Biomedical subjects
Publications and source records attributed to S Ushiro.
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To investigate if neurotensin (NT) could induce activation of urokinase-type plasminogen activator (uPA) in vascular endothelial cells, we utilized the acetyl-NT (8-13) analogue, TJN-950, in which the C-terminal leucine is reduced to leucinol. TJN-950 inhibited the binding of 125I-NT to membranes of newborn rat brains and of COS-7 cells transfected with rat NT receptor cDNA, but at 10(4) higher doses than NT (8-13). However, TJN-950 was as effective as NT in inducing the fibrinolytic activity in bovine vascular aortic and human umbilical vein endothelial cells, and enhanced the migration of vascular endothelial cells. Moreover, administration of TJN-950 induced neovascularization in the rat cornea in vivo. TJN-950 had no effect on expression of uPA, plasminogen activator inhibitor-1 or uPA receptor mRNA. The binding of 125I-TJN-950 to cell membranes was blocked by unlabeled uPA and TJN-950, but not the amino-terminal or 12-32 fragment of uPA. TJN-950 may enhance uPA activity in vascular endothelial cells by interacting with the uPA receptor, resulting in induction of angiogenesis.
Preparations of Tripterygium wilfordii, "Thunder God vine", have been used in China to treat rheumatoid arthritis. Rheumatoid arthritis, as well as solid tumors, is closely associated with neovascularization. Antiarthritic drugs therefore may modulate tumor growth as well as neovascularization. We found that a compound purified from T. wilfordii, the nortriterpenoid, demethylzeylasteral (TZ-93), inhibited the proliferation of vascular endothelial cells approximately 30 times more effectively than it did for the proliferation of human tumor cells. In in vitro assays using bovine aortic endothelial cells, TZ-93 at non-toxic doses inhibited cell migration, expression of urokinase-type plasminogen activator (uPA) mRNA and uPA activity. Exogenous addition of uPA restored the inhibitory effect of TZ-93 on cell migration. In dorsal air-sac assays in BALB/c mice, the oral administration of 3 mg/kg/day TZ-93 for 5 days partially inhibited, and 30 mg/kg/day almost completely abrogated, the development of capillary networks induced by human hepatoblastoma cells. Similarly, 0.3 mg/kg/day TZ-93 partially inhibited, and 3 or 30 mg/kg/day almost completely blocked, the growth of mouse B16-F10 melanoma cells in a tumor implantation assay. The highest dose of TZ-93 significantly reduced the growth of well-vascularized tumors with volumes of more than 500 mm3. TZ-93 treatment of tumor-bearing mice significantly decreased the density of microvessels in the tumors. We conclude that TZ-93 may be useful in treating highly vascularized and metastatic tumors as well as other angiogenic diseases.
Irsogladine used clinically as an anti-gastric ulcer agent, at 10(-6)-10(-4)M, inhibited cell proliferation and tubular morphogenesis of vascular endothelial cells, but the proliferation of human epidermoid cancer or glioma cells was not inhibited by this drug, even at 10(-4)M. In vivo studies demonstrated that p.o. administration of irsogladine significantly inhibited tumor growth of human glioma cells in mice, and histological analysis showed a dramatic decrease of the neovascularization in the tumors. In mice transplanted with chambers containing human glioma cells or hepatic cancer cells, irsogladine also inhibited angiogenesis. These in vivo and in vitro assays demonstrate that irsogladine may be a unique and potent inhibitor of tumor angiogenesis.
Neovascularization is often required for rapid growth of solid tumors and also limits vascular metastasis of tumor cells. Neovascularization-targeting agents are a recent innovation that may be a novel means of anticancer therapy. These antiangiogenic drugs have been developed by targeting cell proliferation of vascular endothelial cells, basement-membrane-degrading enzymes, angiogenic factors/receptors, extracellular matrix, angiogenesis signaling, and cell-cell/cell-matrix interactions. In this report, we describe how tumor angiogenesis occurs and how antiangiogenic agents are developed.
Epidermal growth factor (EGF) or transforming growth factor-alpha (TGF-alpha) stimulates cell migration, proliferation and the formation of tube-like structures of human microvascular endothelial cells in culture. Heparin-binding EGF-like growth factor(HB-EGF), which shows 35% homology with EGF/TGF-alpha, is a member of the EGF family, and it is ubiquitous in many tissues and organs. We examined whether or not HB-EGF induced angiogenic responses in human microvascular endothelial cells. HB-EGF inhibited the binding of (125) I-EGF to the EGF receptor and induced autophosphorylation of the receptor on endothelial cells. Exogenous HB-EGF induced the loss of more than 70% of the EGF receptor from the cell surface within 30 min, with similar kinetics to that of EGF. The level of c-fos mRNA markedly increased at 30 min in response to HB-EGF as well as EGF. A gel shift assay demonstrated the activation of the transcription factor p91 by HB-EGF and EGF. This factor directly interacts with EGF receptor and mediates the activation of c-fos gene promoter. HB-EGF enhanced the mRNA expression of tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) mRNA. However, the enhancement of t-PA and PAI-1 by HB-EGF was less than that by EGF. Heparitinase/chlorate, which digests the heparan sulfate proteoglycan of the endothelial cell surface, restored both t-PA and PAI-1 mRNA levels in response to HB-EGF in a manner similar to that by EGF. HB-EGF at 10 ng/ml developed tube-like structures in type I collagen gel at similar levels to that of EGF at 10 ng/ml, suggesting that HB-EGF is also a potent angiogenic factor in the model system for angiogenesis. The tubulogenesis activity of HB-EGF is discussed in relation to the expression of the t-PA and PAI-1 genes.
Human omental microvascular endothelial (HOME) cells seeded on Matrigel begin to migrate within 1 h, forming honeycomb-like structures and capillary-like networks within 18 h. Cross-sections of the capillary networks show them to be tube-like structures. Northern blot analysis showed that tissue-type plasminogen activator (t-PA) mRNA synthesis increased from the initial state at 0 h after seeding on Matrigel, reaching a steady state after 4 h. This elevated cellular t-PA mRNA level decreased markedly at 24 h. In contrast, the cellular plasminogen activator inhibitor-1 (PAI-1) mRNA level demonstrated biphasic curves during the 24 h after seeding on Matrigel: the PAI-1 mRNA level was increased eightfold initially at 4 h over that at 0 h, then declined, and again secondarily increased to greater than tenfold at 18 h. Cellular levels of both 72 kD type IV collagenase and tissue inhibitor of metalloproteinase (TIMP-2) mRNA were increased only a slightly within 2-4 h. These elevated mRNA levels were maintained for 18 h, while the TIMP-1 mRNA level increased up to 18 h, reaching around three times the level at 0 h. However, on collagen-coated dishes, cellular levels of t-PA, PAI-1, 72 kD type IV collagenase, TIMP-1, and TIMP-2 mRNA were not greatly changed during incubation for 24 h. On Matrigel, the cellular t-PA mRNA level at 18 h after seeding was greatly increased when treated with specific anti-transforming growth factor-beta (TGF-beta) antibody. In contrast, both PAI-1 and TIMP-1 mRNA levels at 18 h were reduced in the presence of anti-TGF-beta antibody. Development of the capillary network on Matrigel was inhibited in the presence of anti-t-PA antibody. Epidermal growth factor (EGF) enhanced t-PA gene expression and TGF-beta inhibited its expression in HOME cells cultured on collagen-coated dishes. On the other hand, TGF-beta enhanced cellular expression of the PAI-1 gene. The formation of a capillary network by HOME cells on Matrigel appears to be balanced by angiogenic EGF and anti-angiogenic TGF-beta through modulation of PA activity.
Our previous studies imply that tumor necrosis factor-alpha (TNF-alpha) and epidermal growth factor (EGF) might share a common signal transduction pathway in human omental microvascular endothelial (HOME) cells. Exposure of cultured HOME cells to TNF-alpha for 10 min enhanced EGF receptor phosphorylation at a rate comparable to EGF. Apparent phosphorylation of tyrosine residues was observed in addition to serine/threonine of the EGF receptor by EGF, but only a slightly if any tyrosine phosphorylation by TNF-alpha. In vitro kinase activity of EGF receptor was also enhanced by TNF-alpha as well as by EGF. Furthermore, expression of the c-fos gene was enhanced in response to either EGF or TNF-alpha. Pretreatment of HOME cells with EGF for 12 h almost completely blocked the induction of the c-fos gene by EGF and partially blocked the c-fos induction by TNF-alpha. TNF-alpha-induced c-fos gene expression appeared to be partly due to its transactivation of EGF receptor. EGF and TNF-alpha could enhance c-fos gene expression when protein kinase C was down-regulated by phorbol ester myristate (PMA). Gel retardation assay with the NF-kappa B consensus sequence showed that NF-kappa B binding activity was dramatically activated by TNF-alpha, but not by EGF or PMA. The binding of another transcription factor, AP-1 (Jun/Fos), was enhanced by EGF, TNF-alpha, and PMA, whereas TNF-alpha could still activate AP-1 after longer exposure to EGF. TNF-alpha-induced activation of c-fos gene appears to be mediated through pleiotropic mechanisms and partly through a common signal with EGF, possibly through EGF receptor in microvascular endothelial cells.
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The cytotoxic and radiosensitizing effects of low concentrations of misonidazole were examined by measurement of the colony-forming ability and growth of HeLa S3 cells. Under hypoxic conditions, cytotoxicity depended on the misonidazole concentration and the exposure time. After 24 hr exposure, the surviving fraction of cells treated with 0.1 mM misonidazole decreased to 0.2. The ability of cells to adhere to the growth surface of plastic dishes was reduced by 0.1 mM misonidazole upon 24 hr hypoxia and this effect persisted even during subsequent euoxia, irrespective of whether the drug was removed from the original growth medium. The growth of aerobic cells was not affected when 0.1 mM misonidazole containing medium, obtained from the hypoxia-treated dishes, was applied, nor when those cells were exposed for 72 hr to freshly prepared 1.0 mM misonidazole. Upon 24 hr exposure, 0.1 mM misonidazole exerted no obvious radiosensitizing effect on hypoxic cells. Based on these results, it is suggested that continuous administration of low doses of misonidazole may be efficacious as a specific chemotherapeutic in the treatment of hypoxic cells in tumor tissue.
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Explore the source record for details and available documents.