Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P42345 (mTOR)
 26,049 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Angiogenin (ANG), originally identified as an angiogenic ribonuclease, has recently been shown to play a direct role in prostate cancer cell proliferation by mediating rRNA transcription. ANG is up-regulated in human prostate cancer and is the most significantly up-regulated gene in AKT-driven prostate intraepithelial neoplasia (PIN) in mice. Enhanced cell proliferation in the PIN lesions requires increased ribosome biogenesis, a multistep process involving an orchestrated production of ribosomal proteins and rRNA. AKT is known to enhance ribosomal protein production through the mammalian target of rapamycin pathway. However, it was unknown how rRNA is proportionally increased. Here, we report that ANG is essential for AKT-driven PIN formation and survival. We showed that up-regulation of ANG in the AKT-overexpressing mouse prostates is an early and lasting event. It occurs before PIN initiation and lasts beyond PIN is fully developed. Knocking down ANG expression by intraprostate injection of lentivirus-mediated ANG-specific small interfering RNA prevents AKT-induced PIN formation without affecting AKT expression and its signaling through the mammalian target of rapamycin pathway. Neomycin, an aminoglycoside that blocks nuclear translocation of ANG, and N65828, a small-molecule enzymatic inhibitor of the ribonucleolytic activity of ANG, both prevent AKT-induced PIN formation and reverse established PIN. They also decrease nucleolar organizer region, restore cell size, and normalize luminal architectures of the prostate despite continuous activation of AKT. All three types of the ANG inhibitor suppress rRNA transcription of the prostate luminal epithelial cells and inhibit AKT-induced PIN, indicating an essential role of ANG in AKT-mediated cell proliferation and survival.
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PMID:Angiogenin-stimulated rRNA transcription is essential for initiation and survival of AKT-induced prostate intraepithelial neoplasia. 1925 15

To evaluate the effect of deferasirox in human myeloid leukemia cells, and to identify the molecular pathways responsible for antiproliferative effects on leukemia cells during chelation therapy, we performed gene expression profiling to focus on the pathway involved in the anticancer effect of deferasirox. The inhibitory concentration (IC50) of deferasirox was 17-50 microM in three human myeloid cell lines (K562, U937, and HL60), while those in fresh leukemia cells obtained from four patients it varied from 88 to 172 microM. Gene expression profiling using Affymerix GeneChips (U133 Plus 2.0) revealed up-regulation of cyclin-dependent kinase inhibitor 1A (CDKN1A) encoding p21CIP, genes regulating interferon (i.e. IFIT1). Pathways related to iron metabolism and hypoxia such as growth differentiation factor 15 (GDF-15) and Regulated in development and DNA damage response (REDD1) were also prominent. Based on the results obtained from gene expression profiling, we particularly focused on the REDD1/mTOR (mammalian target of rapamycin) pathway in deferasirox-treated K562 cells, and found an enhanced expression of REDD1 and its down-stream protein, tuberin (TSC2). Notably, S6 ribosomal protein as well as phosphorylated S6, which is known to be a target of mTOR, was significantly repressed in deferasirox-treated K562 cells, and REDD1 small interfering RNA restored phosphorylation of S6. Although iron chelation may affect multiple signaling pathways related to cell survival, our data support the conclusion that REDD1 functions up-stream of tuberin to down-regulate the mTOR pathway in response to deferasirox. Deferasirox might not only have benefit for iron chelation but also may be an antiproliferative agent in some myeloid leukemias, especially patients who need both iron chelation and reduction of leukemia cells.
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PMID:The oral iron chelator deferasirox represses signaling through the mTOR in myeloid leukemia cells by enhancing expression of REDD1. 1929 23

The phosphatidylinositol-3-kinase (PI3K)/Akt signalling pathway is frequently deregulated in pancreatic cancers, and is believed to be an important determinant of their biological aggression and drug resistance. NVP-BEZ235 is a novel, dual class I PI3K/mammalian target of rapamycin (mTor) inhibitor undergoing phase I human clinical trials. To simulate clinical testing, the effects of NVP-BEZ235 were studied in five early passage primary pancreatic cancer xenografts, grown orthotopically. These tumours showed activated PKB/Akt, and increased levels of at least one of the receptor tyrosine kinases that are commonly activated in pancreatic cancers. Pharmacodynamic effects were measured following acute single doses, and anticancer effects were determined in separate groups following chronic drug exposure. Acute oral dosing with NVP-BEZ235 strongly suppressed the phosphorylation of PKB/Akt, followed by recovery over 24 h. There was also inhibition of Ser235/236 S6 ribosomal protein and Thr37/46 4E-BP1, consistent with the effects of NVP-BEZ235 as a dual PI3K/mTor inhibitor. Chronic dosing with 45 mg kg(-1) of NVP-BEZ235 was well tolerated, and produced significant tumour growth inhibition in three models. These results predict that agents targeting the PI3K/Akt/mTor pathway might have anticancer activity in pancreatic cancer patients, and support the testing of combination studies involving chemotherapy or other molecular targeted agents.
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PMID:Activity of a novel, dual PI3-kinase/mTor inhibitor NVP-BEZ235 against primary human pancreatic cancers grown as orthotopic xenografts. 1931 33

Mammalian target of rapamycin (mTOR), a well known Akt substrate, regulates multiple cellular functions including cell growth and protein synthesis. The current study identifies a novel role of the Akt/mTOR pathway as a regulator of CNS myelination. Previously, we showed that overexpressing constitutively active Akt in oligodendrocytes in a transgenic mouse model induces enhanced CNS myelination, with no changes in the proliferation or survival of oligodendrocyte progenitor or mature cells. The present study focused on the signaling mechanisms regulating this hypermyelination induced by Akt. Activation of mTOR and its downstream substrates (p70S6 kinase and S6 ribosomal protein) was observed in Akt-overexpressing oligodendrocytes. When mTOR signaling was inhibited chronically in vivo with rapamycin starting at 6 weeks of age, the observed hypermyelination was reduced to approximately the amount of myelin seen in wild-type mice. mTOR inhibition had little impact on wild-type myelination between 6 and 12 weeks of age, suggesting that, in normal adults, myelination is relatively complete and is no longer regulated by mTOR signaling. However, when mTOR was chronically inhibited in young adult wild-type mice, myelination was reduced. These results suggest that, during active myelination, the major Akt signal regulating CNS myelination is the mTOR pathway.
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PMID:Akt signals through the mammalian target of rapamycin pathway to regulate CNS myelination. 1947 13

The mammalian target of rapamycin(mTOR)and its molecular pathways are supposed to be activated frequently in human renal cell carcinoma as well as other cancers. It has a kinase activity for 40S ribosomal protein kinase and eukaryotic translation initiation factor 4E-binding protein 1. These proteins, when phosphorylated, promote protein translation and RNA transcription in the nutrient-rich condition. mTOR inhibitors such as Temsirolimus (CCI779) and Everolimus (RAD001) are effective for suppressing cell growth with inhibiting mTOR kinase activity. Rapamycin and its related analogs such as Temsirolimus and Everolimus are less toxic for humans compared with other anti-VEGFR inhibitors and has been used as an immunosuppressive agent. These agents have an inhibitory activity against the mTORC1 complex. Since they do not have inhibitory activity against mTORC2 complex, the ability of mTOR inhibition by Temsirolimus is supposed to be 40 to 50% of full inhibition in mTOR kinase. Temsirolimus has modest anticancer activity against advanced clinical RCC patients with poor risk. The objective response rate was only 7%, 26% of patients experienced minor responses and another 17% of patients had stable disease that lasted 6 months. The median time to tumor progression and median survival for the study patients were 5.8 and 15.0 months, respectively. The overall survival of patients treated with Temsirolimus alone was statistically longer than in those treated with IFN alone in the 626 cases in phase II study. Combinations of mTOR with other anti- VEGFR agents were not effective. Vertical therapies of mTOR inhibitor in combination with AKT inhibitors, or newly development of stronger mTOR kinase which can suppress both mTORC1 and mTORC2 are planned at present.
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PMID:[Mammalian target of rapamycin, its mode of action and clinical response in metastatic clear cell carcinoma]. 1962 Jul 95

The AKT/mammalian target of rapamycin (mTOR) signaling pathway plays a critical role in glioblastoma multiforme (GBM) oncogenesis due to activation of AKT. We studied two distinct complexes, mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2), through which mTOR controls cell survival, growth and motility. Inhibition of mTOR by rapamycin (RAPA) resulted in time-dependent suppression of S6 ribosomal protein (pS6KSer235/236; mTORC1 substrate) and caused transient suppression of pAKTSer473 (mTORC2 substrate) at 1 to 3 h followed by a consistent increase from 6 to 24 h. Inhibition of mTOR or phosphoinositide 3-kinase (PI3K) suppressed platelet-derived growth factor (PDGF)- or fibronectin (FN)-induced activation of p70S6KThr389. Combined inhibition of mTOR and PI3K abolished PDGF- or FN-induced activation of STAT3Ser727. Expression of pAKT was suppressed by siRNA silencing of mTORC2 co-protein rictor, but not by mTORC1 co-protein raptor. GBM cell proliferation and motility paralleled the activation of mTORC2. Combined inhibition of mTOR and PI3K had an additive effect on suppressing cell growth and motility. PDGF-induced nuclear localization of mTOR was blocked by pre-treatment with RAPA. The results demonstrated that an activation of mTORC2 occurs when mTORC1 is inhibited by RAPA. Therefore, simultaneous suppression of mTORC1 and mTORC2 may provide novel therapy for GBM.
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PMID:Involvement of mTORC1 and mTORC2 in regulation of glioblastoma multiforme growth and motility. 1972 9

A 3-year-old boy with right hemimegalencephaly (HME) showed massive calcification in the subcortical white matter and progressive atrophy of the affected hemisphere. Hemispherotomy was successful in amelioration of the patient's intractable epilepsy, and a surgical specimen from the epileptic focus was examined pathologically. Disarrangement of cortical layers along with dysmorphic appearance of neurons, balloon cells in the cortex and white matter, bi-layered calcifications in the superficial cortical layer and subcortical white matter, heterotopic neurons in the white matter, and diffuse astrogliosis were noted. Perivascular clustering of alpha-B-crystallin positive balloon cells was occasionally observed in the area of calcification. A diffuse increase was observed in the number of CD68-positive microglia/macrophages, particularly in perivascular and peri-calcification areas. These cells were often located within the calcification foci, which implicates their participation in the calcification process. Phosphorylated S6 ribosomal protein (P-S6) was expressed in large-sized neurons and numerous balloon cells, as well as in CD68-positive cells. In contrast, phosphorylated mammalian target of rapamycin (mTOR) was expressed in a small percentage of astrocytes, and phosphorylated p70S6 kinase was rarely identified in perivascular cells. These findings suggest that inflammatory processes have contributed to the pathogenesis of progressive calcification and atrophy in the megalencephalic hemisphere in this patient. Dissociation of expression of mTOR cascade components is common to other reported cases of HME, but P-S6 expression in microglia/macrophages has not been recognized. The cellular mechanism and significance of P-S6-specific activation of the mTOR cascade in HME, particularly in the inflammatory cell lineage, should be explored further.
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PMID:Activation of microglia/macrophages expressing phosphorylated S6 ribosomal protein in a case of hemimegalencephaly with progressive calcification and atrophy. 1980 89

The essential amino acids (EAA) activate anabolic signalling through mechanisms, which are unclear in detail but include increased signalling through the mammalian target of rapamycin complex 1 (mTORC1). Of all the EAA, the branched chain amino acid (BCAA) leucine has been suggested as the most potent in stimulating protein synthesis, although there have been no studies investigating the effects of each EAA on anabolic signalling pathways. We therefore undertook a systematic analysis of the effect of each EAA on mTORC1 signalling in C2C12 myotubes whereby cells were serum (4 h) and amino acid (1 h) starved before stimulation with 2 mM of each amino acid. Immunoblotting was used to detect phosphorylated forms of protein kinase B (Akt)/mTORC1 signalling enzymes. The phosphorylation of Akt was unchanged by incubation with EAA. Phosphorylation of mTOR and 4E binding protein-1 (4EBP1) were increased 1.67 +/- 0.1-fold and 2.5 +/- 0.1-fold, respectively, in response to leucine stimulation but not in response to any other EAA. The phosphorylation of ribosomal s6 kinase (p70S6K1) was increased by stimulation with all EAA with the exceptions of isoleucine and valine. However, the increase with leucine was significantly greater, 5.9 +/- 0.3-fold compared to 1.6-2.0-fold for the non-BCAA EAA. This pattern of activation was identical in ribosomal protein s6 (RPS6) with the additional effect of leucine being 3.8 +/- 0.3-fold versus 1.5-2.0-fold. Phosphorylation of eukaryotic initiation/elongation factors eIF2alpha and eEF2 were unaffected by EAA. We conclude that leucine is unique amongst the amino acids in its capacity to stimulate both mTOR and 4EBP1 phosphorylation and to enhance p70S6K1 signalling.
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PMID:Distinct anabolic signalling responses to amino acids in C2C12 skeletal muscle cells. 1988 15

Evidence exists that protein kinase C and the mammalian target of rapamycin are important regulators of cardiac hypertrophy. We examined the contribution of these signaling kinases to cardiac growth in spontaneously hypertensive rats (SHRs). Systolic blood pressure was increased (P<0.001) at 10 weeks in SHRs versus Wistar-Kyoto controls (162+/-3 versus 128+/-1 mm Hg) and was further elevated (P<0.001) at 17 weeks in SHRs (184+/-7 mm Hg). Heart:body weight ratio was not different between groups at 10 weeks but was 22% greater (P<0.01) in SHRs versus Wistar-Kyoto controls at 17 weeks. At 10 weeks, activation of Akt and S6 ribosomal protein was greater (P<0.01) in SHRs but returned to normal by 17 weeks. In contrast, SHRs had protein kinase C activation only at 17 weeks. To determine whether mammalian target of rapamycin regulates the initial development of hypertrophy, rats were treated with rapamycin (2 mg/kg per day IP) or saline vehicle from 13 to 16 weeks of age. Rapamycin inhibited cardiac mammalian target of rapamycin in SHRs, as evidenced by reductions (P<0.001) in phosphorylation of S6 ribosomal protein and eukaryotic translation initiation factor-4E binding protein 1. Rapamycin treatment also reduced (P<0.001) heart weight and hypertrophy by 47% and 53%, respectively, in SHRs in spite of increased (P<0.001) systolic blood pressure versus untreated SHRs (213+/-8 versus 189+/-6 mm Hg). Atrial natriuretic peptide, brain natriuretic peptide, and cardiac function were unchanged between SHRs treated with rapamycin or vehicle. These data show that mammalian target of rapamycin is required for the development of cardiac hypertrophy evoked by rising blood pressure in SHRs.
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PMID:Mammalian target of rapamycin is a critical regulator of cardiac hypertrophy in spontaneously hypertensive rats. 1988 61

The ERK and mTOR pathways show multiple interconnections that coordinate growth activation and the regulation of protein translation. Although drugs that target these pathways appear to have limited anti-cancer effects as single agents, we hypothesized that the monotherapy anticancer efficacy of these agents could be enhanced by their combination. The MEK inhibitor AZD6244 (ARRY-142886) and the mTOR inhibitor rapamycin were tested as single agents and in combination, using BxPC-3 and MIA PaCa-2 pancreatic cancer models in vivo. In both models, S6 ribosomal protein was almost completely inhibited with combined treatment, but only partially inhibited with the single agents. In addition, 48 h treatment with the drug combination produced greater apoptosis, revealed by caspase 3 cleavage, and growth inhibition measured using bromodeoxyuridine incorporation, compared to the single agents. AZD6244 but not rapamycin exhibited a significant anti-angiogenic effect, as shown by tumor VEGF ELISA assay and CD31 analysis. Plasma and tumor pharmacokinetic analyses indicated that AZD6244 accumulates in tumor tissue at concentrations that produce target inhibition and cell cycle arrest in vitro. In chronic dosing experiments, the drug combination was well tolerated, and showed greater growth inhibition compared to the single agents. These results are consistent with the hypothesis that ERK and mTOR signaling interact at multiple levels to regulate tumor growth in vivo, and support the testing of MEK plus mTOR inhibitor combinations in pancreatic cancer patients.
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PMID:Effects of combined inhibition of MEK and mTOR on downstream signaling and tumor growth in pancreatic cancer xenograft models. 2000 39


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