Analysis of serum cancer procoagulant activity and its possible use as a tumor marker

Thromboembolism in Cancer Patients: Pathogenesis and Treatment

In this review we summarize the causes of cancer related thrombosis as well as modern treatment approaches. Malignancy as a risk factor for thromboembolism is becoming increasingly recognized by clinicians caring for these patients. The probability of thrombosis occurring in an individual patient is dependent on several factors, including accompanying medical problems, the type of cancer, the clinical stage, performance status, and the treatment modalities employed. Thrombophilia with a history of thromboembolism is important as well. The overall risk of thrombosis is sevenfold that of noncancer patients. Though much has been learned about the pathogenesis of cancer-related thrombosis, we are in fact just beginning to understand the cross-talk between cancer cells and their related microenvironment, and such investigations are likely to increase our knowledge of cancer-related thrombosis mechanisms. Research in these areas may also suggest new strategies for cancer prevention, metastasis suppression, and new treatments. Drugs used in cancer therapy are increasingly recognized to directly contribute to the thrombotic tendency. Few studies provide data on the optimal management of cancer patients with thrombosis. It has been learned that retreating with the same drug can be very hazardous. In general the approach to prevention of thrombosis is the same as for noncancer patients, recognizing that specific cancer types and stage can place a patient in a high-risk category. Initial coumadin therapy fails in a significant number of patients with cancer. Recognition of the cancer patients at highest risk for coumadin failure is challenging. Low-molecular-weight heparins appear to be more effective in such situations where coumadin is likely to fail or has failed, but these drugs are thought to be costlier. Newer agents such as Factor Xa inhibitors and TF inhibitors are currently under investigation and may be found useful in the management of cancer-related thrombosis.

Transcripts involved in hemostasis: Exploring salivary complexes from Haementeria vizottoi leeches through transcriptomics, phylogenetic studies and structural features

Throughout evolution, parasites have adapted in order to successfully intervene in the host defense, producing specific peptides and proteins. Interestingly, these peptides and proteins have been exploited as potential drug candidates against several diseases. Furthermore, biotechnology studies and cDNA libraries have remarkably contributed to identify potentially bioactive molecules. In this regard, herein, a cDNA library of salivary complexes from Haementeria vizottoi leeches was constructed, the transcriptome was characterized and a phylogenetic analysis was performed considering antistasin-like and antiplatelet-like proteins. Hundred twenty three transcripts were identified coding for putative proteins involved in animal feeding (representing about 10% of the expression level). These sequences showed similarities with myohemerythrins, carbonic anhydrases, anticoagulants, antimicrobials, proteases and protease inhibitors. The phylogenetic analysis, regarding antistasin-like and antiplatetlet-like proteins, revealed two main clades in the Rhynchobdellida leeches. As expected, the sequences from H. vizottoi have presented high similarities with those types of proteins. Thus, our findings could be helpful not only to identify new coagulation inhibitors, but also to better understand the biological composition of the salivary complexes.

The efficacy and safety of low-molecular-weight heparin use for cancer treatment: a meta-analysis

BACKGROUND

Low-molecular-weight heparin (LMWH) has an anti-tumour effect in-vitro and in animal models of malignancy; however, the evidence from clinical trials is controversial. Thus, we performed a meta-analysis from the results of randomised controlled trials (RCTs) to assess LMWH efficacy and safety in cancer patients who had no venous thromboembolism (VTE).

METHODS

We searched the MEDLINE, EMBASE and CENTRAL (The Cochrane Central Register of Controlled Trails) databases covering all papers published up until April 2012. Two reviewers (D. H. Che and J. Y. Cao) extracted the data independently. The inclusion criteria used were patients with cancer who had no VTE and were treated with LMWH. The outcomes of interest included the 1-year mortality rate, VTE, bleeding and major bleeding complications. The results were presented as a relative risk (RR), and the STATA 11.0 package was used for comprehensive quantitative analysis.

RESULTS

A total of 11 studies with 3835 cases and 3449 controls were included. The meta-analysis showed significant differences in the rates of bleeding with an RR: 1.32 [95% confidence interval (95% CI, 1.08-1.62)] and VTE with an RR: 0.53 (95% CI, 0.42-0.67) in cancer patients when LMWH was compared with placebo or no anticoagulant. There were no significant differences in the 1-year mortality rate with an RR: 0.97 (95% CI, 0.92-1.02) and major bleeding with an RR: 1.22 (95% CI, 0.87-1.71).

CONCLUSION

LMWH does not significantly reduce the 1-year mortality rate for cancer patients. Although LMWH can prevent VTE, we should consider the risk-effect ratio (in case of an increased bleeding event) when we use LMWH in the patients with cancer. Thus, further research is still needed to confirm these results.

Functional protease profiling with reporter peptides in serum specimens of colorectal cancer patients: demonstration of its routine diagnostic applicability

Background

The progression of many solid tumors is characterized by the release of tumor-associated proteases and the detection of tumor specific proteolytic activity in serum specimens is a promising diagnostic tool in oncology. Here we describe a mass spectrometry-based functional proteomic profiling approach that tracks the ex-vivo degradation of a synthetic endoprotease substrate in serum specimens of colorectal tumor patients.

Methods

A reporter peptide (RP) with the amino acid sequence WKPYDAAD was synthesized that has a known cleavage site for the cysteine-endopeptidase cancer procoagulant (EC 3.4.22.26). The RP was added to serum specimens from colorectal cancer patients (n = 30), inflammatory controls (n = 30) and healthy controls (n = 30) and incubated under strictly standardized conditions. The proteolytic fragment of the RP was quantified with liquid chromatography / mass spectrometry (LC/MS).

Results

RP-spiking showed good intra- and inter-day reproducibility with coefficients of variation (CVs) that did not exceed a value of 10%. The calibration curve for the anchor peptide was linear in the concentration range of 0.4 – 50 μmol/L. The median concentration of the RP-fragment in serum specimens from tumor patients (TU: 17.6 μmol/L, SD 9.0) was significantly higher when compared to non-malignant inflammatory controls (IC: 11.1 μmol/L, SD 6.1) and healthy controls (HC: 10.3 μmol/L, SD 3.1). Highest area under receiver operating characteristic (AUROC) values were seen for discrimination of TU versus HC (0.89) followed by TU versus IC (0.77). IC and HC could barely be separated indicated by an AUROC value of 0.57. The proteolytic activity towards the RP was conserved in serum specimens that were kept at room temperature for up to 24 hours prior to the analysis.

Conclusion

The proteolytic cleavage of reporter peptides is a surrogate marker for tumor associated proteolytic activity in serum specimens of cancer patients. A simple, robust and highly reproducible LC/MS method has been developed that allows the quantification of proteolytic fragments in serum specimens. The preanalytical impact of sample handling is minimal as the tumor-associated proteolytic activity towards the reporter peptide is stable for at least up to 24 h. Taken together, the functional protease profiling shows characteristics that are in line with routinely performed diagnostic assays. Further work will focus on the identification of additional reporter peptides for the construction of a multiplex assay to increase diagnostic accuracy of the functional protease profiling.

Functional protease profiling for diagnosis of malignant disease

Clinical proteomic profiling by mass spectrometry (MS) aims at uncovering specific alterations within mass profiles of clinical specimens that are of diagnostic value for the detection and classification of various diseases including cancer. However, despite substantial progress in the field, the clinical proteomic profiling approaches have not matured into routine diagnostic applications so far. Their limitations are mainly related to high-abundance proteins and their complex processing by a multitude of endogenous proteases thus making rigorous standardization difficult. MS is biased towards the detection of low-molecular-weight peptides. Specifically, in serum specimens, the particular fragments of proteolytically degraded proteins are amenable to MS analysis. Proteases are known to be involved in tumour progression and tumour-specific proteases are released into the blood stream presumably as a result of invasive progression and metastasis. Thus, the determination of protease activity in clinical specimens from patients with malignant disease can offer diagnostic and also therapeutic options. The identification of specific substrates for tumour proteases in complex biological samples is challenging, but proteomic screens for proteases/substrate interactions are currently experiencing impressive progress. Such proteomic screens include peptide-based libraries, differential isotope labelling in combination with MS, quantitative degradomic analysis of proteolytically generated neo-N-termini, monitoring the degradation of exogenous reporter peptides with MS, and activity-based protein profiling. In the present article, we summarize and discuss the current status of proteomic techniques to identify tumour-specific protease-substrate interactions for functional protease profiling. Thereby, we focus on the potential diagnostic use of the respective approaches.

Endoprotease Profiling with Double-Tagged Peptide Substrates: A New Diagnostic Approach in Oncology

Background: The measurement of disease-related proteolytic activity in complex biological matrices like serum is of emerging interest to improve the diagnosis of malignant diseases. We developed a mass spectrometry (MS)-based functional proteomic profiling approach that tracks degradation of artificial endoprotease substrates in serum specimens.

Methods: The synthetic reporter peptides that are cleaved by tumor-associated endopeptidases were systematically optimized with regard to flanking affinity tags, linkers, and stabilizing elements. Serum specimens were incubated with reporter peptides under standardized conditions and the peptides subsequently extracted with affinity chromatography before MS. In a pilot study an optimized reporter peptide with the cleavage motif WKPYDAADL was added to serum specimens from colorectal tumor patients (n = 50) and healthy controls (n = 50). This reporter peptide comprised a known cleavage site for the cysteine-endopeptidase “cancer procoagulant.”

Results: Serial affinity chromatography using biotin- and 6xHis tags was superior to the single affinity enrichment using only 6xHis tags. Furthermore, protease-resistant stop elements ensured signal accumulation after prolonged incubation. In contrast, signals from reporter peptides without stop elements vanished completely after prolonged incubation owing to their total degradation. Reporter-peptide spiking showed good reproducibility, and the difference in proteolytic activity between serum specimens from cancer patients and controls was highly significant (P < 0.001).

Conclusions: The introduction of a few structural key elements (affinity tags, linkers, d-amino acids) into synthetic reporter peptides increases the diagnostic sensitivity for MS-based protease profiling of serum specimens. This new approach might lead to functional MS-based protease profiling for improved disease classification.

Procoagulant factors in patients with cancer

BACKGROUND

Clotting activation and thromboembolic manifestations are common features in patients with cancer. Tumor cells can directly activate the clotting through two procoagulants: tissue factor (TF) and cancer procoagulant (CP).

AIMS

The aim was to evaluate the levels of TF and CP in patients with different tumors in order to: (1) establish an association between these markers and the tumor localization, (2) establish a correlation between the levels of procoagulants and the status of the disease, (3) evaluate if the treatment with chemotherapy induced some modifications on the levels of procoagulants, (4) evaluate the possibility of using procoagulants as predictors in the development of thrombosis.

METHODS

Sixty-one patients with different types of cancer (lung, breast, digestive and genitourinary) and 20 normal controls were included. The activity of TF and CP was studied in serum samples. Statistical analysis of the data was performed by two-tailed Fisher exact test.

RESULTS

The TF was increased in 72.5 and 0% (p < 0.01) of cancer patients and normal controls, respectively. PC was found to be increased in 88% of the cancer patients but in healthy controls it was increased in only 15% (p < 0.01). The patients with genitourinary cancer presented the highest values of both procoagulants coinciding with a major prevalence of thrombotic events. The activity CP was found in 93% of patients with stages I and II but in patients with stages II and IV disease it was found in 85% (not significant). There were no differences in the levels of both procoagulants between the patients treated with chemotherapy and those with other treatments.

CONCLUSIONS

TF and CP are elevated in patients with cancer. The highest values of both procoagulants are in the genitourinary cancer group in agreement with the greater presence of thrombosis observed in this group. Clinical follow up is important in order to determine the potential value of these procoagulants and the tendency to develop thrombosis in patients with cancer.

Cancer procoagulant in patients with adenocarcinomas

Cancer procoagulant (CP) is a cysteine proteinase that may be produced by malignant and foetal tissue. The possible role of CP in the pathogenesis of cancer-related thrombosis has been suggested recently. The purpose of the study was to evaluate coagulation prothrombotic markers and their relation to CP concentration in the blood of patients with gastrointestinal adenocarcinomas (GIAC). The study group consisted of 45 patients with confirmed diagnosis of adenocarcinoma (stomach, 18 patients; colon, 27 patients) and without evident metastatic disease. In 24 patients further observation showed metastases. The control group for CP was composed of 10 healthy subjects. Blood samples were drawn on the admission day, before any treatment. Among 45 patients with GIAC, deep venous thrombosis was observed in two (4.4%). In all patients the CP activity in the serum was found, and the mean CP activity shortened the coagulation time almost three times compared with the healthy control group. Also, the mean thrombin-antithrombin complex concentration was above the normal range. A significant elevation of the mean prothrombin fragment 1+2 plasma content in this group of patients was noticed. Despite these observations, CP remained within the normal range and did not correlate with thrombin-antithrombin complex or prothrombin fragment 1+2 plasma concentrations. A positive correlation was observed between serum CP and fibrinogen concentration, and a negative correlation between CP and free protein S plasma content (P = 0.04 and P = 0.025, respectively). A negative correlation between activated protein C resistance ratio and protein C activity in the plasma was confirmed. Protein C activity in the plasma showed a correlation with free protein S plasma content. Analysis of factors influencing the activated partial thromboplastin time revealed the presence of antiphospholipid antibodies in seven persons from the study group (in three cases of IgG and in four cases of IgM class). Our data suggest that CP is a minor risk factor for deep venous thrombosis in GIAC patients. To confirm this, however, the number of patients and controls should be larger. After 3 years of observation, the follow-up in 10 living GIAC patients showed nobody with thromboembolic disease.

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.

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.

Cancer and venous thromboembolism

Neoplastic cells can activate the clotting system directly, thereby generating thrombin, or indirectly, by stimulating mononuclear cells to synthesize and express various procoagulants. Clinical manifestations of increased thrombin generation may be accentuated by down-regulation of endothelial cell counterregulatory mechanisms, such as decreased hepatic synthesis of antithrombin III and protein C. Cancer cells and chemotherapeutic agents can injure endothelial cells, thereby intensifying hypercoagulability. In addition, normal endothelial cell function. may be disrupted by various defects in platelet function. Currently, primary prevention of venous thrombosis should be considered for cancer patients (1) during and immediately after chemotherapy, (2) when long-term indwelling central venous catheters are placed; or (3) when hospitalization for cancer is characterized by prolonged immobilization, trauma, or surgery. Secondary prevention of recurrent venous thrombosis usually necessitates anticoagulation. In some patients with cancer, the condition is resistant to warfarin, and long-term adjusted high-dose heparin is required. For patients unable to tolerate heparin or warfarin because of major bleeding problems, placement of an inferior vena caval filter should be considered. The diagnosis of venous thrombosis may help to uncover previously occult carcinoma by prompting a complete physical examination, chest roentgenography, and mammography. However, extensive cancer screening with total-body computed tomography or magnetic resonance imaging has not been shown to be cost effective for patients with venous thrombosis.

Diagnosis of cancer-associated vascular disorders

BACKGROUND

Unexplained thromboembolism may be an early indicator of the presence of a malignant tumor before signs and symptoms of the tumor itself become obvious.

METHODS

A survey of the MEDLINE data-base was conducted concerning cancer-associated vascular disorders and their role in the diagnosis of hidden cancer. The spectrum of vascular disorders heralding occult cancer and the associated laboratory abnormalities were scrutinized.

RESULTS

Deep venous thrombosis was associated with a significantly higher frequency of malignancy during the first 6 months after diagnosis. Malignancies were found using simple clinical and diagnostic methods; additional screening was not cost-efficient. Other signs associated with deep venous thrombosis that increased the probability of an occult cancer were age older than 50 years, multiple sites of venous thrombosis, associated venous and arterial thromboembolism, thromboembolism resistant to warfarin therapy, and paraneoplastic syndrome. Among vascular syndromes, only cutaneous leukocytoclastic vasculitis presenting after the age of 50 years was consistently associated with cancer. Preliminary data with an antigen specific to tumor tissue, the cancer procoagulant, suggested its possible role as a tumor marker. The sensitivity for all samples analyzed from cancer patients was 80% and the specificity was 83%.

CONCLUSIONS

Data from the literature enabled us to outline clinical clues that might distinguish patients with cancer-associated vasculopathies from those unaffected by malignancies. Preliminary data with an antigen specific to tumor tissue, the cancer procoagulant, suggested its possible role in detecting early stage cancer. However, large-scale prospective studies are not currently available to evaluate the role of these clues and laboratory assays in the diagnosis of early stage cancer.

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.

Markers of coagulation and fibrinolysis in portal blood from patients with and without gastric malignancy

BACKGROUND

The origin of coagulation and fibrinolysis abnormalities in cancer patients is unknown. The aim of this study was to measure markers of coagulation and fibrinolysis in portal and peripheral blood from patients with and without gastric malignancy.

METHODS

Blood samples were drawn from the portal vein and a peripheral vein in 39 patients undergoing elective gastric surgery, 18 for gastric malignancy and 21 for benign disorders, and analyzed for prothrombin fragment 1 + 2 (F1 + 2), thrombin-anti-thrombin III complex (TAT), fibrinogen and fibrin degradation products (FgDP, FbDP), and fibrinopeptide A (FpA).

RESULTS AND CONCLUSIONS

In portal blood, levels of F1 + 2, TAT, FpA, FgDP, and FbDP did not differ in the two groups. In peripheral blood, levels of FpA and FbDP were higher in cancer patients, but in a multiple regression model malignancy did not contribute significantly to variation in peripheral FpA or FbDP levels. In both groups FpA levels were higher in portal blood than in peripheral blood.

Factor IXi-antithrombin (IXiAT) and thrombin-antithrombin (TAT) complexes in lung cancer patients

Coagulation activation frequently occurs in cancer patients, resulting in thromboembolic complications and/or intravascular coagulation activation. The mechanisms leading to these alterations still are poorly understood. One explanation for the coagulation activation in malignant diseases is the presence of a direct factor X-activating cancer procoagulant. Coagulation activation in lung cancer patients develops at earlier stages than factor X activation; we demonstrated increased factor IXiAT complexes in addition to elevated TAT complexes. The increases of factor IXiAT complexes were not dependent upon the stage of the disease. In contrast, TAT complexes were higher in patients suffering from advanced pulmonary non-small cell carcinoma than in patients with limited disease. In conclusion, coagulation activation in pulmonary cancer patients occurs at earlier steps in the coagulation cascade than factor X activation. While this activation is not dependent upon the stage of the disease, the observation that TAT complexes showed higher elevations in patients with advanced than in those with limited pulmonary non-small cell carcinoma could be an indication of a cancer procoagulant that directly activates factor X.