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)

Integrins are widely expressed plasma membrane adhesion molecules that tether cells to matrix proteins and to one another in cell-cell interactions. Integrins also transmit outside-in signals that regulate functional responses of cells, and are known to influence gene expression by regulating transcription. In previous studies we found that platelets, which are naturally occurring anucleate cytoplasts, translate preformed mRNA transcripts when they are activated by outside-in signals. Using strategies that interrupt engagement of integrin alphaIIbbeta3 by fibrinogen and platelets deficient in this integrin, we found that alphaIIbbeta3 regulates the synthesis of B cell lymphoma 3 (Bcl-3) when platelet aggregation is induced by thrombin. We also found that synthesis of Bcl-3, which occurs via a specialized translation control pathway regulated by mammalian target of rapamycin (mTOR), is induced when platelets adhere to immobilized fibrinogen in the absence of thrombin and when integrin alphaIIbbeta3 is engaged by a conformation-altering antibody against integrin alphaIIbbeta3. Thus, outside-in signals delivered by integrin alphaIIbbeta3 are required for translation of Bcl-3 in thrombin-stimulated aggregated platelets and are sufficient to induce translation of this marker protein in the absence of thrombin. Engagement of integrin alpha2beta1 by collagen also triggered synthesis of Bcl-3. Thus, control of translation may be a general mechanism by which surface adhesion molecules regulate gene expression.
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PMID:Integrin-dependent control of translation: engagement of integrin alphaIIbbeta3 regulates synthesis of proteins in activated human platelets. 988 53

The immunosuppressant rapamycin, an immunophilin-binding antibiotic, has been studied in follicular B-cell lymphoma lines that express the highest level of the BCL-2 protein. The growth rate of human follicular B-cell lymphoma lines was slowed more efficiently than that of other human B-cell lines or non-B-cell lines. This effect was dependent on the arrest of cells in the G(1) phase; the number of apoptotic cells was not increased. Rapamycin inhibited apoptosis or caspase activation induced by cytotoxic drugs, whereas caspase activation by doxorubicin was not inhibited. The increase in the cellular concentration of BCL-2 protein was related to its concentration in the steady state and was unrelated to the amount of bcl-2 mRNA. The increase of BCL-2 level in the cells rather than its level in the steady state may be important for drug resistance. The biochemical target of rapamycin, the mTOR kinase, may be a candidate sensitising agent for chemotherapy. This effect of rapamycin shows that G(1) arrest and protection from apoptosis are combined events susceptible to regulation by pharmacological means.
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PMID:Rapamycin increases the cellular concentration of the BCL-2 protein and exerts an anti-apoptotic effect. 1159 94

The mammalian target of rapamycin (mTOR) is emerging as a promising target for antitumor therapy. However, the mechanism that contributes to its regulation in B lymphomas remains unknown. This study shows that in follicular lymphoma (FL) cells, mTOR is active because the cells displayed rapamycin-sensitive phosphorylation of p70S6 kinase and 4E-BP1. Moreover, immunohistochemistry applied on lymph node tissue sections obtained from patients with FL revealed that, in most cases, p70S6 kinase was highly phosphorylated compared to normal tonsillar tissue. In FL cells, mTOR was under control of both phospholipase D (PLD) and phosphatidylinositol 3-kinase (PI3K). Moreover, we demonstrated that Syk plays a central role in mTOR activation because we found that both expression and activity are elevated compared to normal or chronic lymphocytic leukemia B cells. We also provide evidence that Syk operates through PLD- and PI3K-independent pathways. Finally, Syk inhibition by piceatannol or by siRNA plasmids resulted in a potent inhibition of mTOR activity in FL cells, as well as in mantle cell lymphoma, Burkitt lymphoma, and diffuse large B-cell lymphoma. These findings suggest that the Syk-mTOR pathway has a critical function in FL survival, and therefore, that Syk could be a promising new target for B-lymphoma therapy.
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PMID:Syk-dependent mTOR activation in follicular lymphoma cells. 1691 21

New activities of human platelets continue to emerge. One unexpected response is new synthesis of proteins from previously transcribed RNAs in response to activating signals. We previously reported that activated human platelets synthesize B-cell lymphoma-3 (Bcl-3) under translational control by mammalian target of rapamycin (mTOR). Characterization of the ontogeny and distribution of the mTOR signaling pathway in CD34+ stem cell-derived megakaryocytes now demonstrates that they transfer this regulatory system to developing proplatelets. We also found that Bcl-3 is required for condensation of fibrin by activated platelets, demonstrating functional significance for mTOR-regulated synthesis of the protein. Inhibition of mTOR by rapamycin blocks clot retraction by human platelets. Platelets from wild-type mice synthesize Bcl-3 in response to activation, as do human platelets, and platelets from mice with targeted deletion of Bcl-3 have defective retraction of fibrin in platelet-fibrin clots mimicking treatment of human platelets with rapamycin. In contrast, overexpression of Bcl-3 in a surrogate cell line enhanced clot retraction. These studies identify new features of post-transcriptional gene regulation and signal-dependant protein synthesis in activated platelets that may contribute to thrombus and wound remodeling and suggest that posttranscriptional pathways are targets for molecular intervention in thrombotic disorders.
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PMID:mTOR-dependent synthesis of Bcl-3 controls the retraction of fibrin clots by activated human platelets. 1711 Apr 54

The inhibition of mTOR is a target for anticancer drugs in posttransplant malignancies. The influence of conversion to sirolimus after malignancy diagnosis was investigated on patient and renal allograft survivals. The 20 renal allograft recipients (4 women, 16 men) of ages 26 to 73 years (mean, 59 years) developed malignancies within 6 to 172 months (mean, 53 months) after transplantation. Three patients developed posttransplant lymphoproliferative disease (PTLD); four, Kaposi sarcoma, three, lung cancer; two, malignant melanoma; two, breast cancer; two, renal cell carcinoma; one, Merkel cell carcinoma; one, cutaneous T-cell lymphoma; one, larynx cancer; and one, gingival cancer. After tumor diagnosis, calcineurin inhibitors, azathioprine, or mycophenolate mofetil (MMF) were discontinued abruptly and sirolimus introduced (2 mg/d; target trough level, 4.0 to 8.0 ng/mL). Prednisone was maintained. The observation time of sirolimus therapy was 4 to 48 months (mean, 14 months). Two patients with PTLD (large B-cell lymphoma) and four with Kaposi sarcoma had full regressions. Eleven patients (larynx cancer, melanoma, breast cancer, T-cell lymphoma, renal cell carcinoma, Merkel cell carcinoma, and skin lymphoma) in addition to sirolimus therapy, underwent oncologic treatment, namely, surgery and/or chemotherapy. Six patients died from disseminated malignancy 4 to 9 months after conversion. One patient with T-cell lymphoma lost his graft; in the remaining patients, serum creatinine level was stable. In conclusion, Conversion to sirolimus resulted in regression of large B-cell lymphoma and Kaposi sarcoma. In patients with advanced or disseminated malignancy, the tumors progressed. Graft function was preserved after conversion to sirolimus.
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PMID:Anticancer effect of sirolimus in renal allograft recipients with de novo malignancies. 1802 73

The concurrent use of rituximab with cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) has established the utility of chemoimmunotherapy for the treatment of aggressive non-Hodgkin's lymphoma (NHL). However, a substantial number of patients with diffuse large B-cell lymphoma (DLBCL) still die from their disease, and improvements in therapy remain necessary. Numerous efforts have been made to improve prognostic tools in DLBCL, including the International Prognostic Index (IPI). Although the IPI has been validated through numerous studies over the past 25 years, currently there are no prospectively generated data that advise the clinician on how to use the IPI to treat specific patient subsets differently from one another. A variety of efforts are underway to develop new therapeutic strategies in aggressive lymphoma, including the use of dose-dense therapy (CHOP-R cycled every 14 rather than 21 days). Several novel agents are undergoing evaluation in DLBCL, as both single agents in the relapsed setting and in combination with R-CHOP. The agents have varying degrees of single-agent activity, and some of their mechanisms are incompletely understood. New agents include lenalidomide, SGN-40, bevacizumab, Syk inhibitors, enzastaurin, histone deacetylase inhibitors, bortezomib, anti-survivin agents, and mTOR inhibitors. These agents offer reason for optimism, but considerable challenges exist in demonstrating that they clearly provide added value, and in the integration, sequence, and combination of these novel drugs into the range of current treatment options available to patients with aggressive NHL.
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PMID:Targeted treatment and new agents in diffuse large B-cell lymphoma. 1876 Jul 4

Using immunohistochemistry with antibodies against the phosphoserine residues in both S6rp and 4E binding protein 1, we identified the activation of the mammalian target of rapamycin (mTORC)1 pathway in 29 cases of AIDS-related lymphoma. These cases represented a diverse spectrum of histological types of non-Hodgkin lymphoma (24 cases) and classic Hodgkin lymphoma (five cases). mTORC1 was also activated in the hyperplastic but not involuted follicles of HIV-associated lymphadenopathy in eight cases, supporting the notion that mTORC1 activation is a common feature of transformed lymphocytes irrespective of either their reactive or malignant phenotype. We also found that in B-cell lines that represent diffuse large B-cell lymphoma, Burkitt lymphoma, Epstein-Barr virus-infected lymphocytes, and human herpesvirus 8-positive primary effusion lymphoma, inhibitors of Syk, MEK, and, seemingly, phosphoinositide 3 kinases suppressed mTORC1 activation, in particular when these inhibitors were used in combination. These findings indicate that AIDS-related lymphoma and other histologically similar types of lymphomas that are derived from transformed B lymphocytes may display clinical responses to inhibitors that directly target mTORC1 or, possibly, upstream activators of the mTORC1 pathway.
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PMID:Activation of mTORC1 signaling pathway in AIDS-related lymphomas. 1960 73

p70S6K/p85S6K and cdc2/cdk1 are members of the serine/threonine protein kinase family. p70S6K/p85S6K is one of the downstream effectors of the PI3K/Akt/mTOR signal transduction pathway. It phosphorylates S6 protein of 40S ribosomal subunit and thus functions in protein synthesis and cell growth. cdc2/cdk1 is a cyclin-dependent protein kinase that controls the cell cycle entry from G2 to M phase. Overexpression of phospho-p70S6K and cdc2/cdk1 has recently been identified in the majority of diffuse large B-cell lymphoma (DLBCL) specimens. Combination of small molecules that target phosphorylation of p70S6K and cdc2/cdk1 synergistically induced cell apoptosis and cell cycle G1 and G2 arrest, suggesting that they are potential molecular targets for DLBCL therapy. This review will summarize recent advances in the study of phospho-p70S6K and cdc2/cdk1 as molecular markers and therapeutic targets for DLBCL. We propose that multilevel inhibition of the PI3K/Akt/mTOR pathway and double brake at the G1 and G2 phases of the cell cycle progression are effective strategies in treating DLBCL that overexpress phospho-p70S6K and cdc2/cdk1.
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PMID:Phospho-p70S6K and cdc2/cdk1 as therapeutic targets for diffuse large B-cell lymphoma. 1961 61

The mammalian target of rapamycin (mTOR) has emerged as an important therapeutic target for diffuse large B-cell lymphoma (DLBCL), as recent studies have demonstrated that 30% of relapsed patients respond to mTOR inhibitors. Why some lymphomas are resistant is incompletely understood. In the present study, we demonstrated that rapamycin inhibits mTORC1 in DLBCL lines and primary tumors but is minimally cytotoxic. Subsequent investigations revealed that rapamycin also activated eIF4E and the mTORC2 target Akt, suggesting a potential mechanism of rapamycin resistance. Furthermore, knockdown of the mTORC2 component rictor, but not the mTORC1 component raptor, inhibited rapamycin-induced Akt phosphorylation in lymphoma cells. Addition of the histone deacetylase inhibitor (HDI) LBH589 (LBH) overcame rapamycin resistance by blocking mTOR, thus preventing Akt activation. Further studies support the involvement of the protein phosphatase PP1 in LBH-mediated Akt dephosphorylation, which could be mimicked by knockdown of HDAC3. This is the first demonstration that a HDI such as LBH can overcome rapamycin resistance through a phosphatase that antagonizes mTORC2 activation. These results provide a mechanistic rationale for a clinical trial of a combination of HDI and mTOR inhibitors for DLBCL.
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PMID:Inhibition of histone deacetylase overcomes rapamycin-mediated resistance in diffuse large B-cell lymphoma by inhibiting Akt signaling through mTORC2. 1964 Nov 86

Temsirolimus, an inhibitor of mammalian target of rapamycin (mTOR), has anti-tumor activity in patients with relapsed or refractory mantle cell lymphoma (MCL) and other mature lymphoid neoplasms. mTOR is an intracellular kinase that controls the mRNA translation of many proteins (eg, cyclin D1) that can act as oncogenes and contribute to lymphomagenesis. Characterized by overexpression of cyclin D1, MCL was identified as a disease that might be susceptible to mTOR inhibition. When single-agent temsirolimus was explored in two phase II studies for treatment of patients with relapsed or refractory MCL, it demonstrated anti-tumor activity, with overall response rates of 38% and 41%. Subsequently, a three-arm, randomized phase III trial was conducted to compare two dosing regimens of temsirolimus with investigator's choice of therapy for heavily pretreated patients with relapsed or refractory MCL (N = 162; randomized 1:1:1). Once-weekly intravenous temsirolimus 175 mg for 3 weeks followed by 75 mg once weekly (175/75) significantly improved progression-free survival (hazard ratio = 0.44; P = .0009) versus investigator's choice therapy. Median progression-free survival durations were 4.8 and 1.9 months, respectively. The objective response rates were 22% in the 175/75 group and 2% in the investigator's choice group (P = .0019). For patients receiving temsirolimus, the most frequent grade 3 or 4 adverse events were thrombocytopenia, anemia, neutropenia, and asthenia. The results of this trial established a recommended clinical dose for temsirolimus monotherapy in patients with relapsed or refractory MCL and validated the importance of mTOR in the pathogenesis of advanced MCL. Objective responses also have been reported for other mature B-cell neoplasms (eg, diffuse large B-cell lymphoma or follicular lymphoma) in the phase II setting. Temsirolimus as monotherapy or in combination with other active agents warrants further investigation for treatment of MCL and other non-Hodgkin lymphomas.
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PMID:Temsirolimus in mantle cell lymphoma and other non-Hodgkin lymphoma subtypes. 1996 99


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