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: EC:2.7.11.24 (mitogen-activated protein kinase)
95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tamoxifen, a selective estrogen-receptor modulator, is effective in the treatment and prevention of breast cancer, but therapeutic resistance is common. Pure steroidal antiestrogens are efficacious in tamoxifen-resistant disease and, unlike tamoxifen, arrest cells in a state of quiescence from which they cannot reenter the cell cycle after growth factor stimulation. We now show that in hydroxytamoxifen-treated cells, transduction of the cell cycle inhibitor p27(Kip1) induces quiescence and insensitivity to growth stimulation by insulin/insulin-like growth factor I and epidermal growth factor/transforming growth factor alpha. Furthermore, reinitiation of cell cycle progression by insulin/insulin-like growth factor I in hydroxytamoxifen-arrested cells involves dissociation of the corepressors nuclear receptor corepressor (N-CoR) and silencing mediator for retinoid and thyroid hormone receptor (SMRT) from nuclear estrogen receptor alpha and redistribution to the cytoplasm, a process that is inhibited by mitogen-activated protein/extracellular signal-regulated kinase, but not phosphatidylinositol 3'-kinase, inhibitors. These data suggest that agents that up-regulate p27(Kip1) or inhibit growth factor signaling via the extracellular signal-regulated kinases should be tested as therapeutic strategies in tamoxifen-resistant breast cancer.
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PMID:p27(Kip1) induces quiescence and growth factor insensitivity in tamoxifen-treated breast cancer cells. 1290 98

The granulin-epithelin precursor, progranulin, PC-cell-derived growth factor or acrogranin, is a high molecular weight secreted mitogen. It is abundantly expressed in rapidly cycling epithelial cells, in the immune system and in neurons, such as cerebellar Purkinje cells. Progranulin contributes to tumorigenesis in diverse cancers, including breast cancer, clear cell renal carcinoma, invasive ovarian carcinoma and glioblastoma. It regulates the rate of epithelial cell division in responsive epithelial cells, and confers an invasive phenotype on these cells. It is involved in the wound response. During embryogenesis, progranulin accelerates blastocyst formation, and is a growth factor for trophectodermal cells. In the neonate, progranulin, regulates the hormone-dependent virilization of the hypothalamus. It activates phosphorylation of Shc, and p44/42 MAPK (mitogen activated protein kinase) in the ERK (extracellular regulated kinase) signaling pathway; PI3K (phosophatidyl inositol-3-kinase), AKT/protein kinase B, and p70S6kinase in the phosophatidyl inositol-3-kinase pathway; and focal adhesion kinase in the adhesion/motility pathway. The signaling properties of progranulin are apparently similar to those of classic growth factors, but the functional properties of progranulin distinguish it from these molecules. Deleting the insulin-like growth factor I receptor from murine embryonic fibroblasts blocks proliferation in response to all classic growth factors, such as epidermal growth factor, or platelet-derived growth factor, whereas progranulin retains mitotic activity on these cells. The defined biological actions of progranulin probably represent a small fraction of its overall functions. Transcriptome analyses show that the progranulin gene is induced in numerous situations that vary from obesity to the transcriptional response of cells to antineoplastic drugs. Here, the biological roles of progranulin will be reviewed, with an emphasis on cancer and cell proliferation.
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PMID:Progranulin (granulin-epithelin precursor, PC-cell derived growth factor, acrogranin) in proliferation and tumorigenesis. 1297 94

Available evidence suggests that insulin-like growth factor I receptor (IGF-IR) expression leads to increased cellular radioresistance. The most direct explanation of these findings predicts that IGF-IR is the source of survival signals in resistant cells. Mutational analysis revealed that protein truncated at amino acid 1245 in the C-terminus retained the ability of IGF-IR to confer radioresistance whereas point mutations at both Tyr-1250 and Tyr-1251 abrogated this effect using IGF-IR-deficient mouse embryo fibroblasts (R-) as a recipient. In cells expressing the latter mutant receptors, both phosphatidylinositol-3(') kinase (PI3-K) and mitogen-activated protein kinase (MAPK) signaling pathways remained intact, and addition of exogenous IGF-I could not change the radiosensitivity of these cells. Further analysis indicated that the abrogation of radioresistance required the presence of His-1293 and Lys-1294. These results suggest a novel regulatory role of the C-terminus of IGF-IR in mediating cellular radioresistance that may be independent of survival signals transmitted through this receptor.
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PMID:Roles of the insulin-like growth factor I receptor C-terminus in cellular radioresistance. 1457 10

Phenotype analysis of female mice lacking androgen receptor (AR) deficient (AR-/-) indicates that the development of mammary glands is retarded with reduced ductal branching in the prepubertal stages, and fewer Cap cells in the terminal end buds, as well as decreased lobuloalveolar development in adult females, and fewer milk-producing alveoli in the lactating glands. The defective development of AR-/- mammary glands involves the defects of insulin-like growth factor I-insulin-like growth factor I receptor and mitogen-activated protein kinase (MAPK) signals as well as estrogen receptor (ER) activity. Similar growth retardation and defects in growth factor-mediated Ras/Raf/MAPK cascade and ER signaling are also found in AR-/- MCF7 breast cancer cells. The restoration assays show that AR NH2-terminal/DNA-binding domain, but not the ligand-binding domain, is essential for normal MAPK function in MCF7 cells, and an AR mutant (R608K), found in male breast cancer, is associated with the excessive activation of MAPK. Together, our data provide the first in vivo evidence showing that AR-mediated MAPK and ER activation may play important roles for mammary gland development and MCF7 breast cancer cell proliferation.
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PMID:Abnormal mammary gland development and growth retardation in female mice and MCF7 breast cancer cells lacking androgen receptor. 1467 1

In this study, we examined the effects of isoform-specific functional inhibitors of lysophosphatidic acid acyltransferase (LPAAT), which converts lysophosphatidic acid to phosphatidic acid, on multiple myeloma (MM) cell growth and survival. The LPAAT-beta inhibitors CT-32176, CT-32458, and CT-32615 induced >95% growth inhibition (P < 0.01) in MM.1S, U266, and RPMI8226 MM cell lines, as well as MM cells from patients (IC(50), 50-200 nM). We further characterized this LPAAT-beta inhibitory effect using CT-32615, the most potent inhibitor of MM cell growth. CT-32615 triggered apoptosis in MM cells via caspase-8, caspase-3, caspase-7, and poly (ADP-ribose) polymerase cleavage. Neither interleukin 6 nor insulin-like growth factor I inhibited CT-32615-induced apoptosis. Dexamethasone and immunomodulatory derivatives of thalidomide (IMiDs), but not proteasome inhibitor PS-341, augmented MM cell apoptosis triggered by LPAAT-beta inhibitors. CT-32615-induced apoptosis was associated with phosphorylation of p53 and c-Jun NH(2)-terminal kinase (JNK); conversely, JNK inhibitor SP600125 and dominant-negative JNK inhibited CT-32615-induced apoptosis. Importantly, CT-32615 inhibited tumor necrosis factor-alpha-triggered nuclear factor-kappaB activation but did not affect either tumor necrosis factor-alpha-induced p38 mitogen-activated protein kinase phosphorylation or interleukin 6-triggered signal transducers and activators of transcription 3 phosphorylation. Finally, although binding of MM cells to bone marrow stromal cells augments MM cell growth and protects against dexamethasone-induced apoptosis, CT-32615 induced apoptosis even of adherent MM cells. Our data therefore demonstrate for the first time that inhibiting LPAAT-beta induces cytotoxicity in MM cells in the bone marrow milieu, providing the framework for clinical trials of these novel agents in MM.
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PMID:Antitumor activity of lysophosphatidic acid acyltransferase-beta inhibitors, a novel class of agents, in multiple myeloma. 1467 6

The insulin-like growth factor I receptor (IGF-IR) is overexpressed in many diverse tumor types and is a critical signaling molecule for tumor cell proliferation and survival. Therapeutic strategies targeting the IGF-IR may therefore be effective broad-spectrum anticancer agents. Through screening of a Fab phage display library, we have generated a fully human antibody (A12) that binds to the IGF-IR with high affinity (4.11 x 10(-11) M) and inhibits ligand binding with an IC(50) of 0.6-1 nM. Antibody-mediated blockade of ligand binding to the IGF-IR inhibited downstream signaling of the two major insulin-like growth factor (IGF) pathways, mitogen-activated protein kinase and phosphatidylinositol 3'-kinase/Akt, in MCF7 human breast cancer cells. As a result, the mitogenic and proliferative potential of IGF-I and IGF-II were significantly reduced. A12 did not block insulin binding to the insulin receptor but could block binding to atypical IGF-IR in MCF7 cells. In addition, A12 was shown to induce IGF-IR internalization and degradation on specific binding to tumor cells, resulting in a significant reduction in cell surface receptor density. In xenograft tumor models in vivo, IGF-IR blockade by A12 was shown to occur rapidly, resulting in significant growth inhibition of breast, renal, and pancreatic tumors. Histological analysis of tumor sections demonstrated a marked increase in apoptotic tumor cells in antibody-treated animals. These results demonstrate that A12 possesses strong antitumor activity in vitro and in vivo and may therefore be an effective therapeutic candidate for the treatment of cancers that are dependent on IGF-IR signaling for growth and survival.
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PMID:A fully human monoclonal antibody to the insulin-like growth factor I receptor blocks ligand-dependent signaling and inhibits human tumor growth in vivo. 1469 8

We developed a mouse monoclonal antibody (4G11) against insulin-like growth factor I receptor by immunizing mice with mouse embryo fibroblasts overexpressing the human insulin-like growth factor-I receptor. Not only did the 4G11 antibody inhibit the binding of [ (125)I]insulin-like growth factor-I to the fibroblast receptor, but 4G11 antibody also potently down-regulated the insulin-like growth factor-I receptor. 4G11 Fab fragment inhibited ligand binding, but did not down-regulate the receptor, suggesting that receptor aggregation is required for down-regulation. 4G11 antibody also down-regulated the receptor in MCF-7 breast cancer cells, a panel of colon cancer cells and MG-63 osteosarcoma cells. Receptor recovery in MCF-7 cells after down-regulation by 4G11 antibody was slow, requiring 32 - 48 h for full recovery. Receptor down-regulation in MCF-7 cells by 4G11 antibody was confirmed by FACS analysis of intact and permeabilized cells. In contrast to 4G11 antibody, insulin-like growth factor-I did not down-regulate the receptor in MCF-7 cells. Down-regulation of the receptor by 4G11 antibody in MCF-7 cells resulted in inhibition of Akt and MAPK activation by insulin-like growth factor-I. We conclude that the ability of a monoclonal antibody to down-regulate the receptor may be an important antibody property in targeting the insulin-like growth factor-I receptor for the treatment of certain cancers.
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PMID:Inhibition of the biologic response to insulin-like growth factor I in MCF-7 breast cancer cells by a new monoclonal antibody to the insulin-like growth factor-I receptor. The importance of receptor down-regulation. 1471 Mar 68

Huntington's disease (HD) is caused by abnormal polyglutamine (polyQ) expansion in the protein huntingtin. We have previously demonstrated the importance of the insulin-like growth factor I (IGF-1)/Akt pathway in HD. Indeed, upon IGF-1 activation, Akt phosphorylates polyQ-huntingtin at serine 421 and abrogates its toxicity. In addition, we have demonstrated that Akt is altered in the brain of HD patients. Here, we investigate the role of the serum- and glucocorticoid-induced kinase (SGK) in HD. We show that SGK phosphorylates huntingtin at serine 421 and that phosphorylation can protect striatal neurons against polyQ-huntingtin-induced toxicity. We find that SGK levels are increased in the brain of HD patients. Using a cellular model of HD, we demonstrate that the SGK dysregulation induced by polyQ-huntingtin occurs via the p38/MAPK pathway. Collectively, our results strongly suggest the involvement of SGK in HD and further imply that IGF-1 downstream signalling is a key transduction pathway that regulates the toxicity of huntingtin.
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PMID:The serum- and glucocorticoid-induced kinase SGK inhibits mutant huntingtin-induced toxicity by phosphorylating serine 421 of huntingtin. 1472 21

Urokinase plasminogen activator (uPA) expression in breast cancer is associated with relapse and a reduction in disease-specific survival. Thus, efforts are under way to identify uPA inhibitors. By screening a chemical library of >1000 compounds, 17-allyaminogeldanamycin (17AAG) was identified as a potent inhibitor of uPA by the National Cancer Institute and is now in Phase I clinical trials. At this time, it remains unclear how 17AAG blocks uPA; one possibility is through disruption of the insulin-like growth factor I receptor (IGF-IR) pathway. This would be consistent with studies from our laboratory showing that activation of IGF-IR results in the induction of uPA protein. In the study described herein, we observed that IGF-IR and uPA were highly expressed in 87 and 55% of breast cancer by screening tumor tissue microarrays representing 930 cases. A significant proportion (52.1% = 354 of 680 cases, P < 0.0001) of the patients had tumors expressing both proteins. uPA alone (P = 0.033) or in combination with IGF-IR (P = 0.0104) was indicative of decreased disease-specific survival. Next, we demonstrated that treating MDA-MB-231 cells with increasing concentrations of 17AAG resulted in IGF-IR degradation (IC(50) = 1.0 micro M) and blocked signal transduction through the Akt and mitogen-activated protein kinase pathways. Finally, we found that 17AAG had a robust inhibitory effect on the production of uPA mRNAand protein in the presence of IGF-I. Thus, our study raises the possibility that 17AAG could prove to be an effective therapeutic agent for a large number of breast cancer patients by inhibiting the IGF-IR and ultimately uPA.
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PMID:Expression of the insulin-like growth factor I receptor and urokinase plasminogen activator in breast cancer is associated with poor survival: potential for intervention with 17-allylamino geldanamycin. 1472 36

The Y1250F/Y1251F mutant of the insulin-like growth factor I receptor (IGF-IR) has tyrosines 1250 and 1251 mutated to phenylalanines and is deficient in IGF-I-mediated suppression of apoptosis in FL5.12 lymphocytic cells. To address the mechanism of loss of function in this mutant we investigated signaling responses in FL5.12 cells overexpressing either a wild-type (WT) or Y1250F/Y1251F (mutant) IGF-IR. Cells expressing the mutant receptor were deficient in IGF-I-induced phosphorylation of the JNK pathway and had decreased ERK and p38 phosphorylation. IGF-I induced phosphorylation of Akt was comparable in WT and mutant expressing cells. The decreased activation of the mitogen-activated protein kinase (MAPK) pathways was accompanied by greatly decreased Ras activation in response to IGF-I. Although phosphorylation of Gab2 was similar in WT and mutant cell lines, phosphorylation of Shc on Tyr(313) in response to IGF-I was decreased in cells expressing the mutant receptor, as was recruitment of Grb2 and Ship to Shc. However, phosphorylation of Shc on Tyr(239), the Src phosphorylation site, was normal. A role for JNK in the survival of FL5.12 cells was supported by the observation that the JNK inhibitor SP600125 suppressed IGF-I-mediated protection from apoptosis. Altogether these data demonstrate that phosphorylation of Shc, and assembly of the Shc complex necessary for activation of Ras and the MAPK pathways are deficient in cells expressing the Y1250F/Y1251F mutant IGF-IR. This would explain the loss of IGF-I-mediated survival in FL5.12 cells expressing this mutant and may also explain why this mutant IGF-IR is deficient in functions associated with cellular transformation and cell migration in fibroblasts and epithelial tumor cells.
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PMID:Impaired Shc, Ras, and MAPK activation but normal Akt activation in FL5.12 cells expressing an insulin-like growth factor I receptor mutated at tyrosines 1250 and 1251. 1496 47


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