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Query: UMLS:C0699790 (colon cancer)
 28,837 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

There is increasing evidence that urokinase secreted by tumor cells can be bound to a cell surface receptor retaining its full potential to activate plasminogen and subsequently cleave basement membrane constituents. This study was undertaken to discriminate between soluble and cell surface bound urokinase as a potential mediator of in vitro invasion by cultured colon cancer. Extracellular matrix invasion by a colon cancer cell line GEO, characterized as being a poor secretor of urokinase and having few receptors (less than 10(4) receptors/cell) was not augmented when these cells were made to secrete up to 8 times as much urokinase, in response to an exogenous urokinase gene driven by the Rous sarcoma virus long terminal repeat promoter. The majority of the plasminogen activator (greater than 95%) appeared in the culture medium, this reflecting the low numbers of binding sites displayed by GEO cells. In contrast, the cell line HCT 116 equipped with 10 times as many binding sites, (greater than 10(5)/cell), the majority of which are occupied with endogenous ligand, was an efficient invader of the extracellular matrix. Inhibition of urokinase binding to the cell surface receptors using an antibody to the A chain of the plasminogen activator reduced invasion by 65%. The cell line RKO is equipped with 3 x 10(5) receptors/cell, 15% of which are tagged with endogenous urokinase. Pretreatment of these cells with a concentration range of urokinase known to result in the majority of these binding sites being charged with the plasminogen activator led to a dose dependent increase in extracellular matrix invasion. Together, these data suggest that for cultured colon cancer, at least, invasion is a function of the amount of cell surface receptor bound urokinase.
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PMID:Role of the urokinase receptor in facilitating extracellular matrix invasion by cultured colon cancer. 164 43

Human colon adenocarcinomas and adjacent normal colon tissues were stained immunohistochemically with three different monoclonal antibodies and one preparation of polyclonal antibodies against each of the two plasminogen activators, uPA (urokinase type) and tPA (tissue type). The staining patterns seen with the respective sets of antibodies were identical. In all of 10 cases, staining for uPA in the normal colon tissue was confined to scattered fibroblastlike cells in the lamina propria. Other cells, including epithelial and endothelial cells, were uPA negative. All the tumor infiltrates contained many more uPA-positive cells than the normal tissues, but the staining was confined to fibroblastlike cells and endothelial cells in the tumor stroma, while no staining of the malignant epithelial cells was detected. Analysis for uPA by enzyme-linked immunosorbent assay (ELISA) in four cases showed an average uPA content of 0.15 ng uPA/mg protein in the normal colon tissues and 1.6 ng uPA/mg protein in the tumors. Tissue-type plasminogen activator immunoreactivity was confined to endothelial cells in both the normal colon tissue and in the colon carcinomas. These findings may indicate that colon cancer cells recruit stromal cells to produce uPA involved in degradation of the extracellular matrix during invasive growth.
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PMID:Localization of urokinase-type plasminogen activator in stromal cells in adenocarcinomas of the colon in humans. 170 28

Fourteen human colon adenocarcinomas were examined by in situ hybridization for the presence of mRNA for plasminogen activator inhibitor type 1 (PAI-1). All specimens contained PAI-1 mRNA in endothelial cells of some vessels in the stroma immediately surrounding the invasive tumor glands, in granulation tissue, and in some capillaries located under the free luminal surface of carcinomatous epithelium. In addition, a limited number of stromal cells in the cancerous areas located at the periphery of newly formed capillary networks, and presumably representing sprouting endothelial cells, contained PAI-1 mRNA. Cancer cells were devoid of detectable PAI-1 mRNA in all cases. PAI-1 mRNA was not seen in three biopsies of normal colon. Together with previous findings of urokinase-type plasminogen activator and its mRNA being located in fibroblast-like cells in the tumor stroma and mRNA for the urokinase receptor in the cancer cells at invasive foci, these results indicate a complex cooperativity among several cell types in regulation of plasminogen activation in colon cancer. A possible role of PAI-1 in protecting the extracellular matrix in the tumor tissue against degradation and a role in tumor-induced angiogenesis are discussed.
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PMID:The plasminogen activation system in human colon cancer: messenger RNA for the inhibitor PAI-1 is located in endothelial cells in the tumor stroma. 185 21

Several urokinase-expressing tumor cells display surface receptors that avidly bind the plasminogen activator. The present study was undertaken to determine the importance of receptor bound urokinase in promoting the invasive phenotype by cultured colon cancer cells. An HCT 116 cell line that elaborates urokinase and displays 11 x 10(4) receptors per cell, 57% of which are tagged with endogenous plasminogen activator, invaded extracellular matrix (Matrigel) in a plasminogen dependent manner. Matrigel invasion was contingent on plasmin production mediated by urokinase, since epsilon-aminocaproic acid diminished the invasive capacity of the HCT 116 cells by 75%. A specific urokinase receptor peptide-antagonist reduced cell invasion in a dose dependent manner with a maximum effect (78% reduction in tumor cell infiltration) being achieved with a 10(-4) M concentration. These results did not reflect a non-specific "shut down" of urokinase expression by the receptor antagonist insofar as steady state urokinase transcript levels were unchanged compared with untreated controls. In addition, LH-RH, a control peptide, failed to suppress Matrigel invasion by HCT 116 cells. The CBS and FET colon cancer cell lines, which secrete amounts of urokinase similar to HCT 116 cells and display one tenth of the receptor number were found to be poorly invasive. Over a three day period, less than 0.8% of these cells invaded the Matrigel in contrast to the 6.9% seen for HCT 116 cells. These data suggest that for cultured colon cancer cells, at least, the display of receptor bound urokinase was a prerequisite for plasminogen dependent invasion.
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PMID:Invasion of extracellular matrix by cultured colon cancer cells: dependence on urokinase receptor display. 216 13

This laboratory recently reported that laminin degradation by cultured colon cancer was plasminogen dependent and reflected the presence of urokinase bound to cell surface receptors. (Schlecte, W.; Murano, G.; Boyd D. Cancer Res., 49:6064-6069; 1989). The present study was undertaken to determine the sensitivity of urokinase receptor directed proteolysis to the type I plasminogen activator inhibitor (PAI-1). Colon cancer cell types, that were highly effective in degrading laminin in vitro, elaborated into their conditioned medium an inhibitor which was indistinguishable from PAI-1 on the basis of its performance in reverse zymography, western blotting, and immunoprecipitation assays. A fraction of this PAI-1 was active, as evidenced by complex formation with the active site of radioactive urokinase. Laminin degradation by the colon cancer cells, however, did not appear to be affected by the endogenous inhibitor, since an antibody to the inhibitor, which blocked urokinase-PAI-1 interactions, had little effect on laminin turnover. Further, addition of exogenous PAI-1, activated by guanidine hydrochloride pretreatment, to the colon cancer cells did not perturb laminin degradation. Because laminin degradation by colonic cells was a function of receptor bound urokinase, presumably immobilized plasminogen activator escaped the neutralizing effect of the inhibitor. These data suggest either a shielding effect of the receptor on the plasminogen activator or a physical separation of activator and inhibitor. Either way, for cultured colon cancer at least, laminin degradation directed by urokinase receptor bound plasminogen activator appeared unaffected by the presence of this inhibitor.
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PMID:Insensitivity of laminin degradation directed by receptor bound urokinase to PAI-1 in cultured colon cancer. 239 Apr 19

The expression of the plasminogen activator, urokinase, and the display of its receptor in response to growth factors were examined in a serum-free adapted colon cancer cell line, CBSsf. Cells propagated in protein-free medium secreted 6.5 +/- 1.0 ng/ml of urokinase/10(6) cells in a 3-day period as determined by enzyme-linked immunosorbent assay. Inclusion of insulin or transferrin into the protein-free medium was without effect on this parameter. However, addition of epidermal growth factor (EGF) to the protein-free medium resulted in a 50% reduction in this parameter. This change was also reflected in the plasminogen-dependent solubilization of immobilized radioactive laminin. Plasminogen-supplemented conditioned medium derived from CBSsf cells grown in protein-free medium solubilized 135,000 +/- 25,000 dpm/10(6) cells of radioactive substrate. This value was decreased to 59,000 +/- 6,000 when conditioned medium was collected in the presence of EGF. Dose-response curves indicated that, while 0.5 ng/ml of EGF were suboptimal for the suppression of urokinase secretion, a concentration of 5.0 ng/ml had a maximum effect on this measurement. Northern hybridization studies indicated that the reduced plasminogen activator reflected, at least in part, translation of a less abundant transcript. Examination of the colon carcinoma cell line for altered urokinase receptor display revealed that EGF caused a dose-dependent increase in the amount of radioactive urokinase bound. This did not reflect reduced occupation of binding sites with endogenous ligand. Scatchard manipulation of the binding data indicated that the increased amount of radioactive plasminogen activator bound to cells cultured with EGF reflected an increase in receptor number from 7,500 to 13,000 sites/cell. Time course studies revealed that the decrease in urokinase secretion precedes changes in receptor display by 5 h. A 60% reduction in assayable urokinase was demonstrated in the conditioned medium from cells treated with the growth peptide for 10 h. However, a 24-h period was required to observe an increase (80%) in the amount of radioligand bound to EGF-treated cells. These data suggest EGF to be a regulator of both urokinase production and urokinase receptor display in a colon cancer cell line.
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PMID:Examination of the effects of epidermal growth factor on the production of urokinase and the expression of the plasminogen activator receptor in a human colon cancer cell line. 253 3

The relevance of urokinase receptors to urokinase-mediated laminin degradation was investigated in cultured colon cancer. Six colon cancer cell lines degraded laminin in a plasminogen-dependent manner. The ability of the individual cell lines to cleave the glycoprotein correlated well (r2 = 0.9242) with the amount of urokinase recovered from the cell surface by a mild acid treatment. A radioreceptor assay indicated that colon cancer cells most active in degrading the laminin, possessed the largest number of urokinase receptors. Moreover, acid treatment which depletes the receptors of endogenous plasminogen activator augmented the specific binding of radioactive urokinase to the colon cancer cells by 12-200%. A cell line (HCT 116) which displayed 1.1 x 10(5) receptors/cell the majority of which were occupied with endogenous urokinase was selected and the effects of a urokinase receptor antagonist on laminin degradation determined. The peptide antagonist reduced laminin turnover by 60-80%. Morphological observations were consistent with these findings. Plasminogen-treated HCT 116 cells retracted from the culture dish and many cells were observed in the culture medium. This effect could be largely reversed by simultaneous treatment with the peptide antagonist. A poor correlation was found between laminin degradation and soluble urokinase (r2 = 0.1074). These data strongly argue for a role of the urokinase receptor in facilitating the action of the plasminogen activator in colon cancer.
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PMID:Examination of the role of the urokinase receptor in human colon cancer mediated laminin degradation. 255 98

Systemic activation of the coagulation mechanism is known to exist in patients with colon cancer. The mechanism of such activation was investigated using immunohistochemical techniques applied to fresh frozen sections of resected primary colon cancer specimens. Tumor cells stained for tissue factor, factor V, and urokinase-type plasminogen activator. Perivascular and intercellular areas stained for fibrinogen and the "a" subunit of factor XIII. Staining was minimal or absent for protein C, protein S, plasminogen activator inhibitors 1-3, factor VII, factor X, and fibrin (the antigenic site on the amino-terminal portion of B beta chain that is exposed following thrombin cleavage of fibrinopeptide B was not detected). The lack of an intact thrombin-generating pathway in situ associated with viable colon cancer cells is consistent with the findings of others that coagulation activation in colon cancer may be triggered by a soluble tumor product that exerts its effect at sites distant from the tumor. These results may explain the absence of clinical responsiveness of colon cancer to antithrombotic drug therapy and may clarify therapeutic strategies for this common tumor.
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PMID:Indirect activation of blood coagulation in colon cancer. 269 22

Diglycerides (DGs) have been found in fecal extracts at concentrations which induce mitogenesis of adenoma and some carcinoma cells but not normal cells in primary culture. DGs containing stearic, oleic, palmitic, and myristic acid side chains were found in fecal extracts from each of eight subjects. Synthetic 1,2-DGs, containing the fatty acids found in endogenous fecal DGs, induced mitogenesis in cultures of premalignant cells from each of 13 adenomas, covering all histological classes, and in cultures from two of four carcinomas. The potent adenoma mitogen, dimyristin, had no mitogenic activity on cultures of normal colonic epithelial cells from seven different subjects. These results suggest DGs may act as endogenous mitogens in the development of human colon cancer. The extent of adenoma mitogenesis was correlated with the chain length of the saturated R-groups: 16 greater than 14 greater than 12 greater than 10 greater than 8 much greater than 18. DGs with oleic acid residues, C18:1, were among the most active, while substitution of even one fatty acid residue with a stearic acid residue, C18:0, reduced or eliminated mitogenic activity. Dimyristin also induced enhanced levels of urokinase secretion from carcinoma cells, in parallel to the phorbol ester tumor promoter, 12-O-tetradecanoylphorbol-13-acetate. These results imply that DGs found in the colon induce a selective growth of benign colonic tumors and some carcinomas, and may enhance the invasive capacity of carcinomas, while leaving normal cells unaffected.
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PMID:Fecal diglycerides as selective endogenous mitogens for premalignant and malignant human colonic epithelial cells. 291 Apr 75

Conditioned medium derived from the colon cancer cell lines was ineffective in solubilizing immobilized radiolabeled laminin. However, substantial degradation was observed in the presence of plasminogen and could be largely blocked by preincubation with polyclonal anti-urokinase antibody. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the solubilized products generated either by the conditioned medium or by authentic urokinase supplemented with plasminogen yielded identical results. Analysis of the spent medium for urokinase by an enzyme-linked immunosorbent assay method revealed a similar profile to that achieved with the laminin degradation assays for the six cell lines tested. However, Northern analysis of urokinase-specific mRNA indicated that protein levels could not be entirely predicted by steady-state levels of the transcript. In a previous study, undifferentiated colon cancer cell lines expressed larger amounts of the plasminogen activator into the conditioned medium compared with their well-differentiated counterparts. However, these earlier studies were performed using cells grown in defined medium which lacked epidermal growth factor (EGF). EGF has been reported to affect plasminogen activator levels. Consequently, to investigate the role of EGF in the modulation of urokinase protein/activity, cell types representative of well- and poorly differentiated colon cancer were examined for their sensitivity of expression to this growth factor. In the absence of EGF, primitive cell types secreted, on average, 5 times more urokinase than their well-differentiated counterparts. In response to EGF, however, well-differentiated cell lines exhibited 4- to 6-fold increases in these parameters while the primitive cell lines were refractory to the peptide. Consequently, the differences in urokinase protein expressed by the well- and poorly differentiated groups of cells were abolished by the presence of EGF. The expression of a well-differentiated phenotype by colon cancer cell types in vivo probably depends to some extent on laminin within a basement membrane. The data presented herein are consistent with the idea that depletion of this glycoprotein from a basement membrane by urokinase-dependent mechanisms may contribute to the undifferentiated phenotype seen with many of these malignancies.
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PMID:Examination of urokinase protein/transcript levels and their relationship with laminin degradation in cultured colon carcinoma. 291 54


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