Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

We sought to elucidate the role of AKT in follicle-stimulating hormone (FSH)-mediated granulosa cell (GC) differentiation. Our results define a signaling pathway in GCs whereby the inactivating phosphorylation of tuberin downstream of phosphatidylinositol (PI) 3-kinase/AKT activity leads to Rheb (Ras homolog enriched in brain) and subsequent mTOR (mammalian target of rapamycin) activation. mTOR then stimulates translation by phosphorylating p70 S6 kinase and, consequently, the 40 S ribosomal protein S6. Activation of this pathway is required for FSH-mediated induction of several follicular differentiation markers, including luteinizing-hormone receptor (LHR), inhibin-alpha, microtubule-associated protein 2D, and the PKA type IIbeta regulatory subunit. FSH also promotes activation of the transcription factor hypoxia-inducible factor-1 (HIF-1). FSH-stimulated HIF-1 activity is inhibited by the PI 3-kinase inhibitor LY294002, the Rheb inhibitor FTI-277 (farnesyltransferase inhibitor-277), and the mTOR inhibitor rapamycin. Finally, we find that the FSH-mediated up-regulation of reporter activities for LHR, inhibin-alpha, and vascular endothelial growth factor is dependent upon HIF-1 activity, because a dominant negative form of HIF-1alpha interferes with the up-regulation of these genes. These results show that FSH enhances HIF-1 activity downstream of the PI 3-kinase/AKT/Rheb/mTOR pathway in GCs and that HIF-1 activity is necessary for FSH to induce multiple follicular differentiation markers.
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PMID:Follicle-stimulating hormone activation of hypoxia-inducible factor-1 by the phosphatidylinositol 3-kinase/AKT/Ras homolog enriched in brain (Rheb)/mammalian target of rapamycin (mTOR) pathway is necessary for induction of select protein markers of follicular differentiation. 1498 27

A series of 30 N10-substituted phenoxazines were synthesized and screened as potential inhibitors of Akt. In cellular assays at 5 mum, 17 compounds inhibited insulin-like growth factor 1 (IGF-I)-stimulated phosphorylation of Akt (Ser-473) by at least 50% but did not inhibit IGF-I-stimulated phosphorylation of Erk-1/2 (Thr-202/Tyr-204). Substitutions at the 2-position (Cl or CF3) did not alter inhibitory activity, whereas N10-substitutions with derivatives having acetyl (20B) or morpholino (12B) side chain lost activity compared with propyl or butyl substituents (7B and 14B). Inhibition of Akt phosphorylation was associated with the inhibition of IGF-I stimulation of the mammalian target of rapamycin phosphorylation (Ser-2448 and Ser-2481), phosphorylation of p70 S6 kinase (Thr-389), and ribosomal protein S6 (Ser-235/236) in Rh1, Rh18, and Rh30 cell lines. The two most potent compounds 10-[4'-(N-diethylamino)butyl]-2-chlorophenoxazine (10B) and 10-[4'-[(beta-hydroxyethyl)piperazino]butyl]-2-chlorophenoxazine (15B) (in vitro, IC50 approximately 1-2 microM) were studied further. Inhibition of Akt phosphorylation correlated with inhibition of its kinase activity as determined in vitro after immunoprecipitation. Akt inhibitory phenoxazines did not inhibit the activity of recombinant phosphatidylinositol 3'-kinase, PDK1, or SGK1 but potently inhibited the kinase activity of recombinant Akt and Akt deltaPH, a mutant lacking the pleckstrin homology domain. Akt inhibitory phenoxazines blocked IGF-I-stimulated nuclear translocation of Akt in Rh1 cells and suppressed growth of Rh1, Rh18, and Rh30 cells (IC50 2-5 microM), whereas "inactive" derivatives were > or = 10-fold less potent inhibitors of cell growth. In contrast to rapamycin analogs, Akt inhibitory phenoxazines induced significant levels of apoptosis under serum-containing culture conditions at concentrations of agent consistent with Akt inhibition. Thus, the cellular responses to phenoxazine inhibitors of Akt appear qualitatively different from the rapamycin analogs. Modeling studies suggest inhibitory phenoxazines may bind in the ATP-binding site, although ATP competition studies were unable to distinguish between competitive and noncompetitive inhibition.
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PMID:Identification of N10-substituted phenoxazines as potent and specific inhibitors of Akt signaling. 1600 6

Mutations of the thyroid hormone receptor beta (TRbeta) gene cause resistance to thyroid hormone (RTH). RTH is characterized by increased serum thyroid hormone associated with nonsuppressible thyroid-stimulating hormone (TSH) and impaired growth. It is unclear how the actions of TRbeta mutants are modulated in vivo to affect the manifestation of RTH. Using a mouse model of RTH that harbors a knockin mutation of the TRbeta gene (TRbetaPV mouse), we investigated the effect of the steroid hormone receptor coactivator 3 (SRC-3) on RTH. In TRbetaPV mice deficient in SRC-3, dysfunction of the pituitary-thyroid axis and hypercholesterolemia was lessened, but growth impairment of RTH was worsened. The lessened dysfunction of the pituitary-thyroid axis was attributed to a significant decrease in growth of the thyroid and pituitary. Serum insulin-like growth factor 1 (IGF-1) was further reduced in TRbetaPV mice deficient in SRC-3. This effect led to reduced signaling of the IGF-1/phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway that is known to mediate cell growth and proliferation. Thus, SRC-3 modulates RTH by at least two mechanisms, one via its role as a receptor coregulator and the other via its growth regulatory role through the IGF-1/PI3K/AKT/mTOR signaling.
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PMID:Dual functions of the steroid hormone receptor coactivator 3 in modulating resistance to thyroid hormone. 1610 15

Tamoxifen is an important selective estrogen receptor (ER) modulator for treatment of steroid hormone positive breast cancer. In addition to the beneficial effect, tamoxifen is one risk factor for endometrial carcinoma (EnCa) development. We hypothesized that, (1) dysregulation of gene expression and protein phosphorylation of the insulin-like growth factor (IGF) and steroid hormone receptor-signaling occur early in benign endometrial tissues and (2) signaling differences would be detected between patients with or without tamoxifen treatment. Seventy-eight tissues, including 2 benign cohorts from patients treated with (n = 24) or without tamoxifen (n = 28) (hyperproliferative endometrium, hyperplasia, polyps), EnCa (n = 12) with endometrium controls (n = 14) were analyzed for expression of 15 genes from the IGF and steroid hormone receptor-signaling, including the target genes Syncytin-1, PAX2 and c-myc. Total and phosphorylated protein expression were examined for ERalpha, PTEN, AKT, mTOR and Syncytin-1. Compared to controls similar significant deregulation of IGF and steroid hormone receptor-signaling, Syncytin-1 and PAX2 occurred in both benign cohorts, irrelevant of tamoxifen treatment. Comparing both benign cohorts with and without tamoxifen significant expression differences were noted. Increased total protein and phosphorylation of pERalpha-Ser118, pPTEN-Thr380, pAKT-Thr308, pAKT-Ser473, pmTOR-Ser2448 and Syncytin-1 were noted in early benign tissue stages associating with tamoxifen, especially polyps. Functional kinetic studies following tamoxifen treatment of the PTEN mutated RL95-2 EnCa cell line, demonstrated a doubling of phosphorylation of pERalpha-Ser118 and a 4.2-fold induction of pAKT-Thr308 along with Syncytin-1 induction. This study supports that dysregulated IGF and steroid hormone receptor signaling is prominent in endometrial benign stages and these alterations could represent clinical indicators for the risk of EnCa and also help in development of new therapies.
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PMID:Early aberrant insulin-like growth factor signaling in the progression to endometrial carcinoma is augmented by tamoxifen. 1881 40

Metastatic breast cancer (MBC) is unfortunately still considered incurable; treatment aims to prolong progression-free and overall survival, relieve disease symptoms, and maintain quality of life. Treatment can include endocrine therapy, radiotherapy, chemotherapy, bisphosphonates, and/or targeted therapy; which is used depends on the characteristics of the disease [e.g., hormone receptor status, disease site(s), and response to previous treatment] and the patient (age, comorbidity, and personal preferences). For most patients with hormone-receptor-positive tumors, the first choice of treatment is further endocrine therapy, but endocrine resistance is a common problem in advanced disease. Several novel anticancer agents have been developed with the aim of overcoming endocrine resistance, many of which target intracellular signaling pathways implicated in disease progression or resistance. Among these, inhibitors of growth factor receptor tyrosine kinases and of mammalian target of rapamycin have shown the most promise in clinical trials. Chemotherapy is the cornerstone of MBC treatment in most women. Important considerations when choosing chemotherapy include the choice of agents, and whether to use single-agent or combination therapy. Anthracyclines are one of the most active cytotoxic agents currently used for the treatment of breast cancer, and for many women, further anthracycline therapy at progression or relapse would be the preferred option. However, lifetime exposure to anthracyclines is limited by cumulative cardiotoxicity, which often prevents rechallenge in later lines of therapy. Newer anthracycline formulations have been developed with lower cardiotoxicity than the conventional anthracycline doxorubicin, but these agents still impair cardiac function, and have maximum recommended lifetime doses. Recently, the concomitant use of cardioprotective agents, such as dexrazoxane, has emerged as an effective approach to reducing the cardiotoxic effects of anthracyclines, thus permitting retreatment. Bisphosphonates, which are not associated with the acute toxicities of cytotoxic chemotherapy drugs, are the established standard of care for patients with metastatic bone disease, and have greatly improved outcomes over the last decade. The search is ongoing for novel agents that will, hopefully, bring a cure closer to reality.
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PMID:Optimal treatment strategies in postmenopausal women with hormone-receptor-positive and HER2-negative metastatic breast cancer. 1910 94

There is now compelling evidence to suggest that the biologic features of breast tumors affect response to specific therapies. Triple-negative breast cancer (TNBC) refers to a heterogeneous group of tumors that do not express the estrogen, progesterone, or HER2/neu receptors. By gene expression analysis, most (but not all) TNBCs are categorized as basal-like. TNBCs are often associated with particularly poor outcomes, with early development of chemotherapy resistance. There have been significant improvements in the outcome of other subtypes of breast cancer, including hormone receptor-positive/HER2+ tumors, attributed to the addition of targeted therapy, including hormonal agents and trastuzumab. However, no specific targeted agents are currently available for the treatment of TNBC. This review aims to collate and describe the most recent data on both cytotoxic and targeted therapies that have demonstrated efficacy in the management of metastatic TNBC. Evidence of response to various agents in early-stage breast cancer will be included, where relevant. Targeted agents that have been investigated in the treatment of TNBC include inhibitors of poly(ADP-ribose) polymerase, angiogenesis, mammalian target of rapamycin, epidermal growth factor receptor, and Src. Several of these agents have shown considerable promise.
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PMID:Challenging clinical scenarios: treatment of patients with triple-negative or basal-like metastatic breast cancer. 2080 62

To date, blockade of growth factor receptors is the mainstay of targeted therapy in metastatic breast cancer (mBC). Monoclonal antibodies such as trastuzumab and bevacizumab represent the first generation of molecular-based therapies. Both the HER2 inhibitors and the vascular endothelial growth factor (VEGF) antagonists have shown synergism with a broad spectrum of established cytotoxins, thus being approved for first-line treatment of mBC in combination with taxanes. As a next step, tyrosine kinase inhibitors (TKIs) have been integrated into daily routine as an alternative approach for targeting HER2: The dual HER1/2 inhibitor lapatinib demonstrated activity in trastuzumab-pretreated mBC patients in combination with capecitabine. Furthermore, chemotherapy-free regimens (trastuzumab or lapatinib plus aromatase inhibitors) have been identified as additional options for hormone receptor (HR)- and HER2-positive patients. Recently published data indicate that a combination of two biologicals such as lapatinib and trastuzumab can be effective as a treatment beyond trastuzumab related progression. Multitarget TKIs have the potential to inhibit several signaling pathways involved in breast cancer-related angiogenesis. Until now, they have failed to show a clear benefit in mBC. On the other hand, poly(ADP-ribose) polymerase (PARP) inhibition, mediated by a new class of small molecules, is an interesting area of investigation. Future directions of research in HER2-positive breast cancer focus on the evaluation of novel antibodies (pertuzumab, T-DM1), and irreversible TKIs (neratinib, BIBW 2992) and inhibitors of HER2-related downstream signaling (mTOR, TORC 1/2, PI3K/Akt) and of receptor cross-talk (IGFR).
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PMID:The Role of Targeted Agents in the Treatment of Metastatic Breast Cancer. 2084 26

This Review outlines the understanding and management of triple-negative breast cancer (TNBC). TNBC shares morphological and genetic abnormalities with basal-like breast cancer (BLBC), a subgroup of breast cancer defined by gene-expression profiling. However, TNBC and BLBC tumors are heterogeneous and overlap is incomplete. Breast cancers found in BRCA1 mutation carriers are also frequently triple negative and basal like. TNBC and BLBC occur most frequently in young women, especially African Americans, and tend to exhibit aggressive, metastatic behavior. These tumors respond to conventional chemotherapy but relapse more frequently than hormone receptor-positive, luminal subtypes and have a worse prognosis. New systemic therapies are urgently needed as most patients with TNBC and/or BLBC relapse with distant metastases, and hormonal therapies and HER2-targeted agents are ineffective in this group of tumors. Poly (ADP-ribose) polymerase inhibitors, angiogenesis inhibitors, EGFR-targeted agents, and src kinase and mTOR inhibitors are among the therapeutic agents being actively investigated in clinical trials in patients with TNBC and/or BRCA1-associated tumors. Increased understanding of the genetic abnormalities involved in the pathogenesis of TNBC, BLBC and BRCA1-associated tumors is opening up new therapeutic possibilities for these hard-to-treat breast cancers.
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PMID:Triple-negative breast cancer: disease entity or title of convenience? 2087 96

Perou's molecular classification defines tumors that neither express hormone receptors nor overexpress HER2 as triple-negative (TN) tumors. These tumors account for approximately 15% of breast cancers. The so-called basaloid tumors are not always synonymous with TN tumors; they differ in the fact that they express different molecular markers, have a higher histologic grade, and have a worse prognosis. Clinically they occur in younger women as interval cancer, and the risk of recurrence is higher within the first 3 years. Distant recurrences in the brain and visceral metastases are more common than in hormone receptor-positive tumors. Therapeutically, despite being highly chemosensitive, their progression-free time is generally short. In terms of chemotherapeutic treatment, anthracyclines and taxanes are useful drugs, and high response rates have been described for the combination of ixabepilone-capecitabine and platinums. The combination with antiangiogenic drugs has also proven useful. A group of new drugs, poly-(ADP-ribose)-polymerase inhibitors, showed favorable results in TN tumors with BRCA mutation. There are currently several ongoing studies with new drugs including epidermal growth factor receptor inhibitors, c-kit inhibitors, Raf/Mek/Map kinase inhibitors and mTOR inhibitors.
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PMID:Triple-negative breast cancer. 2105 Apr 24

The goal of this study was to determine whether gene expression differences exist between inflammatory breast cancers (IBC) and T stage-matched non-IBC patients stratified by hormone receptor and HER2 status. We used Affymetrix GeneChips to analyze 82 tumor samples (25 T4d patients, and 57 T4a-c patients) of newly diagnosed breast cancers. Genes that were differentially expressed between the IBC and non-IBC specimens were identified using the t test, and differential expression of gene sets was assessed using gene set analysis. Three distinct clinical subtypes of IBC and non-IBC were compared: ER-positive/HER2-normal, HER2-amplified, and ER-negative/HER2-normal. When we compared expression data from all IBC with all non-IBC, we found no significant differences after adjusting for multiple testing. When IBC and non-IBC tumors were compared by clinical subtype, however, significant differences emerged. Complement and immune system-related pathways were overexpressed in ER-positive/HER2-normal IBC. Protein translation and mTOR signaling were overexpressed in HER2-amplified IBC. Apoptosis-, neural-, and lipid metabolism-related pathways were overexpressed in ER-negative/HER2-normal IBC compared with non-IBC of the same receptor phenotype. In this T stage-matched case-control study, the survival curves of patients with IBC and non-IBC were similar for all three clinical subtypes. IBC tumors can be divided into molecular and clinical subtypes similar to those of non-IBC. Clinical subtypes of IBC show molecular differences compared with similar subtypes of non-IBC.
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PMID:Different gene expressions are associated with the different molecular subtypes of inflammatory breast cancer. 2115 52


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