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)

We have shown previously that hyperinsulinemia inhibits interferon-alpha-dependent activation of phosphatidylinositol 3-kinase (PI3-kinase) through mammalian target of rapamycin (mTOR)-induced serine phosphorylation of insulin receptor substrate (IRS)-1. Here we report that chronic insulin and high glucose synergistically inhibit interleukin (IL)-4-dependent activation of PI3-kinase in macrophages via the mTOR pathway. Resident peritoneal macrophages (PerMPhis) from diabetic (db/db) mice showed a 44% reduction in IRS-2-associated PI3-kinase activity stimulated by IL-4 compared with PerMPhis from heterozygote (db/+) control mice. IRS-2 from db/db mouse PerMPhis also showed a 78% increase in Ser/Thr-Pro motif phosphorylation without a difference in IRS-2 mass. To investigate the mechanism of this PI3-kinase inhibition, 12-O-tetradecanoylphorbol-13-acetate-matured U937 cells were treated chronically with insulin (1 nm, 18 h) and high glucose (4.5 g/liter, 48 h). In these cells, IL-4-stimulated IRS-2-associated PI3-kinase activity was reduced by 37.5%. Importantly, chronic insulin or high glucose alone did not impact IL-4-activated IRS-2-associated PI3-kinase. Chronic insulin + high glucose did reduce IL-4-dependent IRS-2 tyrosine phosphorylation and p85 association by 54 and 37%, respectively, but did not effect IL-4-activated JAK/STAT signaling. When IRS-2 Ser/Thr-Pro motif phosphorylation was examined, chronic insulin + high glucose resulted in a 92% increase in IRS-2 Ser/Thr-Pro motif phosphorylation without a change in IRS-2 mass. Pretreatment of matured U937 cells with rapamycin blocked chronic insulin + high glucose-dependent IRS-2 Ser/Thr-Pro motif phosphorylation and restored IL-4-dependent IRS-2-associated PI3-kinase activity. Taken together these results indicate that IRS-2-dependent IL-4 signaling in macrophages is impaired in models of type 2 diabetes mellitus through a mechanism that relies on insulin/glucose-dependent Ser/Thr-Pro motif serine phosphorylation mediated by the mTOR pathway.
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PMID:Insulin receptor substrate-2-dependent interleukin-4 signaling in macrophages is impaired in two models of type 2 diabetes mellitus. 1512 81

Deregulated phosphatidylinositol 3-kinase (PI3K) signaling pathway is widely implicated in tumor growth and resistance to chemotherapy. While a strong rationale exists for pharmacological targeting of PI3K, only a few proof-of-principle in vivo efficacy studies are currently available. PWT-458, pegylated-17-hydroxywortmannin, is a novel and highly potent inhibitor of PI3K in animal models. Upon in vivo cleavage of its poly(ethyleneglycol) (PEG), PWT-458 releases its active moiety 17-hydroxywortmannin (17-HWT), the most potent inhibitor in its class. Here we show that a single intravenous injection of PWT-458 rapidly inhibited PI3K signaling, as measured by a complete loss of AKT (Ser-473) phosphorylation in xenograft tumors grown in nude mice. Following a daily X5 dosing regimen, PWT-458 demonstrated single-agent antitumor activity in nude mouse xenograft models of U87MG glioma, nonsmall cell lung cancer (NSCLC) A549, and renal cell carcinoma (RCC) A498. Efficacious doses ranged from 0.5 mg/kg to 10 mg/kg, achieving a superior therapeutic index over 17-HWT. PWT-458 augmented anticancer efficacy of a suboptimal dose of paclitaxel against A549 and U87MG tumors. Combination treatment of PWT-458 and an mTOR inhibitor, Pegylated-Rapamycin (Peg-Rapa), resulted in an enhanced antitumor efficacy in U87MG. Finally, PWT-458 in combination with interferon-alpha (Intron-A) caused a dramatic regression of RCC A498, which was not achieved by either agent alone. These studies identify PWT-458 as an effective anticancer agent and provide strong proof-of-principle for targeting the PI3K pathway as novel anticancer therapy.
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PMID:PWT-458, a novel pegylated-17-hydroxywortmannin, inhibits phosphatidylinositol 3-kinase signaling and suppresses growth of solid tumors. 1590 1

Cytokine-based immunotherapy was the only viable option in metastatic, nonresectable renal cell carcinoma (RCC) for many years. Systemic immunotherapy has become increasingly established as a standard therapy during the last 15 years. In this context, interleukin-2 (IL-2) and interferon-alpha (IFN-alpha) turned out to be the most effective single agents in RCC. Subsequently, the approved subcutaneous application of these compounds was the preferred administration route in Germany. Response rates with cytokine combination therapy were almost similar to those of more aggressive concepts using additional chemotherapeutic agents.Currently, new compounds targeting specific signaling pathways are readily available and have passed clinical testing. Such small molecules like tyrosine kinase inhibitors, monoclonal antibodies, or the mTOR inhibitor CCI-779 may dramatically change the established concepts of systemic RCC treatment. This paper gives an overview of established, current, and evolving concepts of systemic therapy in RCC.
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PMID:[Systemic therapy of metastatic renal cell carcinoma]. 1662 45

Immunotherapy with interleukin-2 and interferon-alpha has been the only viable option in metastatic renal cell cancer for almost two decades. In the last several years, significant advances in the understanding of the underlying biological and molecular mechanisms of renal cell carcinoma, particularly the role of tumour angiogenesis, have led to the identification of rational therapeutic targets and permitted the design of molecularly targeted therapeutics. At present, new compounds targeting specific signalling pathways are available and have successfully passed clinical testing. The use of small molecules, such as multitargeted tyrosine kinase inhibitors, the mTOR inhibitors and monoclonal antibodies, is dramatically changing the existing concepts of systemic treatment for metastatic kidney cancer.
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PMID:Kidney cancer therapy: new perspectives and avenues. 1715 3

The year 2006 will mark a turning point in the daily management of patients with metastatic renal cell carcinoma. The impact of immunotherapy with interferon-alpha or interleukin-2 has been shown to be restricted to a minority of patients. The growing understanding of molecular mechanisms involved in the pathogenesis of the disease, especially clear-cell carcinoma, has led to the development of multiple targeted therapies with significant clinical benefits. Two compounds that predominantly inhibit the tyrosine kinase activity of the vascular endothelial growth factor receptor have been shown to improve the progression-free survival of patients in first- (sunitinib versus interferon-alpha) or second-line (sorafenib versus placebo) treatment. Temsirolimus, an agent that inhibits the serine-threonine kinase activity of the mammalian target of rapamycin, offers better overall survival than interferon in patients with poor-risk characteristics. Further studies are needed to determine the optimal combinations of these agents in metastatic disease and to assess their impact in the adjuvant setting.
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PMID:Targeted therapies in metastatic renal cell carcinoma: the light at the end of the tunnel. 1718 90

Traditional therapies have offered patients with advanced gastrointestinal neuroendocrine tumors limited benefit. Selected patients with hepatic metastases may benefit from surgical debulking, embolization, or other ablative therapies. While somatostatin analogs are highly effective in controlling symptoms of hormonal secretion, they are only rarely associated with tumor regression. The clinical benefit associated with the administration of systemic agents such as interferon-alpha or cytotoxic chemotherapy is less clear, and the widespread use of such regimens has been limited by their relatively modest anti-tumor activity, as well as concerns regarding their potential toxicity. The mixed clinical results seen with these agents in neuroendocrine tumors have led to great interest in the development of novel treatment approaches for patients with advanced disease. Recent clinical studies of novel agents, particularly those targeting the vascular endothelial growth factor pathway and mammalian target of rapamycin, have demonstrated promising activity in patients with advanced neuroendocrine tumors. Ongoing randomized studies should help better define the role these and other targeted agents will play in the future treatment of patients with this disease.
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PMID:Gastrointestinal neuroendocrine tumors: a role for targeted therapies? 1763 38

Until 2006, immunotherapy (interferon-alpha or interleukin 2) was the standard medical treatment for metastatic renal cell carcinoma (RCC), and its results were disappointing: despite a few cases of complete response with prolonged survival, median survival was one year. Better understanding of the molecular mechanisms of tumor angiogenesis, especially in clear cell carcinoma, has led to the development of multiple targeted therapies to inhibit key effectors: vascular endothelial growth factor (VEGF), VEGF receptor, and mTOR (target of rapamycin). Two inhibitors targeting several protein kinases, including the VEGF receptor, have increased progression-free survival in patients with metastatic RCC and are now commercially available: sunitinib (Sutent) as first-line treatment and sorafenib (Nexavar) as second-line treatment. These targeted therapies will certainly affect overall survival, but it is too early for any firm conclusions. Their side-effects, usually low or moderate, include asthenia, anorexia, diarrhea, hand-and-foot syndrome and hypertension. Optimal management is required to ensure prolonged exposure. Other drugs have been effective: bevacizumab (Avastin), a monoclonal antibody inhibiting VEGF, increases progression-free survival as second-line treatment, and temsirolimus (Torisel), an mTOR protein kinase inhibitor, increases overall survival in the population of patients with poor prognosis. These targeted drugs will serve as the basis for development of future therapeutic strategies.
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PMID:[Renal cell carcinoma and antiangiogenic therapies]. 1803 17

Renal cell carcinoma (RCC) affects 38,000 individuals in the U.S. yearly. Seventy-five percent of cases are clear-cell carcinomas, and a majority is driven by dysfunction of the von Hippel-Lindau (VHL) gene. VHL loss of function and other non-VHL pathways leading to RCC share aberrant activation of the hypoxic response, such as upregulation of vascular endothelial growth factor (VEGF) and consequent neoangiogenesis. Metastatic RCC has been notoriously resistant to therapy. For decades, its treatment has been based on nephrectomy and limited use of toxic and often inefficient immunotherapy with interleukin-2 or interferon-alpha. However, new biologic agents are beginning to break the resistance barrier. Small-molecule multikinase inhibitors that target VEGF receptors (sunitinib and sorafenib) have a favorable toxicity profile and can prolong time to progression and preserve quality of life when used in newly diagnosed or previously treated patients. The anti-VEGF antibody bevacizumab enhances the response rate and prolongs disease control when added to interferon-alpha. Temsirolimus, a mammalian target of rapamycin inhibitor, prolongs the survival duration of patients with poor-risk disease. Despite three new drugs being approved for RCC in the past 2 years, responses are mostly partial and of limited duration. Multiple new drugs and drug combinations are undergoing clinical trials and will likely impact the treatment of RCC in future years. Compounds found to be active in the metastatic setting are now being tried in earlier stage disease in an attempt to improve curability. However, no method has yet been validated to predict patient response to these newer treatments.
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PMID:Renal cell carcinoma: new developments in molecular biology and potential for targeted therapies. 1816 17

Temsirolimus, an ester of sirolimus (rapamycin), selectively inhibits the kinase mammalian target of rapamycin and consequently blocks the translation of cell cycle regulatory proteins and prevents the over expression of angiogenic growth factors. Patients with advanced renal cell carcinoma and a poor prognosis who received a once-weekly intravenous infusion of temsirolimus 25 mg experienced significant survival benefits compared with patients receiving standard interferon-alpha (IFNalpha) therapy (3-18 MU subcutaneously three times weekly) in a large phase III clinical study. Median overall survival was 10.9 versus 7.3 months, progression-free survival was 5.5 versus 3.1 months. Objective response rates were 8.6% in temsirolimus recipients versus 4.8% in IFNalpha recipients. Temsirolimus monotherapy recipients experienced significantly fewer grade 3 or 4 adverse events and had numerically fewer withdrawals for adverse events than patients receiving IFNalpha.
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PMID:Temsirolimus: in advanced renal cell carcinoma. 1837 Apr 42

Treatment of patients with metastatic renal cell carcinoma is evolving rapidly due to the advent of novel targeted therapies. Improved knowledge of the underlying pathogenesis has led to the development of drugs that modulate the dominant signal transduction pathways for this disease, which results in inhibition of angiogenesis. Recent evidence indicates that the receptor tyrosine kinase inhibitor sunitinib prolongs progression-free survival compared with interferon-alpha, especially in patients with intermediate risk. Immunotherapy with interferon-alpha or high-dose interleukin-2 should still be considered for low-risk patients, particularly those with clear-cell tumours and metastases of the lung only. In patients who fail treatment with interferon-alpha, sorafenib has been shown to improve progression-free survival. High-risk patients may benefit from treatment with temsirolimus, which inhibits mammalian target of rapamycin (mTOR) kinase activity and has shown to improve overall survival. These angiogenesis inhibitors did not receive mention in the recently published guideline 'Renal cell carcinoma'.
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PMID:[Angiogenesis inhibitors for the systemic treatment of metastatic renal cell carcinoma: sunitinib, sorafenib, bevacizumab and temsirolimus]. 1838 Mar 84


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