Role of urokinase in colorectal neoplasia

Blood and tissue fibrinolytic profiles in patients with colorectal carcinoma

In patients with colorectal cancer, profound alterations of the plasminogen activator system have been described at the tumor level, but conflicting results have been obtained for fibrinolytic parameters in plasma. Components of the fibrinolytic system, including tissue-type and urokinase-type plasminogen activators and their inhibitors type 1 and 2, were measured in tissue and/or plasma from 41 patients with colorectal cancer and in 40 controls. Procoagulant activity of freshly isolated mononuclear cells (basal activity) and the procoagulant activity and fibrinolytic proteins produced by the cells after incubation for 18 h without exogenous stimulation were also evaluated. Malignant tissue extracts had significantly higher levels of urokinase-type plasminogen activator and plasminogen activator inhibitor-1, but lower levels of tissue-type plasminogen activator than normal mucosa. Plasminogen activator inhibitor-1 alone was higher in advanced (Dukes' stages C + D) than limited (B) tumors. Plasminogen activator inhibitor-2 was not different in malignant tissue and normal mucosa. Plasma levels of plasminogen activator inhibitor-1 antigen were significantly increased in cancer patients compared with controls, but there were no differences in tissue-type and urokinase-type plasminogen activator, in plasminogen activator inhibitor-2, and D-dimer levels. Intra-patient analysis revealed no significant correlation between tumor and plasma levels of plasminogen activators or type 1 inhibitor. Tissue-type plasminogen activator, but not the urokinase type or inhibitor type 1, was higher in venous than in arterial blood collected at the tumor site during surgery. Basal procoagulant activity of mononuclear cells and the procoagulant activity and inhibitor type-2 produced by the cells after short-term culture were comparable in patients and controls. These findings indicate that, at least in our patients with colorectal cancer, the profound changes occurring at tumor level are barely detectable in the blood. Thus, the clinical relevance of plasma fibrinolytic parameters, especially urokinase-type plasminogen activator antigen, as tumor markers in colorectal cancer remains to be established.

Biochemical markers for colorectal cancer. Diagnostic and therapeutic implications

The development of the understanding of oncogenes, tumor suppressor genes, and signal transduction has provided a significant advance in the concepts of the mechanisms of carcinogenesis in the colon and rectum. The tools provided by the molecular geneticist and the immunobiologist may yield powerful new techniques for screening individuals at risk, for identifying those patients with biologically more aggressive tumors, for developing novel therapies targeted directly at tumor cells, and for providing the means for more sensitive and specific detection of recurrence of disease.

Peptide and protein drugs: II. Non-parenteral routes of delivery

In this second part of a two-part review, the absorption and delivery of peptide and protein drugs via non-parenteral routes are discussed. Approaches considered include the absorption enhancers, iontophoretic methods, the use of absorption inhibitors and prod rugs.

Direct measurement of collagenase in colonic anastomosis

Collagenase has been implicated in colonic anastomotic dehiscence but the enzyme has not previously been specifically measured in colonic healing. A 72 h tissue culture method for colonic tissue and a radiochemical assay for collagenase were adapted to measure the enzyme in healing rabbit colon, with specificity of the assay confirmed by sodium dodecylsulphate polyacrylamide gel electrophoresis. Normal and postoperative colon secreted collagenase, predominantly in a latent form, in the first 24 h of culture. Total activity reached a plateau after 48 and 72 h in culture, when 50-70 per cent of the enzyme was in an active form. At these times in culture, activity was significantly higher than after 24 h (P less than 0.001). One day after anastomosis the total amount of collagenase secreted in culture was higher than normal but the increase did not achieve significance. Three days after anastomosis the colon secreted more collagenase than explants from 1 day postoperative tissue (P less than 0.002). The proportion of active enzyme in the first 24 h in culture was also increased. Since active collagenase can be measured in culture medium from both normal and postoperative colon, the tissue may be secreting plasminogen activator which allows plasmin to activate the enzyme. The increase in collagenase after operation coincided with a decrease in collagen concentration in the colon wall, measured by hydroxyproline. This supports previous suggestions that collagenase contributes to anastomotic dehiscence. However, the findings must be interpreted with caution as the variance of the results was shown to be predominantly due to time in culture, suggesting this could be a bigger influence than the operation itself. In addition, our previously reported immunohistochemical study of this system indicated that collagenase only occurred in a localized region, restricted to the everted portion of the anastomosis, with the activity being tightly controlled by its inhibitor, tissue inhibitor of metalloproteinases.

Adjuvant portal liver infusion in colorectal cancer with 5-fluorouracil/heparin versus urokinase versus control. Results of a prospective randomized clinical trial (colorectal adenocarcinoma trial I)

This prospectively randomized clinical trial was carried out in four Dutch hospitals to reduce the development of metachronous liver metastases and to get a better survival in patients with colorectal malignancies after surgically radical en bloc resection of the primary tumor and the regional lymph nodes. Three hundred seventeen patients were randomized to participate in three trial arms. One group of patients was treated by surgery alone (control group); in the other patients a catheter was placed in the dilated umbilical vein and advanced until the tip was lying in the left branch of the portal vein. Fifty percent of these patients got immediate postoperative portal infusion with 1 g 5-fluorouracil (5-FU) and 5000 U heparin daily for 7 days; the others received portal vein infusion with urokinase 10.000 U/hour for 24 hours only. Three hundred four patients were eligible. Overall hospital mortality was 3.6% (11 patients) and was not influenced by adjuvant treatment. After a median follow-up of 44 months 66 patients have died with relapse and 21 as a result of other causes. The chance of developing liver metastases and other distant metastases after portal infusion with 5-FU/heparin was one third of the chance in the control group (P less than 0.001). Only an insignificant reduction of the average death rate in the 5-FU/heparin group was found. In the urokinase group no significant effect in reducing metastases or in survival was noted. Before recommending cytotoxic portal infusion as an adjuvant treatment in patients with colorectal cancer, detailed analysis of other ongoing portal infusion studies has to be awaited and careful calculations have to be made regarding how many patients really can be saved by this treatment.

Modulation of the urokinase receptor in human colon cell lines by N,N-dimethylformamide

The present study documents the effect of the planar, polar differentiation promoter N,N-dimethylformamide (DMF) on urokinase binding to colon carcinoma cells. Exposure of the colon carcinoma cell lines to the agent resulted in enhanced specific binding of radioactive urokinase to all cells tested. Insulin binding to the cells was, however, unaffected by DMF. A DMF exposure period of 45 h was required to observe maximum urokinase binding to two representative cell lines FET and RKO. Optimal stimulation of both cell lines occurred with 0.8% DMF. Scatchard analysis revealed the dissociation constants to be unchanged by the agent with the increased binding of radioactive plasminogen activator reflecting an up-regulation of binding sites. In this regard, the cell line RKO upon exposure to DMF, displayed approx. 700,000 receptors/cell, the highest value published, to date, for any cell line.