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)

In addition to their role in cellular homeostasis, pathways that regulate autophagy affect both tumorigenesis and tumor response to treatment. Therefore, understanding the regulation of autophagy in treated cancer cells is relevant to the discovery of molecular targets for the development of anti-cancer drugs. Our recent report points to radiation-induced inactivation of the mTOR pathway as an underlying mechanism of radiation-induced autophagy in the human breast cancer cell line MCF-7. Most importantly, radiation-induced inactivation of this pathway was detrimental to cell survival and was associated with reversal of mitochondrial ATPase activity and mitochondrial hyperpolarization, decreased level of eukaryotic initiation factor 4G (eIF4G) and increased phosphorylation of p53. Future analysis of the interrelationship among these events and the role each of them plays in cell survival following radiation will increase our ability to employ the mTOR pathway in anti-cancer therapy.
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PMID:Pathways that regulate autophagy and their role in mediating tumor response to treatment. 1692 Dec 71

Mutant or aberrant regulation of expressing products of p53 gene results in losing its tumor suppressive function, which is often seen in many malignancies, including breast cancer. Oncoprotein MDM2 plays a primary role in regulating P53, and these two form an automregulatory feedback loop. mdm2/p53 passway performs important function in development, progression,therapy and prognosis of breast cancer. Besides, more and more studies show that some other molecular markers in breast cancer, such as PI3K/Akt/mTOR, p14ARF, and Her2/neu can regulate this passway unneglectedly. The purpose of this review is to summarize not only the relations between mdm2/p53 passway and pathological characters, therapy and prognosis of breast cancer, but also the relations of this passway with some other molecular proteins in breast cancer.
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PMID:[Advances in study of murine double minute 2/p53 passway with breast cancer]. 1706 34

Signal transduction pathways play a crucial role in breast cancer development, progression, and response to different therapies. A major problem in breast cancer therapy is the heterogeneity among different tumor types and cell lines commonly used in preclinical studies. To characterize the signaling pathways of some of the commonly used breast cancer cell lines and dissect the relationship among a number of pathways and some key genetic and molecular events in breast cancer development, such as p53 mutation, ErbB2 expression, and estrogen receptor (ER)/progesterone receptor (PR) status, we performed pathway profiling of 14 breast cancer cell lines by measuring the expression and phosphorylation status of 40 different cell signaling proteins with 53 specific antibodies using a protein lysate array. Cluster analysis of the expression data showed that there was close clustering of phosphatidylinositol 3-kinase, Akt, mammalian target of rapamycin (mTOR), Src, and platelet-derived growth factor receptor beta (PDGFRbeta) in all of the cell lines. The most differentially expressed proteins between ER- and PR-positive and ER- and PR-negative breast cells were mTOR, Akt (pThr308), PDGFRbeta, PDGFRbeta (pTyr751), panSrc, Akt (pSer473), insulin-like growth factor-binding protein 5 (IGFBP5), Src (pTyr418), mTOR (pSer2448), and IGFBP2. Many apoptotic proteins, such as apoptosis-inducing factor, IGFBP3, bad, bax, and cleaved caspase 9, were overexpressed in mutant p53-carrying breast cancer cells. Hexokinase isoenzyme 1, ND2, and c-kit were the most differentially expressed proteins in high and low ErbB2-expressing breast cancer cells. This study demonstrated that ER/PR status, ErbB2 expression, and p53 status are major molecules that impact downstream signaling pathways.
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PMID:Dissection of signaling pathways in fourteen breast cancer cell lines using reverse-phase protein lysate microarray. 1712 30

Cholesterol-lowering statins have been shown to have anticancer effects in different models and sensitize human tumor cells to cytostatic drugs. We have investigated the effect of statins on Akt/protein kinase B signaling and the sensitizing effect of cytostatic drugs. It was found that insulin- and cytostatic drug-induced Akt phosphorylation and nuclear translocation was inhibited by pravastatin and atorvastatin in HepG2, A549, and H1299 cells in an mTOR-dependent manner. Statins also induced mTOR-dependent phosphorylation of insulin receptor substrate 1. In p53 wild-type cells (HepG2 and A549), pretreatment with statins did not sensitize cells to etoposide in concentrations which induced p53 stabilization. In line with our previous data, statins were found to attenuate the etoposide-induced p53 response. However, silencing p53 by RNA interference rescued the sensitizing effect. We also show that in a p53-deficient cell line (H1299), pretreatment with atorvastatin sensitized cells to etoposide, doxorubicin, and 5-fluorouracil and increased the level of apoptosis. Taken together, these data suggest that a mTOR-dependent, statin-induced inhibition of Akt phosphorylation and nuclear translocation sensitizes cells to cytostatic drugs. However, this effect can be counteracted in p53 competent cells by the ability of statins to destabilize p53.
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PMID:Statins induce mammalian target of rapamycin (mTOR)-mediated inhibition of Akt signaling and sensitize p53-deficient cells to cytostatic drugs. 1712 17

Bladder cancer is one of the most common cancers in the world, leading to approximately 145,000 deaths annually. Bladder cancer is typically managed by surgical removal of the tumor; however, the recurrence rate is disappointingly very high, often requiring systemic chemotherapy. Improvement in the diagnosis and prognosis of bladder cancer will only come from a comprehensive understanding of the genetic factors that lead to its development. In this review, we focus on the chromosomal deletions that contribute to the downregulation of tumor suppressor pathways in bladder cancer. Chromosomal deletions are not a random event, since bladder cancer progression has been associated with specific chromosomal deletions and this progression correlates with specific stages of tumor development. The most commonly found chromosomal deletion in all stages of bladder cancer involves deletions in chromosome 9, resulting in the loss of three genes encoding proteins that activate the Rb and p53 tumor suppressors. Additionally, chromosome 9 harbors the TSC1 tumor suppressor which downregulates the well-known anti-apoptotic Akt/mTOR pathway. Hence, deletions on one chromosome may have a crucial influence on the initial steps in tumor development. Other deletions targeting the tumor suppressors Rb, p53, FHIT and LZTS1 occur at later stages of tumor development. Considering the central importance of these tumor suppressor pathways in the formation and evolution of tumors, the time has come to evaluate available drugs in bladder cancer that target the positive regulators of these pathways.
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PMID:Chromosomal deletions in bladder cancer: shutting down pathways. 1712 40

Despite the understanding of the importance of phosphoinositide 3-kinase (PI 3-K) signaling pathway in the regulation of cellular proliferation, little is known about its role during phorbol 12-myristate 13-acetate (PMA)-induced differentiation in human leukemia cells. Here, we report a novel finding that PI 3-K inhibition by LY294002 significantly increases p21WAF1/Cip1 expression in PMA-stimulated human leukemia cells NB4 and THP1. LY294002 potentiated expression of p21WAF1/Cip1 via a p53-independent mechanism and did not affect mitogen activated protein kinase (MAPK) activation. Electrophoretic mobility shift (EMSA) experiments revealed that blocking of PI 3-K was associated with increased binding of transcription factor Sp1 to the PMA-responsive sites on the p21WAF1/Cip1 promoter. Pretreatment with rapamycin, an inhibitor of mTOR kinase, decreased the expression of p21WAF1/Cip1 protein in PMA-stimulated NB4 cells. The level of PMA-induced p21WAF1/Cip1 protein expression was lower in NB4 cells overexpressing wild type protein kinase C zeta (PKC zeta) compared to those transfected with empty vector or with kinase inactive PKC zeta. Sp1 binding to the p21WAF1/Cip1 promoter was completely lost in a wild type PKC zeta overexpressing and PMA-stimulated NB4 cells. We demonstrate that PI 3-K signaling pathway suppresses PMA-induced expression of p21WAF1/Cip1 in human leukemia cells, and that this effect is partly mediated by PKC zeta.
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PMID:PI 3-K signaling pathway suppresses PMA-induced expression of p21WAF1/Cip1 in human leukemia cells. 1728 1

The cyclin-dependent kinase inhibitor p21(Cip1) regulates multiple cellular functions and protects cells from genotoxic and other cellular stresses. Activation of apoptosis signal-regulating kinase 1 (ASK1) induced by inhibition of mTOR signaling leads to sustained phospho-c-Jun that is suppressed in cells with functional p53 or by forced expression of p21(Cip1). Here we show that small deletions of p21(Cip1) around S98 abrogate its association with ASK1 but do not affect binding to Cdk1, hence distinguishing between the cell cycle-regulating functions of p21(Cip1) and its ability to suppress activation of the ASK1/Jun N-terminal protein kinase (JNK) pathway. p21(Cip1) is phosphorylated in vitro by both ASK1 and JNK1 at S98. In vivo phosphorylation of p21(Cip1), predominantly carried out by ASK1, is associated with binding to ASK1 and inactivation of ASK1 kinase function. Binding of p21(Cip1) to ASK1 requires ASK1 kinase function and may involve phosphorylation of S98.
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PMID:Negative regulation of ASK1 by p21Cip1 involves a small domain that includes Serine 98 that is phosphorylated by ASK1 in vivo. 1732 29

Coordination of cell death and survival is crucial during embryogenesis and adulthood, and alteration of this balance can result in degeneration or cancer. Growth factor receptors such as Met can activate phosphatidyl-inositol-3' kinase (PI3K), a major intracellular mediator of growth and survival. PI3K can then antagonize p53-triggered cell death, but the underlying mechanisms are not fully understood. We used genetic and pharmacological approaches to uncover Met-triggered signaling pathways that regulate hepatocyte survival during embryogenesis. Here, we show that PI3K acts via mTOR (Frap1) to regulate p53 activity both in vitro and in vivo. mTOR inhibits p53 by promoting the translation of Mdm2, a negative regulator of p53. We also demonstrate that the PI3K effector Akt is required for Met-triggered Mdm2 upregulation, in addition to being necessary for the nuclear translocation of Mdm2. Inhibition of either mTOR or Mdm2 is sufficient to block cell survival induced by Hgf-Met in vitro. Moreover, in vivo inhibition of mTOR downregulates Mdm2 protein levels and induces p53-dependent apoptosis. Our studies identify a novel mechanism for Met-triggered cell survival during embryogenesis, involving translational regulation of Mdm2 by mTOR. Moreover, they reinforce mTOR as a potential drug target in cancer.
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PMID:Met acts on Mdm2 via mTOR to signal cell survival during development. 1732 61

The oncoprotein MDM2, a major ubiquitin E3 ligase of tumor suppressor p53, has been suggested as a novel target for human cancer therapy based on its p53-dependent and p53-independent activities. We have identified curcumin, which has previously been shown to have anticancer activity, as an inhibitor of MDM2 expression. Curcumin down-regulates MDM2, independent of p53. In a human prostate cancer cell lines PC3 (p53(null)), curcumin reduced MDM2 protein and mRNA in a dose- and time-dependent manner, and enhanced the expression of the tumor suppressor p21(Waf1/CIP1). The inhibitory effects occur at the transcriptional level and seem to involve the phosphatidylinositol 3-kinase/mammalian target of rapamycin/erythroblastosis virus transcription factor 2 pathway. Curcumin induced apoptosis and inhibited proliferation of PC3 cells in culture, but both MDM2 overexpression and knockdown reduced these effects. Curcumin also inhibited the growth of these cells and enhanced the cytotoxic effects of gemcitabine. When it was administered to tumor-bearing nude mice, curcumin inhibited growth of PC3 xenografts and enhanced the antitumor effects of gemcitabine and radiation. In these tumors, curcumin reduced the expression of MDM2. Down-regulation of the MDM2 oncogene by curcumin is a novel mechanism of action that may be essential for its chemopreventive and chemotherapeutic effects. Our observations help to elucidate the process by which mitogens up-regulate MDM2, independent of p53, and identify a mechanism by which curcumin functions as an anticancer agent.
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PMID:Curcumin, a dietary component, has anticancer, chemosensitization, and radiosensitization effects by down-regulating the MDM2 oncogene through the PI3K/mTOR/ETS2 pathway. 1733 26

Carcinoid and islet-cell carcinoma are often also known as low-grade neuroendocrine carcinomas. They are often slow-growing but can be resistant to standard therapy. While somatostatin analogues are often used to control hormonal syndromes, there is currently no therapy approved in the US for control of carcinoid tumor growth. For islet-cell carcinoma, streptozocin-based chemotherapy may induce tumor shrinkage, but second-line option are limited. This chapter reviews the molecular biology of neuroendocrine tumors, including the roles of MENIN, TSC2, NF-1, vHL, p53, bcl-2, bax, VEGF, IGF, PDGF, EGFR, and mTOR. Recently, there has been interest in developing molecularly targeted therapy for this group of diseases. Phase-II studies with imatinib, bevacizumab, sunitinib, gefitnib, temsirolimus, and everolimus (RAD001) have completed accrual. Encouraging results have been observed in studies with VEGF and mTOR inhibitors. Phase-III study of bevacizumab is planned in the US. Large-scale multinational phase-II and -III studies of everolimus are under way.
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PMID:Neuroendocrine tumors. Molecular targeted therapy for carcinoid and islet-cell carcinoma. 1738 71


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