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

In recent years, significant milestones have been reached in the field of transplantation through the development of immunosuppressive drugs that inhibit lymphocyte activation, cytokine signal transduction, and cellular proliferation. However, the widespread tissue distribution of the molecular targets exploited to date-calcineurin, mammalian target of rapamycin (mTOR), and inosine monophosphate dehydrogenase-produces an array of collateral toxicities. Avoiding these side effects requires new strategies that selectively block destructive immune responses: a fifth generation of immunosuppressants. These agents must target molecules that are critical for and specific to the adaptive immune response.
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PMID:The emerging matrix of immunosuppressive agents. 1452 43

T cell anergy has been demonstrated to play a role in maintaining peripheral tolerance to self Ags as well as a means by which tumors can evade immune destruction. Although the precise pathways involved in anergy induction have yet to be elucidated, it has been linked to TCR engagement in the setting of cell cycle arrest. Indeed, rapamycin, which inhibits T cell proliferation in G(1), has the ability to promote tolerance even in the presence of costimulation. To better define the role of the cell cycle in regulating anergy induction, we used the novel cyclophilin-binding ligand, sanglifehrin A (SFA). We demonstrate that SFA can inhibit TCR-induced cytokine and chemokine production without preventing TCR-induced anergy. Our data also indicate that despite its ability to induce G(1) arrest, SFA does not induce anergy in the presence of costimulation. Furthermore, although SFA blocks proliferation to exogenous IL-2, it does not prevent IL-2-induced reversal of anergy. When we examined the phosphorylation of 4EBP-1, a downstream substrate of the mammalian target of rapamycin, we found that rapamycin, but not SFA, inhibited the mammalian target of rapamycin activity. Based on these data, we propose that the decision as to whether TCR engagement will lead to productive activation or tolerance is dictated by a rapamycin -inhibitable pathway, independent of the G(1)-->S phase cell cycle progression.
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PMID:The novel cyclophilin binding compound, sanglifehrin A, disassociates G1 cell cycle arrest from tolerance induction. 1506 56

Cell cycle aberrations occurring at the G(1)/S checkpoint often lead to uncontrolled cell proliferation and tumor growth. We recently demonstrated that IL-1beta inhibits insulin-like growth factor (IGF)-I-induced cell proliferation by preventing cells from entering the S phase of the cell cycle, leading to G(0)/G(1) arrest. Notably, IL-1beta suppresses the ability of the IGF-I receptor tyrosine kinase to phosphorylate its major docking protein, insulin receptor substrate-1, in MCF-7 breast carcinoma cells. In this study, we extend this juxtamembrane cross-talk between cytokine and growth factor receptors to downstream cell cycle machinery. IL-1beta reduces the ability of IGF-I to activate Cdk2 and to induce E2F-1, cyclin A, and cyclin A-dependent phosphorylation of a retinoblastoma tumor suppressor substrate. Long-term activation of the phosphatidylinositol 3-kinase/Akt signaling pathway, but not the mammalian target of rapamycin or mitogen-activated protein kinase pathways, is required for IGF-I to hyperphosphorylate retinoblastoma and to cause accumulation of E2F-1 and cyclin A. In the absence of IGF-I to induce Akt activation and cell cycle progression, IL-1beta has no effect. IL-1beta induces p21(Cip1/Waf1), which may contribute to its inhibition of IGF-I-activated Cdk2. Collectively, these data establish a novel mechanism by which prolonged Akt phosphorylation serves as a convergent target for both IGF-I and IL-1beta; stimulation by growth factors such as IGF-I promotes G(1)-S phase progression, whereas IL-1beta antagonizes IGF-I-induced Akt phosphorylation to induce cytostasis. In this manner, Akt serves as a critical bridge that links proximal receptor signaling events to more distal cell cycle machinery.
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PMID:IL-1beta suppresses prolonged Akt activation and expression of E2F-1 and cyclin A in breast cancer cells. 1518 2

We have reported recently that IgG from patients with Graves' disease (GD) can induce the expression of the CD4-specific T lymphocyte chemoattractant, IL-16, and RANTES, a C-C chemokine, in their fibroblasts. This induction is mediated through the insulin-like growth factor-1 receptor (IGF-1R) pathway. We now report that Abs from individuals with active rheumatoid arthritis (RA-IgG) stimulate in their synovial fibroblasts the expression of these same cytokines. IgG from individuals without known autoimmune disease fails to elicit this chemoattractant production. Furthermore, RA-IgG fails to induce IL-16 or RANTES expression in synovial fibroblasts from donors with osteoarthritis. RA-IgG-provoked IL-16 and RANTES production also appears to involve the IGF-1R because receptor-blocking Abs prevent the response. RA fibroblasts transfected with a dominant-negative mutant IGF-1R fail to respond to RA-IgG. IGF-1 and the IGF-1R-specific analog Des(1-3) also induce cytokine production in RA fibroblasts. RA-IgG-provoked IL-16 expression is inhibited by rapamycin, a specific macrolide inhibitor of the Akt/FRAP/mammalian target of rapamycin/p70(s6k) pathway, and by dexamethasone. GD-IgG can also induce IL-16 in RA fibroblasts, and RA-IgG shows similar activity in GD fibroblasts. Thus, IgGs from patients with RA, like those associated with GD, activate IGF-1R, and in so doing provoke T cell chemoattraction expression in fibroblasts, suggesting a potential common pathway in the two diseases. Immune-competent cell trafficking to synovial tissue is integral to the pathogenesis of RA. Recognition of this novel RA-IgG/fibroblast interaction and its functional consequences may help identify therapeutic targets.
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PMID:Synovial fibroblasts from patients with rheumatoid arthritis, like fibroblasts from Graves' disease, express high levels of IL-16 when treated with Igs against insulin-like growth factor-1 receptor. 1532 22

IL-8 plays an integral role in promoting the malignant phenotype in breast cancer, and its production is directly influenced by inflammatory cytokines in the tumor microenvironment. Here, we show that activation of IL-1beta receptors on malignant HS578t and MDA-MB-231 breast cancer cells strongly induces IL-8 expression and that RNA stabilization is persistently activated at least 12-24 hr after stimulation. SB 203580 and rapamycin reversed the RNA stabilization effect of IL-1beta in a dose-dependent manner, suggesting involvement of the p38/MAP kinase and mTOR pathways. A luciferase reporter assay indicated that the stabilization effect was dependent on cis elements in the 3'-untranslated region (UTR) of the IL-8 transcript. By UV cross-linking, we identified multiple cellular factors that interact with the IL-8 3'UTR, ranging 34-76 kDa. Immunoprecipitation analysis indicated that HuR, KSRP and TIAR bound to one or more loci in the 3'UTR. While the cross-linking patterns were similar, quantitative immunoprecipitation of native IL-8 RNA from IL-1beta-stimulated cytoplasmic extract revealed a 20-fold greater association of transcript with the stabilizing factor HuR vs. the destabilizing factor KSRP. In conclusion, IL-1beta is a potent cytokine stimulus for IL-8 RNA stabilization in breast cancer cells, possibly by enhanced binding of cytoplasmic HuR to the 3'UTR.
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PMID:IL-1beta induces stabilization of IL-8 mRNA in malignant breast cancer cells via the 3' untranslated region: Involvement of divergent RNA-binding factors HuR, KSRP and TIAR. 1551 71

Wyeth (formerly American Home Products) is developing temsirolimus [Cell cycle inhibitor-779, CCI 779], an ester analogue of sirolimus, for the treatment of cancer, multiple sclerosis and rheumatoid arthritis. Temsirolimus binds to the cytosolic protein, FKBP, which subsequently inhibits mTOR (mammalian target of rapamycin). Inhibition of mTOR blocks a number of signal transduction pathways that suppress translation of several key proteins regulating the cell cycle. These effects lead to a cell cycle block at the G1 phase. In animal models of human cancers, temsirolimus inhibited the growth of a diverse range of cancer types even when an intermittent dosing schedule was used. The compound also appears to have potential for the blockade of inflammatory responses associated with autoimmune and rheumatic diseases by inhibiting T-cell proliferation. On 11 March 2002, American Home Products changed its name and the name of its subsidiary Wyeth-Ayerst to Wyeth. During the first half of 2004, Wyeth initiated ongoing recruitment into a US phase III trial comparing orally administered temsirolimus plus letrozole versus letrozole alone as first-line treatment among approximately 1200 postmenopausal women with advanced breast cancer. The multicentre, randomised, double-blind, placebo-controlled trial is estimated to last 34 months. All subjects will have the option of participating in the long-term follow-up phase of the trial that involves follow-up every 3 months until disease progression; the primary endpoint is overall progression-free survival. In August 2004, the US FDA granted temsirolimus fast-track status for the first-line treatment of poor-prognosis patients with advanced renal cell carcinoma. Previously in March 2002, temsirolimus received fast-track status from the FDA for the treatment of renal cell carcinoma in patients who failed to respond to interleukin-2 treatment. Wyeth intends to file a NDA for temsirolimus for this indication by 2006. Researchers from Wyeth presented the findings from a preclinical study of temsirolimus at the 67th Annual Scientific Meeting of the American College of Rheumatology and the 38th Annual Meeting Association of Rheumatology Health Professionals (ACR/ARHP-2003) [Orlando, FL, USA; October 2003]. The aim of this study was to determine the effect of temsirolimus on lymphocyte proliferation and cytokine production. Since lymphocytes and cytokines are significantly involved in the pathogenesis of rheumatoid arthritis, temsirolimus could have disease-modifying antirheumatic drug (DMARD) activity against rheumatoid arthritis via the inhibition of these factors. According to Wyeth's investor presentation in June 2004, the patent covering temsirolimus is due for expiry in 2014.
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PMID:Temsirolimus: CCI 779, CCI-779, cell cycle inhibitor-779. 1556 43

Skeletal muscle is a major insulin target tissue and has a prominent role in the control of body amino acid economy, being the principal store of free and protein-bound amino acids and a dominant locus for amino acid metabolism. Interplay between diverse stimuli (e.g., hormonal/nutritional/mechanical) modulates muscle insulin action to serve physiological need through the action of factors such as intramuscular signaling molecules. Ceramide, a product of sphingolipid metabolism and cytokine signaling, has a potent contra-insulin action with respect to the transport and deposition of glucose in skeletal muscle, although ceramide effects on muscle amino acid turnover have not previously been documented. Here, membrane permeant C2-ceramide is shown to attenuate the basal and insulin-stimulated activity of the Na+-dependent System A amino acid transporter in rat muscle cells (L6 myotubes) by depletion of the plasma membrane abundance of SNAT2 (a System A isoform). Concomitant with transporter down-regulation, ceramide diminished both intramyocellular amino acid abundance and the phosphorylation of translation regulators lying downstream of mTOR. The physiological outcome of ceramide signaling in this instance is a marked reduction in cellular protein synthesis, a result that is likely to represent an important component of the processes leading to muscle wasting in catabolic conditions.
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PMID:Ceramide down-regulates System A amino acid transport and protein synthesis in rat skeletal muscle cells. 1561 Nov 52

Insulin and TNF-alpha exert opposing effects on skeletal muscle protein synthesis that are mediated in part by the rapamycin-sensitive mammalian target of rapamycin (mTOR) pathway and the PD-98059-sensitive, extracellular signal-regulated kinase (ERK)1/2 pathway. The present study examined the separate and combined effects of insulin (INS), TNF, PD-98059, or dnMEK1 adenovirus on the translational control of protein synthesis in C(2)C(12) myotubes. Cultures were treated with INS, TNF, PD-98059, dnMEK1, or a combination of INS + TNF with PD-98059 or dnMEK1. INS stimulated protein synthesis, enhanced eIF4E.eIF4G association, and eIF4G phosphorylation and repressed eIF4E.4E-BP1 association vs. control. INS also promoted phosphorylation of ERK1/2, S6K1, and 4E-BP1 and dephosphorylation of eIF4E. TNF alone did not have an effect on protein synthesis (vs. control), eIF4E.eIF4G association, or the phosphorylation of eIF4G, S6K1, or 4E-BP1, although it transiently increased ERK1/2 and eIF4E phosphorylation. When myotubes were treated with TNF + INS, the cytokine blocked the insulin-induced stimulation of protein synthesis. This appeared to be due to an attenuation of insulin-stimulated eIF4E.eIF4G association, because other stimulatory effects of INS, e.g., phosphorylation of ERK1/2, 4E-BP1, S6K1, eIF4G, and eIF4E and eIF4E.4E-BP1 association, were unaffected. Finally, treatment of myotubes with PD-98059 or dnMEK1 adenovirus before TNF + INS addition resulted in a derepression of protein synthesis and the association of eIF4G with eIF4E. These findings suggest that TNF abrogates insulin-induced stimulation of protein synthesis in myotubes through a decrease in eIF4F complex assembly independently of S6K1 and 4E-BP1 signaling and dependently on a MEK1-sensitive signaling pathway.
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PMID:Acute treatment with TNF-alpha attenuates insulin-stimulated protein synthesis in cultures of C2C12 myotubes through a MEK1-sensitive mechanism. 1570 78

v-ErbB is an oncogene related to the Epidermal Growth Factor Receptor (EGFR). EGFR overexpression has been observed in many pathological situations. There is a truncated form of EGFR, referred to as EGFvIII, which resembles v-ErbB in biological properties and is often expressed in certain human tumors. Aberrant EGFR expression in human cancers is often constitutive and may occur in the presence of mutated oncogenes or tumor suppressor genes. To circumvent these problems, we subcloned v-ErbB into a vector which contains the estrogen receptor hormone binding domain (ER) which renders the v-ErbB:ER protein dependent upon beta-estradiol for activity. v-ErbB:ER conditionally abrogated the cytokine dependence of hematopoietic cells more efficiently than activated v-Ha-Ras, v-Src, Raf or Akt. Abrogation of cytokine-dependence by v-ErbB:ER was not due to the synthesis of autocrine growth factors. Treatment of v-ErbB:ER cells with the EGFR inhibitor AG1478 efficiently induced apoptosis. Induction of apoptosis and prevention of cell cycle progression by the EGFR inhibitor were only observed when the cells were grown in response to v-ErbB:ER activation demonstrating specificity. In contrast, the other inhibitors suppressed cell cycle progression when the cells were grown in response to v-ErbB:ER or the cytokine interleukin-3. When MEK and either EGFR or PI3K/mTOR inhibitors were added, an enhanced apoptotic response was observed. Thus this conditional ErbB construct is useful to elucidate EGFR signaling and anti-apoptotic pathways in the absence of autocrine cytokine expression.
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PMID:Conditional EGFR promotes cell cycle progression and prevention of apoptosis in the absence of autocrine cytokines. 1591 60

Metastatic renal-cell carcinoma (mRCC) is highly resistant to cytotoxic agents or hormones and is currently mainly treated with cytokine-based therapy. Transient responses and moderate survival advantages have been achieved in a subset of patients with these aspecific biological response modifiers. Side-effects are considerable, especially with high-dose interleukin (IL)-2. Efforts made in the field of specific immunotherapy have focused on optimization of dendritic cell vaccination and on administration of monoclonal antibodies, either cold (unconjugated) or hot (radioactively labeled). Furthermore, allogeneic bone marrow transplantation is able to induce remissions but, regrettably, is related to substantial morbidity and mortality. Neutralization of the biological activity of some immunosuppressive cytokines produced by RCC (IL-6 and tumor necrosis factor-alpha) with monoclonal antibodies is currently under investigation. Insights gained into the processes and pathways underlying carcinogenesis have led to the development of new treatment strategies. These treatments can be used for clear cell RCC, since they focus on blocking gene products that are upregulated by mutations in the von Hippel-Lindau gene. Specific strategies include anti-vascular endothelial growth factor monoclonal antibody (bevacizumab) or inhibition of its receptor kinases (oral SU11248 or PTK787), or targeting the Raf kinase pathway (by BAY 43-9006) or the mammalian target of rapamycin (mTOR) pathway (by CCI-779). Early clinical results are promising, but their place in the treatment of RCC has to be determined.
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PMID:Novel treatment strategies in clear-cell metastatic renal cell carcinoma. 1602 18


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