Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P31749 (AKT)
 22,954 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The relationship between breast cancer-associated fatty acid synthase (FAS; oncogenic antigen-519) and chemotherapy-induced cell damage has not been studied. We examined the ability of C75, a synthetic slow-binding inhibitor of FAS activity, to modulate the cytotoxic activity of the microtubule-interfering agent Taxol (paclitaxel) in SK-Br3, MDA-MB-231, MCF-7 and multidrug-resistant MDR-1 (P-Glycoprotein)-overexpressing MCF-7/AdrR breast cancer cells. When the combination of C75 with Taxol in either concurrent (C75 + Taxol 24 hr) or sequential (C75 24 hr --> Taxol 24 hr) schedules were tested for synergism, addition or antagonism using the isobologram and the median-effect plot analyses, co-exposure of C75 and Taxol mostly demonstrated synergistic effects, whereas sequential exposure to C75 followed by Taxol mainly showed additive or antagonistic interactions. Because the nature of the cytotoxic interactions was definitely schedule-dependent in MCF-7 cells, we next evaluated the effects of C75 on Taxol-induced apoptosis as well as Taxol-activated cell death and cell survival-signaling pathways in this breast cancer cell model. An ELISA for histone-associated DNA fragments demonstrated that C75 and Taxol co-exposure caused a synergistic enhancement of apoptotic cell death, whereas C75 pre-treatment did not enhance the apoptosis-inducing activity of Taxol. Co-exposure to C75 and Taxol induced a remarkable nuclear accumulation of activated p38 mitogen-activated protein kinase (p38 MAPK), which was accompanied by a synergistic nuclear accumulation of the p53 tumor-suppressor protein that was phosphorylated at Ser46, a p38 MAPK-regulated pro-apoptotic modification of p53. As single agents, FAS blocker C75 and Taxol induced a significant stimulation of the proliferation and cell survival mitogen-activated protein kinase extracellular signal-regulated kinase (ERK1/ERK2 MAPK) activity, whereas, in combination, they interfered with ERK1/ERK2 activation. Moreover, the combined treatment of C75 and Taxol inactivated the anti-apoptotic AKT (protein kinase B) kinase more than either agent alone, as evidenced by a synergistic down-regulation of AKT phosphorylation at its activating site Ser(473) without affecting AKT protein levels. To rule out a role for non-FAS C75-mediated effects, we finally used the potent and highly sequence-specific mechanism of RNA interference (RNAi) to block FAS-dependent signaling. Importantly, SK-Br3 and multi-drug resistant MCF-7/AdrR cells transiently transfected with sequence-specific double-stranded RNA oligonucleotides targeting FAS gene demonstrated hypersensitivity to Taxol-induced apoptotic cell death. Our findings establish for the first time that FAS blockade augments the cytotoxicity of anti-mitotic drug Taxol against breast cancer cells and that this chemosensitizing effect is schedule-dependent. We suggest that the alternate activation of both the pro-apoptotic p38 MAPK-p53 signaling and the cytoprotective MEK1/2 --> ERK1/2 cascade, as well as the inactivation of the anti-apoptotic AKT activity may explain, at least in part, the sequence-dependent enhancement of Taxol-induced cytotoxicity and apoptosis that follows inhibition of FAS activity in breast cancer cells. If chemically stable FAS inhibitors demonstrate systemic anticancer effects of FAS inhibition in vivo, these findings may render FAS as a valuable molecular target to enhance the efficacy of taxanes-based chemotherapy in human breast cancer.
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PMID:Pharmacological and small interference RNA-mediated inhibition of breast cancer-associated fatty acid synthase (oncogenic antigen-519) synergistically enhances Taxol (paclitaxel)-induced cytotoxicity. 1565

Activation of activator protein-1 (AP-1) and increased expression of cyclooxygenase-2 (COX-2) have been clearly shown to play a functional role in UVB-induced skin tumor promotion. In this study, we examined UVB-induced signal transduction pathways in SKH-1 mouse epidermis leading to increases in COX-2 expression and AP-1 activity. We observed rapid increases in p38 mitogen-activated protein kinase (MAPK) signaling through activation of p38 MAPK and its downstream target, MAPK activated protein kinase-2. UVB also increased phosphatidylinositol 3-kinase (PI3K) signaling as observed through increases in AKT and GSK-3beta phosphorylation. Activation of the p38 MAPK and PI3K pathways results in the phosphorylation of cyclic AMP-responsive element binding protein, which was also observed in UVB-irradiated SKH-1 mice. Topical treatment with SB202190 (a specific inhibitor of p38 MAPK) or LY294002 (a specific inhibitor of PI3K) significantly decreased UVB-induced AP-1 activation by 84% and 68%, respectively, as well as COX-2 expression. Our data show that in mouse epidermis, UVB activation of the p38 MAPK and PI3K pathways leads to AP-1 activation and COX-2 expression.
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PMID:Inhibition of p38 mitogen-activated protein kinase and phosphatidylinositol 3-kinase decreases UVB-induced activator protein-1 and cyclooxygenase-2 in a SKH-1 hairless mouse model. 1575 75

Overexpression of cyclooxygenase-2 (COX-2) is frequently observed in several human cancers, including lung, colon, and head and neck. Malignancies are also associated with the dysregulation of cell cycle events and concomitant elevated activity of cyclin-dependent kinases (CDK). CDK2 is a key cell cycle regulatory protein that controls the transition of cells from G(1) to S phase. In this study, we furnish several lines of evidence that show a functional role for the CDK2 in interleukin-1beta (IL-1beta)-induced COX-2 expression in H358 human non-small cell lung carcinoma cell line by blocking CDK2 activity. First, we show that BMS-387032, a potent CDK2 inhibitor, blocks IL-1beta-induced expression as well as steady-state mRNA levels of COX-2. Second, we show that small interfering RNA that abrogates CDK2 expression also blocks IL-1beta-induced COX-2 expression. Third, results from in vitro kinase assays clearly show that IL-1beta induces CDK2 activity in H358 cells and this activity is significantly inhibited by BMS-387032. Moreover, CDK2 inhibition blocks IL-1beta-induced binding to the NF-IL6 element of the COX-2 promoter and inhibits transcription of the COX-2 gene. We also observed that BMS-387032 does not inhibit endogenous expression of COX-2 or prostaglandin synthesis in lung carcinoma cells. Finally, we provide evidence showing that IL-1beta-induced signaling events, such as p38 mitogen-activated protein kinase, phosphorylated stress-activated protein kinase/c-Jun NH(2)-terminal kinase, phosphorylated AKT, and phosphorylated extracellular signal-regulated kinase 1/2, are not inhibited by CDK2 inhibitor. Taken together, the data suggest that CDK2 activity may play an important event in the IL-1beta-induced COX-2 expression and prostaglandin E(2) synthesis and might represent a novel target for BMS-387032.
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PMID:The cyclin-dependent kinase 2 inhibitor down-regulates interleukin-1beta-mediated induction of cyclooxygenase-2 expression in human lung carcinoma cells. 1645 36

Mammalian target of rapamycin (mTOR) inhibitors curtail cap-dependent translation. However, they can also induce post-translational modifications of proteins. We assessed both effects to understand the mechanism by which mTOR inhibitors like rapamycin sensitize multiple myeloma cells to dexamethasone-induced apoptosis. Sensitization was achieved in multiple myeloma cells irrespective of their PTEN or p53 status, enhanced by activation of AKT, and associated with stimulation of both intrinsic and extrinsic pathways of apoptosis. The sensitizing effect was not due to post-translational modifications of the RAFTK kinase, Jun kinase, p38 mitogen-activated protein kinase, or BAD. Sensitization was also not associated with a rapamycin-mediated increase in glucocorticoid receptor reporter expression. However, when cap-dependent translation was prevented by transfection with a mutant 4E-BP1 construct, which is resistant to mTOR-induced phosphorylation, cells responded to dexamethasone with enhanced apoptosis, mirroring the effect of coexposure to rapamycin. Thus, sensitization is mediated by inhibition of cap-dependent translation. A high-throughput screening for translational efficiency identified several antiapoptotic proteins whose translation was inhibited by rapamycin. Immunoblot assay confirmed rapamycin-induced down-regulated expressions of XIAP, CIAP1, HSP-27, and BAG-3, which may play a role in the sensitization to apoptosis. Studies in a xenograft model showed synergistic in vivo antimyeloma effects when dexamethasone was combined with the mTOR inhibitor CCI-779. Synergistic effects were associated with an enhanced multiple myeloma cell apoptosis in vivo. This study supports the strategy of combining dexamethasone with mTOR inhibitors in multiple myeloma and identifies a mechanism by which the synergistic effect is achieved.
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PMID:Mechanism by which mammalian target of rapamycin inhibitors sensitize multiple myeloma cells to dexamethasone-induced apoptosis. 1648 35

Podocyte apoptosis initiates progressive glomerulosclerosis in TGF-beta1 transgenic and CD2AP-knockout (CD2AP-/-) mice. It was previously shown that in both mouse models, activation of the TGF-beta pathway is the key event during development of podocyte apoptosis. Furthermore, CD2AP is an important modifier of TGF-beta-induced survival signaling via activation of the phosphoinositol 3-kinase/AKT signaling pathway. This article presents IGF-binding protein-3 (IGFBP-3) as a new modulator of apoptosis and survival signaling in glomerular podocytes. High expression of IGFBP-3 protein in the urine of diseased CD2AP-/- mice was discovered, and IGFBP-3 expression in glomerular podocytes and parietal cells was detected. IGFBP-3 can induce changes in podocyte actin cytoskeleton, leads to apoptosis in cultured murine podocytes, and can enhance TGF-beta1-induced apoptosis in vitro. For studying this process on a molecular level, proapoptotic p38 mitogen-activated protein kinase pathways and antiapoptotic phosphoinositol 3-kinase/AKT pathways were examined in cultured murine podocytes. It was found that IGFBP-3 increments the level of TGF-beta1-induced phosphorylated p38 mitogen-activated protein kinase and decreases the phosphorylation of antiapoptotic AKT. This effect is specific for the co-stimulation of IGFBP-3 with TGF-beta1 because a combination of IGFBP-3 with bone morphogenic protein-7 (BMP-7), another member of the TGF-beta superfamily, results in apoptosis opposing signaling effects with a strong increase of phosphorylated AKT and subsequent functional effects. These results demonstrate that the IGF/IGFBP axis plays an important role in the development of podocyte apoptosis by modulation of TGF-beta and BMP-7-induced pro- and antiapoptotic signals.
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PMID:IGF-binding protein-3 modulates TGF-beta/BMP-signaling in glomerular podocytes. 1667 19

In vitro Kaposi's sarcoma-associated herpesvirus (KSHV) infection of primary human dermal microvascular endothelial (HMVEC-d) cells and human foreskin fibroblast (HFF) cells is characterized by the induction of preexisting host signal cascades, sustained expression of latency-associated genes, transient expression of a limited number of lytic genes, and induction of several cytokines, growth factors, and angiogenic factors. Since NF-kappaB is a key molecule involved in the regulation of several of these factors, here, we examined NF-kappaB induction during de novo infection of HMVEC-d and HFF cells. Activation of NF-kappaB was observed as early as 5 to 15 min postinfection by KSHV, and translocation of p65-NF-kappaB into nuclei was detected by immunofluorescence assay, electrophoretic mobility shift assay, and p65 enzyme-linked immunosorbent assay. IkappaB phosphorylation inhibitor (Bay11-7082) reduced this activation significantly. A sustained moderate level of NF-kappaB induction was seen during the observed 72 h of in vitro KSHV latency. In contrast, high levels of ERK1/2 activation at earlier time points and a moderate level of activation at later times were observed. p38 mitogen-activated protein kinase was activated only at later time points, and AKT was activated in a cyclic manner. Studies with UV-inactivated KSHV suggested a role for virus entry stages in NF-kappaB induction and a requirement for KSHV viral gene expression in sustained induction. Inhibition of NF-kappaB did not affect target cell entry by KSHV but significantly reduced the expression of viral latent open reading frame 73 and lytic genes. KSHV infection induced the activation of several host transcription factors, including AP-1 family members, as well as several cytokines, growth factors, and angiogenic factors, which were significantly affected by NF-kappaB inhibition. These results suggest that during de novo infection, KSHV induces sustained levels of NF-kappaB to regulate viral and host cell genes and thus possibly regulates the establishment of latent infection.
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PMID:Kaposi's sarcoma-associated herpesvirus induces sustained NF-kappaB activation during de novo infection of primary human dermal microvascular endothelial cells that is essential for viral gene expression. 1728 75

Ansamycin antibiotics that target heat shock protein 90 function are being developed as anticancer agents but are also known to be dose limiting in patients due to hepatotoxicity. Herein, to better understand how the normal tissue toxicity of geldanamycins could be ameliorated to improve the therapeutic index of these agents, we examined the interactions of 17-allylamino-17-demethoxygeldanamycin (17AAG) and the secondary bile acid deoxycholic acid (DCA) in hepatocytes and fibroblasts. DCA and 17AAG interacted in a greater than additive fashion to cause hepatocyte cell death within 2 to 6 h of coadministration. As single agents DCA, but not 17AAG, enhanced the activity of extracellular signal-regulated kinase 1/2, AKT, c-Jun NH(2)-terminal kinase 1/2 (JNK1/2), and p38 mitogen-activated protein kinase (MAPK). Combined exposure of cells to DCA and 17AAG further enhanced JNK1/2 and p38 MAPK activity. Inhibition of JNK1/2 or p38 MAPK, but not activator protein-1, suppressed the lethality of 17AAG and of 17AAG and DCA. Constitutive activation of AKT, but not MAPK/extracellular signal-regulated kinase kinase 1/2, suppressed 17AAG- and DCA-induced cell killing and reduced activation of JNK1/2. DCA and 17AAG exposure promoted association of BAX with mitochondria, and functional inhibition of BAX or caspase-9, but not of BID and caspase-8, suppressed 17AAG and DCA lethality. DCA and 17AAG interacted in a greater than additive fashion to promote and prolong the generation of reactive oxygen species (ROS). ROS-quenching agents, inhibition of mitochondrial function, expression of dominant-negative thioredoxin reductase, or expression of dominant-negative apoptosis signaling kinase 1 suppressed JNK1/2 and p38 MAPK activation and reduced cell killing after 17AAG and DCA exposure. The potentiation of DCA-induced ROS production by 17AAG was abolished by Ca(2+) chelation and ROS generation, and cell killing following 17AAG and DCA treatment was abolished in cells lacking expression of PKR-like endoplasmic reticulum kinase. Thus, DCA and 17AAG interact to stimulate Ca(2+)-dependent and PKR-like endoplasmic reticulum kinase-dependent ROS production; high levels of ROS promote intense activation of the p38 MAPK and JNK1/2 pathways that signal to activate the intrinsic apoptosis pathway.
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PMID:17-Allylamino-17-demethoxygeldanamycin enhances the lethality of deoxycholic acid in primary rodent hepatocytes and established cell lines. 1730 59

Rituximab (chimeric anti-CD20 monoclonal antibody) is the first Food and Drug Administration approved antitumor antibody and is used in the treatment of B-non-Hodgkin's lymphoma (B-NHL). It is used as single monotherapy or in combination with chemotherapy and has improved the treatment outcome of patients with B-NHL. The in vivo mechanisms of rituximab-mediated antitumor effects include antibody-dependent cellular cytotoxicity (ADCC), complement-dependent cell cytotoxicity (CDC), growth-inhibition and apoptosis. A subset of patients does not initially respond to rituximab and several responsive patients develop resistance to further rituximab treatment. The mechanism of rituximab unresponsiveness is not known. Besides the above-postulated mechanisms, rituximab has been shown to trigger the cells via CD-20. Studies performed with B-NHL cell lines as model systems revealed several novel mechanisms of rituximab-mediated effects that are involved in chemo/immunosensitization and the development of resistance to rituximab. Rituximab has been shown to inhibit the p38 mitogen-activated protein kinase, nuclear factor-kappaB (NF-kappaB), extracellular signal-regulated kinase 1/2 (ERK 1/2) and AKT antiapoptotic survival pathways, all of which result in upregulation of phosphatase and tensin homolog deleted on chromosome ten and Raf kinase inhibitor protein and in the downregulation of antiapoptotic gene products (particularly Bcl-2, Bcl-(xL) and Mcl-1), and resulting in chemo/immunosensitization. Further, rituximab treatment inhibits the overexpressed transcription repressor Yin Yang 1 (YY1), which negatively regulates Fas and DR5 expression and its inhibition leads to sensitization to Fas ligand and tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis. Rituximab-resistant clones were generated as model to examine the mechanism of in vivo rituximab unresponsiveness. These clones showed reduced expression of CD20 and hyperactivation of the above antiapoptotic signaling pathways and failure of rituximab to trigger the cells leading to inhibition of ADCC, CDC and chemo/immunosensitization. Interference with the hyperactivated pathways with various pharmacological and proteasome inhibitors reversed resistance. Furthermore, the above findings have identified several gene products that can serve as new prognostic/diagnostic biomarkers as well as targets for therapeutic intervention in B-NHL.
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PMID:Rituximab-induced inhibition of antiapoptotic cell survival pathways: implications in chemo/immunoresistance, rituximab unresponsiveness, prognostic and novel therapeutic interventions. 1753 16

Human beta-defensin (HBD)-2 is an inducible antimicrobial peptide that plays an important role in innate immunity. Glucocorticoids, on the other hand, exert immunosuppressive and anti-inflammatory actions. We have previously reported that interleukin (IL)-1beta induces HBD-2 mRNA expression through the activation of nuclear factor-kappaB (NF-kappaB) transcriptional factor, as well as p38 mitogen-activated protein kinase (MAPK), c-Jun N-terminal kinase (JNK), or phosphatidylinositol-3-kinase/AKT in A549 cells. In this study, we further investigated whether dexamethasone (Dex) controls IL-1beta-induced HBD-2 mRNA expression in A549 cells and the molecular mechanism associated with it. Dex suppressed IL-1beta-induced HBD-2 mRNA expression, which is mediated by a glucocorticoid receptor, at the transcriptional level. Interestingly, Dex attenuated IL-1beta-mediated activation of p38 MAPK and JNK, but not of AKT. Dex increased the expression of MAPK phosphatase (MKP)-1, which dephosphorylated p38 MAPK, but not JNK, by IL-1beta. However, although Dex did not inhibit the nuclear translocation of p65 NF-kappaB in response to IL-1beta, it profoundly inhibited NF-kappaB promoter- and HBD-2 promoter-driven luciferase activities. These results suggest that Dex acts to inhibit IL-1beta-induced HBD-2 mRNA expression through blockage of the nuclear transcriptional activation of p65 NF-kappaB as well as through inactivation of p38 MAPK and JNK. Specifically, Dex-induced MKP-1 expression is responsible for the inactivation of p38 MAPK, but not JNK, in response to IL-1beta in A549 cells.
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PMID:Dexamethasone suppresses interleukin-1beta-induced human beta-defensin 2 mRNA expression: involvement of p38 MAPK, JNK, MKP-1, and NF-kappaB transcriptional factor in A549 cells. 1764 39

Calcium is a second messenger for many signaling pathways in B cells, but its role as a receptor ligand has not been well characterized. However, pulses of free calcium were found to cause the rapid release of internal calcium stores in normal human B cells. This response appeared to be mediated by a cell surface protein with receptor properties as it could be blocked by pretreatment with trypsin and with kinase and phospholipase Cgamma inhibitors. The calcium receptor on B cells was not the conventional calcium-sensing receptor (CaSR) since B cells did not express CaSR and calcium-induced responses could not be blocked by specific CaSR inhibitors. B-cell responses to extracellular calcium activated phosphoinositide-3 kinase/AKT, calcineurin, extracellular signal regulated kinase, p38 mitogen-activated protein kinase, protein kinase C, Ca(2+)/calmodulin kinase II, and nuclear factor-kappaB signaling pathways, and resulted in transcription of the early response gene, CD83. This extracellular calcium sensor enhanced B-cell responses to Toll-like receptor, B-cell receptor, and cytokine receptor agonists. These findings suggest a means by which B cells prepare to engage in immune responses by responding to calcium fluctuations in their environment.
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PMID:Extracellular calcium sensing promotes human B-cell activation and function. 1772 42


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