in GAC. Mouse gastric epithelial cells from CK19-Cre-Arid1Afl/fl and wild-type mice were used to determine the activation of oncogenic genes due to loss of Arid1A. Functional studies were performed to determine the significance of loss of ARID1A and the sensitivity of ARID1A-deficient cancer cells to mTOR inhibition in GAC. RESULTS: More than 30% of GAC cases had alterations (mutations or deletions) of ARID1A and ARID1A expression was negatively associated with phosphorylation of S6 and SOX9 in GAC tissues and patient-derived xenografts (PDXs). Activation of mTOR signalling (increased pS6) and SOX9 nuclear expression were strongly increased in Arid1A-/- mouse gastric tissues which could be curtailed by RAD001, an mTOR inhibitor. Knockdown of ARID1A in GAC cell lines increased pS6 and nuclear SOX9 and increased sensitivity to an mTOR inhibitor which was further amplified by its combination with fluorouracil both in vitro and in vivo in PDXs. CONCLUSIONS: The loss of ARID1A activates pS6 and SOX9 in GAC, which can be effectively targeted by an mTOR inhibitor. Therefore, our studies suggest a new therapeutic strategy of clinically targeting the mTOR pathway in patients with GAC with ARID1A deficiency.

Small activating RNA-activated NIS gene promotes 131I uptake and inhibits thyroid cancer via AMPK/mTOR pathway.

BACKGROUND: Sodium/iodide symporter (NIS) acts as a vital role in regulation of iodide uptake in thyroid cancer. However, the efficient approach to increase NIS expression and the mechanism of NIS-mediated iodide uptake in thyroid cancer remain unclear. METHODS: Small activating RNA (saRNA) was used to promote NIS expression. And the cell viability, apoptosis, and autophagy were detected using Cell count-kit 8 (CCK-8), Annexin V-FITC/PI double staining, and GFP-LC3 immunofluorescence assays, respectively. The protein levels of caspase 3, Bax, Bcl-2, ATG5, ATG12, LC3B Ⅱ to LC3B Ⅰ, Beclin 1, P62, AMPK, mTOR, P70S6K, actin, and phosphorylation of AMPK, mTOR, P70S6K were determined by western blotting. Moreover, a nude murine node with transplanted NC-dsRNA or NIS-482-transfected SW579 cells was used to examine the effect of NIS-mediated autophagy in vivo. And the levels of caspase 3 and ki67 were examined by immunohistochemical staining assay. RESULTS: saRNA mediated NIS mRNA and protein upregulated in SW579 cells. saRNA-mediated NIS expression inhibited cell proliferation, induced apoptosis and autophagy, and promoted iodide uptake in SW579 cells. Moreover, the effects of NIS on cells were enhanced by autophagy activator Rapamycin whereas reversed by autophagy inhibitor 3-Methyladenine (3-MA). For mechanism analysis, we found that NIS upregulation exerted the effects on cell proliferation, apoptosis, autophagy, and iodide uptake via regulating AMPK/mTOR pathway. We also demonstrated that saRNA-mediated NIS expression promoted iodide uptake in vivo. CONCLUSION: saRNA-mediated NIS expression acted as a critical role in increasing iodide uptake via AMPK/mTOR pathway in thyroid cancer.

Hsa_circ_0007059 sponges miR-421 to repress cell growth and stemness in hepatocellular carcinoma by the PTEN-AKT/mTOR pathway.

BACKGROUND: Hepatocellular carcinoma (HCC) is a substantial health concern worldwide. Increasing studies have suggested that circle RNAs (circRNAs) function as new regulators in HCC progression. The present work explored the role of hsa_circ_0007059 (circ_0007059) in the developing process of hepatocarcinogenesis. METHODS: The circ_0007059 level in HCC was determined by reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) and northern blot. Its biological role in HCC cells was assessed using 3-(4,5-Dimethylthiazol-2-yl)- 2,5-diphenyltetrazolium bromide (MTT), colony formation, flow cytometry, Transwell, sphere formation and western blotting analyses. Bioinformatics analysis, luciferase reporter, and RNA immunoprecipitation (RIP) assays were used to test the regulatory mechanisms of circ_0007059. RESULTS: Our results revealed that circ_0007059 expression was downregulated in HCC samples and cells. Moreover, circ_0007059 overexpression inhibited HCC cell proliferation, migration, invasion, and stem cell-like property, and strengthened cell apoptosis. In mechanism, circ_0007059 suppressed AKT/mTOR pathway by positively regulating phosphatase and tensin homolog (PTEN) expression. Additionally, circ_0007059 acted as a positive regulator of PTEN through controlling the availability of miR-421. Rescue assays demonstrated that PTEN knockdown or SC79 (AKT agonist) eliminated the effect of circ_0007059 on HCC cell phenotypes. CONCLUSION: Circ_0007059 sponges miR-421 to inhibit oncogenic cellular process in HCC by mediating the PTEN-AKT/mTOR pathway.

Screening for Active Compounds Targeting Human Natural Killer Cell Activation Identifying Daphnetin as an Enhancer for IFN-γ Production and Direct Cytotoxicity.

Natural killer (NK) cells are a potent weapon against tumor and viral infection. Finding active compounds with the capacity of enhancing NK cell effector functions will be effective to develop new anti-cancer drugs. In this study, we initially screened 287 commercially available active compounds by co-culturing with peripheral blood mononuclear cells (PBMCs). We found that five compounds, namely, Daphnetin, MK-8617, LW6, JIB-04, and IOX1, increased the IFN-γ+ NK cell ratio in the presence of IL-12. Further studies using purified human primary NK cells revealed that Daphnetin directly promoted NK cell IFN-γ production in the presence of IL-12 but not IL-15, while the other four compounds acted on NK cells indirectly. Daphnetin also improved the direct cytotoxicity of NK cells against tumor cells in the presence of IL-12. Through RNA-sequencing, we found that PI3K-Akt-mTOR signaling acted as a central pathway in Daphnetin-mediated NK cell activation in the presence of IL-12. This was further confirmed by the finding that both inhibitors of PI3K-Akt and its main downstream signaling mTOR, LY294002, and rapamycin, respectively, can reverse the increase of IFN-γ production and cytotoxicity in NK cells promoted by Daphnetin. Collectively, we identify a natural product, Daphnetin, with the capacity of promoting human NK cell activation via PI3K-Akt-mTOR signaling in the presence of IL-12. Our current study opens up a new potential application for Daphnetin as a complementary immunomodulator for cancer treatments.

Sanse Powder Essential Oil Nanoemulsion Negatively Regulates TRPA1 by AMPK/mTOR Signaling in Synovitis: Knee Osteoarthritis Rat Model and Fibroblast-Like Synoviocyte Isolates.

Synovitis is the primary driving factor for the occurrence and development of knee osteoarthritis (KOA) and fibroblast-like synoviocytes (FLSs) and plays a crucial role during this process. Our previous works revealed that transient receptor potential ankyrin 1 (TRPA1) ion channels mediate the amplification of KOA synovitis. In recent years, essential oils have been proved to have blocking effect on transient receptor potential channels. Meanwhile, the therapeutic effect of Sanse Powder on KOA synovitis has been confirmed in clinical trials and basic studies; although, the mechanism remains unclear. In the present study, Sanse Powder essential oil nanoemulsion (SP-NEs) was prepared, and then chemical composition, physicochemical properties, and stability were investigated. Besides, both in MIA-induced KOA rats and in LPS-stimulated FLSs, we investigated whether SP-NES could alleviate KOA synovitis by interfering with AMP-activated protein kinase- (AMPK-) mammalian target of rapamycin (mTOR), an energy sensing pathway proved to negatively regulate the TRPA1. Our research shows that the top three substances in SP-NEs were tumerone, delta-cadinene, and Ar-tumerone, which accounted for 51.62% of the total, and should be considered as the main pharmacodynamic ingredient. Less inflammatory cell infiltration and type I collagen deposition were found in the synovial tissue of KOA rats treated with SP-NEs, as well as the downregulated expressions of interleukin (IL)-1ß, IL-18, and TRPA1. Besides, SP-NEs increased the phosphorylation level of AMPK and decreased the phosphorylation level of mTOR in the KOA model, and SP-NEs also upregulated expressions of peroxisome proliferator-activated receptor-gamma (PPARγ) and PPARγ coactivator-1α and downstream signaling molecules of AMPK-mTOR in vivo and in vitro. To conclude, a kind of Chinese herbal medicine for external use which is effective in treating synovitis of KOA was extracted and prepared into essential oil nanoemulsion with stable properties in the present study. It may alleviate synovitis in experimental KOA through the negative regulation of TRPA1 by AMPK-mTOR signaling.

Slit2-Mediated Metabolic Reprogramming in Bone Marrow-Derived Macrophages Enhances Antitumor Immunity.

Slit2 exerts antitumor effects in various cancers; however, the underlying mechanism, especially its role in regulating the immune, especially in the bone marrow niche, system is still unknown. Elucidating the behavior of macrophages in tumor progression can potentially improve immunotherapy. Using a spontaneous mammary tumor virus promoter-polyoma middle T antigen (PyMT) breast cancer mouse model, we observed that Slit2 increased the abundance of antitumor M1 macrophage in the bone marrow upon differentiation in vitro. Moreover, myeloablated PyMT mice injected with Slit2-treated bone marrow allografts showed a marked reduction in tumor growth, with enhanced recruitment of M1 macrophage in their tumor stroma. Mechanistic studies revealed that Slit2 significantly enhanced glycolysis and reduced fatty acid oxidation in bone marrow-derived macrophages (BMDMs). Slit2 treatment also altered mitochondrial respiration metabolites in macrophages isolated from healthy human blood that were treated with plasma from breast cancer patients. Overall, this study, for the first time, shows that Slit2 increases BMDM polarization toward antitumor phenotype by modulating immune-metabolism. Furthermore, this study provides evidence that soluble Slit2 could be developed as novel therapeutic strategy to enhance antitumor immune response.

Tumor-derived microparticles promote the progression of triple-negative breast cancer via PD-L1-associated immune suppression.

Membrane vesicles, including exosomes and microparticles (MPs), serve to package and transfer the cellular cargo during inter/extracellular communication, which is of great interest in cancer development, especially in the dissemination of signal transduction-associated traits from donor cells to recipient cells. Although increasing evidence suggests that microparticles (MPs) contribute to the development of cancer, their unique characteristics remain to be exploited. Here, we examined the secretion of MPs in tumor tissues from triple-negative breast cancer (TNBC) patients and found that the tumor cells could release MPs loaded with immune checkpoint molecular programmed cell death ligand 1 (PD-L1), especially in patients treated with traditional clinical interventions, such as chemotherapy and radiotherapy. These PD-L1-loading MPs contribute to the suppressive immune microenvironment, eventually resulting in the tumor progression in TNBC. Mechanically, we proved that PD-L1-loading MPs could suppress the activation and function of functional cluster of differentiation CD8+ T cells. Meanwhile, the PD-L1-loading MPs could mediate the differentiation of macrophages toward the immune-suppressive M2 phenotype via the activation of the TANK-binding kinase 1 (TBK1)/signal transducer and activator of transcription 6 (STAT6) signal and suppression of the serine-threonine kinase (AKT)/mammalian target of rapamycin (mTOR) signal. Given the increasing MP production induced by traditional clinical interventions, we further combined chemotherapy with the PD-L1 inhibitor atezolizumab (ATZ) to efficiently abrogate the immunosuppression caused by the PD-L1-loading MPs. Therefore, our study unveils the mechanism by which tumor cells systemically evade immune surveillance by releasing the PD-L1-loading MPs, and provides new insights into clinical TNBC immunotherapy.

Restoration of Parkinson's Disease-Like Deficits by Activating Autophagy through mTOR-Dependent and mTOR-Independent Mechanisms in Pharmacological and Transgenic Models of Parkinson's Disease in Mice.

We studied the possibilities of inhibition of neurodegeneration in MPTP-induced model of Parkinson's disease (PD) in C57Bl/6J mice and transgenic model of early PD stage (5-monthold B6.Cg-Tg(Prnp-SNCA*A53T)23Mkle/J mice) by autophagy activation through mTOR-dependent and mTOR-independent pathways with rapamycin and trehalose, respectively. Therapy with autophagy inducers in a "postponed" mode (7 days after MPTP intoxication) restored the expression of the dopaminergic neuron marker tyrosine hydroxylase and markedly improved cognitive function in the conditioned passive avoidance response (CPAR; fear memory). The transgenic model also showed an increase in the expression of tyrosine hydroxylase in the nigrostriatal system of the brain. An enhanced therapeutic effect of the combined treatment with the drugs was revealed on the expression of tyrosine hydroxylase, but not in the CPAR test. Thus, activation of both pathways of autophagy regulation in PD models with weakened neuroinflammation can restore the dopaminergic function of neurons and cognitive activity in mice.

Dual mTORC1/2 inhibitor AZD2014 diminishes myeloid-derived suppressor cells accumulation in ovarian cancer and delays tumor growth.

Mechanistic target of rapamycin (mTOR) forms two distinct complexes, mTOR complex 1 (mTORC1) and mTORC2. Here we investigated the antitumor effect of dual mTORC1/2 inhibitor AZD2014 on epithelial ovarian cancer (EOC) and its potential effect on immunosuppressive myeloid-derived suppressor cells (MDSCs). Immunohistochemical analysis of mTORC1 and mTORC2 was performed on a human ovarian cancer tissue microarray. High mTORC2 expression level was associated with shorter survival in EOC, whereas mTORC1 was not correlate with patients' prognosis. AZD2014 suppressed mTOR signaling pathway in ovarian cancer cells, inhibited proliferation and induced G1-phase cell cycle arrest and apoptosis. In tumor-bearing mice, AZD2014 treatment limited tumor growth, reduced peritoneal ascites, and prolonged survival. AZD2014 specifically reduced MDSCs migration and accumulation in EOC peritoneal fluid but not in the spleen. Moreover, subsequent AZD2014 treatment after cisplatin chemotherapy delayed EOC recurrence. Collectively, we observed that high mTORC2 expression level in EOC indicated a poor prognosis. Remarkably, in tumor-bearing mice, AZD2014 diminished MDSC accumulation and delayed tumor growth and recurrence.

Metformin Increases Protein Phosphatase 2A Activity in Primary Human Skeletal Muscle Cells Derived from Lean Healthy Participants.

OBJECTIVE: To investigate if PP2A plays a role in metformin-induced insulin sensitivity improvement in human skeletal muscle cells. Participants. Eight lean insulin-sensitive nondiabetic participants (4 females and 4 males; age: 21.0 ± 1.0 years; BMI: 22.0 ± 0.7 kg/m2; 2-hour OGTT: 97.0 ± 6.0 mg/dl; HbA1c: 5.3 ± 0.1%; fasting plasma glucose: 87.0 ± 2.0 mg/dl; M value; 11.0 ± 1.0 mg/kgBW/min). DESIGN: A hyperinsulinemic-euglycemic clamp was performed to assess insulin sensitivity in human subjects, and skeletal muscle biopsy samples were obtained. Primary human skeletal muscle cells (shown to retain metabolic characteristics of donors) were cultured from these muscle biopsies that included 8 lean insulin-sensitive participants. Cultured cells were expanded, differentiated into myotubes, and treated with 50 µM metformin for 24 hours before harvesting. PP2Ac activity was measured by a phosphatase activity assay kit (Millipore) according to the manufacturer's protocol. RESULTS: The results indicated that metformin significantly increased the activity of PP2A in the myotubes for all 8 lean insulin-sensitive nondiabetic participants, and the average fold increase is 1.54 ± 0.11 (P < 0.001). CONCLUSIONS: These results provided the first evidence that metformin can activate PP2A in human skeletal muscle cells derived from lean healthy insulin-sensitive participants and may help to understand metformin's action in skeletal muscle in humans.

Contributions of TOR Signaling on Photosynthesis.

The target of rapamycin (TOR) protein kinase is an atypical Ser/Thr protein kinase and evolutionally conserved among yeasts, plants, and mammals. TOR has been established as a central hub for integrating nutrient, energy, hormone, and environmental signals in all the eukaryotes. Despite the conserved functions across eukaryotes, recent research has shed light on the multifaceted roles of TOR signaling in plant-specific functional and mechanistic features. One of the most specific features is the involvement of TOR in plant photosynthesis. The recent development of tools for the functional analysis of plant TOR has helped to uncover the involvement of TOR signaling in several steps preceding photoautotrophy and maintenance of photosynthesis. Here, we present recent novel findings relating to TOR signaling and its roles in regulating plant photosynthesis, including carbon nutrient sense, light absorptions, and leaf and chloroplast development. We also provide some gaps in our understanding of TOR function in photosynthesis that need to be addressed in the future.

Allosteric Modulation of GSK-3ß as a New Therapeutic Approach in Limb Girdle Muscular Dystrophy R1 Calpain 3-Related.

Limb-girdle muscular dystrophy R1 calpain 3-related (LGMDR1) is an autosomal recessive muscular dystrophy produced by mutations in the CAPN3 gene. It is a rare disease and there is no cure or treatment for the disease while the pathophysiological mechanism by which the absence of calpain 3 provokes the dystrophy in muscles is not clear. However, key proteins implicated in Wnt and mTOR signaling pathways, which regulate muscle homeostasis, showed a considerable reduction in their expression and in their phosphorylation in LGMDR1 patients' muscles. Finally, the administration of tideglusib and VP0.7, ATP non-competitive inhibitors of glycogen synthase kinase 3ß (GSK-3ß), restore the expression and phosphorylation of these proteins in LGMDR1 cells, opening the possibility of their use as therapeutic options.

Oncogenic Mutations in PI3K/AKT/mTOR Pathway Effectors Associate with Worse Prognosis in BRAFV600E -Driven Papillary Thyroid Cancer Patients.

PURPOSE: The extent to which routine genomic sequencing can identify relevant secondary genomic alterations among BRAFV600E -mutant papillary thyroid carcinoma (PTC) is unknown. Such markers would prove highly valuable for prognostic purposes. EXPERIMENTAL DESIGN: We reviewed clinicopathologic data of 225 patients with BRAFV600E -mutant PTC and integrated them with genomic data derived from targeted next-generation sequencing (NGS) on tumor specimens. We defined patient subgroups based on bona fide secondary oncogenic events (separate from BRAFV600E ) and compared their clinical features and outcomes with those without additional oncogenic alterations. RESULTS: Additional oncogenic alterations were identified in 16% of tumors. Patients in the "BRAF+additional mutations" group were more likely to be at high American Thyroid Association (ATA) risk of recurrence (48.6% vs. 17.6%; P = 0.0009), had larger baseline tumor (2.7 vs. 1.9 cm; P = 0.0005) and more advanced stage at presentation (14.3% vs. 1.1% stage 4; P < 0.0001). Importantly, over a 65-month follow-up, disease-specific mortality (DSM) was increased when additional mutations were identified (13.8% vs. 1.4% in the BRAF-only group; P = 0.005). Separately, we identified a subcluster of patients harboring oncogenic mutations in key effectors of the PI3K/AKT/mTOR pathway, which were independently associated with DSM (OR = 47.9; 95% confidence interval, 3.5-1,246.5; P = 0.0043). CONCLUSIONS: Identification of additional PIK3/AKT/mTOR alterations in patients with BRAFV600E -mutant PTC provides important and actionable prognostic risk stratification. These data support genomic profiling of PTC tumors to inform prognosis and clinical strategy.

mTOR Signaling in Metabolic Stress Adaptation.

The mechanistic target of rapamycin (mTOR) is a central regulator of cellular homeostasis that integrates environmental and nutrient signals to control cell growth and survival. Over the past two decades, extensive studies of mTOR have implicated the importance of this protein complex in regulating a broad range of metabolic functions, as well as its role in the progression of various human diseases. Recently, mTOR has emerged as a key signaling molecule in regulating animal entry into a hypometabolic state as a survival strategy in response to environmental stress. Here, we review current knowledge of the role that mTOR plays in contributing to natural hypometabolic states such as hibernation, estivation, hypoxia/anoxia tolerance, and dauer diapause. Studies across a diverse range of animal species reveal that mTOR exhibits unique regulatory patterns in an environmental stressor-dependent manner. We discuss how key signaling proteins within the mTOR signaling pathways are regulated in different animal models of stress, and describe how each of these regulations uniquely contribute to promoting animal survival in a hypometabolic state.

p38-MAPK-mediated translation regulation during early blastocyst development is required for primitive endoderm differentiation in mice.

Successful specification of the two mouse blastocyst inner cell mass (ICM) lineages (the primitive endoderm (PrE) and epiblast) is a prerequisite for continued development and requires active fibroblast growth factor 4 (FGF4) signaling. Previously, we identified a role for p38 mitogen-activated protein kinases (p38-MAPKs) during PrE differentiation, but the underlying mechanisms have remained unresolved. Here, we report an early blastocyst window of p38-MAPK activity that is required to regulate ribosome-related gene expression, rRNA precursor processing, polysome formation and protein translation. We show that p38-MAPK inhibition-induced PrE phenotypes can be partially rescued by activating the translational regulator mTOR. However, similar PrE phenotypes associated with extracellular signal-regulated kinase (ERK) pathway inhibition targeting active FGF4 signaling are not affected by mTOR activation. These data indicate a specific role for p38-MAPKs in providing a permissive translational environment during mouse blastocyst PrE differentiation that is distinct from classically reported FGF4-based mechanisms.

Akt3-mTOR regulates hippocampal neurogenesis in adult mouse.

Akt signaling has been associated with adult neurogenesis in the hippocampal dentate gyrus (DG). We reported cognitive dysfunction in Akt3 knockout (Akt3-KO) mice with the down-regulation of mTOR activation. However, little is known about the effects of Akt3 signaling on hippocampal neurogenesis. Herein, we show that progenitor cells, neuroblasts, and mature newborn neurons in hippocampal DG expressed Akt3 protein. The Akt3 phosphorylation in hippocampal DG was increased after voluntary wheel running for 7 days in wild-type mice (running WT mice), but not in Akt3-KO mice (running Akt3-KO mice). Subsequently, we observed that the proliferation of progenitor cells was suppressed in Akt3-KO mice and the mTOR inhibitor rapamycin-treated mice, whereas enhanced in running WT mice rather than running Akt3-KO mice. Neurite growth of neuroblasts was impaired in Akt3-KO mice and rapamycin-treated mice. In contrast, neither differentiation of progenitor cells nor migrating of newly generated neurons was altered in Akt3-KO mice or running WT mice. The levels of p70S6K and 4EBP1 phosphorylation were declined in Akt3-KO mice and elevated in running WT mice depending on mTOR activation. Furthermore, telomerase activity, telomere length, and expression of telomerase reverse transcriptase (TERT) were decreased in Akt3-KO mice but increased in running WT mice rather than running Akt3-KO mice, which required the mTOR activation. The study provides in vivo evidence that Akt3-mTOR signaling plays an important role in the proliferation of progenitor cells and neurite growth through positive regulated TERT expression and activation of p70S6K and 4EBP1.

Organ-specific cholesterol metabolic aberration fuels liver metastasis of colorectal cancer.

Rationale: Metastasis, the development of secondary malignant growth at a distance from a primary tumor, is the main cause of cancer-associated death. However, little is known about how metastatic cancer cells adapt to and colonize in the new organ environment. Here we sought to investigate the functional mechanism of cholesterol metabolic aberration in colorectal carcinoma (CRC) liver metastasis. Methods: The expression of cholesterol metabolism-related genes in primary colorectal tumors (PT) and paired liver metastases (LM) were examined by RT-PCR. The role of SREBP2-dependent cholesterol biosynthesis pathway in cell growth and CRC liver metastasis were determined by SREBP2 silencing in CRC cell lines and experimental metastasis models including, intra-splenic injection models and liver orthotropic injection model. Growth factors treatment and co-culture experiment were performed to reveal the mechanism underlying the up-regulation of SREBP2 in CRC liver metastases. The in vivo efficacy of inhibition of cholesterol biosynthesis pathway by betulin or simvastatin were evaluated in experimental metastasis models. Results: In the present study, we identify a colorectal cancer (CRC) liver metastasis-specific cholesterol metabolic pathway involving the activation of SREBP2-dependent cholesterol biosynthesis, which is required for the colonization and growth of metastatic CRC cells in the liver. Inhibiting this cholesterol biosynthesis pathway suppresses CRC liver metastasis. Mechanically, hepatocyte growth factor (HGF) from liver environment activates SREBP2-dependent cholesterol biosynthesis pathway by activating c-Met/PI3K/AKT/mTOR axis in CRC cells. Conclusion: Our findings support the notion that CRC liver metastases show a specific cholesterol metabolic aberration. Targeting this cholesterol biosynthesis pathway could be a promising treatment for CRC liver metastasis.

mTOR deletion in neural crest cells disrupts cardiac outflow tract remodeling and causes a spectrum of cardiac defects through the mTORC1 pathway.

A critical cell type participating in cardiac outflow tract development is a subpopulation of the neural crest cells, the cardiac neural crest cells (NCCs), whose defect causes a spectrum of cardiovascular abnormalities. Accumulating evidence indicates that mTOR, which belongs to the PI3K-related kinase family and impacts multiple signaling pathways in a variety of contexts, plays a pivotal role for NCC development. Here, we investigated functional roles of mTOR for cardiac neural crest development using several lines of mouse genetic models. We found that disruption of mTOR caused NCC defects and failure of cardiac outflow tract separation, which resulted in a spectrum of cardiac defects including persistent truncus arteriosus, ventricular septal defect and ventricular wall defect. Specifically, mutant neural crest cells showed reduced migration into the cardiac OFT and prematurely exited the cell cycle. A number of critical factors and fundamental signaling pathways, which are important for neural crest and cardiomyocyte development, were impaired. Moreover, actin dynamics was disrupted by mTOR deletion. Finally, by phenotyping the neural crest Rptor and Rictor knockout mice respectively, we demonstrate that mTOR acts principally through the mTORC1 pathway for cardiac neural crest cells. Altogether, these data established essential roles of mTOR for cardiac NCC development and imply that dysregulation of mTOR in NCCs may underline a spectrum of cardiac defects.