mTOR controls cell cycle progression through its cell growth effectors S6K1 and 4E-BP1/eukaryotic translation initiation factor 4E

Proteomic Analysis of Breast Cancer Resistance to the Anticancer Drug RH1 Reveals the Importance of Cancer Stem Cells

Antitumor drug resistance remains a major challenge in cancer chemotherapy. Here we investigated the mechanism of acquired resistance to a novel anticancer agent RH1 designed to be activated in cancer cells by the NQO1 enzyme. Data show that in some cancer cells RH1 may act in an NQO1-independent way. Differential proteomic analysis of breast cancer cells with acquired resistance to RH1 revealed changes in cell energy, amino acid metabolism and G2/M cell cycle transition regulation. Analysis of phosphoproteomics and protein kinase activity by multiplexed kinase inhibitor beads showed an increase in the activity of protein kinases involved in the cell cycle and stemness regulation and downregulation of proapoptotic kinases such as JNK in RH1-resistant cells. Suppression of JNK leads to the increase of cancer cell resistance to RH1. Moreover, resistant cells have enhanced expression of stem cell factor (SCF) and stem cell markers. Inhibition of SCF receptor c-KIT resulted in the attenuation of cancer stem cell enrichment and decreased amounts of tumor-initiating cells. RH1-resistant cells also acquire resistance to conventional therapeutics while remaining susceptible to c-KIT-targeted therapy. Data show that RH1 can be useful to treat cancers in the NQO1-independent way, and targeting of the cancer stem cells might be an effective approach for combating resistance to RH1 therapy.

A Novel AURKA Mutant-Induced Early-Onset Severe Hepatocarcinogenesis Greater than Wild-Type via Activating Different Pathways in Zebrafish

Aurora A kinase (AURKA) is an important regulator in mitotic progression and is overexpressed frequently in human cancers, including hepatocellular carcinoma (HCC). Many AURKA mutations were identified in cancer patients. Overexpressing wild-type Aurka developed a low incidence of hepatic tumors after long latency in mice. However, none of the AURKA mutant animal models have ever been described. The mechanism of mutant AURKA-mediated hepatocarcinogenesis is still unclear. A novel AURKA mutation with a.a.352 Valine to Isoleucine (V352I) was identified from clinical specimens. By using liver-specific transgenic fish overexpressing both the mutant and wild-type AURKA, the AURKA(V352I)-induced hepatocarcinogenesis was earlier and much more severe than wild-type AURKA. Although an increase of the expression of lipogenic enzyme and lipogenic factor was observed in both AURKA(V352I) and AURKA(WT) transgenic fish, AURKA(V352I) has a greater probability to promote fibrosis at 3 months compared to AURKA(WT). Furthermore, the expression levels of cell cycle/proliferation markers were higher in the AURKA(V352I) mutant than AURKA(WT) in transgenic fish, implying that the AURKA(V352I) mutant may accelerate HCC progression. Moreover, we found that the AURKA(V352I) mutant activates AKT signaling and increases nuclear β-catenin, but AURKA(WT) only activates membrane form β-catenin, which may account for the differences. In this study, we provide a new insight, that the AURKA(V352I) mutation contributes to early onset hepatocarcinogenesis, possibly through activation of different pathways than AURKA(WT). This transgenic fish may serve as a drug-screening platform for potential precision medicine therapeutics.

Gephyrin suppresses lung squamous cell carcinoma development by reducing mTOR pathway activation

Background: The mTOR pathway is altered in a multitude of cancers, including lung cancer; however, abnormal activation in this pathway is less common in lung adenocarcinoma (LUAD) than in lung squamous cell carcinoma (LUSC). Gephyrin is a highly conserved and widely expressed ancient protein in vertebrate tissues. Its role and molecular mechanism in lung cancer development are largely unknown. Method: We analyzed the expression profile of gephyrin and overall survival rates in LUAD and LUSC. The LUSC cells (H520 and SK-MES-1) were transfected with pLV-gephyrin to establish gephyrin stable overexpression cell lines. Real-time quantitative PCR and Western blot were performed to detect the mRNA and protein levels. The cell growth and cell cycle were detected by the MTT assay and flow cytometry. Finally, a xenograft tumor model was established to determine cell tumorigenesis in vivo. Results: Our results show that gephyrin was reduced in LUAD and LUSC, and its low expression in LUSC patients indicated poor prognosis. Gephyrin overexpression suppressed LUSC cell proliferation, arrested cell cycle progression, and decreased the expression of cell-cycle related proteins such as cyclin D1, cyclin-dependent kinase-2 (CDK2), and proliferation-related protein proliferating cell nuclear antigen (PCNA). Conversely, knockdown of gephyrin promoted LUSC cell growth. Moreover, gephyrin reduced mTOR pathway activation to inhibit cyclin D1 and CDK2 translation. Mechanistically, gephyrin suppressed mTOR pathway activation by promoting mTOR degradation. Furthermore, gephyrin overexpression suppressed LUSC tumorigenesis. Conclusion: Gephyrin suppressed LUSC development by reducing mTOR pathway activation, implicating gephyrin as a potential molecular target for LUSC management.

Molecular Comparison of Imatinib-Naïve and Resistant Gastrointestinal Stromal Tumors: Differentially Expressed microRNAs and mRNAs

Despite the success of imatinib in advanced gastrointestinal stromal tumor (GIST) patients, 50% of the patients experience resistance within two years of treatment underscoring the need to get better insight into the mechanisms conferring imatinib resistance. Here the microRNA and mRNA expression profiles in primary (imatinib-naïve) and imatinib-resistant GIST were examined. Fifty-three GIST samples harboring primary KIT mutations (exon 9; n = 11/exon 11; n = 41/exon 17; n = 1) and comprising imatinib-naïve (IM-n) (n = 33) and imatinib-resistant (IM-r) (n = 20) tumors, were analyzed. The microRNA expression profiles were determined and from a subset (IM-n, n = 14; IM-r, n = 15) the mRNA expression profile was established. Ingenuity pathway analyses were used to unravel biochemical pathways and gene networks in IM-r GIST. Thirty-five differentially expressed miRNAs between IM-n and IM-r GIST samples were identified. Additionally, miRNAs distinguished IM-r samples with and without secondary KIT mutations. Furthermore 352 aberrantly expressed genes were found in IM-r samples. Pathway and network analyses revealed an association of differentially expressed genes with cell cycle progression and cellular proliferation, thereby implicating genes and pathways involved in imatinib resistance in GIST. Differentially expressed miRNAs and mRNAs between IM-n and IM-r GIST were identified. Bioinformatic analyses provided insight into the genes and biochemical pathways involved in imatinib-resistance and highlighted key genes that may be putative treatment targets.

Isoleucine Regulates the Synthesis of Pancreatic Enzymes via the Activation of mRNA Expression and Phosphorylation in the Mammalian Target of Rapamycin Signalling Pathways in Pancreatic Tissues

This study aimed to investigate the effects of isoleucine (Ile) on the synthesis and secretion of digestive enzymes and cellular signalling in the pancreatic tissue of dairy goats. The pancreatic tissues were incubated in buffer containing 0, 0.40, 0.80, and 1.60 mM Ile. High levels of Ile significantly increased the buffer release and total concentration of ɑ-amylase in the tissues (P < 0.001). The total trypsin and chymotrypsin concentrations in each of the Ile groups were significantly higher than those in the control group (P < 0.05); however, lipase was not affected. High levels of Ile significantly increased ɑ-amylase mRNA expression (P < 0.001) but had no effect on the mRNA expression of trypsin, chymotrypsin, or lipase. Ile did not affect S6K1 phosphorylation levels. High levels of Ile significantly increased the expression of the γ isoform of 4EBP1 (P < 0.001), which indicated that the phosphorylation of 4EBP1 was significantly increased. The phosphorylation level of eEF2 gradually decreased with the addition of Ile (P < 0.001). These results suggested that high doses of Ile can regulate the excretion of enzymes, especially ɑ-amylase, in the pancreatic tissues of dairy goats by modulating mTOR signalling, and this regulation is independent of the mTOR-S6K1 pathway.

Activation of PTEN by inhibition of TRPV4 suppresses colon cancer development

Transient receptor potential vanilloid type 4 (TRPV4) is a Ca²⁺-permeable cation channel that is known to be an osmosensor and thermosensor. Currently, limited evidence shows that TRPV4 plays opposite roles in either promoting or inhibiting cancer development in different cancer types. Furthermore, the precise biological functions and the underlying mechanisms of TRPV4 in carcinogenesis are still poorly understood. In this study, we demonstrated that TRPV4 is upregulated in colon cancer and associated with poor prognosis. Contrary to the reported cell death-promoting activity of TRPV4 in certain cancer cells, TRPV4 positively regulates cell survival in human colon cancer in vitro and in vivo. Inhibition of TRPV4 affects the cell cycle progression from the G1 to S phase through modulating the protein expression of D-type cyclins. Apoptosis and autophagy induced by TRPV4 silencing attenuate cell survival and potentiate the anticancer efficacy of chemotherapeutics against colon cancer cells. In addition, PTEN is activated by inhibition of TRPV4 as indicated by the dephosphorylation and increased nuclear localization. Knockdown of PTEN significantly abrogates TRPV4 silencing induced growth inhibition and recovers the capability of clonogenicity, as well as reduced apoptosis in colon cancer cells. Thus, PTEN regulates the antigrowth effects induced by TRPV4 inhibition through both phosphatase-dependent and independent mechanisms. In conclusion, inhibition of TRPV4 suppresses colon cancer development via activation of PTEN pathway. This finding suggests that downregulation of TPRV4 expression or activity would conceivably constitute a novel approach for the treatment of human colon cancer.

Lin28-mediated temporal promotion of protein synthesis is crucial for neural progenitor cell maintenance and brain development in mice

Neural progenitor cells (NPCs) undergo rapid proliferation during neurulation. This rapid growth generates a high demand for mRNA translation in a timing-dependent manner, but its underlying mechanism remains poorly understood. Lin28 is an RNA-binding protein with two paralogs, Lin28a and Lin28b, in mammals. Mice with Lin28b deletion exhibit no developmental defects, whereas we have previously reported that Lin28a deletion leads to microcephaly. Here, we find that Lin28a/b double knockout (dKO) mice display neural tube defects (NTDs) coupled with reduced proliferation and precocious differentiation of NPCs. Using ribosomal protein 24 hypomorphic mice (Rpl24^Bst/+ ) as a genetic tool to dampen global protein synthesis, we found that Lin28a^-/-;Rpl24^Bst/+ compound mutants exhibited NTDs resembling those seen in Lin28a/b dKO mice. Increased NPC numbers and brain sizes in Lin28a-overexpressing mice were rescued by Rpl24^Bst/+ heterozygosity. Mechanistically, polysome profiling revealed reduced translation of genes involved in the regulation of cell cycle, ribosome biogenesis and translation in dKO mutants. Ribosome biogenesis was reduced in dKO and increased in Lin28a-overexpressing NPCs. Therefore, Lin28-mediated promotion of protein synthesis is essential for NPC maintenance and early brain development.

Septin6 regulates cell growth and casein synthesis in dairy cow mammary epithelial cells via mTORC1 pathway

This research paper addresses the hypothesis that Septin6 is a key regulatory factor influencing amino acid (AA)-mediated cell growth and casein synthesis in dairy cow mammary epithelial cells (DCMECs). DCMECs were treated with absence of AA (AA-), restricted concentrations of AA (AAr) or normal concentrations of AA (AA+) for 24 h. Cell growth, expression of CSN2 and Septin6 were increased in response to AA supply. Overexpressing or inhibiting Septin6 demonstrated that cell growth, expression of CSN2, mTOR, p-mTOR, S6K1 and p-S6K1 were up-regulated by Septin6. Furthermore, overexpressing or inhibiting mTOR demonstrated that the increase in cell growth and expression of CSN2 in response to Septin6 overexpression were inhibited by mTOR inhibition, and vice versa. Our hypothesis was supported; we were able to show that Septin6 is an important positive factor for cell growth and casein synthesis, it up-regulates AA-mediated cell growth and casein synthesis through activating mTORC1 pathway in DCMECs.

Mammalian cell growth dynamics in mitosis

The extent and dynamics of animal cell biomass accumulation during mitosis are unknown, primarily because growth has not been quantified with sufficient precision and temporal resolution. Using the suspended microchannel resonator and protein synthesis assays, we quantify mass accumulation and translation rates between mitotic stages on a single-cell level. For various animal cell types, growth rates in prophase are commensurate with or higher than interphase growth rates. Growth is only stopped as cells approach metaphase-to-anaphase transition and growth resumes in late cytokinesis. Mitotic arrests stop growth independently of arresting mechanism. For mouse lymphoblast cells, growth in prophase is promoted by CDK1 through increased phosphorylation of 4E-BP1 and cap-dependent protein synthesis. Inhibition of CDK1-driven mitotic translation reduces daughter cell growth. Overall, our measurements counter the traditional dogma that growth during mitosis is negligible and provide insight into antimitotic cancer chemotherapies.

Cell cycle control by the target of rapamycin signalling pathway in plants

Cells need to ensure a sufficient nutrient and energy supply before committing to proliferate. In response to positive mitogenic signals, such as light, sugar availability, and hormones, the target of rapamycin (TOR) signalling pathway promotes cell growth that connects to the entry and passage through the cell division cycle via multiple signalling mechanisms. Here, we summarize current understanding of cell cycle regulation by the RBR-E2F regulatory hub and the DREAM-like complexes, and highlight possible functional relationships between these regulators and TOR signalling. A genetic screen recently uncovered a downstream signalling component to TOR that regulates cell proliferation, YAK1, a member of the dual specificity tyrosine phosphorylation-regulated kinase (DYRK) family. YAK1 activates the plant-specific SIAMESE-RELATED (SMR) cyclin-dependent kinase inhibitors and therefore could be important to regulate both the CDKA-RBR-E2F pathway to control the G1/S transition and the mitotic CDKB1;1 to control the G2/M transition. TOR, as a master regulator of both protein synthesis-driven cell growth and cell proliferation is also central for cell size homeostasis. We conclude the review by briefly highlighting the potential applications of combining TOR and cell cycle knowledge in the context of ensuring future food security.

The mTOR pathway: Implications for DNA replication

DNA replication plays a central role in genome health. Deleterious alteration of replication dynamics, or "replication stress", is a key driver of genome instability and oncogenesis. The replication stress response is regulated by the ATR kinase, which functions to mitigate replication abnormalities through coordinated efforts that arrest the cell cycle and repair damaged replication forks. mTOR kinase regulates signaling networks that control cell growth and metabolism in response to environmental cues and cell stress. In this review, we discuss interconnectivity between the ATR and mTOR pathways, and provide putative mechanisms for mTOR engagement in DNA replication and the replication stress response. Finally, we describe how connectivity between mTOR and replication stress may be exploited for cancer therapy.

Cell cycle genes are downregulated after adipogenic triggering in human adipose tissue-derived stem cells by regulation of mRNA abundance

The adipogenic process is characterized by the expression of adipocyte differentiation markers that lead to changes in cell metabolism and to the accumulation of lipid droplets. Moreover, during early adipogenesis, cells undergo a strong downregulation of translational activity with a decrease in cell size, proliferation and migration. In the present study, we identified that after 24 hours of adipogenic induction, human adipose tissue-derived stem cells (hASCs) undergo a G1-cell cycle arrest consistent with reduced proliferation, and this effect was correlated with a shift in polysome profile with an enrichment of the monosomal fraction and a reduction of the polysomal fraction. Polysome profiling analysis also revealed that this change in the monosomal/polysomal ratio was related to a strong downregulation of cell cycle and proliferation genes, such as cyclins and cyclin-dependent kinases (CDKs). Comparing total and polysome-associated mRNA sequencing, we also observed that this downregulation was mostly due to a reduction of cell cycle and proliferation transcripts via control of total mRNA abundance, rather than by translational control.

Differential effects of the Akt inhibitor MK-2206 on migration and radiation sensitivity of glioblastoma cells

Background

Most tumor cells show aberrantly activated Akt which leads to increased cell survival and resistance to cancer radiotherapy. Therefore, targeting Akt can be a promising strategy for radiosensitization. Here, we explore the impact of the Akt inhibitor MK-2206 alone and in combination with the dual PI3K and mTOR inhibitor PI-103 on the radiation sensitivity of glioblastoma cells. In addition, we examine migration of drug-treated cells.

Methods

Using single-cell tracking and wound healing migration tests, colony-forming assay, Western blotting, flow cytometry and electrorotation we examined the effects of MK-2206 and PI-103 and/or irradiation on the migration, radiation sensitivity, expression of several marker proteins, DNA damage, cell cycle progression and the plasma membrane properties in two glioblastoma (DK-MG and SNB19) cell lines, previously shown to differ markedly in their migratory behavior and response to PI3K/mTOR inhibition.

Results

We found that MK-2206 strongly reduces the migration of DK-MG but only moderately reduces the migration of SNB19 cells. Surprisingly, MK-2206 did not cause radiosensitization, but even increased colony-forming ability after irradiation. Moreover, MK-2206 did not enhance the radiosensitizing effect of PI-103. The results appear to contradict the strong depletion of p-Akt in MK-2206-treated cells. Possible reasons for the radioresistance of MK-2206-treated cells could be unaltered or in case of SNB19 cells even increased levels of p-mTOR and p-S6, as compared to the reduced expression of these proteins in PI-103-treated samples. We also found that MK-2206 did not enhance IR-induced DNA damage, neither did it cause cell cycle distortion, nor apoptosis nor excessive autophagy.

Conclusions

Our study provides proof that MK-2206 can effectively inhibit the expression of Akt in two glioblastoma cell lines. However, due to an aberrant activation of mTOR in response to Akt inhibition in PTEN mutated cells, the therapeutic window needs to be carefully defined, or a combination of Akt and mTOR inhibitors should be considered.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5517-4) contains supplementary material, which is available to authorized users.

mTORC1 signaling activation increases intestinal stem cell activity and promotes epithelial cell proliferation

The crypt-villus axis of the intestine undergoes a continuous renewal process that is driven by intestinal stem cells (ISCs). However, the homeostasis is disturbed under constant exposure to high ambient temperatures, and the precise mechanism is unclear. We found that both EdU⁺ and Ki67⁺ cell ratios were significantly reduced after exposure to 41°C, as well as the protein synthesis rate of IPEC-J2 cells, and the expression of ubiquitin and heat shock protein 60, 70, and 90 were significantly increased. Additionally, heat exposure decreased enteroid expansion and budding efficiency, as well as induced apoptosis after 48 hr; however, no significant difference was observed in the apoptosis ratio after 24 hr. In the process of heat exposure, the mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway was significantly inhibited in both IPEC-J2 cells and enteroids. Correspondingly, treatment of IPEC-J2 and enteroids with the mTORC1 agonist MHY1485 at 41°C significantly attenuated the inhibition of proliferation and protein synthesis, increased the ISC activity, and promoted expansion and budding of enteroid. In summary, we conclude that the mTORC1 signaling pathway regulates intestinal epithelial cell and stem cell activity during heat exposure-induced injury.

Loss of postnatal quiescence of neural stem cells through mTOR activation upon genetic removal of cysteine string protein-α

Neural stem cells continuously generate newborn neurons that integrate into and modify neural circuitry in the adult hippocampus. The molecular mechanisms that regulate or perturb neural stem cell proliferation and differentiation, however, remain poorly understood. Here, we have found that mouse hippocampal radial glia-like (RGL) neural stem cells express the synaptic cochaperone cysteine string protein-α (CSP-α). Remarkably, in CSP-α knockout mice, RGL stem cells lose quiescence postnatally and enter into a high-proliferation regime that increases the production of neural intermediate progenitor cells, thereby exhausting the hippocampal neural stem cell pool. In cell culture, stem cells in hippocampal neurospheres display alterations in proliferation for which hyperactivation of the mechanistic target of rapamycin (mTOR) signaling pathway is the primary cause of neurogenesis deregulation in the absence of CSP-α. In addition, RGL cells lose quiescence upon specific conditional targeting of CSP-α in adult neural stem cells. Our findings demonstrate an unanticipated cell-autonomic and circuit-independent disruption of postnatal neurogenesis in the absence of CSP-α and highlight a direct or indirect CSP-α/mTOR signaling interaction that may underlie molecular mechanisms of brain dysfunction and neurodegeneration.

Induction of AMPK activation by N,N'-diarylurea FND-4b decreases growth and increases apoptosis in triple negative and estrogen-receptor positive breast cancers

Purpose

Triple negative breast cancer (TNBC) is the most lethal and aggressive subtype of breast cancer. AMP-activated protein kinase (AMPK) is a major energy regulator that suppresses tumor growth, and 1-(3-chloro-4-((trifluoromethyl)thio)phenyl)-3-(4-(trifluoromethoxy)phenyl)urea (FND-4b) is a novel AMPK activator that inhibits growth and induces apoptosis in colon cancer. The purpose of this project was to test the effects of FND-4b on AMPK activation, proliferation, and apoptosis in breast cancer with a particular emphasis on TNBC.

Materials and methods

(i) Estrogen-receptor positive breast cancer (ER+BC; MCF-7, and T-47D), TNBC (MDA-MB-231 and HCC-1806), and breast cancer stem cells were treated with FND-4b for 24h. Immunoblot analysis assessed AMPK, acetyl-CoA carboxylase (ACC), ribosomal protein S6, cyclin D1, and cleaved PARP. (ii) Sulforhodamine B growth assays were performed after treating ER+BC and TNBC cells with FND-4b for 72h. Proliferation was also assessed by counting cells after 72h of FND-4b treatment. (iii) Cell death ELISA assays were performed after treating ER+BC and TNBC cells with FND-4b for 72h.

Results

(i) FND-4b increased AMPK activation with concomitant decreases in ACC activity, phosphorylated S6, and cyclin D1 in all subtypes. (ii) FND-4b decreased proliferation in all cells, while dose-dependent growth decreases were found in ER+BC and TNBC. (iii) Increases in apoptosis were observed in ER+BC and the MDA-MB-231 cell line with FND-4b treatment.

Conclusions

Our findings indicate that FND-4b decreases proliferation for a variety of breast cancers by activating AMPK and has notable effects on TNBC. The growth reductions were mediated through decreases in fatty acid synthesis (ACC), mTOR signaling (S6), and cell cycle flux (cyclin D1). ER+BC cells were more susceptible to FND-4b-induced apoptosis, but MDA-MB-231 cells still underwent apoptosis with higher dose treatment. Further development of FND compounds could result in a novel therapeutic for TNBC.

Inhibiting 4E-BP1 re-activation represses podocyte cell cycle re-entry and apoptosis induced by adriamycin

Podocyte loss is one of the determining factors for the progression toward glomerulosclerosis. Podocyte is terminally differentiated and does not typically proliferate following injury and loss. However, recent evidence suggested that during renal injury, podocyte could re-enter the cell cycle, sensitizing the cells to injury and death, but the molecular mechanisms underlying it, as well as the cell fate determination still remained unclear. Here, using NPHS2 Cre; mT/mG transgenic mice and primary podocytes isolated from the mice, we investigated the effect of mammalian target of rapamycin complex 1 (mTORC1)/4E-binding protein 1 (4E-BP1) signaling pathway on cell cycle re-entry and apoptosis of podocyte induced by adriamycin. It was found that podocyte cell cycle re-entry could be induced by adriamycin as early as the 1st week in vivo and the 2nd hour in vitro, accompanied with 4E-BP1 activation and was followed by podocyte loss or apoptosis from the 4th week in vivo or the 4th hour in vitro. Importantly, targeting 4E-BP1 activation by the RNA interference of 4E-BP1 or pharmacologic rapamycin (inhibitor of mTORC1, blocking mTORC1-dependent phosphorylation of its substrate 4E-BP1) treatment was able to inhibit the increases of PCNA, Ki67, and the S-phase fraction of cell cycle in primary podocyte during 2–6 h of adriamycin treatment, and also attenuated the following apoptotic cell death of podocyte detected from the 4th hour, suggesting that 4E-BP1 could be a regulator to manipulate the amount of cell cycle re-entry provided by differentiated podocyte, and thus regulate the degree of podocyte apoptosis, bringing us a new potential podocyte-protective substance that can be used for therapy.

Estrogen Receptor Beta (ERβ) Mediated-CyclinD1 Degradation via Autophagy Plays an Anti-Proliferation Role in Colon Cells

Dysfunction of autophagic degradation machinery causes tumorigenesis, including colorectal cancer (CRC). Overexpression of CyclinD1 in CRC has been reported. Recent evidence also suggests that ERβ deficiency is related to the pathogenesis of CRC. Very little is known, however, about the detailed molecular mechanisms underlying the relationship among ERβ, autophagy, and CyclinD1 in CRC. Here, results showed that ERβ played an anti-proliferation role in HCT116 through impairing cell cycle but not apoptosis. Additionally, CyclinD1 accumulation was increased in response to chloroquine (CQ) or in MEF Atg7 knockout cells. Further, ERβ could inhibit the mammalian target of rapamycin (mTOR) or activate Bcl-2/adenovirus E1B 19-kDa-interacting protein 3 (BNIP3) to promote autophagy in HCT116. In summary, these results indicate that ERβ-mediated CyclinD1 degradation can inhibit colon cancer cell growth via autophagy.

Wound Healing Potential of Spirulina Protein on CCD-986sk Cells

Wound healing is a dynamic and complex process. The proliferation and migration of dermal fibroblasts are crucial for wound healing. Recent studies have indicated that the extracts from Spirulina platensis have a positive potential for wound healing. However, its underlying mechanism is not fully understood. Our previous study showed that spirulina crude protein (SPCP) promoted the viability of human dermal fibroblast cell line (CCD-986sk cells). In this study, we further investigated the wound healing effect and corresponding mechanisms of SPCP on CCD-986sk cells. Bromodeoxyuridine (BrdU) assay showed that SPCP promoted the proliferation of CCD-986sk cells. The wound healing assay showed that SPCP promoted the migration of CCD-986sk cells. Furthermore, cell cycle analysis demonstrated that SPCP promoted CCD-986sk cells to enter S and G₂/M phases from G₀/G₁ phase. Western blot results showed that SPCP significantly upregulated the expression of cyclin D1, cyclin E, cyclin-dependent kinase 2 (Cdk2), cyclin-dependent kinase 4 (Cdk4), and cyclin-dependent kinase 6 (Cdk6), as well as inhibited the expression of CDK inhibitors p21 and p27 in CCD-986sk cells. In the meanwhile, SPCP promoted the phosphorylation and activation of phosphoinositide 3-kinase (PI3K) and protein kinase B (Akt). However, the phosphorylation of Akt was significantly blocked by PI3K inhibitor (LY294002), which in turn reduced the SPCP-induced proliferation and migration of CCD-986sk cells. Therefore, the results presenting in this study suggested that SPCP can promote the proliferation and migration of CCD-986sk cells; the PI3K/Akt signaling pathway play a positive and important role in these processes.

Norgalanthamine Stimulates Proliferation of Dermal Papilla Cells via Anagen-Activating Signaling Pathways

Norgalanthamine has been shown to possess hair-growth promoting effects, including increase in hair-fiber length in cultured rat vibrissa follicles and increase in dermal papilla cell (DPC) proliferation. However, the intracellular mechanisms that underlie the action of norgalanthamine in DPCs have not been investigated. In this study, we addressed the ability of norgalanthamine to trigger anagen-activating signaling pathways in DPCs. Norgalanthamine significantly increased extracellular signal-regulated kinase (ERK) 1/2 phosphorylation at 0.1 µM, a concentration at which DPC proliferation was also induced. Furthermore, the increases in norgalanthamine-induced ERK 1/2 activation and subsequent DPC proliferation were suppressed by the mitogen-activated protein kinase/ERK kinase (MEK) 1/2 inhibitor, U0126. A 0.1 µM dose of norgalanthamine also increased phosphorylation of AKT, which was followed by an increase in glycogen synthase kinase 3β phosphorylation and nuclear translocation of β-catenin. In addition, LY294002, a phosphatidylinositol 3 kinase (PI3K) inhibitor, blocked the effect of norgalanthamine on DPC proliferation. These results suggest that norgalanthamine can stimulate the anagen phase of the hair cycle in DPCs via activation of the ERK 1/2, PI3K/AKT, and Wnt/β-catenin pathways.

Phospholipase D and the Mitogen Phosphatidic Acid in Human Disease: Inhibitors of PLD at the Crossroads of Phospholipid Biology and Cancer

Lipids are key building blocks of biological membranes and are involved in complex signaling processes such as metabolism, proliferation, migration, and apoptosis. Extracellular signaling by growth factors, stress, and nutrients is transmitted through receptors that activate lipid-modifying enzymes such as the phospholipases, sphingosine kinase, or phosphoinositide 3-kinase, which then modify phospholipids, sphingolipids, and phosphoinositides. One such important enzyme is phospholipase D (PLD), which cleaves phosphatidylcholine to yield phosphatidic acid and choline. PLD isoforms have dual role in cells. The first involves maintaining cell membrane integrity and cell signaling, including cell proliferation, migration, cytoskeletal alterations, and invasion through the PLD product PA, and the second involves protein-protein interactions with a variety of binding partners. Increased evidence of elevated PLD expression and activity linked to many pathological conditions, including cancer, neurological and inflammatory diseases, and infection, has motivated the development of dual- and isoform-specific PLD inhibitors. Many of these inhibitors are reported to be efficacious and safe in cells and mouse disease models, suggesting the potential for PLD inhibitors as therapeutics for cancer and other diseases. Current knowledge and ongoing research of PLD signaling networks will help to evolve inhibitors with increased efficacy and safety for clinical studies.

Novel Targets for Fast Antidepressant Responses: Possible Role of Endogenous Neuromodulators

The available medications for the treatment of major depressive disorder have limitations, particularly their limited efficacy, delayed therapeutic effects, and the side effects associated with treatment. These issues highlight the need for better therapeutic agents that provide more efficacious and faster effects for the management of this disorder. Ketamine, an N-methyl-D-aspartate receptor antagonist, is the prototype for novel glutamate-based antidepressants that has been shown to cause a rapid and sustained antidepressant effect even in severe refractory depressive patients. Considering the importance of these findings, several studies have been conducted to elucidate the molecular targets for ketamine's effect. In addition, efforts are under way to characterize ketamine-like drugs. This review focuses particularly on evidence that endogenous glutamatergic neuromodulators may be able to modulate mood and to elicit fast antidepressant responses. Among these molecules, agmatine and creatine stand out as those with more published evidence of similarities with ketamine, but guanosine and ascorbic acid have also provided promising results. The possibility that these neuromodulators and ketamine have common neurobiological mechanisms, mainly the ability to activate mechanistic target of rapamycin and brain-derived neurotrophic factor signaling, and synthesis of synaptic proteins in the prefrontal cortex and/or hippocampus is presented and discussed.

MEK-inhibitor PD184352 enhances the radiosensitizing effect of the Hsp90 inhibitor NVP-AUY922: the role of cell type and drug-irradiation schedule

Targeting MEK protein in cancer cells usually leads to acquired resistance to MEK inhibitors and activation of the prosurvival protein Akt. Since both MEK and Akt are clients of the Hsp90 chaperone system, the present study explores the responses of irradiated lung carcinoma A549 and glioblastoma SNB19 cell lines to combined MEK and Hsp90 inhibition. Unexpectedly, the MEK inhibitor PD184352 administered 24 h prior to irradiation, enhanced cell survival through upregulation of not only MEK and Erk1/2 but also of Akt. In contrast, PD184352 added 1 h before irradiation strongly reduced the expression of Erk and did not upregulate Akt in both cell lines. As a result, the MEK inhibitor increased the radiosensitizing effect of the Hsp90 inhibitor NVP-AUY922 in glioblastoma SNB19 cells. Possible reasons for the enhanced cell killing under this short-term pretreatment schedule may be a down-regulation of Erk during or directly after irradiation, increased DNA damage and/or a strong G₂/M arrest 24 h after irradiation. In addition, an 1-h pretreatment with PD184352 and/or NVP-AUY922 under schedule II induced neither G₁ arrest nor up-regulation of p-Akt in both cell lines as it did under schedule I. Yet, a long-term treatment with the MEK inhibitor alone caused a strong cytostatical effect. We conclude that the duration of drug pretreatment before irradiation plays a key role in the targeting of MEK in tumor cells. However, due to an aberrant activation of prosurvival proteins, the therapeutic window needs to be carefully defined, or a combination of inhibitors should be considered.

β-N-methylamino-L-alanine (BMAA) suppresses cell cycle progression of non-neuronal cells

β-N-methylamino-L-alanine (BMAA), a natural non-proteinaceous amino acid, is a neurotoxin produced by a wide range of cyanobacteria living in various environments. BMAA is a candidate environmental risk factor for neurodegenerative diseases such as amyotrophic lateral sclerosis and Parkinson-dementia complex. Although BMAA is known to exhibit weak neuronal excitotoxicity via glutamate receptors, the underlying mechanism of toxicity has yet to be fully elucidated. To examine the glutamate receptor-independent toxicity of BMAA, we investigated the effects of BMAA in non-neuronal cell lines. BMAA potently suppressed the cell cycle progression of NIH3T3 cells at the G1/S checkpoint without inducing plasma membrane damage, apoptosis, or overproduction of reactive oxygen species, which were previously reported for neurons and neuroblastoma cells treated with BMAA. We found no evidence that activation of glutamate receptors was involved in the suppression of the G1/S transition by BMAA. Our results indicate that BMAA affects cellular functions, such as the division of non-neuronal cells, through glutamate receptor-independent mechanisms.

PI3K/Akt/mTOR signalling pathway activation in patients with ER-positive, metachronous, contralateral breast cancer treated with hormone therapy

Oestrogen receptor (ER)-positive, metachronous, contralateral breast cancer (MCBC) sometimes develops during or soon after completion of hormone therapy (HT), but it is uncertain whether it is HT-resistant. We examined the association between ER-positive second cancer and activation of the phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) and mitogen-activated protein kinase (MAPK) pathways, which are associated with HT resistance. We examined the treatment-free interval (time after completion of HT for initial cancer) in 41 patients with ER-positive MCBC with a history of adjuvant HT for initial cancer (HT group), and initial-to-second period duration (time after operation of initial cancer to onset of second cancer) in 17 patients with ER-positive MCBC in whom adjuvant HT was not applied to the initial tumour (control group or no HT group). Phosphorylated S6 (pS6) and phosphorylated MAPK (pMAPK) were used as indicators of PI3K/Akt/mTOR and MAPK pathway activity, respectively. Tumours were classified as showing negative, positive or strongly positive staining, and the correlation between staining and treatment-free interval or initial-to-second period duration was evaluated using the Spearman's rank correlation coefficient (ρ). Treatment-free interval and pS6 staining showed a negative correlation (ρ=-0.5355; P=0.0003) in the HT group. There was no correlation between initial-to-second period duration and pS6 staining in the no HT group (ρ=-0.0814; P=0.756). There was no correlation between pMAPK signalling and the treatment-free interval in the HT group (ρ=-0.1560; P=0.330) or the initial-to-second period duration in the no HT group (ρ=-0.0116; P=0.965). Development of a second ER-positive cancer during or soon after completion of HT for the initial cancer may be associated with activation of the PI3K/Akt/mTOR pathway. Care should be taken during follow-up and when selecting adjuvant therapy for second cancer.

Pleiotropic Action of Novel Bruton's Tyrosine Kinase Inhibitor BGB-3111 in Mantle Cell Lymphoma

Bruton's tyrosine kinase (BTK) is a key mediator of BCR-dependent cell growth signaling and a clinically effective therapeutic target in mantle cell lymphoma (MCL). The molecular impact of BTK inhibition remains unclear particularly in hematopoietic malignancies. We analyzed the molecular mechanisms of BTK inhibition with the novel inhibitor BGB-3111 (zanubrutinib) in MCL models. The efficacy of BGB-3111 was investigated using growth proliferation/cell viability and apoptosis assays in MCL cell lines and patient-derived xenograft (PDX) MCL cells. The activity and mechanisms of BGB-3111 were further confirmed using a cell line xenograft model, an MCL PDX mouse model, and a human phosphokinase profiler array and reverse phase protein array. Finally, the mechanisms related to resistance to BTK inhibition were analyzed by creating cell lines with low levels of BTK using CRISPR/Cas 9 genome editing. We found that inhibition of BTK leads to suppression of tumor growth, which was mediated via potent suppression of AKT/mTOR, apoptosis, and metabolic stress. Moreover, targeted disruption of the BTK gene in MCL cells resulted in resistance to BTK inhibition and the emergence of novel survival mechanisms. Our studies suggest a general efficacy of BTK inhibition in MCL and potential drug resistance mechanism via alternative signaling pathways.

CDK4/6 Inhibition in Cancer: Beyond Cell Cycle Arrest

Pharmacologic inhibitors of cyclin-dependent kinases 4 and 6 (CDK4/6) have recently entered the therapeutic armamentarium of clinical oncologists, and show promising activity in patients with breast and other cancers. Although their chief mechanism of action is inhibition of retinoblastoma (RB) protein phosphorylation and thus the induction of cell cycle arrest, CDK4/6 inhibitors alter cancer cell biology in other ways that can also be leveraged for therapeutic benefit. These include modulation of mitogenic kinase signaling, induction of a senescence-like phenotype, and enhancement of cancer cell immunogenicity. We describe here the less-appreciated effects of CDK4/6 inhibitors on cancer cells, and suggest ways by which they might be exploited to enhance the benefits of these agents for cancer patients.

Expression of the miR-150 tumor suppressor is restored by and synergizes with rapamycin in a human leukemia T-cell line

miR-150 functions as a tumor suppressor in malignancies of the lymphocyte lineage and its expression is significantly reduced in these cells. However, the mechanism of miR-150 repression is unknown and so are pharmacological interventions that can reverse it. Here, we report that reduced expression of miR-150 in human Jurkat T-cell acute lymphoblastic leukemia (T-ALL) cells is mediated by constitutive mTOR signaling, a common characteristic of T-ALL cell lines and clinical isolates. Activating mTOR signaling in non-malignant T cells also resulted in a significant miR-150 down-regulation. Conversely, treatment with a pharmacological mTOR inhibitor, rapamycin, increased miR-150 expression in a dose-dependent manner in Jurkat cells, as well as in other leukemia cells. Interestingly, ectopic over-expression of miR-150 acted in a feed-forward loop and further sensitized Jurkat cells to a rapamycin-induced cell cycle arrest by targeting a large network of cell cycle genes. These findings suggest that miR-150 is normally expressed in quiescent T lymphocytes to reinforce an anti-proliferative state, and that mTOR signaling promotes cell proliferation in part by inhibiting miR-150 expression. Restoration of the miR-150-dependent anti-proliferative loop constitutes a novel mechanism underlying the efficacy of rapamycin in a T-ALL cell line. Further investigation of this mechanism in clinical isolates of T-ALL and other hematopoietic malignancies could help better guide development of targeted therapies.

mTOR Complexes as a Nutrient Sensor for Driving Cancer Progression

Recent advancement in the field of molecular cancer research has clearly revealed that abnormality of oncogenes or tumor suppressor genes causes tumor progression thorough the promotion of intracellular metabolism. Metabolic reprogramming is one of the strategies for cancer cells to ensure their survival by enabling cancer cells to obtain the macromolecular precursors and energy needed for the rapid growth. However, an orchestration of appropriate metabolic reactions for the cancer cell survival requires the precise mechanism to sense and harness the nutrient in the microenvironment. Mammalian/mechanistic target of rapamycin (mTOR) complexes are known downstream effectors of many cancer-causing mutations, which are thought to regulate cancer cell survival and growth. Recent studies demonstrate the intriguing role of mTOR to achieve the feat through metabolic reprogramming in cancer. Importantly, not only mTORC1, a well-known regulator of metabolism both in normal and cancer cell, but mTORC2, an essential partner of mTORC1 downstream of growth factor receptor signaling, controls cooperatively specific metabolism, which nominates them as an essential regulator of cancer metabolism as well as a promising candidate to garner and convey the nutrient information from the surrounding environment. In this article, we depict the recent findings on the role of mTOR complexes in cancer as a master regulator of cancer metabolism and a potential sensor of nutrients, especially focusing on glucose and amino acid sensing in cancer. Novel and detailed molecular mechanisms that amino acids activate mTOR complexes signaling have been identified. We would also like to mention the intricate crosstalk between glucose and amino acid metabolism that ensures the survival of cancer cells, but at the same time it could be exploitable for the novel intervention to target the metabolic vulnerabilities of cancer cells.

Discovery and characterization of conserved binding of eIF4E 1 (CBE1), a eukaryotic translation initiation factor 4E-binding plant protein

In many eukaryotes, translation initiation is regulated by proteins that bind to the mRNA cap-binding protein eukaryotic translation initiation factor 4E (eIF4E). These proteins commonly prevent association of eIF4E with eIF4G or form repressive messenger ribonucleoproteins that exclude the translation machinery. Such gene-regulatory mechanisms in plants, and even the presence of eIF4E-interacting proteins other than eIF4G (and the plant-specific isoform eIFiso4G, which binds eIFiso4E), are unknown. Here, we report the discovery of a plant-specific protein, conserved binding of eIF4E 1 (CBE1). We found that CBE1 has an evolutionarily conserved eIF4E-binding motif in its N-terminal domain and binds eIF4E or eIFiso4E in vitro CBE1 thereby forms cap-binding complexes and is an eIF4E-dependent constituent of these complexes in vivo Of note, plant mutants lacking CBE1 exhibited dysregulation of cell cycle-related transcripts and accumulated higher levels of mRNAs encoding proteins involved in mitosis than did WT plants. Our findings indicate that CBE1 is a plant protein that can form mRNA cap-binding complexes having the potential for regulating gene expression. Because mammalian translation factors are known regulators of cell cycle progression, we propose that CBE1 may represent such first translation factor-associated plant-specific cell cycle regulator.

Integrative Analyses of Transcriptome Sequencing Identify Functional miRNAs in the Chicken Embryo Fibroblasts Cells Infected With Reticuloendotheliosis Virus

In this study, we found a much higher proportion of reticuloendotheliosis virus (REV) infected chicken embryo fibroblasts (CEF) were in active cell division phase than that of control cells which indicated that REV can affect the fate of CEF. So, we performed high-throughput sequencing and transcriptomic analysis to identify functional miRNAs, in order to figure out the possible mechanism in the interaction of REV with CEF. In total, 50 differentially expressed miRNAs (DEmiRNAs) were identified. Then target genes of DEmiRNAs were predicted and identified by transcriptome profile results. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment were conducted to analyze the identified target genes of miRNAs which showed that metabolism, cell cycle, and apoptosis were the most related pathways involved in infection of REV. We analyzed the genes related to cell cycle which indicated that CyclinD1-CDK6 complex played an important role in regulating the transition of the cell cycle from G1 phase to S phase during REV infection. Fluorescence microscope identification showed that REV inhibited the apoptosis of CEF which was in accordance with transcriptome results. A novel miRNA, named novel-72 was found, KEGG analysis was conducted to predict the biological function of its target genes which showed that those target genes were significantly enriched in mTOR signaling pathway and functioned to promote cell cycle and cell growth during the REV infection. In conclusion, REV could induce the up-regulation of cell metabolism, cell cycle and mTOR signaling pathway while inhibit apoptosis of the cell.

Emerging Role of mTOR Signaling-Related miRNAs in Cardiovascular Diseases

Mechanistic/mammalian target of rapamycin (mTOR), an atypical serine/threonine kinase of the phosphoinositide 3-kinase- (PI3K-) related kinase family, elicits a vital role in diverse cellular processes, including cellular growth, proliferation, survival, protein synthesis, autophagy, and metabolism. In the cardiovascular system, the mTOR signaling pathway integrates both intracellular and extracellular signals and serves as a central regulator of both physiological and pathological processes. MicroRNAs (miRs), a class of short noncoding RNA, are an emerging intricate posttranscriptional modulator of critical gene expression for the development and maintenance of homeostasis across a wide array of tissues, including the cardiovascular system. Over the last decade, numerous studies have revealed an interplay between miRNAs and the mTOR signaling circuit in the different cardiovascular pathophysiology, like myocardial infarction, hypertrophy, fibrosis, heart failure, arrhythmia, inflammation, and atherosclerosis. In this review, we provide a comprehensive state of the current knowledge regarding the mechanisms of interactions between the mTOR signaling pathway and miRs. We have also highlighted the latest advances on mTOR-targeted therapy in clinical trials and the new perspective therapeutic strategies with mTOR-targeting miRs in cardiovascular diseases.

Bufadienolides from Venenum Bufonis Inhibit mTOR-Mediated Cyclin D1 and Retinoblastoma Protein Leading to Arrest of Cell Cycle in Cancer Cells

Objective

Bufadienolides, the main components in Venenum Bufonis secreted from toads, have been proved to be with significant anticancer activity aside from the positive inotropic action as cardenolides. Here an underlying anticancer mechanism was further elucidated for an injection made from Venenum Bufonis containing nine bufadienolides.

Methods

One solution reagent and cell cycle analyses were for determining effect of bufadienolides on cancer cells. Western blotting was used for protein expression.

Results

Bufadienolides inhibit cell proliferation and arrest cells in G1 phase. Bufadienolides also inhibit the mammalian target of rapamycin (mTOR) signaling pathway, which is evidenced by the data that bufadienolides inhibit type I insulin-like growth factor- (IGF-1-) activated phosphorylation of mTOR by a concentration- and time-dependent way, as well as phosphorylation of p70 S6 kinase 1 (S6K1) and eukaryotic initiation factor 4E (eIF4E) binding protein 1 (4E-BP1). Subsequent results indicated that cyclin D1 expression and phosphorylation of retinoblastoma protein (Rb)—two characterized regulators in cell cycle of G1—are also inhibited and the process is dependent on mTOR pathway.

Conclusion

Bufadienolides inhibit proliferation partially due to arresting cell cycle in G1 phase, which is mediated by inhibiting mTOR-cyclin D1/Rb signal pathway.

The Intracellular Cleavage Product of the NG2 Proteoglycan Modulates Translation and Cell-Cycle Kinetics via Effects on mTORC1/FMRP Signaling

The NG2 proteoglycan is expressed by oligodendrocyte precursor cells (OPCs) and is abundantly expressed by tumors such as melanoma and glioblastoma. Functions of NG2 include an influence on proliferation, migration and neuromodulation. Similar to other type-1 membrane proteins, NG2 undergoes proteolysis, generating a large ectodomain, a C-terminal fragment (CTF) and an intracellular domain (ICD) via sequential action of α- and γ-secretases which is enhanced by neuronal activity. Functional roles of NG2 have so far been shown for the full-length protein, the released ectodomain and CTF, but not for the ICD. In this study, we characterized the role of the NG2 ICD in OPC and Human Embryonic Kidney (HEK) cells. Overexpressed ICD is predominantly localized in the cell cytosol, including the distal processes of OPCs. Nuclear localisation of a fraction of the ICD is dependent on Nuclear Localisation Signals. Immunoprecipitation and Mass Spectrometry followed by functional analysis indicated that the NG2 ICD modulates mRNA translation and cell-cycle kinetics. In OPCs and HEK cells, ICD overexpression results in an mTORC1-dependent upregulation of translation, as well as a shift of the cell population toward S-phase. NG2 ICD increases the active (phosphorylated) form of mTOR and modulates downstream signaling cascades, including increased phosphorylation of p70S6K1 and increased expression of eEF2. Strikingly, levels of FMRP, an RNA-binding protein that is regulated by mTOR/p70S6K1/eEF2 were decreased. In neurons, FMRP acts as a translational repressor under activity-dependent control and is mutated in Fragile X Syndrome (FXS). Knock-down of endogenous NG2 in primary OPC reduced translation and mTOR/p70S6K1 phosphorylation in Oli-neu. Here, we identify the NG2 ICD as a regulator of translation in OPCs via modulation of the well-established mTORC1 pathway. We show that FXS-related FMRP signaling is not exclusive to neurons but plays a role in OPCs. This provides a signal cascade in OPC which can be influenced by the neuronal network, since the NG2 ICD has been shown to be generated by constitutive as well as activity-dependent cleavage. Our results also elucidate a possible role of NG2 in tumors exhibiting enhanced rates of translation and rapid cell cycle kinetics.

Radio-sensitizing effects of VE-821 and beyond: Distinct phosphoproteomic and metabolomic changes after ATR inhibition in irradiated MOLT-4 cells

Current anti-cancer strategy takes advantage of tumour specific abnormalities in DNA damage response to radio- or chemo-therapy. Inhibition of the ATR/Chk1 pathway has been shown to be synthetically lethal in cells with high levels of oncogene-induced replication stress and in p53- or ATM- deficient cells. In the presented study, we aimed to elucidate molecular mechanisms underlying radiosensitization of T-lymphocyte leukemic MOLT-4 cells by VE-821, a higly potent and specific inhibitor of ATR. We combined multiple approaches: cell biology techniques to reveal the inhibitor-induced phenotypes, and quantitative proteomics, phosphoproteomics, and metabolomics to comprehensively describe drug-induced changes in irradiated cells. VE-821 radiosensitized MOLT-4 cells, and furthermore 10 μM VE-821 significantly affected proliferation of sham-irradiated MOLT-4 cells. We detected 623 differentially regulated phosphorylation sites. We revealed changes not only in DDR-related pathways and kinases, but also in pathways and kinases involved in maintaining cellular metabolism. Notably, we found downregulation of mTOR, the main regulator of cellular metabolism, which was most likely caused by an off-target effect of the inhibitor, and we propose that mTOR inhibition could be one of the factors contributing to the phenotype observed after treating MOLT-4 cells with 10 μM VE-821. In the metabolomic analysis, 206 intermediary metabolites were detected. The data indicated that VE-821 potentiated metabolic disruption induced by irradiation and affected the response to irradiation-induced oxidative stress. Upon irradiation, recovery of damaged deoxynucleotides might be affected by VE-821, hampering DNA repair by their deficiency. Taken together, this is the first study describing a complex scenario of cellular events that might be ATR-dependent or triggered by ATR inhibition in irradiated MOLT-4 cells. Data are available via ProteomeXchange with identifier PXD008925.

EB-3D a novel choline kinase inhibitor induces deregulation of the AMPK-mTOR pathway and apoptosis in leukemia T-cells

Choline kinase alpha 1 (ChoKα1) has recently become an interesting therapeutic target since its overexpression has been associated to tumorigenesis in many cancers. Nevertheless, little is known regarding hematological malignancies. In this manuscript, we investigated the effect of a novel and selective ChoKα inhibitor EB-3D in T acute lymphoblastic leukemia (T-ALL). The effect of EB-3D was evaluated in a panel of T-leukemia cell lines and ex-vivo primary cultures derived from pediatric T-ALL patients. We also evaluated in detail, using Reverse Phase Protein Array (RPPA), protein phosphorylation level changes in T-ALL cells upon treatment. The drug exhibits a potent antiproliferative activity in a panel of T-leukemia cell lines and primary cultures of pediatric patients. Moreover, the drug strongly induces apoptosis and more importantly it enhanced T-leukemia cell sensitivity to chemotherapeutic agents, such as dexamethasone and l-asparaginase. In addition, the compound induces an early activation of AMPK, the main regulator of cellular energy homeostasis, by its phosphorylation at residue T712 of catalytic subunit α, and thus repressing mTORC1 pathway, as shown by mTOR S2448 dephosphorylation. The inhibition of mTOR in turn affects the activity of several known downstream targets, such as 4E-BP1, p70S6K, S6 Ribosomal Protein and GSK3 that ultimately may lead to a reduction of protein synthesis and cell death. Taken together, our findings suggest that targeting ChoKα may be an interesting option for treating T-ALL and that EB-3D could represent a valuable therapeutic tool.

TOR signaling in plants: conservation and innovation

Target of rapamycin (TOR) is an evolutionarily conserved protein kinase that plays a central role in both plants and animals, despite their distinct developmental programs and survival strategies. Indeed, TOR integrates nutrient, energy, hormone, growth factor and environmental inputs to control proliferation, growth and metabolism in diverse multicellular organisms. Here, we compare the molecular composition, upstream regulators and downstream signaling relays of TOR complexes in plants and animals. We also explore and discuss the pivotal functions of TOR signaling in basic cellular processes, such as translation, cell division and stem/progenitor cell regulation during plant development.

Chemoresistance and targeting of growth factors/cytokines signalling pathways: towards the development of effective therapeutic strategy for endometrial cancer

Endometrial cancer tends to be an aggressive malignancy. Although the disease prognosis can be good at the early stages of disease, the advanced condition is not curable. Chemotherapy regimens and hormone-based therapy in combination with surgery are major approaches for the management of endometrial cancers. However, intrinsic chemoresistance reduces the success rate and increases the possibility of disease relapse. Investigation of underlying mechanisms revealed altered activation of PI3K/AKT, MAPK, fibroblast growth factor (FGF), mTOR and WNT pathways and reduced gene expression of tumor suppressor p53 in recurrent endometrial cancer. A PTEN mutation, deletion or degradation induces positive p-AKT expression, while PI3K knock-down increases the level of pro-apoptotic proteins and decreases the level of anti-apoptotic ones in cancerous cells. Additionally, RAS proteins trigger both the RAF-MEK-ERK and PI3K-PTEN-AKT signalling mechanisms, thus conferring resistance to anti-tumor agents. FGF up-regulates angiogenesis via receptor-mediated tyrosine kinase activation. Single nucleotide polymorphism, gene amplification or missense mutations of FGFR2 are associated with endometrial cancer. The mTOR complex integrates the nutrient and mitogen signals via AMPKs, S6 kinase 1 (S6K1) and eukaryotic initiation factors, causing unrestricted endometrial cellular proliferation. WNT signalling molecules, such as frizzled receptors, β-catenin, PORCN, RSPO3 and DKK1 undergo dysregulation, and drugs targeting these pathways are under clinical trials in patients with endometrial cancer. Common therapies for endometrial tumor include platinum-based anti-neoplastics, taxanes, nucleoside analogues, immune modulators, FGFR and tyrosine kinase inhibitors, small-molecule mTOR inhibitors and drugs that trigger cell cycle arrest in the G1 phase. Taken together, the current review elucidates the mechanism underlying endometrial cancer, existing therapies and chemoresistance, and points towards the need for novel therapeutics that may promote disease-free survival.

A Blood Pact: the Significance and Implications of eIF4E on Lymphocytic Leukemia

Elevated levels of eukaryotic initiation factor 4E (eIF4E) are implicated in neoplasia, with cumulative evidence pointing to its role in the etiopathogenesis of hematological diseases. As a node of convergence for several oncogenic signaling pathways, eIF4E has attracted a great deal of interest from biologists and clinicians whose efforts have been targeting this translation factor and its biological circuits in the battle against leukemia. The role of eIF4E in myeloid leukemia has been ascertained and drugs targeting its functions have found their place in clinical trials. Little is known, however, about the pertinence of eIF4E to the biology of lymphocytic leukemia and a paucity of literature is available in this regard that prospectively evaluates the topic to guide practice in hematological cancer. A comprehensive analysis on the significance of eIF4E translation factor in the clinical picture of leukemia arises, therefore, as a compelling need. This review presents aspects of eIF4E involvement in the realm of the lymphoblastic leukemia status; translational control of immunological function via eIF4E and the state-of-the-art in drugs will also be outlined.

Novel mechanism of cannabidiol-induced apoptosis in breast cancer cell lines

Studies have emphasized an antineoplastic effect of the non-psychoactive, phyto-cannabinoid, Cannabidiol (CBD). However, the molecular mechanism underlying its antitumor activity is not fully elucidated. Herein, we have examined the effect of CBD on two different human breast cancer cell lines: the ER-positive, well differentiated, T-47D and the triple negative, poor differentiated, MDA-MB-231 cells. In both cell lines, CBD inhibited cell survival and induced apoptosis in a dose dependent manner as observed by MTT assay, morphological changes, DNA fragmentation and ELISA apoptosis assay. CBD-induced apoptosis was accompanied by down-regulation of mTOR, cyclin D1 and up-regulation and localization of PPARγ protein expression in the nuclei and cytoplasmic of the tested cells. The results suggest that CBD treatment induces an interplay among PPARγ, mTOR and cyclin D1 in favor of apoptosis induction in both ER-positive and triple negative breast cancer cells, proposing CBD as a useful treatment for different breast cancer subtypes.

Brain Somatic Mutations in MTOR Disrupt Neuronal Ciliogenesis, Leading to Focal Cortical Dyslamination

Focal malformations of cortical development (FMCDs), including focal cortical dysplasia (FCD) and hemimegalencephaly (HME), are major etiologies of pediatric intractable epilepsies exhibiting cortical dyslamination. Brain somatic mutations in MTOR have recently been identified as a major genetic cause of FMCDs. However, the molecular mechanism by which these mutations lead to cortical dyslamination remains poorly understood. Here, using patient tissue, genome-edited cells, and mouse models with brain somatic mutations in MTOR, we discovered that disruption of neuronal ciliogenesis by the mutations underlies cortical dyslamination in FMCDs. We found that abnormal accumulation of OFD1 at centriolar satellites due to perturbed autophagy was responsible for the defective neuronal ciliogenesis. Additionally, we found that disrupted neuronal ciliogenesis accounted for cortical dyslamination in FMCDs by compromising Wnt signals essential for neuronal polarization. Altogether, this study describes a molecular mechanism by which brain somatic mutations in MTOR contribute to the pathogenesis of cortical dyslamination in FMCDs.

Cell size sensing in animal cells coordinates anabolic growth rates and cell cycle progression to maintain cell size uniformity

Cell size uniformity in healthy tissues suggests that control mechanisms might coordinate cell growth and division. We derived a method to assay whether cellular growth rates depend on cell size, by monitoring how variance in size changes as cells grow. Our data revealed that, twice during the cell cycle, growth rates are selectively increased in small cells and reduced in large cells, ensuring cell size uniformity. This regulation was also observed directly by monitoring nuclear growth in live cells. We also detected cell-size-dependent adjustments of G1 length, which further reduce variability. Combining our assays with chemical/genetic perturbations confirmed that cells employ two strategies, adjusting both cell cycle length and growth rate, to maintain the appropriate size. Additionally, although Rb signaling is not required for these regulatory behaviors, perturbing Cdk4 activity still influences cell size, suggesting that the Cdk4 pathway may play a role in designating the cell’s target size.

Animal cells come in many different sizes. In humans, for example, egg cells are thousands of times larger than sperm cells. Yet cells of any given type are often strikingly similar in size. The cells that line the surface of organs including the skin and kidneys are especially uniform; in fact a loss of size uniformity in certain tumors is a sign of malignancy. What kind of regulation could enable separate cells within a tissue to have the same size?

One possibility is that each type of cell is programmed with a specific target size, and that a cell can sense if it strays from its target and take steps to compensate. Animal cells sensing their own size was first reported in the 1960s, and now Ginzberg et al. confirm that human cells grown in the laboratory do indeed monitor their size and correct deviations from their target. It turns out that two separate and independent processes help to keep all the cells in the population roughly uniform in size. Firstly, proliferating human cells that are smaller than their target size spend longer growing before they divide. Secondly, at two time points between cell divisions, large cells adjust their growth rate such that they grow slower than small cells.

To show these processes in action, Ginzberg et al. introduced mutations or chemicals that perturbed the length of time between cell divisions or the rate of a cell’s growth. As expected, most of these perturbations had only a modest influence on cell size, due to the cell’s compensatory strategies. Cells that had less time to grow compensated by more quickly making new protein molecules, meaning that they still had enough material to build two new cells by the time they had to divide. In contrast, if a cell’s division was artificially delayed, it reduced its growth rate to stop it from becoming too large. Similarly, cells grown in conditions that slow the production of proteins extended the time between their cell divisions to give them enough time to accumulate the material required for two new cells.

In a recent related study, Liu, Ginzberg et al. identified some of the molecules that a human cell uses to sense its own size. Together these two studies now pave the road to answering a fundamental question in cell biology: what is the elusive cell size sensor? Understanding how cells sense their size will open a window onto how quantitative information is programmed, sensed and communicated within living cells. These findings will shed also new light onto how cells specialize into cell types of different sizes, and what happens when cells lose the ability to sense or regulate their size in diseases like cancers.

Effects of single amino acid deficiency on mRNA translation are markedly different for methionine versus leucine

Although amino acids are known regulators of translation, the unique contributions of specific amino acids are not well understood. We compared effects of culturing HEK293T cells in medium lacking either leucine, methionine, histidine, or arginine on eIF2 and 4EBP1 phosphorylation and measures of mRNA translation. Methionine starvation caused the most drastic decrease in translation as assessed by polysome formation, ribosome profiling, and a measure of protein synthesis (puromycin-labeled polypeptides) but had no significant effect on eIF2 phosphorylation, 4EBP1 hyperphosphorylation or 4EBP1 binding to eIF4E. Leucine starvation suppressed polysome formation and was the only tested condition that caused a significant decrease in 4EBP1 phosphorylation or increase in 4EBP1 binding to eIF4E, but effects of leucine starvation were not replicated by overexpressing nonphosphorylatable 4EBP1. This suggests the binding of 4EBP1 to eIF4E may not by itself explain the suppression of mRNA translation under conditions of leucine starvation. Ribosome profiling suggested that leucine deprivation may primarily inhibit ribosome loading, whereas methionine deprivation may primarily impair start site recognition. These data underscore our lack of a full understanding of how mRNA translation is regulated and point to a unique regulatory role of methionine status on translation initiation that is not dependent upon eIF2 phosphorylation.

Inhibition of protein arginine methyltransferase 5 enhances hepatic mitochondrial biogenesis

Protein arginine methyltransferase 5 (PRMT5) regulates gene expression either transcriptionally by symmetric dimethylation of arginine residues on histones H4R3, H3R8, and H2AR3 or at the posttranslational level by methylation of nonhistone target proteins. Although emerging evidence suggests that PRMT5 functions as an oncogene, its role in metabolic diseases is not well-defined. We investigated the role of PRMT5 in promoting high-fat-induced hepatic steatosis. A high-fat diet up-regulated PRMT5 levels in the liver but not in other metabolically relevant tissues such as skeletal muscle or white and brown adipose tissue. This was associated with repression of master transcription regulators involved in mitochondrial biogenesis. In contrast, lentiviral short hairpin RNA-mediated reduction of PRMT5 significantly decreased phosphatidylinositol 3-kinase/AKT signaling in mouse AML12 liver cells. PRMT5 knockdown or knockout decreased basal AKT phosphorylation but boosted the expression of peroxisome proliferator-activated receptor α (PPARα) and PGC-1α with a concomitant increase in mitochondrial biogenesis. Moreover, by overexpressing an exogenous WT or enzyme-dead mutant PRMT5 or by inhibiting PRMT5 enzymatic activity with a small-molecule inhibitor, we demonstrated that the enzymatic activity of PRMT5 is required for regulation of PPARα and PGC-1α expression and mitochondrial biogenesis. Our results suggest that targeting PRMT5 may have therapeutic potential for the treatment of fatty liver.

PI3K/Akt/mTOR Signaling Pathway and the Biphasic Effect of Arsenic in Carcinogenesis

Arsenic is a naturally occurring, ubiquitous metalloid found in the Earth’s crust. In its inorganic form, arsenic is highly toxic and carcinogenic and is widely found across the globe and throughout the environment. As an International Agency for Research on Cancer–defined class 1 human carcinogen, arsenic can cause multiple human cancers, including liver, lung, urinary bladder, skin, kidney, and prostate. Mechanisms of arsenic-induced carcinogenesis remain elusive, and this review focuses specifically on the role of the PI3K/AKT/mTOR pathway in promoting cancer development. In addition to exerting potent carcinogenic responses, arsenic is also known for its therapeutic effects against acute promyelocytic leukemia. Current literature suggests that arsenic can achieve both therapeutic as well as carcinogenic effects, and this review serves to examine the paradoxical effects of arsenic, specifically through the PI3K/AKT/mTOR pathway. Furthermore, a comprehensive review of current literature reveals an imperative need for future studies to establish and pinpoint the exact conditions for which arsenic can, and through what mechanisms it is able to, differentially regulate the PI3K/AKT/mTOR pathway to maximize the therapeutic and minimize the carcinogenic properties of arsenic.

Multiscale systems pharmacological analysis of everolimus action in hepatocellular carcinoma

Dysregulation of mTOR pathway is common in hepatocellular carcinoma (HCC). A translational quantitative systems pharmacology (QSP), pharmacokinetic (PK), and pharmacodynamic (PD) model dissecting the circuitry of this pathway was developed to predict HCC patients' response to everolimus, an mTOR inhibitor. The time course of key signaling proteins in the mTOR pathway, HCC cells viability, tumor volume (TV) and everolimus plasma and tumor concentrations in xenograft mice, clinical PK of everolimus and progression free survival (PFS) in placebo and everolimus-treated patients were extracted from literature. A comprehensive and multiscale QSP/PK/PD model was developed, qualified, and translated to clinical settings. Model fittings and simulations were performed using Monolix software. The S6-kinase protein was identified as critical in the mTOR signaling pathway for describing everolimus lack of efficacy in HCC patients. The net growth rate constant (kg) of HCC cells was estimated at 0.02 h^-1 (2.88%RSE). The partition coefficient of everolimus into the tumor (kp) was determined at 0.06 (12.98%RSE). The kg in patients was calculated from the doubling time of TV in naturally progressing HCC patients, and was determined at 0.004 day^-1. Model-predicted and observed PFS were in good agreement for placebo and everolimus-treated patients. In conclusion, a multiscale QSP/PK/PD model elucidating everolimus lack of efficacy in HCC patients was successfully developed and predicted PFS reasonably well compared to observed clinical findings. This model may provide insights into clinical response to everolimus-based therapy and serve as a valuable tool for the clinical translation of efficacy for novel mTOR inhibitors.