Inactive urokinase and increased levels of its inhibitor type 1 in colorectal cancer liver metastasis

Good or bad: Paradox of plasminogen activator inhibitor 1 (PAI-1) in digestive system tumors

The fibrinolytic system is involved in many physiological functions, among which the important members can interact with each other, either synergistically or antagonistically to participate in the pathogenesis of many diseases. Plasminogen activator inhibitor 1 (PAI-1) acts as a crucial element of the fibrinolytic system and functions in an anti-fibrinolytic manner in the normal coagulation process. It inhibits plasminogen activator, and affects the relationship between cells and extracellular matrix. PAI-1 not only involved in blood diseases, inflammation, obesity and metabolic syndrome but also in tumor pathology. Especially PAI-1 plays a different role in different digestive tumors as an oncogene or cancer suppressor, even a dual role for the same cancer. We term this phenomenon "PAI-1 paradox". PAI-1 is acknowledged to have both uPA-dependent and -independent effects, and its different actions can result in both beneficial and adverse consequences. Therefore, this review will elaborate on PAI-1 structure, the dual value of PAI-1 in different digestive system tumors, gene polymorphisms, the uPA-dependent and -independent mechanisms of regulatory networks, and the drugs targeted by PAI-1 to deepen the comprehensive understanding of PAI-1 in digestive system tumors.

Role of meprin metalloproteases in metastasis and tumor microenvironment

A crucial step for tumor cell extravasation and metastasis is the migration through the extracellular matrix, which requires proteolytic activity. Hence, proteases, particularly matrix metalloproteases (MMPs), have been discussed as therapeutic targets and their inhibition should diminish tumor growth and metastasis. The metalloproteases meprin α and meprin β are highly abundant on intestinal enterocytes and their expression was associated with different stages of colorectal cancer. Due to their ability to cleave extracellular matrix (ECM) components, they were suggested as pro-tumorigenic enzymes. Additionally, both meprins were shown to have pro-inflammatory activity by cleaving cytokines and their receptors, which correlates with chronic intestinal inflammation and associated conditions. On the other hand, meprin β was identified as an essential enzyme for the detachment and renewal of the intestinal mucus, important to prevent bacterial overgrowth and infection. Considering this, it is hard to estimate whether high activity of meprins is generally detrimental or if these enzymes have also protective functions in certain cancer types. For instance, for colorectal cancer, patients with high meprin β expression in tumor tissue exhibit a better survival prognosis, which is completely different to prostate cancer. This demonstrates that the very same enzyme may have contrary effects on tumor initiation and growth, depending on its tissue and subcellular localization. Hence, precise knowledge about proteolytic enzymes is required to design the most efficient therapeutic options for cancer treatment. In this review, we summarize the current findings on meprins' functions, expression, and cancer-associated variants with possible implications for tumor progression and metastasis.

Multifaceted Role of the Urokinase-Type Plasminogen Activator (uPA) and Its Receptor (uPAR): Diagnostic, Prognostic, and Therapeutic Applications

The plasminogen activator (PA) system is an extracellular proteolytic enzyme system associated with various physiological and pathophysiological processes. A large body of evidence support that among the various components of the PA system, urokinase-type plasminogen activator (uPA), its receptor (uPAR), and plasminogen activator inhibitor-1 and -2 (PAI-1 and PAI-2) play a major role in tumor progression and metastasis. The binding of uPA with uPAR is instrumental for the activation of plasminogen to plasmin, which in turn initiates a series of proteolytic cascade to degrade the components of the extracellular matrix, and thereby, cause tumor cell migration from the primary site of origin to a distant secondary organ. The components of the PA system show altered expression patterns in several common malignancies, which have identified them as ideal diagnostic, prognostic, and therapeutic targets to reduce cancer-associated morbidity and mortality. This review summarizes the various components of the PA system and focuses on the role of uPA-uPAR in different biological processes especially in the context of malignancy. We also discuss the current state of knowledge of uPA-uPAR-targeted diagnostic and therapeutic strategies for various malignancies.

Silencing of plasminogen activator inhibitor-1 suppresses colorectal cancer progression and liver metastasis

BACKGROUND

Plasminogen activator inhibitor-1 (PAI-1) is reported to be expressed in many cancer cell types and regarded as one of the most informative biochemical markers for poor prognosis. However, no previous study has evaluated whether PAI-1 could serve as a target in antitumor and antimetastasis therapies of colorectal cancer (CRC).

METHODS

The plasma level of PAI-1 in CRC patients was detected and its correlation with the clinicopathologic features was evaluated. PAI-1 protein expression was assessed by Western blot assay and immunohistochemistry. The biologic consequences of PAI-1 silencing in colon cancer cell lines and CRC bearing nude mice were also investigated.

RESULTS

Plasma PAI-1 level was higher in CRC patients with liver metastasis and correlated with liver metastasis, tumor size, differentiation, serosa infiltration, Duke's stage, and lymphatic metastasis. PAI-1 protein expression in the CRC tissue of patients with liver metastasis was significantly greater than that in those without liver metastasis. In addition, the abilities of proliferation, invasion, and migration of CRC cells transfected with lentivirus expressing PAI-1 small interfering RNA were reduced significantly. Nude mice inoculated with PAI-1 knockdown cells also had fewer metastatic nodules in the liver and smaller tumor volumes.

CONCLUSION

Plasma PAI-1 level was increased in CRC patients with liver metastasis, and PAI-1 silencing may significantly compromise the malignant behaviors of CRC cells in vitro and in vivo. These findings may provide evidence for PAI-1 targeted therapy of CRC.

Impact of proteolytic enzymes in colorectal cancer development and progression

Tumor invasion and metastasis is a highly complicated, multi-step phenomenon. In the complex event of tumor progression, tumor cells interact with basement membrane and extracellular matrix components. Proteolytic enzymes (proteinases) are involved in the degradation of extracellular matrix, but also in cancer invasion and metastasis. The four categories of proteinases (cysteine-, serine-, aspartic-, and metalloproteinases) are named and classified according to the essential catalytic component in their active site. We and others have shown that proteolytic enzymes play a major role not only in colorectal cancer (CRC) invasion and metastasis, but also in malignant transformation of precancerous lesions into cancer. Tissue and serum-plasma antigen concentrations of proteinases might be of great value in identifying patients with poor prognosis in CRC. Our results, in concordance with others indicate the potential tumor marker impact of proteinases for the early diagnosis of CRC. In addition, proteinases may also serve as potential target molecules for therapeutic agents.

Involvement of urokinase-type plasminogen activator system in cancer: an overview

Currently, there are several studies supporting the role of urokinase-type plasminogen activator (uPA) system in cancer. The association of uPA to its receptor triggers the conversion of plasminogen into plasmin. This process is regulated by the uPA inhibitors (PAI-1 and PAI-2). Plasmin promotes degradation of basement membrane and extracellular matrix (ECM) components as well as activation of ECM latent matrix metalloproteases. Degradation and remodeling of the surrounding tissues is crucial in the early steps of tumor progression by facilitating expansion of the tumor mass, release of tumor growth factors, activation of cytokines as well as induction of tumor cell proliferation, migration, and invasion. Hence, many tumors showed a correlation between uPA system component levels and tumor aggressiveness and survival. Therefore, this review summarizes the structure of the uPA system, its contribution to cancer progression, and the clinical relevance of uPA family members in cancer diagnosis. In addition, the review evaluates the significance of uPA system in the development of cancer-targeted therapies.

ARNTL2 and SERPINE1: potential biomarkers for tumor aggressiveness in colorectal cancer

PURPOSE

Cathepsin and plasmin may favor cancer cell invasion degrading extracellular matrix. Plasmin formation from plasminogen is regulated by plasminogen activator inhibitor type-1 (PAI-1). ARNTL2 activates the promoters of the PAI-1 gene, officially called SERPINE1, driving the circadian variation in circulating PAI-1 levels.

METHODS

We evaluated ARNTL2 and SERPINE1 expression in 50 colorectal cancer specimens and adjacent normal tissue and in colon cancer cell lines.

RESULTS

We found up-regulation of ARNTL2 (P = 0.004) and SERPINE1 (P = 0.002) in tumor tissue. A statistically significant association was found between high ARNTL2 mRNA levels and vascular invasion (P < 0.0001), and between high SERPINE1 mRNA levels and microsatellite instability (MSI-H and MSI-L, P = 0.025). Sorting the subjects into quartile groups, a statistically significant association was found between high ARNTL2 expression and lymph node involvement (P < 0.001), between high SERPINE1 expression and grading (P < 0.001) and between high SERPINE1 expression and MSI H-L (P < 0.0001). In SW480 cells, a more proliferative model compared to CaCo2 cells, there were higher mRNA levels of ARNTL2 (P < 0.001) and SERPINE1 (P = 0.001).

CONCLUSION

ARNTL2 and SERPINE1 expression is increased in colorectal cancer and in a highly proliferative colon cancer cell line and is related to tumor invasiveness and aggressiveness.

Enhanced activity of meprin-α, a pro-migratory and pro-angiogenic protease, in colorectal cancer

Meprin-α is a metalloprotease overexpressed in cancer cells, leading to the accumulation of this protease in a subset of colorectal tumors. The impact of increased meprin-α levels on tumor progression is not known. We investigated the effect of this protease on cell migration and angiogenesis in vitro and studied the expression of meprin-α mRNA, protein and proteolytic activity in primary tumors at progressive stages and in liver metastases of patients with colorectal cancer, as well as inhibitory activity towards meprin-α in sera of cancer patient as compared to healthy controls. We found that the hepatocyte growth factor (HGF)- induced migratory response of meprin-transfected epithelial cells was increased compared to wild-type cells in the presence of plasminogen, and that the angiogenic response in organ-cultured rat aortic explants was enhanced in the presence of exogenous human meprin-α. In patients, meprin-α mRNA was expressed in colonic adenomas, primary tumors UICC (International Union Against Cancer) stage I, II, III and IV, as well as in liver metastases. In contrast, the corresponding protein accumulated only in primary tumors and liver metastases, but not in adenomas. However, liver metastases lacked meprin-α activity despite increased expression of the corresponding protein, which correlated with inefficient zymogen activation. Sera from cancer patients exhibited reduced meprin-α inhibition compared to healthy controls. In conclusion, meprin-α activity is regulated differently in primary tumors and metastases, leading to high proteolytic activity in primary tumors and low activity in liver metastases. By virtue of its pro-migratory and pro-angiogenic activity, meprin-α may promote tumor progression in colorectal cancer.

Plasma concentrations of VCAM-1 and PAI-1: a predictive biomarker for post-operative recurrence in colorectal cancer

This prospective study used antibody suspension bead arrays to identify biomarkers capable of predicting post-operative recurrence with distal metastasis in patients with colorectal cancer. One hundred colorectal cancer patients who underwent surgery were enrolled in this study. The median follow-up period was 3.9 years. The pre-operative plasma concentrations of 24 angiogenesis-related molecules were analyzed with regard to the TNM stage and the development of post-operative recurrence. The concentrations of half of the examined molecules (13/24) increased significantly according to the TNM stage (P < 0.05). Meanwhile, a multivariate logistic regression analysis revealed that the concentrations of vascular cell adhesion molecule 1 (VCAM-1) and plasminogen activator inhibitor-1 (PAI-1) were significantly higher in the post-operative recurrence group. The VCAM-1 and PAI-1 model discriminated post-operative recurrence with an area under the curve of 0.82, a sensitivity of 0.75, and a specificity of 0.73. A leave-one-out cross-validation was applied to the model to assess the prediction performance, and the result indicated that the cross-validated error rate was 12.5% (12/96). In conclusion, our results demonstrate that antibody suspension bead arrays are a powerful tool to screen biomarkers in the clinical setting, and the plasma levels of VCAM-1 and PAI-1 together may be a promising biomarker for predicting post-operative recurrence in patients with colorectal cancer.

Serum cathepsin B and plasma urokinase-type plasminogen activator levels in gastrointestinal tract cancers

Cathepsin B (CATB) and urokinase-type plasminogen activator (UPA) play an important part in cancer invasion and metastasis. The behavior of CATB and UPA has not been evaluated in the same experimental setting in different gastrointestinal tumors and in precancerous lesions. Serum CATB and plasma UPA levels were determined by enzyme-linked immunoadsorbent assay and their sensitivity, specificity, and diagnostic accuracy have been calculated in patients with colorectal (n=72), gastric (n=30), hepatocellular (n=28), and pancreatic cancer (n=15) as well as in gastric epithelial dysplasia (n=25), colorectal adenomas (n=30), and tumor-free control patients (n=44). Serum CATB and plasma UPA antigen concentrations were significantly higher in patients with cancer than in controls. When all tumors were considered, the sensitivity, specificity, and diagnostic accuracy of CATB (89, 86, and 89%) were higher than that of UPA (76, 70, and 74%). CATB demonstrated in all types of tumors a better diagnostic accuracy than UPA. The positive predictive values of CATB (95%) and UPA (89%) may suggest their use in the evaluation of patients with a suspicion of malignancy. CATB and UPA were significantly higher in patients with gastric epithelial dysplasia and colorectal adenomas than in controls. Antigen levels of CATB and UPA were significantly correlated in both cancers and precancerous lesions. At the time of clinical presentation, serum CATB and plasma UPA antigen levels are sensitive indicators of gastrointestinal malignancies. Determination of serum CATB and plasma UPA levels may be useful to identify patients at a higher risk for progression to cancer, who could be subjected to a more strict follow-up protocol.

Tumor marker utility and prognostic relevance of cathepsin B, cathepsin L, urokinase-type plasminogen activator, plasminogen activator inhibitor type-1, CEA and CA 19-9 in colorectal cancer

BACKGROUND

Cathepsin B and L (CATB, CATL), urokinase-type plasminogen activator (uPA) and its inhibitor PAI-1 play an important role in colorectal cancer invasion. The tumor marker utility and prognostic relevance of these proteases have not been evaluated in the same experimental setting and compared with that of CEA and CA-19-9.

METHODS

Protease, CEA and CA 19-9 serum or plasma levels were determined in 56 patients with colorectal cancer, 25 patients with ulcerative colitis, 26 patients with colorectal adenomas and 35 tumor-free control patients. Protease, CEA, CA 19-9 levels have been determined by ELISA and electrochemiluminescence immunoassay, respectively; their sensitivity, specificity, diagnostic accuracy have been calculated and correlated with clinicopathological staging.

RESULTS

The protease antigen levels were significantly higher in colorectal cancer compared with other groups. Sensitivity of PAI-1 (94%), CATB (82%), uPA (69%), CATL (41%) were higher than those of CEA or CA 19-9 (30% and 18%, respectively). PAI-1, CATB and uPA demonstrated a better accuracy than CEA or CA 19-9. A combination of PAI-1 with CATB or uPA exhibited the highest sensitivity value (98%). High CATB, PAI-1, CEA and CA 19-9 levels correlated with advanced Dukes stages. CATB (P = 0.0004), CATL (P = 0.02), PAI-1 (P = 0.01) and CA 19-9 (P = 0.004) had a significant prognostic impact. PAI-1 (P = 0.001), CATB (P = 0.04) and CA 19-9 (P = 0.02) proved as independent prognostic variables.

CONCLUSION

At the time of clinical detection proteases are more sensitive indicators for colorectal cancer than the commonly used tumor markers. Determinations of CATB, CATL and PAI-1 have a major prognostic impact in patients with colorectal cancer.

Plasminogen Activation Inhibitor-1 Improves the Predictive Accuracy of Prostate Cancer Nomograms

PURPOSE

We tested whether the addition of preoperative circulating plasminogen activator inhibitor type I levels improves the accuracy of standard preoperative and postoperative models for prediction of biochemical recurrence after radical prostatectomy.

MATERIALS AND METHODS

Preoperative plasma levels of plasminogen activator inhibitor type I were measured in 429 consecutive patients treated with radical prostatectomy for clinically localized prostate cancer. The patients were randomly divided into a development (67%, 286) and a split sample validation cohort (33%, 143). Cox regression analysis was used to develop prognostic nomograms for prediction of biochemical recurrence.

RESULTS

In standard univariate analyses categorically coded preoperative plasminogen activator inhibitor type I was significantly associated with biochemical recurrence (p <0.001). In standard preoperative and postoperative multivariate analyses preoperative plasminogen activator inhibitor type I was independently associated with biochemical recurrence (p <0.001 and p = 0.002, respectively). In the split sample validation cohort the addition of plasminogen activator inhibitor type I increased the predictive accuracy of the preoperative multivariate model by 1.2%, 7.7%, 10.3%, 6.7% and 5.4% at 1, 2, 3, 4 and 5 years, respectively (p values <0.001). Moreover, the addition of plasminogen activator inhibitor type I increased the predictive accuracy of the postoperative model by 0.5%, 1.1%, 4.0%, 2.4% and 3.6% at 1, 2, 3, 4 and 5 years, respectively (p values <0.001).

CONCLUSIONS

Preoperative circulating plasminogen activator inhibitor type I is a predictor of biochemical recurrence, and it enhances the accuracy of preoperative and postoperative nomograms. After external validation these nomograms may assist clinical decision making regarding treatment choice and followup as well as identification of patients at high risk for biochemical recurrence who may benefit from neoadjuvant and/or adjuvant treatment.

Tissue level, activation and cellular localisation of TGF-beta1 and association with survival in gastric cancer patients

Transforming growth factor-β1 (TGF-β1), a tumour suppressing as well as tumour-promoting cytokine, is stored as an extracellular matrix-bound latent complex. We examined TGF-β1 activation and localisation of TGF-β1 activity in gastric cancer. Gastric tumours showed increased stromal and epithelial total TGF-β1 staining by immunohistochemistry. Active TGF-β1 was present in malignant epithelial cells, but most strongly in smooth muscle actin expressing fibroblasts. Normal gastric mucosa from the same patient showed some staining for total, and little for active TGF-β1. Active TGF-β1 levels were determined by ELISA on tissue homogenates, confirming a strong increase in active TGF-β1 in tumours compared to corresponding normal mucosa. Moreover, high tumour TGF-β1 activity levels were significantly associated with clinical parameters, including worse survival of the patients. Total and active TGF-β1 levels were not correlated, suggesting a specific activation process. Of the different proteases tested, active TGF-β1 levels were only correlated with urokinase activity levels. The correlation with urokinase activity suggests a role for plasmin in TGF-β1 activation in the tumour microenvironment, resulting in transformation of resident fibroblasts to tumour promoting myofibroblasts. In conclusion we have shown localisation and clinical relevance of TGF-β1 activity levels in gastric cancer.

Prognostic value of plasminogen activator inhibitor-1 in head and neck squamous cell carcinoma

BACKGROUND

Tumor cell biological factors, such as urokinase plasminogen activator (uPA) and its inhibitor plasminogen activator inhibitor-1 (PAI-1), cathepsin D, and c-myc play a role in tumor invasion, metastasis, and proliferation. In this study, the prognostic importance of these factors in patients with primary head and neck squamous cell carcinoma (HNSCC) was evaluated and correlated with clinicopathologic variables.

METHODS

In 46 paired primary tumors and normal tissues, levels of uPA, PAI-1, cathepsin D, and c-myc amplification were determined. The clinical follow-up was over 10 years. Relationships between cell biological factors and patient and tumor characteristics were studied by the Mann-Whitney test. The Cox proportional hazard model was used for univariate and multivariate analysis.

RESULTS

In this study, only a high level of PAI-1 was associated with a significantly shorter disease-free survival (p < .01). PAI-1 levels were higher in tumors with perineural invasion (p < .01). Both PAI-1 and uPA levels were higher in patients who smoked (p < .01 and p = .02). In univariate analysis, smoking (p= .04), excessive alcohol intake (p = .02), perineural invasion (p = .001), and vaso-invasion (p = .009) were associated with a shorter disease-free survival. The only factor related to overall survival was perineural invasion (p = .045). The combination of a high PAI-1 level and perineural invasion appeared to be a significant predictor of a shorter disease-free interval (p = .01).

CONCLUSION

PAI-1 may present a novel prognostic factor for patients with HNSCC. Perineural invasion and PAI-1 level combined seemed to be prognostic for disease-free survival.

Protease Activity of Urokinase and Tumor Progression in a Syngeneic Mammary Cancer Model

BACKGROUND

We and others have previously shown that plasminogen activators generate endogenous angiogenesis inhibitors and induce antiangiogenic activity. Here we assessed the effects of plasminogen activator overexpression on tumor progression in a syngeneic mammary cancer model.

METHODS

Genes encoding murine tissue plasminogen activator (tPA), urokinase (uPA), and vector controls were stably transfected into 4T1 murine mammary cancer cells, and cell proliferation in vitro was analyzed. Cells were also implanted into female BALB/c mice (n = 12 per group), and tumor growth, lung metastases, and survival were compared. Tumor cell proliferation and microvessel formation were analyzed by immunohistochemistry using antibodies to proliferating cell nuclear antigen and CD31, respectively. 4T1 cells transfected with proteolytically inactive uPA mutants (A and B) were assayed for proliferation in vitro and tumor growth in vivo by using the same syngeneic model (eight to 10 mice per group). All statistical tests were two-sided.

RESULTS

In vitro growth of uPA- and tPA-overexpressing and control 4T1 cells was similar. In vivo, however, inhibition of tumor growth and lung metastasis were inhibited in the mice carrying tPA- and uPA-overexpressing tumors, compared with controls (tumor weight at day 34: control, mean = 1760 mg, 95% confidence interval [CI] = 1434 to 2087 mg; tPA, mean = 921, 95% CI = 624 to 1217 mg; P < .001; uPA, mean = 395 mg, 95% CI = 161 to 629 mg; P < .001; number of lung metastases at day 34: control, mean = 117, 95% CI = 74 to 159; tPA, mean = 33, 95% CI = 13 to 52; uPA, mean = 15, 95% CI = 4 to 25; P < .001). Median survival was 42 (95% CI = 36 to 44), 55 (95% CI = 48 to 61), and 73 (95% CI = 51 to 86) days in the control, tPA, and uPA groups, respectively (P < .001). uPA- and tPA-expressing tumors had reduced angiogenesis and cell proliferation compared with controls. Tumors overexpressing uPA mutants grew faster than tumors expressing wild-type uPA (tumor volume at day 30: wild-type uPA, mean = 203, 95% CI = 121 to 285 mm3; control, mean = 534, 95% CI = 460 to 608 mm3; P < .001; mutant A, mean = 600, 95% CI = 520 to 679 mm3; P < .001; and mutant B, mean = 435, 95% CI = 358.9 to 511 mm3; P = .005).

CONCLUSIONS

In this mouse model, uPA expression delayed tumor progression and had antiangiogenic and antiproliferative effects that may be mediated by uPA's protease activity. These results challenge the current dogma of proteases being exclusively tumor promoting and provide further rationale for exploring plasminogen activators as antitumor agents.

Assessment of serum matrix metalloproteinases MMP-2 and MMP-9 after human liver transplantation: increased serum MMP-9 level in acute rejection

BACKGROUND

Alterations in synthesis and breakdown of extracellular matrix components play a role in acute rejection after orthotopic liver transplantation (OLT). Matrix metalloproteinases (MMPs) are capable of degrading basement membranes and are involved in the process of tissue remodelling in inflammation and liver fibrosis.

METHODS

We examined MMP-2 and MMP-9 in serum of 33 patients before and during 1 year after OLT, in 60 controls as well as in some specimens of cirrhotic liver and control liver tissue.

RESULTS

Serum MMP-2 levels before OLT were significantly higher compared with controls and decreased approximately 50% after OLT. Also, the MMP-2 content of cirrhotic liver specimens was significantly higher compared with normal liver. MMP-9 in serum and liver tissue of patients were similar to controls, but serum levels showed a peak at 1 week after OLT. At this time-point, total and active/inhibitor-complexed MMP-9 was significantly higher in patients with rejection (n=13) compared with those without rejection (n=20). The relative amount of MMP-9 in the active/inhibitor-complexed form did not differ between each group over time. Immunohistochemical staining at 1 week after OLT showed increased numbers of MMP-9-positive inflammatory cells in the portal triads of patients with rejection.

CONCLUSIONS

Patients with acute allograft rejection have elevated serum levels of MMP-9 1 week after OLT, which was most likely derived from inflammatory cells. An increased MMP-2 serum level and liver tissue content was found in patients with cirrhosis, which decreased after OLT. These observations indicate active involvement of MMP-2 and -9 in end-stage liver disease and OLT.

The active fraction of plasmatic plasminogen activator inhibitor type 1 as a possible indicator of increased risk for metastatic melanoma

Plasminogen activator inhibitor type 1 (PAI1) is considered to be the main regulator of fibrinolytic activity in blood and has been identified as a key-enzyme in the metastasis and vascularization of solid tumors. The aim of this study was to determine whether high or low plasma levels and/or activity of PAI1 correlate with the presence of metastatic disease for patients with melanoma. We hypothesized that the presence of metastases could result in a disturbance of the fibrinolytic balance of the blood. To test our hypothesis, we have developed a unique enzyme-linked immunosorbent assay (ELISA) that can measure both the total amount as well as the active fraction of PAI1 in the plasma. We then used this novel assay to analyze the plasmatic PAI1 levels and activity of patients with advanced melanoma (AM, n = 18) and primary melanoma (PM, n = 21) and compare it to a control population (n = 38). We found no statistically significant difference in the total plasmatic PAI1 levels between the controls and patients with PM or AM (P = 0.6199). In contrast, there was a significant difference in the active fraction of PAI1 between the controls and patients with PM or AM (P = 0.0076). The difference between the control and AM groups was highly significant (P = 0.0042). A value of less than 44% active PAI1 was shown to be clinically meaningful by linear discriminant analysis. Surprisingly, the difference between the control and PM groups was also significant--although borderline (P = 0.0488). Of the patients with PM, 19% had PAI1 activity values less than 44%, which strongly supports further investigations to determine whether plasmatic PAI1 activity might be a biological marker of increased metastatic risk.

p53 Phosphorylation at serine 15 is required for transcriptional induction of the plasminogen activator inhibitor-1 (PAI-1) gene by the alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine

The alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) is a widely spread environmental carcinogen that causes DNA lesions leading to cell killing. MNNG can also induce a cell-protective response by inducing the expression of DNA repair/transcription-related genes. We recently demonstrated that urokinase-type plasminogen activator, an extracellular protease to which no DNA repair functions have been assigned, was induced by MNNG. Here, we show that the physiological inhibitor of urokinase-type plasminogen activator, PAI-1, is also induced by MNNG in a p53-dependent fashion, because MNNG induced PAI-1 in p53-expressing cells but not in p53-/- cells. MNNG induced p53 phosphorylation at serine 15, resulting in stabilization of the p53 protein, and this phosphorylation event was central for p53-dependent PAI-1 transcription. Finally, we showed that PAI-1 transcriptional induction by MNNG required a p53-responsive element located at -136 base pairs in the PAI-1 promoter, because specific mutation of this site abrogated the induction. Because PAI-1 is a prognostic factor in many metastatic cancers, being involved in the control of tumor invasiveness, our finding that a genotoxic agent induces the PAI-1 gene via p53 adds a new feature to the role of the tumor-suppressor p53 protein. Our results also suggest the possibility that genotoxic agents contribute to tumor metastasis by inducing PAI-1 without involving genetic modification.

Preoperative plasma plasminogen activator inhibitor type-1 and serum C-reactive protein levels in patients with colorectal cancer. The RANX05 Colorectal Cancer Study Group

BACKGROUND

Preoperative plasma plasminogen activator inhibitor-1 (PAI-1) is a prognostic variable in patients with colorectal cancer. It has been suggested, however, that plasma PAI-1 is a nonspecific prognostic parameter similar to the acute-phase reactant C-reactive protein (CRP). In the present study we analyzed the association between plasma PAI-1 and serum CRP in patients scheduled for elective resection of colorectal cancer. In addition, the prognostic value of PAI-1 and CRP was studied in this patient cohort.

METHODS

PAI-1 and CRP were analyzed in citrated plasma and serum, respectively, obtained preoperatively from 594 patients. Patients who required preoperative blood transfusion received SAGM blood, in which soluble PAI-1 is not present. None of the patients received pre- or postoperative adjuvant chemotherapy, and all were followed in the outpatient clinic for at least 5 years or until death. The association of PAI-1 and CRP, respectively, with survival was tested using the median value of PAI-1 and the upper normal limit for CRP. Analyses were performed by inclusion of all patients, and in the subgroup of patients, who underwent curative resection.

RESULTS

The median follow-up period was 6.8 (5.4-7.9) years. The median value of plasma PAI-1 was 35.8 ng/ml, and values greater than 94 nmol/L identified patients with increased CRP levels. Comparison of the molecules showed that PAI-1 was weakly correlated with CRP (r = .26; P <.0001). Both molecules showed a Dukes independent distribution. In univariate survival analyses high levels of PAI-1 were found associated with poor prognosis and low levels with good prognosis (P = .02, HR: 1.3). Similarly, high levels of CRP were found associated with poor prognosis and low levels with good prognosis (P <.0001, HR: 1.9). In a multivariate statistical analysis including Dukes classification, gender, age, tumor location, perioperative blood transfusion, PAI-1 and CRP, plasma PAI-1 was a dependent prognostic variable, while serum CRP (P <.0001; HR: 1.4; 95% CI: 1.3-1.5) was found to be a Dukes independent prognostic variable. Similar analyses, excluding patients with Dukes' D disease showed serum CRP to be an independent prognostic variable (P <.0001; HR: 1.3: 95% CI: 1.2-1.5).

CONCLUSIONS

This study did not show a strong correlation between plasma PAI-1 and serum CRP in patients with colorectal cancer. Serum CRP was found to be a Dukes independent prognostic variable in this patient cohort, and was found to identify a subgroup of curatively resected patients at risk for short survival.

Plasminogen activator inhibitor 1 may promote tumour growth through inhibition of apoptosis

Plasminogen activator inhibitor 1 (PAI-1) has been found to be a bad prognostic factor in a number of tumours but the reason has not been fully explained. The human prostate cancer cell line PC-3 and the human promyelocytic leukaemia cell line HL-60 were used in this study to determine the effect of PAI-1 on spontaneous and induced apoptosis in culture. Apoptosis was induced with camptothecin or etoposide. Addition of a stable variant of PAI-1 or wild-type PAI-1 to these cells resulted in a significant inhibition of apoptosis. In contrast, both the latent form of PAI-1 and the stable variant of PAI-1 inactivated by a specific neutralizing monoclonal antibody, or the stable variant of PAI-1 in a complex with recombinant urokinase did not inhibit apoptosis. This indicated that the inhibitory activity of PAI-1 was required for its anti-apoptotic effect but the urokinase-type plasminogen activator receptor was not involved. These findings provide an explanation for the bad prognostic correlation of high PAI-1 levels in tumours. The anti-apoptotic effect was also found in non-tumoural cells including human umbilical vein endothelial cells and the benign human breast epithelial cell line MCF-10A, suggesting that this is a novel physiologic function of PAI-1.

Proteases in gastrointestinal neoplastic diseases

Cysteine and serine proteases are involved in cancer invasion and metastasis. In the past few years we investigated the tissue levels of these proteases in gastric cancer (GC), gastric precancerous changes (CAG), colorectal cancer (CRC) and the plasma and serum levels of proteases in several gastrointestinal tumours, using ELISA methods. Significantly higher antigen levels were found not only in GC tissue but also in CAG with respect to the levels found normal tissue; with respect to CAG, patients with dysplasia had higher levels than patients without dysplasia. The same findings were obtained in CRC. In general protease levels correlated with the major histomorphological parameters, such as grading and histotype in GC as well as in CRC. Tissue protease levels had a strong prognostic impact in GC, in which UPA was singled out by multivariate analysis as the major prognostic factor, and CRC. The plasma levels of urokinase-type plasminogen activator (UPA) and the serum levels of cathepsin B were significantly increased in patients with gastrointestinal tumours. In conclusions, cysteine and serine proteases may have a part not only in GC and CRC invasion and metastasis, but also in the progression of gastric precancerous changes into cancer. They are strong prognostic factors in GC and CRC. These proteases may also have a role as tumour markers in the early diagnosis of gastrointestinal tract tumours.

In vivo inhibition of cysteine proteinases delays the onset of growth of human pancreatic cancer explants

An animal model was used to study the effects of oral treatment with a small molecular selective inhibitor of cysteine proteinases, Z-Phe-Arg-fluoromethylketone (Z-Phe-Arg-FMK) on primary tumour development. Poorly differentiated rapidly growing and moderately differentiated slowly growing human pancreatic tumours were implanted in the neck of nude mice that were orally treated or not with the inhibitor. Growth rates of the tumours were determined during 38 days after implantation. The poorly differentiated tumours were not affected by treatment with the inhibitor. Development of the moderately differentiated tumours was inhibited significantly by Z-Phe-Arg-FMK treatment. Moreover, the amount of stroma was increased and the volume of cancer cells was reduced in the moderately differentiated tumours that had grown in the treated animals. Reduction in size of the tumours was not achieved by reduction in growth rate but in a delay of the onset of growth. It is concluded that cysteine proteinases play a transient role at the start of tumour development only when cancer cells are surrounded by stroma as was the case in the moderately differentiated but not in the poorly differentiated pancreatic tumours. However, this role of cysteine proteinases can easily be taken over by other proteinases.

The role of cysteine and serine proteases in colorectal carcinoma

BACKGROUND

Cathepsin B (CATB) and cathepsin L (CATL), which are cysteine proteases, urokinase-(UPA) and tissue-type plasminogen activator (TPA), both serine proteases, and their inhibitor type-1 (PAI-1) are believed to play an important role in colorectal carcinoma (CRC) invasion and metastasis. The objective of this study was to measure CATB, CATL, UPA, TPA, and PAI-1 in the same cancerous tissue (CANCER) and in tissues obtained from a tumor free area (NORMAL) to compare their respective prognostic roles in patients with CRC.

METHODS

CANCER and NORMAL samples were obtained from 60 CRC patients undergoing surgery (36 males and 24 females; mean age, 63.8 years [range, 27-85 years]). The antigen concentrations were measured using an enzyme-linked immunoadsorbent assay method. The CANCER tissue also was examined in terms of major histomorphologic parameters such as differentiation, vascular invasion, degree of necrosis, and mucus production.

RESULTS

Significantly higher antigen levels were found: 1) in CANCER versus NORMAL (with respect to CATL, UPA, and PAI-1, with significantly lower levels for TPA); 2) in CRC with versus without metastasis (CATB, CATL, and PAI-1); 3) in poorly versus well differentiated CRC (UPA and PAI-1); and 4) in advanced Dukes stages (PAI-1). CATB and CATL significantly correlated with UPA and PAI-1. Finally, CATL (P = 0.0001), UPA (P = 0.006), PAI-1 (P = 0.006), Dukes stage (P = 0.0001), presence of metastases (P = 0.003), and vascular invasion (P = 0.03) had a significant prognostic impact.

CONCLUSIONS

The simultaneous up-regulation of cysteine and serine proteases in CRC confirms their role in colorectal tumor biology and particularly in the process of invasion and metastasis. Together with Dukes stage, determinations of CATL, UPA, and PAI-1 have a major prognostic impact in patients with CRC.

Protein markers in colorectal cancer: predictors of liver metastasis

OBJECTIVE

To assess the significance of the expression of five protein markers (nm23, p53, c-erbB-2, u-PA, and VEGF) to the development of metastasis in colorectal cancer.

SUMMARY BACKGROUND DATA

The metastatic cascade is a complex multistep process involving several genetic alterations, angiogenesis activation, and tissue proteolysis. Although the prognosis of colorectal cancer depends on the stage of the tumor, the development of metastasis is difficult to predict.

METHODS

Paraffin-embedded specimens of 58 patients who underwent surgery for colorectal cancer were retrospectively analyzed by immunohistochemistry, and the coexpression of these protein markers was related to patient outcome.

RESULTS

The risk of developing liver secondaries was correlated with the expression of nm23 protein (p < 0.0001); this was also the case in those patients with Dukes' stage B showing positive nm23 immunostaining (p = 0.006). The determination of the number of positive markers or the cumulative intensity score did not improve the predictive value over and above that of nm23 protein alone.

CONCLUSION

Expression of nm23 protein is correlated with the risk of developing liver metastasis. Its evaluation alone may help to determine which patients who have undergone apparently curative resection of a colorectal cancer have an increased risk of liver recurrence, especially those with Dukes' stage B tumors who might be considered for adjuvant chemotherapy.

Prognostic significance of urokinase (uPA) and its inhibitor PAI-1 for survival in advanced ovarian carcinoma stage FIGO IIIc

Strong evidence has accumulated on the prognostic value of tumour-associated proteolytic factors in patients afflicted with solid malignant tumours, including advanced ovarian cancer. We evaluated the prognostic impact of the protease urokinase plasminogen activator (uPA) and its inhibitor PAI-1 on overall survival in patients with advanced ovarian cancer stage FIGO IIIc in order to select patients at risk. uPA and PAI-1 antigen were determined by ELISA in primary tumour tissue extracts of 86 ovarian cancer patients FIGO stage IIIc enrolled in a prospective study. Univariate and multivariate analyses were performed using the Cox proportional hazard model. The time-varying coefficient model of Gray was used to assess the time-dependent strength of prognostic factors tumour mass, uPA and PAI-1 on overall survival. In all patients, uPA and PAI-1 (optimized cut-offs of 2.0 and 27.5 ng mg(-1) protein respectively), in addition to the traditional prognostic parameters of residual tumour mass, nodal status, grading and ascites volume, were of prognostic significance in univariate analysis for overall survival. Even in patients with residual tumour mass (n = 43), the statistically independent prognostic impact of PAI-1 persisted, allowing further discrimination between low- and high-risk patients. In multivariate analysis, residual tumour mass (P < 0.001, relative risk (RR) 4.5), PAI-1 (P < 0.001; RR 3.1) and nodal status (P = 0.022, RR 2.6) turned out to be strong, statistically independent prognostic parameters. Evaluation of the time-dependent prognostic impact of residual tumour mass and PAI-1 on overall survival (n = 86, 50 months) revealed that the prognostic power of these factors increased with time. In patients with advanced ovarian cancer, both residual tumour mass and PAI-1 are statistically independent strong prognostic factors. Even within patient subgroups with or without residual tumour mass, PAI-1 allowed selection of patients at risk who might benefit from individualized therapy protocols.

Expression of urokinase-type plasminogen activator receptor and plasminogen activator inhibitor-1 in gastric cancer

In gastric cancer, the urokinase-type plasminogen activator (uPA) system plays important roles in invasion and metastasis, processes which entail proteolysis and adhesion. Both the urokinase-type plasminogen activator receptor (uPAR) and the plasminogen activator inhibitor-1 (PAI-1) are thought to be important factors in this system. To clarify the relationship between these two factors and gastric cancer invasiveness, we evaluated the expression of uPAR and PAI-1 in 91 cases of gastric cancer by immunohistochemistry and in situ hybridization. Urokinase-type plasminogen activator receptor-mRNA, PAI-1-mRNA, uPAR and PAI-1 protein were diffusely distributed in the cytoplasm of the cancer cells and concentrated at invasive foci. Urokinase-type plasminogen activator receptor protein expression correlated with lymphatic, venous invasion (P< 0.01) and lymph node metastasis (P< 0.05); uPAR-mRNA expression correlated with lymphatic, venous invasion and lymph node metastasis (P< 0.05). Plasminogen activator inhibitor-1 protein expression correlated with lymphatic, venous invasion, lymph node metastasis and depth of invasion (P<0.01); PAI-1-mRNA expression was linked to lymphatic, venous invasion (P< 0.01), lymph node metastasis and depth of invasion (P< 0.05). This suggests that the proteolytic activity of uPAR and the cellular motility of PAI-1 in gastric cancer cells may determine penetration of lymphatic and blood vessels, whereby lymph node metastasis may be promoted and that the promotion of cellular motility by PAI-1 may influence the depth of cancer invasion.

Absence of host plasminogen activator inhibitor 1 prevents cancer invasion and vascularization

Acquisition of invasive/metastatic potential through protease expression is an essential event in tumor progression. High levels of components of the plasminogen activation system, including urokinase, but paradoxically also its inhibitor, plasminogen activator inhibitor 1 (PAI1), have been correlated with a poor prognosis for some cancers. We report here that deficient PAI1 expression in host mice prevented local invasion and tumor vascularization of transplanted malignant keratinocytes. When this PAI1 deficiency was circumvented by intravenous injection of a replication-defective adenoviral vector expressing human PAI1, invasion and associated angiogenesis were restored. This experimental evidence demonstrates that host-produced PAI is essential for cancer cell invasion and angiogenesis.

Review article: short chain fatty acids in health and disease

Short chain fatty acids (SCFAs) have been the subject of much research over the past few decades. They play a vital role in maintenance of colonic integrity and metabolism. They are produced when dietary fibre is fermented by colonic bacteria. SCFAs are avidly absorbed in the colon, at the same time as sodium and water absorption and bicarbonate secretion. Once absorbed, SCFAs are used preferentially as fuel for colonic epithelial cells and have trophic effects on the epithelium. Clinically, SCFAs have been studied as possible therapeutic agents in diversion colitis, ulcerative colitis, radiation proctitis, pouchitis and antibiotic-associated diarrhoea. Although some promising effects have been observed in uncontrolled studies, a specific therapeutic role for SCFAs remains to be defined. SCFAs may be the effector of the beneficial role of fibre in prevention of colon cancer.

Heterogeneous suppression of experimentally induced colon cancer metastasis in rat liver lobes by inhibition of extracellular cathepsin B

Metastatic rat colon cancer cells but not normal rat hepatocytes showed activity of cathepsin B on their plasma membranes. Activity was visualized in living cells with a new fluorogenic substrate, [Z-Arg]2-cresyl violet, and confocal microscopy. When these cancer cells were injected into the portal vein of rats, the animals developed tumors in the liver in a heterogeneous fashion. Three- to four-fold more tumors were found in the small caudate lobe than in the other three large lobes of the liver. Oral treatment with a selective water-soluble inhibitor of extracellular cathepsin B, Mu-Phe-homoPhe-fluoromethylketone, resulted in 60% reduction of the number of tumors and 80% reduction of the volume of tumors in the three large lobes whereas tumor development was not affected in the small caudate lobe. This study supports the conclusions that (a) extracellular cathepsin B plays a crucial but complex role in liver colonisation by rat colon carcinoma cells in vivo, (b) its selective inhibition suppresses tumor growth heterogeneously in the liver and (c) the caudate lobe of the liver is a relatively large risk factor for tumor development.

Plasminogen activator and matrix metalloproteinase production and extracellular matrix degradation by rat prostate cancer cells in vitro: correlation with metastatic behavior in vivo

BACKGROUND

The plasminogen activation (PA) and metalloproteinase (MMP) system are involved in tumor cell migration and invasion.

METHODS

The proteolytic activity of cell lines originating from the rat Dunning R-3327 prostate tumor was analyzed by measuring in vitro extracellular matrix degradation, enzyme activity, and mRNA levels of enzymes, inhibitors, and receptors, and compared with their known metastatic behavior in vivo.

RESULTS

Only the highly metastatic sublines AT-3, MATLu, and MATLyLu showed a high extracellular matrix degradation mediated by urokinase-type plasminogen activator (u-PA). Relatively high levels of u-PA were present in the aggressive cell lines. u-PA receptor mRNA was produced in all cells, and all but AT-1 produced LDL-receptor-related-protein (LRP) mRNA. t-PA mRNA was only found in HIF and MATLu. In gelatin, zymography lysis was observed at 72 kD and 74-76 kD in MATLu and MATLyLu cells, respectively. MMP-2 mRNA was present in all cell lines except AT-1 and AT-2, and MMP-3 mRNA was present in AT-2, AT-3, and MATLu.

CONCLUSIONS

These in vitro experiments show that in different rat prostate cancer sublines, proteolytic activity and u-PA-mediated extracellular matrix degradation correlate with their known metastatic behavior in vivo.

Urokinase-type plasminogen activator receptor in gastric cancer: tissue expression and prognostic role

The urokinase-type plasminogen activator (UPA) and its inhibitor PAI-1 are thought to play an important part in gastric cancer (GC) invasion and metastasis. Little is known about the behavior and prognostic impact of the receptor for UPA (UPAR). The aims of the present study were: (1) to measure UPAR, UPA and PAI-1 levels in GC and in non-malignant tissue distant from the tumor (NORM); (2) to evaluate their relationship with histomorphological parameters; and (3) to determine their prognostic value. UPAR, UPA and PAI-1 levels were determined by ELISA in GC and NORM samples from 20 patients with GC undergoing surgery. The GC was also examined in terms of the presence (n = 10) or absence (n = 10) of metastasis, differentiation (five differentiated, 15 undifferentiated) and histotype. Survival was analysed using life table analysis. UPAR, UPA and PAI-1 were significantly higher in GC vs NORM, in the presence of metastasis (UPAR, UPA) and in undifferentiated GC (UPAR, PAI-1). UPAR significantly correlated with UPA and PAI-1. Low levels of UPAR (P = 0.04), UPA (P = 0.007) and PAI-1 (P = 0.02) were associated with a better survival. Our results demonstrate a sharp increase in UPAR in GC and suggest a prognostic role for it. The concomitant activation of UPAR, UPA and PAI-1 in GC confirm the important role of the plasminogen activator system in the process of invasion and metastasis.

Plasmin and plasminogen activator inhibitor type 1 promote cellular motility by regulating the interaction between the urokinase receptor and vitronectin

The urokinase receptor (uPAR) coordinates plasmin-mediated cell-surface proteolysis and promotes cellular adhesion via a binding site for vitronectin on uPAR. Because vitronectin also binds plasminogen activator inhibitor type 1 (PAI-1), and plasmin cleavage of vitronectin reduces PAI-1 binding, we explored the effects of plasmin and PAI-1 on the interaction between uPAR and vitronectin. PAI-1 blocked cellular binding of and adhesion to vitronectin by over 80% (IC50 approximately 5 nM), promoted detachment of uPAR-bearing cells from vitronectin, and increased cellular migration on vitronectin. Limited cleavage of vitronectin by plasmin also abolished cellular binding and adhesion and induced cellular detachment. A series of peptides surrounding a plasmin cleavage site (arginine 361) near the carboxy-terminal end of vitronectin were synthesized. Two peptides spanning res 364-380 blocked binding of uPAR to vitronectin (IC50 approximately 8-25 microM) identifying this region as an important site of uPAR-vitronectin interaction. These data illuminate a complex regulatory scheme for uPAR-dependent cellular adhesion to vitronectin: Active urokinase promotes adhesion and also subsequent detachment through activation of plasmin or complex formation with PAI-1. Excess PAI-1 may also promote migration by blocking cellular adhesion and/or promoting detachment, possibly accounting in part for the strong correlation between PAI-1 expression and tumor cell metastasis.

Time-varying prognostic impact of tumour biological factors urokinase (uPA), PAI-1 and steroid hormone receptor status in primary breast cancer

In breast cancer, several investigations have demonstrated that the tumour biological factors uPA urokinase-type plasminogen activator) and its inhibitor PAI-1 are statistically independent, strong prognostic factors for disease-free (DFS) and overall survival (OS). However, statistical analyses performed for varying follow-up periods suggested a time variation of prognostic strength. We therefore investigated the time-dependent prognostic power of uPA, PAI-1 and steroid hormone receptor status applying the time-varying coefficient model of Gray. uPA and PAI-1 were analysed by enzyme-linked immunosorbent assay in tumour tissue extracts from 314 breast cancer patients. Hormone receptors (oestrogen and progesterone) were determined by radioligand binding or by immunohistochemistry. Univariate and multivariate analyses (Cox proportional hazards model) of DFS and OS were performed for all patients, including 147 node-negative patients. Median follow-up of patients still alive at time of analysis (n = 232) was 58 months. Although initially of high prognostic impact, a continuous decrease over time in the prognostic power of hormone receptor status and uPA was observed. In contrast, the prognostic impact of PAI-1 increased over time and reached similar strength as the lymph node status. The time-dependent risk profile of prognostic factors may have important clinical implications in regard to follow-up and patients' individual risk situation. Evaluation of time dependency of prognostic factors may also give a more profound insight into the dynamics of breast cancer metastasis.

Contribution of plasminogen activators and their inhibitors to the survival prognosis of patients with Dukes' stage B and C colorectal cancer

Despite the advances in pre-, peri- and post-operative medical care of colorectal carcinoma patients, the prognosis has improved only marginally over recent decades. Thus, additional prognostic indicators would be of great clinical value to select patients for adjuvant therapy. In previous studies we found that colorectal carcinomas have a marked increase of the urokinase-type of plasminogen activator (u-PA), and the inhibitors PAI-1 and PAI-2, whereas the tissue-type plasminogen activator (t-PA) is found to be decreased in comparison with adjacent normal mucosa. In the present study we evaluated the prognostic value of several plasminogen activation parameters, determined in both normal and carcinomatous tissue from colorectal resection specimens, for overall survival of 136 Dukes' stage B and C colorectal cancer patients, in relation to major clinicopathological parameters. Uni- and multivariate analyses indicated that a high PAI-2 antigen level in carcinoma, a low t-PA activity and antigen level and a high u-PA/t-PA antigen ratio in adjacent normal mucosa are significantly associated with a poor overall survival. A high ratio of u-PA antigen in the carcinomas and t-PA antigen in normal mucosa, i.e. u-PA(C)/t-PA(N), was found to be predictive of a poor overall survival as well. All these parameters were found to be prognostically independent of the clinicopathological parameters. Multivariate analysis of combinations of these prognostically significant plasminogen activation parameters revealed that they are important independent prognostic indicators and have in fact a better prognostic value than their separate components. Based on these combined parameters, subgroups of patients with Dukes' stage B and C colorectal cancer could be identified as having either a high or a low risk regarding overall survival. In conclusion, these findings emphasize the relevance of the intestinal plasminogen activation system for survival prognosis of patients with colorectal cancer and, in the future, might constitute a patient selection criterion for adjuvant therapy.

Is plasminogen activator inhibitor-1 the molecular switch that governs urokinase receptor-mediated cell adhesion and release?

Induction of the urokinase type plasminogen activator receptor (uPAR) promotes cell adhesion through its interaction with vitronectin (VN) in the extracellular matrix, and facilitates cell migration and invasion by localizing uPA to the cell surface. We provide evidence that this balance between cell adhesion and cell detachment is governed by PA inhibitor-1 (PAI-1). First, we demonstrate that uPAR and PAI-1 bind to the same site in VN (i.e., the amino-terminal somatomedin B domain; SMB), and that PAI-1 competes with uPAR for binding to SMB. Domain swapping and mutagenesis studies indicate that the uPAR-binding sequence is located within the central region of the SMB domain, a region previously shown to contain the PAI-1-binding motif. Second, we show that PAI-1 dissociates bound VN from uPAR and detaches U937 cells from their VN substratum. This PAI-1 mediated release of cells from VN appears to occur independently of its ability to function as a protease inhibitor, and may help to explain why high PAI-1 levels indicate a poor prognosis for many cancers. Finally, we show that uPA can rapidly reverse this effect of PAI-1. Taken together, these results suggest a dynamic regulatory role for PAI-1 and uPA in uPAR-mediated cell adhesion and release.

The plasminogen activation system in tumour invasion and metastasis

The involvement of proteases in the metastatic spread of tumour cells and in tumour related processes, such as angiogenesis and ulceration, has been known for many decades. This chapter reviews the involvement of one proteolytic system--the plasminogen activation system--in tumour progression. In recent years, many biochemical properties of the various components of the plasminogen activation system have become known. These properties and the functional relationship between the components are discussed in the first section. Since interfering with proteolysis by tumour cells and by newly formed endothelial cells can be an objective for future therapy, experimental tumour models have been used to study the effects of inhibitors of plasminogen activation. The second section deals with this issue. Finally, the presence of the various components of the plasminogen activation system in human tumours is reviewed. Following the availability of specific ELISAs, antibodies and molecular probes, the content and the cellular distribution of the components of the plasminogen activation system have recently been mapped in various human tumours.

Prognostic value of the plasminogen activation system in patients with gastric carcinoma

BACKGROUND

Patients with gastric cancer have a poor prognosis and can be cured by surgery only if the cancer is detected in an early stage. Extended surgery, down staging with chemotherapy before operation, and new postoperative treatments are recent approaches to increase survival rates. Categorizing patients' prognoses as good or poor by pathophysiologic markers, however, may be of great help in selecting therapies for these patients. For example, plasminogen activation (PA) parameters, that play an important role in tumor invasion and metastasis, have prognostic value for several human malignancies.

METHODS

We evaluated the relation between several PA parameters in tissue with standard clinicopathologic parameters and with the overall survival of 50 consecutive patients with gastric carcinoma.

RESULTS

Univariate analysis showed that a low tissue-type plasminogen activator (t-PA) activity in normal mucosa and in carcinomas and a high antigen level of inhibitor type-1 (PAI-1), and, to a lesser extent, of urokinase-type plasminogen activator (u-PA) receptor, in carcinomas are associated with a poor overall survival of the patients. In contrast, of the 14 clinicopathological parameters only the number of eosinophils in the tumors was associated with survival. Multivariate analysis revealed that the t-PA and PAI-1 levels are independently associated with survival.

CONCLUSIONS

Plasminogen activation parameters in both normal and carcinomatous tissue of the stomach of patients with gastric carcinoma are of particular clinical interest because of their prognostic impact on overall survival.

Increase of a urokinase receptor-related low-molecular-weight molecule in colorectal adenocarcinomas

Proteolytic activity is important for tumor growth and metastasis. Plasminogen and urokinase-type plasminogen activator (u-PA) constitute one of the most extensively studied proteolytic systems believed to participate in these processes. u-PA cleaves plasminogen to plasmin, which in turn degrades surrounding extracellular matrix and allows tumor cells to migrate to other areas. The specific receptor for u-PA (u-PAR) has also been implicated as an essential modulator in this pathway. Eleven paired samples of colorectal cancers and normal mucosal tissues from the same patients were removed at surgery. The tissues were homogenized and the supernatants assayed for u-PAR immunoreactivity, u-PAR antigen concentration, u-PAR binding activity and u-PA activity. Immunoblot analysis showed that a major u-PAR species of approximately 55 kDa was present in all tissues. In addition, a protein band of approximately 41 kDa, which crossreacted with anti-u-PAR antibodies, was also found in the tumors. This protein band was either absent, or present in relatively small amounts in the normal colorectal tissues. Cross-linking experiments showed that the approximately 55 kDa band only, and not the approximately 41 kDa band, was able to bind either single chain urokinase-type plasminogen activator (scu-PA) or the amino terminal fragment of urokinase (ATF). The tumor samples also exhibited highly elevated u-PA activity and u-PAR antigen relative to the corresponding normal tissues. Elevated u-PA activity appeared to correlate with elevated u-PAR antigen in colorectal cancers, but not in the normal tissues. These increases were also associated with increase of the u-PAR-related, low-molecular-weight protein in the tumor samples. The measurement of u-PAR and the u-PAR-related protein, in addition to u-PA activity, could have diagnostic or prognostic value in this type of cancer.

Role of short-chain fatty acids in the prevention of colorectal cancer

Short-chain fatty acids (SCFAs: acetate, propionate, n-butyrate) arising in the large bowel during bacterial fermentation of dietary fibre and starch have paradoxical effects on colonic epithelial proliferation. While the three major SCFAs stimulate proliferation of normal crypt cells, n-butyrate and, to a lesser degree, propionate inhibit growth of colon cancer cell lines. At the molecular level, n-butyrate causes histone acetylation, favours differentiation, induces apoptosis and regulates the expression of various oncogenes. To understand the complex effects of SCFAs on carcinogenesis, it is important to study the intermediate stages of the adenoma-carcinoma sequence where a "switch" from stimulation to suppression of cell proliferation must occur.

Prognostic value of plasminogen activators and their inhibitors in colorectal cancer

Colorectal tumorigenesis is associated with remarkable changes in the plasminogen activation system at the tissue level. The sequence of normal mucosa-adenomatous polyp-adenocarcinoma-metastasis is accompanied by an increase in the urokinase-type of plasminogen activator, the urokinase receptor and the inhibitors type-1 and type-2, with a concurrent decrease in the tissue-type plasminogen activator. Overall survival analysis of colorectal cancer patients, with a follow-up of more than 5 years, revealed that several of these components, in both the carcinomas and their corresponding normal mucosa, are of prognostic value independent of major clinicopathological parameters. Therefore, the plasminogen activation cascade not only contributes to the invasive and metastatic growth of colorectal tumours, but might also have a clinical impact with respect to adjuvant and intervention therapy.

Plasminogen activator inhibitor type 1 in cancer: therapeutic and prognostic implications

Degradation of the extracellular matrix plays a crucial role in cancer invasion. This degradation is accomplished by the concerted action of several enzyme systems, including generation of the serine protease plasmin by the urokinase pathway of plasminogen activation, different types of collagenases and other metalloproteinases, and other extracellular enzymes. The degradative enzymes are involved also in tissue remodelling under non-malignant conditions, and the main difference appears to be that mechanisms which regulates these processes under normal conditions are defective in cancer. Specific inhibitors have been identified for most of the proteolytic enzymes, e.g. plasminogen activator inhibitors (PAI's) and tissue inhibitors of metalloproteinases (TIMP's). It has been contemplated that these inhibitors counteracted the proteolytic activity of the enzymes, thereby inhibiting extracellular tissue degradation which in turn should prevent tumor cell invasion. This review focuses on plasminogen inhibitor type 1 (PAI-1). It is described that PAI-1 is not produced by the epithelial cancer cell but by the stromal cells in the tumors, suggesting a concerted action between stroma and tumor cells in the processes controlling proteolysis in cancer. The specific localization of PAI-1 to the tumor stroma and in many cases to areas surrounding the tumor vessels has lead us to suggest that PAI-1 serves to protect the tumor stroma from the ongoing uPA-mediated proteolysis. This hypothesis is supported by recent clinical data showing increased levels of PAI-1 in metastases as compared to the primary tumor as well as data demonstrating that high levels of PAI-1 in tumor extracts from breast, lung, gastric and ovarian cancer is associated with a shorter overall survival.(ABSTRACT TRUNCATED AT 250 WORDS)