VEGI, a new member of the TNF family activates nuclear factor-kappa B and c-Jun N-terminal kinase and modulates cell growth.
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Recently a new member of the human tumor necrosis factor (TNF) family named as VEGI was reported. However, very little is known about the biological activities displayed by this cytokine. In this report, we show that in myeloid cells VEGI activated the transcription factor kappa B (NF-kappa B) as determined by the electrophoretic mobility shift assay, induced degradation of I kappa B alpha, and nuclear translocation of p65 subunit of NF-kappa B. VEGI also activated NF-kappa B-dependent reporter gene expression. In addition, VEGI activated c-Jun N-terminal kinase. When examined for growth modulatory effects, VEGI inhibited the proliferation of breast carcinoma (MCF-7), epithelial (HeLa), and myeloid (U-937 and ML-1a) tumor cells; and activated caspase-3 leading to PARP cleavage. VEGI-induced cytotoxicity was potentiated by inhibitors of protein synthesis. VEGI also induced proliferation of normal human foreskin fibroblast cells. The activity of VEGI could neither be neutralized by antibodies against TNF, nor could it compete with TNF binding, indicating that the activity of VEGI is not due to TNF and it binds to a distinct receptor. These results suggest that VEGI, a new member of the TNF family, has a signaling pathway similar to TNF and is most likely a multifunctional cytokine. (+info)
Modulation of endothelial cell growth arrest and apoptosis by vascular endothelial growth inhibitor.
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Vascular endothelial growth inhibitor (VEGI), a new member of the tumor necrosis factor family, is an endothelial cell-specific gene and a potent inhibitor of endothelial cell proliferation, angiogenesis, and tumor growth. We report here that VEGI mediates the following two activities in endothelial cells: early G(1) arrest in G(0)/G(1) cells responding to growth stimuli, and programmed death in proliferating cells. G(0)/G(1)-synchronized bovine aortic endothelial cells were treated with VEGI before and after the onset of the growth cycle. When the cells were stimulated with growth conditions but treated simultaneously with VEGI, a reversible, early-G(1) growth arrest occurred, evidenced by the lack of late G(1) markers such as hyperphosphorylation of the retinoblastoma gene product and upregulation of the c-myc gene. Additionally, VEGI treatment led to inhibition of the activities of cyclin-dependent kinases CDK2, CDK4, and CDK6. In contrast, VEGI treatment of cells that had entered the growth cycle resulted in apoptotic cell death, as evidenced by terminal deoxytransferase labeling of fragmented DNA, caspase 3 activation, and annexin V staining, all of which were lacking in nonproliferating cells treated with VEGI. Additionally, stress-signaling proteins p38 and JNK were not as fully activated by VEGI in quiescent as compared with proliferating populations. These findings suggest a dual role for VEGI, the maintenance of growth arrest and induction of apoptosis, in the modulation of the endothelial cell cycle. (+info)
TL1A is a TNF-like ligand for DR3 and TR6/DcR3 and functions as a T cell costimulator.
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DR3 is a death domain-containing receptor that is upregulated during T cell activation and whose overexpression induces apoptosis and NF-kappaB activation in cell lines. Here we show that an endothelial cell-derived TNF-like factor, TL1A, is a ligand for DR3 and decoy receptor TR6/DcR3 and that its expression is inducible by TNF and IL-1alpha. TL1A induces NF-kappaB activation and apoptosis in DR3-expressing cell lines, while TR6-Fc protein antagonizes these signaling events. Interestingly, in T cells, TL1A acts as a costimulator that increases IL-2 responsiveness and secretion of proinflammatory cytokines both in vitro and in vivo. Our data suggest that interaction of TL1A with DR3 promotes T cell expansion during an immune response, whereas TR6 has an opposing effect. (+info)
A novel secreted splice variant of vascular endothelial cell growth inhibitor.
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Vascular endothelial cell growth inhibitor (VEGI), a member of the tumor necrosis factor (TNF) family, is an endothelial cell-specific inhibitor of angiogenesis. Overexpression by cancer cells of a secretable VEGI fusion protein resulted in abrogation of xenograft tumor progression, but overexpression of full-length VEGI was completely without effect. This finding indicates that secretion is essential for VEGI action. Here we report the identification of two new VEGI isoforms consisting of 251 and 192 amino acid residues. Both isoforms show endothelial cell-specific expression and share a C-terminal 151-residue segment with the previously described VEGI, which comprises 174 residues. The isoforms are generated from a 17 kb human gene by alternative splicing. Their expression is regulated in parallel by inflammatory cytokines TNF-alpha and interferon-gamma. VEGI-251, the most abundant isoform, contains a putative secretion signal. VEGI protein is detected in conditioned media of endothelial cells and VEGI-251-transfected mammalian cells. Overexpression of VEGI-251 in endothelial cells causes dose-dependent cell death. VEGI-251-transfected cancer cells form xenograft tumors of reduced growth rate and microvessel density compared with tumors of empty vector transfectants. These findings support the view that endothelial cell-secreted VEGI may function as an autocrine inhibitor of angiogenesis and a naturally existing modulator of vascular homeostasis. (+info)
TL1A-induced NF-kappaB activation and c-IAP2 production prevent DR3-mediated apoptosis in TF-1 cells.
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We recently identified TL1A, an endothelium-derived T cell costimulator and a ligand for tumor necrosis factor receptor superfamily members DR3 and decoy receptor 3. To elucidate the signaling events triggered by TL1A-DR3 interaction and to understand the molecular mechanisms regulating DR3-mediated apoptosis, we have studied the effect of TL1A and an agonistic DR3 monoclonal antibody in human erythroleukemic TF-1 cells, which express DR3 endogenously. TL1A induced the formation of a DR3 signaling complex containing TRADD, TRAF2, and RIP and activated the NF-kappaB and the ERK, JNK, and p38 mitogen-activated protein kinase pathways. However, TL1A or an agonistic DR3 monoclonal antibody did not induce apoptosis in these cells nor were there detectable levels of FADD or procaspase-8 seen in the signaling complex. Interestingly, DR3-mediated apoptosis was induced in TF-1 cells in the presence of a NF-kappaB pathway-specific inhibitor but not in the presence of mitogen-activated protein kinase inhibitors, either alone or in combination, suggesting that DR3-induced NF-kappaB activation was responsible for resistance to apoptosis in these cells. Consistent with this, we found that TL1A significantly increased the production of c-IAP2, a known NF-kappaB-dependent anti-apoptotic protein, and that the NF-kappaB inhibitor or cycloheximide prevented its synthesis. Furthermore, inhibition of c-IAP2 production by RNA interference significantly sensitized TF-1 cells to TL1A-induced apoptosis. Our study identifies a molecular mechanism by which TL1A and DR3 regulate cell fate in TF-1 cells. (+info)
Expression, localization, and functional activity of TL1A, a novel Th1-polarizing cytokine in inflammatory bowel disease.
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TL1A is a novel TNF-like factor that acts as a costimulator of IFN-gamma secretion through binding to the death domain-containing receptor, DR3. The aim of this study was to test the hypothesis that TL1A may play an important role in inflammatory bowel disease (IBD) by functioning as a Th1-polarizing cytokine. The expression, cellular localization, and functional activity of TL1A and DR3 were studied in intestinal tissue specimens as well as isolated lamina propria mononuclear cells from IBD patients and controls. TL1A mRNA and protein expression was up-regulated in IBD, particularly in involved areas of Crohn's disease (CD; p < 0.03 vs control). TL1A production was localized to the intestinal lamina propria in macrophages and CD4(+) and CD8(+) lymphocytes from CD patients as well as in plasma cells from ulcerative colitis patients. The amount of TL1A protein and the number of TL1A-positive cells correlated with the severity of inflammation, most significantly in CD. Increased numbers of immunoreactive DR3-positive T lymphocytes were detected in the intestinal lamina propria from IBD patients. Addition of recombinant human TL1A to cultures of PHA-stimulated lamina propria mononuclear from CD patients significantly augmented IFN-gamma production by 4-fold, whereas a minimal effect was observed in control patients. Our study provides evidence for the first time that the novel cytokine TL1A may play an important role in a Th1-mediated disease such as CD. (+info)
Soluble decoy receptor 3 induces angiogenesis by neutralization of TL1A, a cytokine belonging to tumor necrosis factor superfamily and exhibiting angiostatic action.
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TL1A is a member of the tumor necrosis factor superfamily and plays an important role in regulating endothelial cell apoptosis. A previous study shows TL1A is able to interact with death receptor 3 and decoy receptor 3 (DcR3). Here, we demonstrate that DcR3 is able to induce angiogenesis in human umbilical vein endothelial cells (HUVECs). DcR3 promotes HUVEC proliferation and migration and up-regulates matrix metalloproteinase-2 mRNA expression and enzyme activity. Furthermore, DcR3 enhances EC differentiation into cord vascular-like structures in vitro, as well as neovascularization in vivo. The effects of DcR3 on HUVECs are also mimicked by anti-TL1A and antideath receptor 3 antibodies. In contrast, human aortic endothelial cells, which do not express TL1A, are not responsive to DcR3 treatment, including cell proliferation, migration, and angiogenic differentiation. These data demonstrate DcR3 might not only help tumor cells to escape immune surveillance but also induce angiogenesis by blocking TL1A action in endothelial cells. The pathological role of DcR3 in promoting cancer progress raises the possibility to target DcR3 for antiangiogenic therapy in the future. (+info)
Effects of endostatin-vascular endothelial growth inhibitor chimeric recombinant adenoviruses on antiangiogenesis.
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AIM: To investigate the inhibitory effects of endostatin-vascular endothelial growth inhibitor (VEGI151) recombinant adenoviruses on neovascularization. METHODS: We used recombinant adenoviruses to treat human vascular endothelial cell line ECV304, human hepatocellular carcinoma cell line HepG2, and murine fibroblast cell line L929, in order to study the chimeric gene expression in these cell lines. Chick choriallantic membrane (CAM) model, rabbit inflammatory corneal neovascularization (CNV) model, and liver cancer-bearing nude mice model were employed to investigate the negative biological effect of fusion molecules on neovascularization in vivo. RESULTS: Western blot showed that the molecular weight of fusion protein was about 41 kD after infection of ECV304, HepG2 and L929 cells with supernatant of AdhENDO-VEGI151. The fusion protein showed a specific inhibitory effect on the proliferation of ECV304 cells, but no inhibitory effect on the growth of HepG2 and L929 cells (F=13112.13, P=0.0001). In the chick choriallantic membrane (CAM) assay, the expressed fusion protein significantly inhibited neovascularization. Rabbit inflammatory corneal neovascularization (CNV) induced by intrastromal sutures resulted in a uniform neovascular response. In this model, direct subconjunctival injection of AdhENDO-VEGI151 expressed the fusion protein in vivo and suppressed the development of CNV. Topical application of AdhENDO-VEGI151 led to a significant suppression of CNV (F=1413.11, P=0.0001), as compared with the control group of AdLacZ. Immunohistochemical staining showed the fusion protein dominantly expressed in corneal epithelium. Compared with the control group of AdLacZ (4075.9+/-1849.9 mm(3)), the average tumor size of group AdhENDO-VEGI151 reduced in size (487.7+/-241.2 mm(3)) (F=14.80, P=0.0085), with an inhibition rate of 88.03%. Immunohistochemical staining showed the adenoviruses carried the fusion gene expressed on liver cancer cell membrane. MVD decreased more significantly in treated mice (30.75+/-3.31%) than in AdLacZ control (50.25+/-8.65%) (F=17.72, P=0.0056) with an inhibition rate of 39%. CONCLUSION: Fusion protein expressed by recombinant adenoviruses has a significant inhibitory effect on neovascularization. (+info)