Three-stage chromogenic assay for the analysis of activation properties of factor X by cancer procoagulant

In Vitro Screening of Synthetic Fluorogenic Substrates for Detection of Cancer Procoagulant Activity

Cancer procoagulant (CP), a direct activator of coagulation factor X, is among one of the tumour cell products or activities which may promote fibrin formation and has been suggested to be selectively associated with the malignant phenotype. At present, the most reliable assay for the quantification of CP activity is the three-stage chromogenic assay which utilises the ability of CP to activate factor X. In this assay, the activation of factor X leads to the formation of activated thrombin from prothrombin and the eventual hydrolyses of a thrombin chromogenic substrate which contains a p-nitroaniline leaving group. The complexity of the three-stage chromogenic assay suggests a need for a direct method of assaying CP activity. This study focuses on the design of a fluorogenic substrate that would enable the direct quantification of CP activity. The results of the study show two promising substrates for the determination of CP activity: Boc-PQVR-AMC and PQVR-AMC. Further analysis showed that Boc-PQVR-AMC could be excluded as a potential substrate for CP since it was also cleaved by collagenase.

The proteolytic profile of human cancer procoagulant suggests that it promotes cancer metastasis at the level of activation rather than degradation

Proteases are essential for tumour progression and many are over-expressed during this time. The main focus of research was the role of these proteases in degradation of the basement membrane and extracellular matrix (ECM), thereby enabling metastasis to occur. Cancer procoagulant (CP), a protease present in malignant tumours, but not normal tissue, is a known activator of coagulation factor X (FX). The present study investigated the function of CP in cancer progression by focussing on its enzymatic specificity. FX cleavage was confirmed using SDS-PAGE and MALDI-TOF MS and compared to the proteolytic action of CP on ECM proteins, including collagen type IV, laminin and fibronectin. Contrary to previous reports, CP cleaved FX at the conventional activation site (between Arg-52 and Ile-53). Additionally, degradation of FX by CP occurred at a much slower rate than degradation by conventional activators. Complete degradation of the heavy chain of FX was only visible after 24 h, while degradation by RVV was complete after 30 min, supporting postulations that the procoagulant function of CP may be of secondary importance to its role in cancer progression. Of the ECM proteins tested, only fibronectin was cleaved. The substrate specificity of CP was further investigated by screening synthetic peptide substrates using a novel direct CP assay. The results indicate that CP is not essential for either cancer-associated blood coagulation or the degradation of ECM proteins. Rather, they suggest that this protease may be required for the proteolytic activation of membrane receptors.

Arsenic trioxide downregulates cancer procoagulant activity in MCF-7 and WM-115 cell lines in vitro

THE AIM OF THE STUDY

To analyze human breast cancer cell line MCF-7 and human malignant melanoma cell line WM-115 in order to characterize the cellular expression of CP and to evaluate whether ATO may affect this activity, as well as the viability of the cells.

MATERIAL AND METHODS

The inhibitory effect of arsenic trioxide on the proliferation of MCF-7 and WM-115 cells were measured with MTT test. The activity of cancer procoagulant after ATO exposure was determined by a specific three-stage chromogenic assay.

RESULTS

ATO decreased the CP activity in a dose- and time-dependent manner in MCF-7 cells with no effect on cell proliferation at the same time. However, it affected the CP activity of WM-115 cells in a different way. Reduction in CP activity was followed by an increase after 48 h incubation. The cells viability results showed dose-and time-correlated response within high arsenic concentrations.

CONCLUSIONS

Arsenic trioxide downregulates the CP expression in human breast cancer and melanoma cells.

Direct analysis reveals an absence of gamma-carboxyglutamic acid in cancer procoagulant from human tissues

Additional carboxylation of glutamic acid by vitamin K-dependent gamma-carboxylase is a common posttranslational modification of many proteins, including some of blood clotting factors. Vitamin K-antagonists, such as warfarin, are often included in the therapy of malignant disease, decreasing the blood coagulation potential. Cancer procoagulant, a direct blood coagulation factor X activator from malignant tissue, is considered as a vitamin K-dependent protein, so it could serve as one of possible targets for the therapy with warfarin. However, there is still no experimental data demonstrating directly the presence of gamma-carboxyglutamic acid (Gla) in a cancer procoagulant molecule. The presence of Gla in cancer procoagulant isolated from human amnion-chorion membranes and from human malignant melanoma WM 115 cell line was analyzed directly, using specific anti-Gla monoclonal antibodies. There was no detectable amount of Gla in cancer procoagulant isolated from fetal or malignant tissue. Cancer procoagulant from human tissues does not contain Gla-rich domain. The finding indicates that cancer procoagulant is rather a poor target for warfarin therapy of malignant disease.

A newly developed oral heparin derivative for deep vein thrombosis: Non-human primate study

The development of orally active heparin will have tremendous clinical importance since it can be used to effectively prevent deep vein thrombosis (DVT) in a long-term chronic treatment. We developed in this study a new orally active heparin derivative (Db-LHD), which has heparin chemically conjugated with deoxycholic acid and DMSO molecules by secondary interactions. Db-LHD was prepared in the powder form in soft capsules. When we administered Db-LHD capsules to monkeys, its oral physiological availability was increased up to 16.6%. The maximum anti-FXa activity at 5 mg/kg of Db-LHD was more than twice the minimum effective anti-FXa activity (MEC, 0.1 IU/mL) for preventing DVT, and the anti-FXa activity in plasma was maintained for 10 h above the MEC in monkeys. Also, we evaluated anti-thrombogenic effect of Db-LHD in a rat thrombosis model. A subcutaneous administration of enoxaparin (100 IU/kg), which was the highest recommended dose for the prevention of venous thromboembolism, reduced thrombus formation by 38.9+/-14.2%. On the other hand, 5 mg/kg (425 IU/kg) of orally administered Db-LHD reduced thrombus formation by 51.0+/-2.0. We propose a new orally active heparin, Db-LHD, in a solid dosage form to effectively prevent DVT and PE.

On the molecular mechanisms for the highly procoagulant pattern of C6 glioma cells

BACKGROUND

That there is a correlation between cancer and procoagulant states is well-known. C6 glioma cell line was originally induced in random-bred Wistar-Furth rats and is morphologically similar to glioblastoma multiforme, the most common aggressive glioma resistant to therapeutic interventions.

OBJECTIVES

In this study we analyzed the molecular mechanisms responsible for the highly procoagulant properties of C6 glioma cells.

METHODS

The presence of tissue factor (TF) and phosphatidylserine (PS) in C6 cells was investigated by flow-cytometric and functional analyses. The assembly of extrinsic tenase, intrinsic tenase and prothrombinase complexes on these cells was studied using enzymatic assays employing plasma or purified proteins.

RESULTS

TF was identified by flow-cytometric and functional [factor (F) Xa formation in the presence of cells and FVIIa] assays. Alternatively, conversion of FX into FXa was also observed in the presence of C6 cells, FIXa and FVIIIa. This effect was both cell- and FVIIIa-dependent, being consistent with formation of the intrinsic tenase complex. C6 cells were also able to activate prothrombin in the presence of FXa and FVa, thus supporting formation of the prothrombinase complex. This ability was similar to positive controls performed with PS-containing vesicles. Accordingly, exposure of PS on C6 cells was demonstrated by flow cytometry employing specific anti-PS antibodies. In addition, annexin V, which blocks PS binding sites, inhibited FX and prothrombin conversion by their respective C6-assembled activating complexes.

CONCLUSION

C6 glioma cells support all procoagulant reactions leading to robust thrombin formation. This ability results from concomitant TF exposure and from the presence of the anionic lipid PS at the outer leaflet of cell membrane. Therefore, this animal cell line may be used to explore new aspects concerning the role of blood coagulation proteins in tumor biology, especially those affecting the central nervous system.

Effect of cancer procoagulant (CP) on the growth and adhesion of MCF-7 cells to vitronectin in vitro

Cancer procoagulant (CP) is a cysteine protease produced by fetal and malignant tissues, activating in vitro blood coagulation factor X. It has been demonstrated that CP is able to stimulate blood platelet adhesion to fibrinogen and collagen. The pro-adhesive properties of CP could play an important role in metastatic spread of cancer as well as in primary tumor growth. Effects of anti-CP antibody on the growth of MCF-7 breast cancer cells and on the cells adhesion to vitronectin have been analyzed in vitro. Addition of polyclonal anti-CP antibody to MCF-7 cell culture resulted in 16-18% (P < 0.001) decrease in the cells viability as compared with the control (other antibody or no antibody in the culture). Preincubation of MCF-7 cells with anti-CP antibody reduced the cells adhesion to vitronectin. Further addition of purified CP (0.5-8 microg/ml) to the MCF-7 cells preincubated with anti-CP antibody resulted in complete recovery of adhesive properties of the cells. However, when high concentration (16 microg/ml) of CP was added to the sample, only partial recovery of the adhesive properties by the cells was observed. Results of the experiments support the hypothesis that CP is involved in the growth of cancer cells, but its pro-coagulative properties are of secondary importance. One of the possible mechanisms of the interactions between CP and malignant cell could be the regulation of the cell adhesion processes.

Characterization of the cell-surface procoagulant activity of T-lymphoblastoid cell lines

The procoagulant activity (PCA) of four T-lymphoblastoid cell lines (CEM-CCRF, Jurkat, Molt-4 and A3.01) at different stages of differentiation has been characterized and compared with that of a monocytoid cell line (THP-1). Four assay systems were employed; the activated partial thromboplastin time (APTT); prothrombin time/tissue factor (TF) activity; a purified factor (F)Xa generation system and cancer procoagulant. High levels of TF activity were seen only with the monocytic cells. However the more differentiated of the T-lymphoblastoid cells (Molt-4 and A3.01) were more active than monocytic cells in supporting FXa generation. This pattern was not repeated for the APTT assay, which was related to cell-surface TF activity, since it was partially inhibited by antiTF antibody. Annexin V totally inhibited the activity observed in all three assay systems, indicating that the PCA of T-lymphoblastoid cells is primarily due to expression of negatively charged phospholipids. However, antiphosphatidylserine antibody even at a high concentration gave only partial inhibition of the activity observed in the APTT and FXa generation systems for the cells compared with almost total inhibition for the phospholipid standard, suggesting either that cellular phosphatidylserine (PS) is less accessible to the antibody, or that PS is not the sole negatively charged phospholipid responsible for this activity. Flow cytometry studies using propidium iodide and annexin V showed that the PCA, although linked to PS exposure, was not the result of apoptosis.

The hypercoagulable state of malignancy: pathogenesis and current debate

A hypercoagulable or prothrombotic state of malignancy occurs due to the ability of tumor cells to activate the coagulation system. It has been estimated that hypercoagulation accounts for a significant percentage of mortality and morbidity in cancer patients. Prothrombotic factors in cancer include the ability of tumor cells to produce and secrete procoagulant/fibrinolytic substances and inflammatory cytokines, and the physical interaction between tumor cell and blood (monocytes, platelets, neutrophils) or vascular cells. Other mechanisms of thrombus promotion in malignancy include nonspecific factors such as the generation of acute phase reactants and necrosis (i.e., inflammation), abnormal protein metabolism (i.e., paraproteinemia), and hemodynamic compromise (i.e., stasis). In addition, anticancer therapy (i.e., surgery/chemotherapy/hormone therapy) may significantly increase the risk of thromboembolic events by similar mechanisms, e.g., procoagulant release, endothelial damage, or stimulation of tissue factor production by host cells. However, not all of the mechanisms for the production of a hypercoagulable state of cancer are entirely understood. In this review, we attempt to describe what is currently accepted about the pathophysiology of the hypercoagulable state of cancer. We also discuss whether or not to screen patients with idiopathic deep venous thrombosis for an underlying malignancy, and whether this would be beneficial to patients. It is hoped that a better understanding of these mechanisms will ultimately lead to the development of more targeted treatment to prevent thromboembolic complications in cancer patients. It is also hoped that antithrombotic strategies may also have a positive effect on the process of tumor growth and dissemination.

Cancer procoagulant and blood platelet activation

The effects of cancer procoagulant (CP), cysteine protease (EC 3.4.22.26), on the pig blood platelet secretory process and platelet aggregation have been studied. The response of platelets to CP was compared with the response of these cells to thrombin. The obtained results show that blood platelets treated with CP (0.5, 1, 2.5, and 5 microg/ml, 2-30 min, 37 degrees C) released adenine nucleotides (P < 0.05) and proteins (P < 0.05). The secretion of compounds from blood platelets after incubation with CP does not correlate with the release of platelet lactic dehydrogenase activity (marker of cell lysis) into the extracellular medium. In comparison with thrombin action, CP stimulates secretory process to a smaller extent than thrombin alone. In the presence of CP, the thrombin action is suppressed (P < 0.05). We noticed that CP does not induce platelet aggregation.

Molecular basis for the relationship between thrombosis and cancer

Cancer patients are highly susceptible to thromboembolic complications, which some have estimated accounts for a significant percentage of the morbidity and mortality of the disease. Not all of the mechanisms for the production of the hypercoagulable state characteristic of cancer are entirely understood. Those that are known seem to interdigitate the biology of cancer with the major regulatory pathways that mediate blood coagulation, platelet-vessel wall interaction, fibrinolysis and inflammatory cytokine production. In other words, the events responsible for thrombosis in cancer appears to be a result of an over exuberant host response in an attempt to delimit tumor growth. In this brief review, therefore, we attempt to put into the context of tumor growth, angiogenesis and metastasis the current information about the pathogenesis of venous thromboembolism (VTE).

Pathogenesis of Thrombosis in Patients with Malignancy

Cancer cells can contribute to activation of the clotting system by their capacity to produce and release procoagulant/fibrinolytic substances and inflammatory cytokines, and by their interaction with host cells (endothelial, monocytes, platelets, and neutrophils). Moreover, anticancer drugs (chemotherapy/hormone therapy) may greatly affect the risk of thromboembolic complications in cancer patients by similar mechanisms, eg, through the release of procoagulants by tumor cells, through endothelial damage, or stimulation of tissue factor production by host cells. The interactions between cancer/metastatic processes and thrombosis have been reviewed here from the pathogenetic viewpoint. We hope that better knowledge of these pathogenetic pathways will lead to the development of more targeted strategies to prevent thromboembolism in cancer patients.

Activation of blood coagulation and the activity of cancer procoagulant (EC 3.4.22.26) in breast cancer patients

The activity of cancer procoagulant (CP), prothrombin time (PT), activated partial thromboplastin time (APTT), the concentration of thrombin-antithrombin complexes (TAT) and the concentration of fibrinogen were analysed in blood of breast cancer patients scheduled for surgery. The serum level of CP activity was dependent on the stage of the disease. The CP activity was increased in 72% of patients with an early stage of cancer and in only 20% of patients with an advanced stage of the disease when compared to the baseline level for non-cancer controls. In all patients PT remained at normal levels (80-120%). There was no significant change in APTT (27-39 s) in early stage cancer patients. Only one patient with advanced cancer had APTT shortened to 23 s. Also one advanced stage patient had significantly elevated level of TAT (14.96 microg/l); in all other patients the concentration of TAT remained at normal levels (1-4.1 microg/l). Forty-four percent of early stage cancer patients and 22% of advanced cancer patients had an elevated level of fibrinogen (Fg) ( > 350 mg%). However, there was no correlation between the level of Fg and the CP activity (P > 0.05). The data suggest that: (1) serum CP activity increases at the early stage of breast cancer and decreases down to the normal level in the advanced stage of the disease; (2) there is no evidence of blood clotting activation in the early stage breast cancer patients; and (3) CP does not facilitate the activation of coagulation in the breast cancer patients or the level of such activation is below the sensitivity of assays used in the experiment.

Cancer Procoagulant and Tissue Factor Are Differently Modulated by All-trans-Retinoic Acid in Acute Promyelocytic Leukemia Cells

All-trans-retinoic acid (ATRA) downregulates the expression of two cellular procoagulants, tissue factor (TF) and cancer procoagulant (CP), in human promyelocytic leukemia cells. To evaluate whether or not changes of the procoagulant activities (PCAs) may share mechanisms with the ATRA-induced cyto-differentiation process, we have characterized the effect of ATRA on the TF and CP expression by NB4 cells, an ATRA maturation-inducible cell line, and two NB4-derived cell lines resistant to ATRA-induced maturation, the NB4.306 and NB4.007/6 cells. Next, we evaluated the effect on the PCAs of the NB4 parental cells of three synthetic retinoid analogues, ie: AM580 (selective for the retinoic acid receptor [RAR] α), capable to induce the granulocytic differentiation of NB4 cells; and CD2019 (selective for RARβ) and CD437 (selective for RARγ), both lacking this capability. Cells were treated with either ATRA or the analogues (10−6 to 10−8 mol/L) for 96 hours. The effect on cell differentiation was evaluated by morphologic changes, cell proliferation, nitro blue tetrazolium reduction assay, and flow cytometry analysis of the CD33 and CD11b surface-antigen expression. PCA was first measured in 20 mmol/L Veronal Buffer cell extracts by the one-stage clotting assay of normal and FVII-deficient plasmas. Further TF and CP have been characterized and quantified in cell-sample preparations by chromogenic and immunological assays. In the first series of experiments, ATRA downregulates both TF and CP in NB4 parental cells, as expected. However, in the differentiation-resistant cell lines, it induced a significant loss of TF but had little or no effect on CP. In a second series of experiments, in the NB4 parental cells, the RARα agonist (AM580) induced cell maturation and reduced 91% CP expression, whereas CD437 and CD2019 had no cyto-differentiating effects and did not affect CP levels. On the other hand, in the same cells the TF expression was reduced by ATRA and AM580, but also by the RARβ agonist CD2019, which did not induce cell maturation. These data indicate that in NB4 cells, ATRA modulation of CP occurs in parallel with signs of cell differentiation, while the regulation of TF appears to be at least in part independent from these processes, and involves both α and β nuclear retinoid receptors.

Application of cancer procoagulant as an early detection tumor marker

BACKGROUND

In spite of many advances in the analytical reagents (antibodies), analytical systems, and the clinical application of tumor markers, the present markers do not detect early stage cancer. Preliminary data with an antigen specific to tumor tissue, cancer procoagulant (CP), suggest its possible role in the detection of early stage cancer. This study was aimed at determining the clinical use of CP as an early stage tumor marker.

METHODS

An improved enzyme-linked immunosorbent assay (ELISA) was developed to measure CP concentration in serum. A panel of 817 blinded serum samples were examined from three groups of people: 573 cancer, 106 benign, and 139 normal.

RESULTS

The sensitivity of all samples analyzed from cancer patients was 80%. The CP ELISA was able to detect ovarian, colon, and kidney cancer at a sensitivity greater than 85%; breast, prostate and small cell lung cancer was detected at a sensitivity of 80-85%. Particularly interesting was the observation that early stage cancers, regardless of site, were detected effectively. In some groups, the CP assay correctly identified 100% of the patients with stage I and II cancer. The assay was able to identify correctly noncancer patient sera at a specificity of 83% for those with benign disease and 82% for the normal individuals.

CONCLUSIONS

The CP assay has potential as an aid in diagnosing early stage malignancies and thereby may significantly improve the survival rate of cancer patients.

Cancer procoagulant

Cancer procoagulant is a unique cysteine proteinase. The enzyme has been purified by several procedures and many of its characteristics and enzymatic properties have been determined. Several sensitive and reproducible assays are now available. Many proteinase inhibitors have been evaluated for their effect on CP; most low molecular weight inhibitors work well in a reduced environment. In the foreseeable future, protein and gene sequence information, expression vectors, molecular probes, and highly specific antibodies and inhibitors should provide the research tools to delineate a functional understanding of CP at the molecular and cellular level.