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)

Inactivating mutations in the tuberous sclerosis complex 2 (TSC2) gene, which encodes tuberin, result in the development of TSC and lymphangioleiomyomatosis (LAM). The tumor suppressor effect of tuberin lies in its GTPase-activating protein activity toward Ras homologue enriched in brain (Rheb), a Ras GTPase superfamily member. The statins, 3-hydroxy-3-methylglutaryl CoA reductase inhibitors, have pleiotropic effects which may involve interference with the isoprenylation of Ras and Rho GTPases. We show that atorvastatin selectively inhibits the proliferation of Tsc2-/- mouse embryo fibroblasts and ELT-3 smooth muscle cells in response to serum and estrogen, and under serum-free conditions. The isoprenoids farnesylpyrophosphate (FPP) and geranylgeranylpyrophosphate (GGPP) significantly reverse atorvastatin-induced inhibition of Tsc2-/- cell growth, suggesting that atorvastatin dually targets a farnesylated protein, such as Rheb, and a geranylgeranylated protein, such as Rho, both of which have elevated activity in Tsc2-/- cells. Atorvastatin reduced Rheb isoprenylation, GTP loading, and membrane localization. Atorvastatin also inhibited the constitutive phosphorylation of mammalian target of rapamycin, S6 kinase, and S6 found in Tsc2-/- cells in an FPP-reversible manner and attenuated the high levels of phosphorylated S6 in Tsc2-heterozygous mice. Atorvastatin, but not rapamycin, attenuated the increased levels of activated RhoA in Tsc2-/- cells, and this was reversed by GGPP. These results suggest that atorvastatin may inhibit both rapamycin-sensitive and rapamycin-insensitive mechanisms of tuberin-null cell growth, likely via Rheb and Rho inhibition, respectively. Atorvastatin may have potential therapeutic benefit in TSC syndromes, including LAM.
 ...
PMID:Selective inhibition of growth of tuberous sclerosis complex 2 null cells by atorvastatin is associated with impaired Rheb and Rho GTPase function and reduced mTOR/S6 kinase activity. 1794 19

The perivascular epithelioid cell (PEC) is a cell type constantly present in a group of tumors called PEComas. PEC expresses myogenic and melanocytic markers, such as HMB45 and actin. Recently, recurrent chromosomal alterations have been demonstrated in PEC. At present, PEComa is a widely accepted entity. In the past 10 years, the use of this term has allowed to report and describe numerous cases permitting to start highlighting the biology of this group of lesions. PEComas are related to the genetic alterations of tuberous sclerosis complex (TSC), an autosomal dominant genetic disease due to losses of TSC1 (9q34) or TSC2 (16p13.3) genes which seem to have a role in the regulation of the Rheb/mTOR/p70S6K pathway. There are some open questions about PEComas regarding its histogenesis, the definition of epithelioid angiomyolipoma and the identification of the histological criteria of malignancy. An innovative therapeutic trial using rapamycin is under way for tumors occurring in TSC such as renal angiomyolipoma and lymphangioleiomyomatosis. Its success could provide the rationale for the use of the same drug in other lesions composed of PECs, especially in the malignant ones.
 ...
PMID:PEComas: the past, the present and the future. 1808 Jan 39

Perivascular epithelioid cell tumours (PEComas) are a family of tumours including classic angiomyolipoma, lymphangioleiomyomatosis, and clear epithelioid cell tumours reported under a variety of names such as epithelioid angiomyolipoma, pulmonary and extrapulmonary clear cell sugar tumour, and PEComa. Our previous comparative genomic hybridization study of PEComas demonstrated recurrent chromosomal aberrations including deletions on chromosome 16p, where the TSC2 gene is located. In this study, we focused on the alteration of chromosome 16p, including TSC2. We collected ten sporadic and two tuberous sclerosis complex-associated PEComas, as well as 14 sporadic classic hepatic and renal angiomyolipomas (AMLs) as controls. We used 16 microsatellite markers distributed along chromosome 16p to test for allelic imbalances on chromosome 16p and at TSC2, and two markers for TSC1. Furthermore, we carried out immunohistochemical staining for phospho-p706K, phospho-AKT, and phospho-S6 to evaluate the effect of TSC2 alterations on the mTOR signalling pathway. Loss of heterozygosity (LOH) was found in 11 PEComas and involved the region of the TSC2 locus in seven. Six classic angiomyolipomas had allelic changes at chromosome 16p. Microsatellite instability was detected in two PEComas. The incidence of genetic aberrations was significantly higher in the PEComa group. Only one PEComa showed LOH at the TSC1 locus. Eleven PEComas and 13 AMLs revealed elevated phospho-p70S6K accompanied by reduced phospho-AKT. Five PEComas and eight classic angiomyolipomas were positive for phospho-S6. The phosphorylation profile indicates functional activation of the mTOR pathway through a disrupted TSC1/2 complex. Our observations of frequent deletion of TSC2 and the mTOR signalling pathway provide evidence that the oncogenetic lineage of PEComa, as a distinct TSC2-linked neoplasm, is similar to that of angiomyolipoma.
 ...
PMID:Constant allelic alteration on chromosome 16p (TSC2 gene) in perivascular epithelioid cell tumour (PEComa): genetic evidence for the relationship of PEComa with angiomyolipoma. 1808 21

Lymphangioleiomyomatosis (LAM), a rare pulmonary disorder, manifests as an abnormal neoplastic growth of smooth muscle-like cells within the lungs. Mutational inactivation of tumor suppressor tuberous sclerosis complex 2 (TSC2) in LAM constitutively activates the mammalian target of rapamycin (mTOR)/p70 S6 kinase 1 (S6K1) signaling pathway and promotes neoplastic growth of LAM cells. In many cell types, type I interferon beta (IFNbeta) inhibits proliferation and induces apoptosis through signal transducers and activators of transcription (STAT)-dependent and STAT-independent signaling pathways, one of which is the mTOR/S6K1 signaling pathway. Our study shows that IFNbeta is expressed in LAM tissues and LAM-derived cell cultures; however, IFNbeta attenuates LAM-derived cell proliferation only at high concentrations, 100 and 1000 U/ml (IC(50) value for IFNbeta is 20 U/ml compared with 1 U/ml for normal human mesenchymal cells, human bronchus fibroblasts and human airway smooth muscle cells). Likewise, IFNbeta only attenuates proliferation of smooth muscle TSC2-null ELT3 cells. Analysis of IFNbeta signaling in LAM cells showed expression of IFNbeta receptor alpha (IFNbetaRalpha) and IFNbetaRbeta, activation and nuclear translocation of STAT1, and phosphorylation of STAT3 and p38 mitogen-activated protein kinase (MAPK), but IFNbeta had little effect on S6K1 activity. However, the re-expression of TSC2 or inhibition of mTOR/S6K1 with rapamycin (sirolimus) augmented antiproliferative effects of IFNbeta in LAM and TSC2-null ELT3 cells. Our study demonstrates that IFNbeta-dependent activation of STATs and p38 MAPK is not sufficient to fully inhibit proliferation of cells with TSC2 dysfunction and that TSC2-dependent inhibition of mTOR/S6K1 cooperates with IFNbeta in inhibiting human LAM and TSC2-null ELT3 cell proliferation.
 ...
PMID:Interferon beta augments tuberous sclerosis complex 2 (TSC2)-dependent inhibition of TSC2-null ELT3 and human lymphangioleiomyomatosis-derived cell proliferation. 1809 73

Proliferation, migration, and differentiation of smooth muscle (SM)-like lymphangioleiomyomatosis (LAM) cells in the lungs are pathologic manifestations of pulmonary LAM, a rare lung disease predominantly afflicting women and exacerbated by pregnancy. LAM cells form nodules throughout the lung without any predominant localization, but can also form small cell clusters dispersed within lung parenchyma. LAM cells have the appearance of "immature" SM-like cells, irregularly distributed within the nodule in contrast to organized SM cell layers in airways and vasculature. Progressive growth of LAM cells leads to the cystic destruction of the lung parenchyma, obstruction of airways and lymphatics, and loss of pulmonary function. Pathogenetically, LAM occurs from somatic or genetic mutations of tumor suppressor genes tuberous sclerosis complex 1 (TSC1) or TSC2. The TSC1/TSC2 protein complex is an integrator of signaling networks regulated by growth factors, insulin, nutrients, and energy. The observation that the TSC1/TSC2 functions as a negative regulator of the mammalian target of rapamycin (mTOR)/p70 S6 kinase (S6K1) signaling pathway yielded the first rapamycin clinical trial for LAM. Although LAM is a rare lung disease, the elucidation of disease-relevant mechanisms of LAM will provide a better understanding of not only SM-like cell growth, migration, and differentiation in LAM but may also offer insights into other metabolic diseases such as cardiovascular diseases, diabetes, and cancer. In this article, we will summarize the progress made in our understanding of LAM, and we will focus on how dysregulation of TSC1/TSC2 signaling results in abnormal proliferation and migration of SM-like LAM cells.
 ...
PMID:Smooth muscle-like cells in pulmonary lymphangioleiomyomatosis. 1809 94

Tuberous sclerosis complex (TSC) is an autosomal-dominant disorder characterized by the formation of hamartomatous lesions in multiple organ systems. It is the second most common neurocutaneous syndrome after neurofibromatosis type 1 and has been recognized since the late 1800s. Although the disease has complete penetrance, there is also high phenotypic variability: some patients have obvious signs at birth, while others remain undiagnosed for many years. In addition to skin lesions, TSC patients develop numerous brain lesions, angiomyolipoma (AMLs), lymphangiomyomatosis (LAM) in the lungs, cardiac rhabdomyomas, skeletal lesions, and vascular anomalies, all of which are well seen with medical imaging. Our knowledge of TSC genetics and pathophysiology has expanded dramatically in recent years: two genetic loci were discovered in the 1990s and recent elucidation of TSC's interaction with the mTOR pathway has changed how we manage the disease. Meanwhile, medical imaging is playing an increasingly important role in the diagnosis, management, and treatment of TSC. We provide an update on the genetics and pathophysiology of TSC, review its clinical manifestations, and explore the breadth of imaging features in each organ system, from prenatal detection of cardiac rhabdomyomas to monitoring rapamycin therapy to treatment of AMLs by interventional radiology.
 ...
PMID:The pathogenesis and imaging of the tuberous sclerosis complex. 1841 39

Lymphangioleiomyomatosis is a rare and progressive lung cystic disease, caused by the infiltration of lung parenchyma by mesenchymal cells characterized by co-expression of contractile proteins and melanocytic markers. The pathogenesis of lymphangioleiomyomatosis is determined by mutations affecting tuberous sclerosis complex (TSC) genes, with eventual deregulation of the Rheb/mTOR/p70S6K pathway, and the potential therapeutic activity of mTOR inhibitors is currently under investigation. To better understand the molecular mechanisms involved in the pathogenesis of lymphangioleiomyomatosis, we investigated the expression of cathepsin-k (a papain-like cysteine protease with high matrix-degrading activity). The rationale of this choice was based on the recent demonstration that mTOR inhibitors can regulate major functional activities of osteoclasts, including the expression of cathepsin-k. The immunohistochemical study included 12 cases of lymphangioleiomyomatosis. Twelve angiomyolipomas and several lung diseases (sarcoidosis, organizing pneumonia, usual interstitial pneumonia, emphysema) were investigated as controls. In all lymphangioleiomyomatosis cases, strong cathepsin-k immunoreactivity was demonstrated, restricted to lymphangioleiomyomatosis cells. Similar expression levels were observed in renal angiomyolipomas. These observations extend the knowledge regarding the immunophenotypic profile of lymphangioleiomyomatosis cells, and provide a useful new marker for diagnosis in difficult cases (eg, in small transbronchial biopsies). The strong expression of such a potent papain-like cysteine protease in lymphangioleiomyomatosis cells can significantly contribute to the progressive remodelling of lung parenchyma observed in this deadly disease, with eventual formation of lung cysts. It is possible to speculate that mTOR inhibitors may exert part of their action by limiting the destructive remodelling of lung structure.
 ...
PMID:Cathepsin-k expression in pulmonary lymphangioleiomyomatosis. 1906 Aug 45

Failure in the regulation of mTOR (mammalian target of rapamycin) appears to be critical to the pathogenesis of the inherited disorder tuberous sclerosis and the related lung disease LAM (lymphangioleiomyomatosis). Both diseases are caused by mutations of TSC1 or TSC2 (TSC is tuberous sclerosis complex) that impair GAP (GTPase-activating protein) activity of the TSC1-TSC2 complex for Rheb, leading to inappropriate activity of signalling downstream of mTORC1 (mTOR complex 1). mTOR inhibitors are already used in a variety of clinical settings including as immunosuppressants, anticancer agents and antiproliferative agents in drug-eluting coronary artery stents. They also represent candidate therapies directed to the underlying molecular pathology in tuberous sclerosis and LAM. Phase I/II clinical trials of the mTORC1 inhibitor rapamycin have demonstrated reduction in size of tuberous-sclerosis- and LAM-associated renal tumours (angiomyolipomas) and some evidence for reversible improvement in lung function in patients with LAM. A case series of tuberous-sclerosis-associated brain tumours were also reported to shrink during rapamycin therapy. An important, although variable, feature of the tuberous sclerosis phenotype is learning difficulty. Recent studies in mouse models carrying heterozygous Tsc2 mutations demonstrated improvement in memory and learning deficits following treatment with rapamycin. These promising pre-clinical and early human trials are being followed by larger-scale randomized control trials of mTOR inhibitors for treatment of renal, lung and brain manifestations of TSC1- and TSC2-associated disease.
 ...
PMID:Therapeutic targeting of mTOR in tuberous sclerosis. 1914 43

Mutations in tuberous sclerosis complex (TSC) genes are associated with dysregulated mammalian target of rapamycin (mTOR)/Akt signaling and unusual neoplasms called perivascular epithelioid cell tumors (PEComas), including angiomyolipomas (AMLs) and lymphangioleiomyomatosis (LAM). Tools that quantify metabolic activity and total body burden of AML and LAM cells would be valuable for the assessment of disease progression and the response to therapy in patients with TSC and LAM. Our hypothesis was that constitutive activation of mTOR in LAM and AML cells would result in increased glucose uptake of [(18)F]2-fluoro-2-deoxyglucose (FDG) on PET scanning, as has been suggested by a single prior case report. After institutional review board approval, FDG-PET scanning was performed in six LAM patients. Six additional LAM patients underwent FDG-PET scanning for clinical evaluation of suspected malignancy. Pleural uptake related to prior therapy was identified in four individuals with a remote history of talc pleurodesis. Focal increased uptake was observed in a supraclavicular lymph node in a patient with Hodgkin lymphoma and in a lung nodule in a patient with a biopsy-documented primary lung adenocarcinoma. In one TSC-LAM patient with a biopsy-documented malignant uterine PEComa, robust uptake was noted in metastatic nodules in the lung but not in the LAM-involved lung parenchyma or the patient's massive abdominal lymphangioleiomyomas. No abnormal uptake was identified in the AMLs or LAM lesions in any patients. This pilot study suggests that FDG-PET scans are negative in patients with benign PEComas and therefore are not likely to be useful for estimating the burden of disease in patients with TSC or LAM, but that FDG-PET scans can be used to identify or exclude other neoplasms in these patients.
 ...
PMID:Utility of [18F]2-fluoro-2-deoxyglucose-PET in sporadic and tuberous sclerosis-associated lymphangioleiomyomatosis. 1934 86

Increased matrix metalloproteinase (MMP) activity has been implicated in the pathogenesis of lymphangioleiomyomatosis (LAM). The objective of this study was to investigate how tuberous sclerosis complex (TSC) 1 or TSC2 deficiency alters MMP expression and regulation. We studied immortalized cells that lack TSC2 derived from an angiomyolipoma of a patient with LAM, a TSC2 addback derivative, and murine embryonic fibroblast cells that lack Tsc1 or -2 and respective controls. Global gene expression analysis was performed in the angiomyolipoma and derivative cell lines. MMP levels in the conditioned media from these cells were analyzed by zymography and ELISA. We found increased MMP-2 expression in cells lacking TSC1/TSC2 compared with their respective controls by zymography. MMP-2 overproduction by these cells was not affected by rapamycin treatment. Gene expression analysis confirmed increased MMP-2 gene expression that was not affected by rapamycin. Furthermore, multiple other genes were found to be overexpressed in rapamycin-treated TSC2-deficient cells compared with TSC2(+) cells. We conclude that TSC1/TSC2 deficiency leads to MMP-2 overproduction that is rapamycin-insensitive, and that several genes exhibit similar patterns, suggesting that TSC1/TSC2-dependent, but mammalian target of rapamycin-independent, pathways may be involved in the pathogenesis of LAM.
 ...
PMID:Rapamycin-insensitive up-regulation of MMP2 and other genes in tuberous sclerosis complex 2-deficient lymphangioleiomyomatosis-like cells. 1939 78


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>