UNIPROT:P05412 - FACTA Search

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Query: UNIPROT:P05412 (c-Jun)
11,453 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We investigate the cytotoxic effect of metal protoporphyrins including ferric protoporphyrin (FePP; hemin), cobalt protoporphyrin (CoPP), and tin protoporphyrin (SnPP) in glioblastoma cells C6 and GBM8401. Data of MTT assay show that FePP and CoPP, but not SnPP, significantly reduce the viability of glioma cells C6 and GBM8401 in the absence of serum. In the condition with fetal bovine serum (FBS) or bovine serum albumin (BSA), the cytotoxic effect of FePP and CoPP was completely inhibited. Binding of FePP, CoPP, and SnPP with BSA was examined via spectrophotometer analysis, and the protective effect of serum against FePP and CoPP-induced cell death was abolished by BSA depletion. A loss in the integrity of DNA with an occurrence of apoptotic events including DNA ladders, caspase 3 and PARP protein cleavage, and chromatin-condensed cells is observed in FePP-treated or CoPP-treated C6 cells. An increase in intracellular peroxide level was examined in FePP, but not CoPP, -treated C6 cells, and N-acetyl-l-cysteine (NAC) addition significantly protected C6 cells from FePP, but not CoPP, -induced cell death with reducing FePP-stimulated reactive oxygen species (ROS) production. Activation of extracellular regulated kinases (ERKs) and c-Jun-N-terminal kinases (JNKs) with an increase in the heme oxygenase-1 (HO-1) protein was observed in FePP-treated or CoPP-treated C6 cells in the absence of FBS or BSA, and adding JNKs inhibitor SP600125 (SP), but not ERKs inhibitor PD98059 (PD), significantly attenuated FePP-induced or CoPP-induced HO-1 protein expression in accordance with reducing JNKs protein phosphorylation. However, PD98059, SP600125, or transfection of C6 cells with antisense HO-1 oligonucleotides show no effect on the cytotoxicity elicited by FePP and CoPP in C6 cells. Effect of serum and BSA on the cytotoxicity of metal protoporphyrins in glioma cells is first demonstrated in the present study, and the roles of ROS, MAPKs, and HO-1 were elucidated.
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PMID:Cytotoxic effects of metal protoporphyrins in glioblastoma cells: roles of albumin, reactive oxygen species, and heme oxygenase-1. 1828 2

Curcumin, a natural compound, is a well-known chemopreventive agent with potent anticarcinogenic activity in a wide variety of tumor cells. Curcumin inhibits cancer cell proliferation in part by suppressing cyclin D1 and inducing expression of the cyclin-dependent kinase inhibitor p21(Waf1/Cip1). Both p53-dependent and p53-independent mechanisms regulate p21(Waf1/Cip1) expression, but the mechanism by which curcumin regulates p21(Waf1/Cip1) expression remains unknown. Here, we report that transcription of the p21(Waf1/Cip1) gene is activated by early growth response-1 (Egr-1) independently of p53 in response to curcumin treatment in U-87MG human glioblastoma cells. Egr-1 is a transcription factor that helps regulate differentiation, growth, and apoptosis in many cell types. Egr-1 expression is induced by curcumin through extracellular signal-regulated kinase (ERK) and c-Jun NH(2)-terminal kinase (JNK), but not the p38, mitogen-activated protein kinase (MAPK) pathways, which mediate the transactivation of Elk-1. Transient expression of Egr-1 enhanced curcumin-induced p21(Waf1/Cip1) promoter activity, whereas suppression of Egr-1 expression by small interfering RNA abrogated the ability of curcumin to induce p21(Waf1/Cip1) promoter activity. In addition, stable knockdown of Egr-1 expression in U-87MG cells suppressed curcumin-induced p21 expression. Our results indicate that ERK and JNK MAPK/Elk-1/Egr-1 signal cascade is required for p53-independent transcriptional activation of p21(Waf1/Cip1) in response to curcumin in U-87MG human glioblastoma cells.
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PMID:p21 Waf1/Cip1 expression by curcumin in U-87MG human glioma cells: role of early growth response-1 expression. 1831

Chronic inflammation and inflammatory cytokines have recently been implicated in the development and progression of various types of cancer. In the brain, neuroinflammatory cytokines affect the growth and differentiation of both normal and malignant glial cells, with interleukin 1 (IL-1) shown to be secreted by the majority of glioblastoma cells. Recently, elevated levels of sphingosine kinase 1 (SphK1), but not SphK2, were correlated with a shorter survival prognosis for patients with glioblastoma multiforme. SphK1 is a lipid kinase that produces the pro-growth, anti-apoptotic sphingosine 1-phosphate, which can induce invasion of glioblastoma cells. Here, we show that the expression of IL-1 correlates with the expression of SphK1 in glioblastoma cells, and neutralizing anti-IL-1 antibodies inhibit both the growth and invasion of glioblastoma cells. Furthermore, IL-1 up-regulates SphK1 mRNA levels, protein expression, and activity in both primary human astrocytes and various glioblastoma cell lines; however, it does not affect SphK2 expression. The IL-1-induced SphK1 up-regulation can be blocked by the inhibition of JNK, the overexpression of the dominant-negative c-Jun(TAM67), and the down-regulation of c-Jun expression by small interference RNA. Activation of SphK1 expression by IL-1 occurs on the level of transcription and is mediated via a novel AP-1 element located within the first intron of the sphk1 gene. In summary, our results suggest that SphK1 expression is transcriptionally regulated by IL-1 in glioblastoma cells, and this pathway may be important in regulating survival and invasiveness of glioblastoma cells.
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PMID:Interleukin-1 regulates the expression of sphingosine kinase 1 in glioblastoma cells. 1907 42

Adrenomedullin is a secreted peptide hormone with multiple functions. Although a number of reports have indicated that adrenomedullin may be involved in tumor progression, its mechanism of action remains obscure. In this study, we have analysed the signal transduction pathway activated by adrenomedullin in human glioma cells. Our results revealed that adrenomedullin induced the phosphorylation of both c-Jun and JNK in glioblastoma cells. Silencing JNK expression with siRNA reversed the phosphorylation of c-Jun induced by adrenomedullin, indicating that JNK is responsible of c-Jun activation. In addition, electrophoretic mobility-shift assays showed that the increase in phosphorylation of c-Jun was associated with increased AP-1 DNA binding activity. Supershift assays and co-immunoprecipitation demonstrated that c-Jun and JunD are part of the AP-1 complex, indicating that activated c-Jun is dimerized with JunD in response to adrenomedullin. Furthermore, adrenomedullin was shown to promote cell transit beyond cell cycle phases with a concomittant increase in cyclin D1 protein level, suggesting that adrenomedullin effects cell proliferation through up-regulation of cyclin D1. The inhibition of JNK activation or the suppression of c-Jun or JunD expression with siRNA impaired the effects of adrenomedullin on cell proliferation and on cyclin D1. Taken together, these data demonstrate that activation of cJun/JNK pathway is involved in the growth regulatory activity of adrenomedullin in glioblastoma cells.
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PMID:Adrenomedullin promotes cell cycle transit and up-regulates cyclin D1 protein level in human glioblastoma cells through the activation of c-Jun/JNK/AP-1 signal transduction pathway. 1916 30

Hypoxia and necrosis are fundamental features of glioblastoma (GBM) and their emergence is critical for the rapid biological progression of this fatal tumor; yet, underlying mechanisms are poorly understood. We have suggested that vaso-occlusion following intravascular thrombosis could initiate or propagate hypoxia and necrosis in GBM. Tissue factor (TF), the main cellular initiator of coagulation, is overexpressed in GBMs and likely favors a thrombotic microenvironment. Epidermal growth factor receptor (EGFR) amplification and PTEN loss are two common genetic alterations seen in GBM but not in lower-grade astrocytomas that could be responsible for TF up-regulation. The most frequent EGFR mutation in GBM involves deletion of exons 2 to 7, resulting in the expression of a constitutively active receptor, EGFRvIII. Here, we show that overexpression of EGFR or EGFRvIII in human glioma cells causes increased basal TF expression and that stimulation of EGFR by its ligand, EGF, leads to a marked dose-dependent up-regulation of TF. In all cases, increased TF expression led to accelerated plasma coagulation in vitro. EGFR-mediated TF expression depended most strongly on activator protein-1 (AP-1) transcriptional activity and was associated with c-Jun NH(2)-terminal kinase (JNK) and JunD activation. Restoration of PTEN expression in PTEN-deficient GBM cells diminished EGFR-induced TF expression by inhibiting JunD/AP-1 transcriptional activity. PTEN mediated this effect by antagonizing phosphatidylinositol 3-kinase activity, which in turn attenuated both Akt and JNK activities. These mechanisms are likely at work in vivo, as EGFR expression was highly correlated with TF expression in human high-grade astrocytoma specimens.
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PMID:Epidermal growth factor receptor and PTEN modulate tissue factor expression in glioblastoma through JunD/activator protein-1 transcriptional activity. 1927 85

Sphingosine-1-phosphate is a potent sphingolipid mediator of diverse processes important for brain tumors, including cell growth, survival, migration, invasion, and angiogenesis. Sphingosine kinase 1 (SphK1), one of the two isoenzymes that produce sphingosine-1-phosphate, is up-regulated in glioblastoma and has been linked to poor prognosis in patients with glioblastoma multiforme (GBM). In the present study, we found that a potent isotype-specific SphK1 inhibitor, SK1-I, suppressed growth of LN229 and U373 glioblastoma cell lines and nonestablished human GBM6 cells. SK1-I also enhanced GBM cell death and inhibited their migration and invasion. SK1-I rapidly reduced phosphorylation of Akt but had no significant effect on activation of extracellular signal-regulated kinase 1/2, another important survival pathway for GBM. Inhibition of the concomitant activation of the c-Jun-NH(2)-kinase pathway induced by SK1-I attenuated death of GBM cells. Importantly, SK1-I markedly reduced the tumor growth rate of glioblastoma xenografts, inducing apoptosis and reducing tumor vascularization, and enhanced the survival of mice harboring LN229 intracranial tumors. Our results support the notion that SphK1 may be an important factor in GBM and suggest that an isozyme-specific inhibitor of SphK1 deserves consideration as a new therapeutic agent for this disease.
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PMID:Targeting sphingosine kinase 1 inhibits Akt signaling, induces apoptosis, and suppresses growth of human glioblastoma cells and xenografts. 1972 67

An increase in MMP-9 gene expression and enzyme activity with stimulating the migration of GBM8401 glioma cells via wound healing assay by 12-O-tetradecanoylphorbol-13-acetate (TPA) was detected in glioblastoma cells GBM8401. TPA-induced translocation of protein kinase C (PKC)alpha from the cytosol to membranes, and migration of GBM8401 elicited by TPA was suppressed by adding the PKCalpha inhibitors, GF109203X and H7. Activation of extracellular signal-regulated kinase (ERK) and c-Jun-N-terminal kinase (JNK) by TPA was identified, and TPA-induced migration and MMP-9 activity was significantly blocked by ERK inhibitor PD98059 and U0126, but not JNK inhibitor SP600125. Activation of NF-kappaB protein p65 nuclear translocation and IkappaBalpha protein phosphorylation with increased NF-kappaB-directed luciferase activity by TPA were observed, and these were blocked by the PD98059 and IkB inhibitor BAY117082 accompanied by reducing migration and MMP-9 activity induced by TPA in GBM8401 cells. Transfection of GBM8401 cells with PKCalpha siRNA specifically reduced PKCalpha protein expression with blocking TPA-induced MMP-9 activation and migration. Additionally, suppression of TPA-induced PKCalpha/ERK/NK-kappaB activation, migration, and MMP-9 activation by flavonoids including kaempferol (Kae; 3,5,7,4'-tetrahydroxyflavone), luteolin (Lut; 5,7,3'4'-tetrahydroxyflavone), and wogonin (Wog; 5,7-dihydroxy-8-methoxyflavone) was demonstrated, and structure-activity relationship (SAR) studies showed that hydroxyl (OH) groups at C4' and C8 are critical for flavonoids' action against MMP-9 enzyme activation and migration/invasion of glioblastoma cells elicited by TPA. Application of flavonoids to prevent the migration/invasion of glioblastoma cells through blocking PKCalpha/ERK/NF-kappaB activation is first demonstrated herein.
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PMID:12-O-tetradecanoylphorbol-13-acetate-induced invasion/migration of glioblastoma cells through activating PKCalpha/ERK/NF-kappaB-dependent MMP-9 expression. 2045 47

Cells dying by necrosis release the high-mobility group box 1 (HMGB1) protein, which has immunostimulatory effects. However, little is known about the direct actions of extracellular HMGB1 protein on cancer cells. Here, we show that recombinant human HMGB1 (rhHMGB1) exerts strong cytotoxic effects on malignant tumor cells. The rhHMGB1-induced cytotoxicity depends on the presence of mitochondria and leads to fast depletion of mitochondrial DNA, severe damage of the mitochondrial proteome by toxic malondialdehyde adducts, and formation of giant mitochondria. The formation of giant mitochondria is independent of direct nuclear signaling events, because giant mitochondria are also observed in cytoplasts lacking nuclei. Further, the reactive oxygen species scavenger N-acetylcysteine as well as c-Jun NH(2)-terminal kinase blockade inhibited the cytotoxic effect of rhHMGB1. Importantly, glioblastoma cells, but not normal astrocytes, were highly susceptible to rhHMGB1-induced cell death. Systemic treatment with rhHMGB1 results in significant growth inhibition of xenografted tumors in vivo. In summary, rhHMGB1 induces a distinct form of cell death in cancer cells, which differs from the known forms of apoptosis, autophagy, and senescence, possibly representing an important novel mechanism of specialized necrosis. Further, our findings suggest that rhHMGB1 may offer therapeutic applications in treatment of patients with malignant brain tumors.
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PMID:Danger signaling protein HMGB1 induces a distinct form of cell death accompanied by formation of giant mitochondria. 2095 71

MicroRNAs (miRNAs) are potent negative regulators of gene expression involved in all aspects of cell biology. They finely modulate virtually all physiological pathways in metazoans, and are deeply implicated in all main pathologies, among which cancer. Mir-221 and miR-222, two closely related miRNAs encoded in cluster from a genomic region on chromosome X, are strongly upregulated in several forms of human tumours. In this work, we report that the ectopic modulation of NF-kB modifies miR-221/222 expression in prostate carcinoma and glioblastoma cell lines, where we had previously shown their oncogenic activity. We identify two separate distal regions upstream of miR-221/222 promoter which are bound by the NF-kB subunit p65 and drive efficient transcription in luciferase reporter assays; consistently, the site-directed mutagenesis disrupting p65 binding sites or the ectopical inhibition of NF-kB activity significantly reduce luciferase activity. In the most distal enhancer region, we also define a binding site for c-Jun, and we show that the binding of this factor cooperates with that of p65, fully accounting for the observed upregulation of miR-221/222. Thus our work uncovers an additional mechanism through which NF-kB and c-Jun, two transcription factors deeply involved in cancer onset and progression, contribute to oncogenesis, by inducing miR-221/222 transcription.
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PMID:NF-kB and c-Jun induce the expression of the oncogenic miR-221 and miR-222 in prostate carcinoma and glioblastoma cells. 2124 48

Neuropilin-1 (NRP-1) is a non-tyrosine kinase receptor for vascular endothelial growth factor (VEGF) that was recently found to play a role in tumor functions. Previous studies demonstrated that NRP-1 was overexpressed in a number of human tumors, including glioblastoma (GBM). However, the role of NRP-1 in glioma progression has yet to be adequately elucidated. Thus, we examined the expression of NRP-1 in human glioma cell lines using Western blotting, and cell cycle distribution and proliferation by transfection of the U373 cell line with NRP-1 short interference RNA (siRNA). Results showed NRP-1 siRNA to significantly reduce NRP-1 gene expression, decrease in vitro cell proliferation and induce cell apoptosis in cultured glioma cells, along with the accumulation of cells in the G1 phase and a decrease in cells in the S phase. Our results further revealed that NRP-1 knockdown decreased the expression levels of Bcl-2 family proteins and deactivated extracellular signal-regulated kinase (ERK) and c-Jun-N-terminal kinase (JNK)/mitogen-activated protein kinase (MAPK) signaling pathways, closely associated with cancer progression. Thus, our results provide a molecular mechanism for the effect of NRP-1 in tumors, rendering NRP-1 an attractive candidate as a therapeutic target in certain types of cancer, such as GBM.
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PMID:RNA interference targeting NRP-1 inhibits human glioma cell proliferation and enhances cell apoptosis. 2184 23

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