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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The extracellular protease urokinase is known to be crucially involved in morphogenesis, tissue repair and tumor invasion by mediating matrix degradation and cell migration. Hepatocyte growth factor/scatter factor (HGF/SF) is a secretory product of stromal fibroblasts, sharing structural motifs with enzymes of the blood clotting cascade, including a zymogen cleavage site. HGF/SF promotes motility, invasion and growth of epithelial and endothelial cells. Here we show that HGF/SF is secreted as a single-chain biologically inactive precursor (pro-HGF/SF), mostly found in a matrix-associated form. Maturation of the precursor into the active alpha beta heterodimer takes place in the extracellular environment and results from a serum-dependent proteolytic cleavage. In vitro, pro-HGF/SF was cleaved at a single site by nanomolar concentrations of pure urokinase, generating the active mature HGF/SF heterodimer. This cleavage was prevented by specific urokinase inhibitors, such as plasminogen activator inhibitor type-1 and protease nexin-1, and by antibodies directed against the urokinase catalytic domain. Addition of these inhibitors to HGF/SF responsive cells prevented activation of the HGF/SF precursor. These data show that urokinase acts as a pro-HGF/SF convertase, and suggest that some of the growth and invasive cellular responses mediated by this enzyme may involve activation of HGF/SF.
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PMID:Extracellular proteolytic cleavage by urokinase is required for activation of hepatocyte growth factor/scatter factor. 133 58

The c-ets1 proteins are transcriptional activators expressed within endothelial cells during blood vessel development in chick embryos. The authors show by in situ hybridization that c-ets1 is transcribed in the endothelia during angiogenesis in human embryos, in granulation tissue, and especially during tumor vascularization. c-ets1 mRNAs were also detected in the fibrocytes of tumor stroma and in the spindle cells of Kaposi's sarcomas, regarded as cells of endothelial origin. It has been shown that the c-ets proteins activate transcription through a PEA3 motif that plays a role in the stimulation of transcription of urokinase-type plasminogen-activator (u-PA), stromelysin and collagenase genes. The authors demonstrate in vitro that the angiogenic factor TNF alpha increases transiently the amount of both c-ets1 and u-PA mRNA in confluent human umbilical vein endothelial cells. Therefore, the authors suggest that the c-ets1 proteins might regulate the transcription of the genes coding for matrix-degrading proteases, which are necessary for both angiogenesis and tumor invasion.
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PMID:c-ets1 proto-oncogene is a transcription factor expressed in endothelial cells during tumor vascularization and other forms of angiogenesis in humans. 137 May 94

We determined the plasma levels of urokinase-type plasminogen activator (u-PA) antigen and alpha-fetoprotein (AFP) in 44 patients with different stages of liver cirrhosis and in 29 patients with liver cirrhosis-based primary liver cancer at the time of first clinical detection of the malignant disease. Sensitivity values of u-PA and AFP in detecting primary liver cancer were 57 and 62%, respectively, and specificity values were 95 and 86%, respectively. A combination of both markers led to a significant increase of sensitivity to 89.7%. The specificity of the combination of both markers was 97.3%. In tumor patients with unilocular disease and tumor patients with multicentric disease and/or metastatic spread, similar sensitivity values could be obtained with both markers. Therefore, a combination of u-PA and AFP can increase the accuracy of detection of primary liver cancer, especially in chronic liver diseases known to be predisposing for primary liver cancer, e.g., liver cirrhosis of long duration.
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PMID:Determination of plasma urokinase-type plasminogen activator antigen in patients with primary liver cancer: characterization as tumor-associated antigen and comparison with alpha-fetoprotein. 137 29

We found recently that 15-deoxyspergualin, an analog of spergualin, which is an antibiotic and includes a spermidine moiety in its structure, exhibits anti-angiogenic activity. We have now carried out in vitro experiments with bovine vascular endothelial cells to determine which events occurring during angiogenesis are affected by this microbial angiogenesis inhibitor. 15-Deoxyspergualin did not inhibit the production of urokinase-type plasminogen activator (u-PA) or type IV collagenase by vascular endothelial cells. The direct inhibition of u-PA activity by 15-deoxyspergualin was not observed either. The angiostatic antibiotic neither affected the migration of vascular endothelial cells nor inhibited the endothelial cell proliferation in a two-dimensional culture system. We also examined the effect of 15-deoxyspergualin on the proliferation of endothelial cells in a three-dimensional culture system involving collagen gel, in which cell growth resembles more closely the endothelial cell proliferation during in vivo angiogenesis than that in a two-dimensional culture system without collagen gel. The antibiotic inhibited cell proliferation in a dose-dependent manner, indicating that the three-dimensional culture system is useful for finding a new angiogenesis inhibitor with a different mode of action from those of angiogenesis inhibitors found by using a two-dimensional assay system; however, no cause-effect relationship has yet been established. Taken together, these results suggest the possible involvement of the inhibition of vascular endothelial cell growth by 15-deoxyspergualin in its angiogenesis-inhibitory effect. 15-Deoxyspergualin appears to be a promising candidate as an angiogenesis inhibitor for controlling aberrant angiogenic responses occurring in different states, including tumor development.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of 15-deoxyspergualin, a microbial angiogenesis inhibitor, on the biological activities of bovine vascular endothelial cells. 138 73

We have studied the capacity of two human breast adenocarcinoma cells, MDA-MB231 and MCF-7, to bind exogenous M(r) 72,000 type IV collagenase by both morphological and radioreceptor binding assays. By indirect immunofluorescence, staining with a specific anti-M(r) 72,000 type IV collagenase antibody was strongly induced when cells were preincubated with the purified enzyme. Scatchard plot analysis indicated the existence of a binding site for the M(r) 72,000 type IV collagenase with high affinity for both cell lines (Kd = 2 x 10(-9) M). These results are the first demonstration of the existence of a tumor cell membrane-associated putative receptor for a member of the matrix metalloproteinase family, as previously evidenced for the urokinase-type plasminogen activator.
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PMID:Tumor cell surface-associated binding site for the M(r) 72,000 type IV collagenase. 139 13

Urokinase-type plasminogen activator (uPA) may be responsible for the invasive and metastasizing capacity of tumor cells. Evidence has been presented that primary breast cancer patients with tumors containing high levels of uPA experience a worse prognosis. In the present study we have assessed uPA status in routinely prepared cytosols of 671 primary human breast tumors and have evaluated its association with disease-free and overall survival. Isotonic regression analysis with length of disease-free survival as an end point revealed 1.15 ng/mg protein as the best cutoff point to discriminate between uPA positive (32% of the tumors) and uPA negative. In both Cox univariate and multivariate regression analysis (including also patient's age, menopausal status, lymph node status, and the number of positive lymph nodes, tumor size, and estrogen and progesterone receptor status), uPA positivity was significantly associated with increased rates of relapse and death. Corrected for all relevant factors in multivariate analyses for subgroups of patients, uPA positivity was significantly associated with an increased relapse rate in the subgroups of node-negative (P = 0.002; relative failure rate, 2.33), node-positive (P < 0.0001; relative failure rate, 1.95), postmenopausal (P < 0.0001; relative failure rate, 2.59), and steroid receptor-positive patients (P < 0.0001, relative failure rate, 2.76). We conclude that uPA positivity of human primary breast tumors is an important independent variable for the identification of patients at high risk for recurrence, also in clinically important subgroups of patients.
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PMID:Prognostic value of urokinase-type plasminogen activator in 671 primary breast cancer patients. 139 37

The study of the plasminogen-plasmin system has, in the past, contributed much to the understanding of fibrinolysis and thrombolysis. Attention is now focused on the role of the components of this system in many biologic functions. Findings of uPA, its receptor and its inhibitor in many tumor tissues and tumor cell lines, strongly implicate their involvement in tumor invasion, tumor cell proliferation and metastasis. The characteristics of the plasminogen activators, the uPA receptor and the plasminogen activator inhibitors as well as their expression and regulation in tumors and tumor cell lines are reviewed.
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PMID:The plasminogen-plasmin system in malignancy. 142 20

Urokinase-type plasminogen activator (u-PA) plays an important role in tumor growth and metastasis. The aim of this work was to study the u-PA production, in vitro and in vivo, in a transplantable murine mammary adenocarcinoma (M3), moderately metastatic to lung, and in a related tumor variant (MM3), highly metastatic to the same organ, during tumor development. At different times post-transplantation, tumors were employed to prepare either primary cell cultures or homogenates. PA activity from conditioned media (CM), cell lysates (CLs) and tumor homogenates (THs) was quantitated by means of a fibrinolytic assay. Immunoneutralization and zymographic assays were performed to identify the PA present in both tumors. PA activity in CM, CLs and THs, that was undetectable at early stages, increased significantly along the growth of M3 adenocarcinoma. Secreted PA activity in MM3 CM was measurable at early stages and consistently increased up to 37 days post-transplantation, but a marked fall of activity was found at 48 days. PA activity in MM3 THs exhibited the same enhancement and late fall found in vitro. A positive correlation was observed between tumor size and THs PA values in both tumors. The PA present in cell cultures and THs was identified as of the u-PA type. These results support the hypothesis that high u-PA levels are important for tumor invasion and that the stage of tumor development is a critical factor in their PA activity.
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PMID:Urokinase-type plasminogen activator activity increases during the growth of two murine mammary adenocarcinomas with different metastasizing abilities. 145 49

Tissue-type plasminogen activator and urokinase are serine proteases secreted by many cell types that participate in biological processes, such as tissue restructuring, cell migration, and tumor metastasis. Clinically, these proteases are used to dissolve coronary fibrin clots that are the proximal causes of acute myocardial infarction. In vivo, the activity of these enzymes is controlled by plasminogen-activator inhibitors, members of the serpin family of protease inhibitors. This study shows that tissue-type plasminogen activator-inhibitor complexes bind in solution to low density lipoprotein receptor-related protein (LRP), a large heterodimeric ubiquitous membrane receptor. In cultured cells, endocytosis and degradation of these complexes is reduced by polyclonal antibodies directed against LRP and inhibited by a M(r) 39,000 protein that binds to LRP and inhibits its interaction with previously known ligands, including apolipoprotein E and alpha 2-macroglobulin. We propose a role for LRP in the clearance of plasminogen activator-inhibitor complexes that is analogous to its function in the endocytosis of alpha 2-macroglobulin-protease complexes.
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PMID:Complexes of tissue-type plasminogen activator and its serpin inhibitor plasminogen-activator inhibitor type 1 are internalized by means of the low density lipoprotein receptor-related protein/alpha 2-macroglobulin receptor. 150 53

Evidence has accumulated that invasion and metastasis in solid tumors require the action of tumor-associated proteases, which promote the dissolution of the surrounding tumor matrix and the basement membranes. Receptor-bound urokinase-type plasminogen activator (uPA) appears to play a key role in these events. uPA converts plasminogen into plasmin and thus mediates pericellular proteolysis during cell migration and tissue remodeling under physiological and pathophysiological conditions. uPA is secreted as an enzymatically inactive proenzyme (pro-uPA) by tumor cells and stroma cells. uPA exerts its proteolytic function on normal cells and tumor cells as an ectoenzyme after having bound to a high-affinity cell surface receptor. After binding, pro-uPA is activated by serine proteases (e.g. plasmin, trypsin or plasma kallikrein) and by the cysteine proteases cathepsin B or L, resp. Receptor-bound enzymatically active uPA converts plasminogen to plasmin which is bound to a different low-affinity receptor on tumor cells. Plasmin then degrades components of the tumor stroma (e.g. fibrin, fibronectin, proteoglycans, laminin) and may activate procollagenase type IV which degrades collagen type IV, a major part of the basement membrane. Hence receptor-bound uPA will promote plasminogen activation and thus the dissolution of the tumor matrix and the basement membrane which is a prerequisite for invasion and metastasis. Tissues of primary cancer and/or metastases of the breast, ovary, prostate, cervix uteri, bladder, lung and of the gastrointestinal tract contain elevated levels of uPA compared to benign tissues. In breast cancer uPA and PAI-1 antigen in tumor tissue extracts are independent prognostic factors for relapse-free and overall survival.
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PMID:Tumor-associated urokinase-type plasminogen activator: biological and clinical significance. 151 91


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