Microvesicle-associated tissue factor procoagulant activity for the preoperative diagnosis of ovarian cancer

Correlation between plasma PSGL-1 and FIGO stage, tumor metastasis, and survival in epithelial ovarian cancer

Plasma circulating P-selectin glycoprotein ligand-1 (PSGL-1) levels and its clinical correlation in patients with epithelial ovarian cancer (EOC) are unknown. The study determined plasma PSGL-1 levels in EOC patients and investigated its relationship with clinicopathological factors and prognosis. Plasma PSGL-1 levels were measured using ELISA in 69 patients with EOC, 34 patients with benign ovarian cystadenoma, and 36 healthy controls. Subsequently, the relationship between PSGL-1 levels and clinicopathological characteristics of patients, as well as the prognosis of EOC patients, was examined. Additionally, the specificity and sensitivity of plasma PSGL-1 were assessed through ROC curve analysis. Plasma PSGL-1 was upregulated in EOC patients compared with healthy subjects and/or patients with benign ovarian cystadenoma (p < 0.01). Elevated levels of PSGL-1 in the plasma were positively associated with advanced FIGO stage (p < 0.001), tumor size (p = 0.001), tumor metastasis (p = 0.036), and tumor recurrence (p = 0.013), while was negatively correlated with residual tumor size (p < 0.001). Kaplan-Meier survival analysis showed that high plasma PSGL-1 levels were associated with progression-free survival (p = 0.0345). In univariate and multivariate Cox regression analyses, PSGL-1 (HR = 1.456, p = 0.009) was an independent prognostic marker. Plasma PSGL-1 levels distinguished EOC patients and healthy individuals (AUC = 0.905), patients at late and early FIGO stages (AUC = 0.886), and metastatic and non-metastatic EOC (AUC = 0.722). The expression of plasma PSGL-1 is significantly increased in patients with EOC, serving as a reliable biomarker to differentiate between healthy individuals and those with EOC. Furthermore, PSGL-1 in patients is correlated with prognostic indicators, such as advanced FIGO stage, tumor lymph node metastasis, and progression-free survival.

Discovery and validation of serum glycoprotein biomarkers for high grade serous ovarian cancer

PURPOSE

This study aimed to identify serum glycoprotein biomarkers for early detection of high-grade serous ovarian cancer (HGSOC), the most common and aggressive histotype of ovarian cancer.

EXPERIMENTAL DESIGN

The glycoproteomics pipeline lectin magnetic bead array (LeMBA)-mass spectrometry (MS) was used in age-matched case-control serum samples. Clinical samples collected at diagnosis were divided into discovery (n = 30) and validation (n = 98) sets. We also analysed a set of preclinical sera (n = 30) collected prior to HGSOC diagnosis in the UK Collaborative Trial of Ovarian Cancer Screening.

RESULTS

A 7-lectin LeMBA-MS/MS discovery screen shortlisted 59 candidate proteins and three lectins. Validation analysis using 3-lectin LeMBA-multiple reaction monitoring (MRM) confirmed elevated A1AT, AACT, CO9, HPT and ITIH3 and reduced A2MG, ALS, IBP3 and PON1 glycoforms in HGSOC. The best performing multimarker signature had 87.7% area under the receiver operating curve, 90.7% specificity and 70.4% sensitivity for distinguishing HGSOC from benign and healthy groups. In the preclinical set, CO9, ITIH3 and A2MG glycoforms were altered in samples collected 11.1 ± 5.1 months prior to HGSOC diagnosis, suggesting potential for early detection.

CONCLUSIONS AND CLINICAL RELEVANCE

Our findings provide evidence of candidate early HGSOC serum glycoprotein biomarkers, laying the foundation for further study in larger cohorts.

Detection of tissue factor-positive extracellular vesicles using the ExoView R100 system

Background

Tissue factor (TF) is essential for hemostasis. TF-expressing extracellular vesicles (TF+ EVs) are released in pathological conditions, such as trauma and cancer, and are linked to thrombosis. Detection of TF+ EV antigenically in plasma is challenging due to their low concentration but may be of clinical utility.

Objectives

We hypthesised that ExoView can allow for direct measurement of TF+ EV in plasma, antigenically.

Methods

We utilized the anti-TF monoclonal antibody 5G9 to capture TF EV onto specialized ExoView chips. This was combined with fluorescent TF+ EV detection using anti-TF monoclonal antibody IIID8-AF647. We measured tumor cell-derived (BxPC-3) TF+ EV and TF+ EVs from plasma derived from whole blood with or without lipopolysaccharide (LPS) stimulation. We used this system to analyze TF+ EVs in 2 relevant clinical cohorts: trauma and ovarian cancer. We compared ExoView results with an EV TF activity assay.

Results

BxPC-3-derived TF+ EVs were identified with ExoView using 5G9 capture with IIID8-AF647 detection. 5G9 capture with IIID8-AF647 detection was significantly higher in LPS+ samples than in LPS samples and correlated with EV TF activity (R2 = 0.28). Trauma patient samples had higher levels of EV TF activity than healthy controls, but activity did not correlate with TF measurements made by ExoView (R2 = 0.15). Samples from patients with ovarian cancer have higher levels of EV TF activity than those from healthy controls, but activity did not correlate with TF measurement by ExoView (R2 = 0.0063).

Conclusion

TF+ EV measurement is possible in plasma, but the threshold and potential clinical applicability of ExoView R100, in this context, remain to be established.

Evaluation of four commercial ELISAs to measure tissue factor in human plasma

Background

Under pathological conditions, tissue factor (TF)-positive extracellular vesicles (EVs) are released into the circulation and activate coagulation. Therefore, it is important to identify methods that accurately quantitate levels of TF in plasma. Enzyme-linked immunosorbent assays (ELISAs) are a fast and simple method to quantitate levels of proteins. However, there are several specific challenges with measuring TF antigen in plasma including its low concentration and the complexity of plasma.

Objectives

We aimed to evaluate the ability of 4 commercial ELISAs to measure TF in human plasma.

Methods

We determined the ability of 4 commercial ELISAs (Imubind, Quantikine, Human SimpleStep, and CD142 Human) to detect recombinant human TF (Innovin) (12.5-100 pg/mL), TF-positive EVs isolated from the culture supernatant from a human pancreatic cancer cell line (57 pg/mL), TF in plasma containing low levels of EV TF activity (1.2-2.6 pg/mL) from lipopolysaccharide-stimulated whole blood, and plasma containing high levels of EV TF activity (151-696 pg/mL) from patients with acute leukemia.

Results

The CD142 Human ELISA could not detect recombinant TF. Imubind and Quantikine but not Human SimpleStep detected recombinant TF spiked into plasma and TF-positive EVs isolated from the culture supernatant of a human pancreatic cancer cell line. Quantikine and Imubind could not detect low levels of TF in plasma from lipopolysaccharide-stimulated whole blood. However, Quantikine but not Imubind detected TF in plasma from acute leukemia patients with high levels of EV TF activity.

Conclusion

Our results indicate that commercial ELISAs have different abilities to detect TF. Quantikine and Imubind could not detect low levels of TF in plasma, but Quantikine detected TF in plasma with high levels of TF.

Tissue factor in cancer-associated thromboembolism: possible mechanisms and clinical applications

Venous and arterial thromboses, called as cancer-associated thromboembolism (CAT), are common complications in cancer patients that are associated with high mortality. The cell-surface glycoprotein tissue factor (TF) initiates the extrinsic blood coagulation cascade. TF is overexpressed in cancer cells and is a component of extracellular vesicles (EVs). Shedding of TF⁺EVs from cancer cells followed by association with coagulation factor VII (fVII) can trigger the blood coagulation cascade, followed by cancer-associated venous thromboembolism in some cancer types. Secretion of TF is controlled by multiple mechanisms of TF⁺EV biogenesis. The procoagulant function of TF is regulated via its conformational change. Thus, multiple steps participate in the elevation of plasma procoagulant activity. Whether cancer cell-derived TF is maximally active in the blood is unclear. Numerous mechanisms other than TF⁺EVs have been proposed as possible causes of CAT. In this review, we focused on a wide variety of regulatory and shedding mechanisms for TF, including the effect of SARS-CoV-2, to provide a broad overview for its role in CAT. Furthermore, we present the current technical issues in studying the relationship between CAT and TF.

Role of extracellular vesicles in cancer-specific interactions between tumour cells and the vasculature

Cancer progression impacts and exploits the vascular system in several highly consequential ways. Among different types of vascular cells, blood cells and mediators that are engaged in these processes, endothelial cells are at the centre of the underlying circuitry, as crucial constituents of angiogenesis, angiocrine stimulation, non-angiogenic vascular growth, interactions with the coagulation system and other responses. Tumour-vascular interactions involve soluble factors, extracellular matrix molecules, cell-cell contacts, as well as extracellular vesicles (EVs) carrying assemblies of molecular effectors. Oncogenic mutations and transforming changes in the cancer cell genome, epigenome and signalling circuitry exert important and often cancer-specific influences upon pathways of tumour-vascular interactions, including the biogenesis, content, and biological activity of EVs and responses of cancer cells to them. Notably, EVs may carry and transfer bioactive, oncogenic macromolecules (oncoproteins, RNA, DNA) between tumour and vascular cells and thereby elicit unique functional changes and forms of vascular growth and remodeling. Cancer EVs influence the state of the vasculature both locally and systemically, as exemplified by cancer-associated thrombosis. EV-mediated communication pathways represent attractive targets for therapies aiming at modulation of the tumour-vascular interface (beyond angiogenesis) and could also be exploited for diagnostic purposes in cancer.

Measurement of tissue factor-positive extracellular vesicles in plasma: strengths and weaknesses of current methods

PURPOSE OF REVIEW

This review evaluates the different methods used to measure levels of tissue factor (TF) in plasma and on extracellular vesicles (EVs). Levels of TF-positive (TF+) EVs in blood are increased in a variety of diseases, such as cancer, sepsis, and viral infection, and are associated with thrombosis. Highly sensitive assays are required to measure the low levels of TF+ EVs in blood.

RECENT FINDINGS

TF antigen levels in plasma have been measured using standard ELISAs, SimpleStep ELISA technology, and solid-phase proximity ligation assay. Some studies reported the detection of TF+ EVs in plasma by flow cytometry. In addition, TF+ EVs can be captured onto beads and chips using anti-TF antibodies. Several assays have been developed to measure TF activity in EVs isolated from plasma. Importantly, activity-based assays are more sensitive than antigen-based assays as a single TF/FVIIa complex can generate large amounts of FXa.

SUMMARY

We recommend isolating EVs from plasma and measuring TF activity using a functional assay in the presence and absence of an anti-TF antibody. We do not recommend using antigen-based assays as these are not sensitive enough to detect the low levels of TF in plasma.

Circulating tissue factor-positive extracellular vesicles and their association with thrombosis in different diseases

Tissue factor (TF) is a procoagulant protein released from activated host cells, such as monocytes, and tumor cells on extracellular vesicles (EVs). TF + EVs are observed in the circulation of patients with various types of diseases. In this review, we will summarize the association between TF + EVs and activation of coagulation and survival in different types of diseases, including cancer, sepsis, and infections with different viruses, such as human immunodeficiency virus (HIV), influenza A virus (IAV), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We will also discuss the source of TF + EVs in various diseases. EVTF activity is associated with thrombosis in pancreatic cancer patients and coronavirus disease 2019 patients (COVID-19) and with disseminated intravascular coagulation in cancer patients. EVTF activity is also associated with worse survival in patients with cancer and COVID-19. Monocytes are the major sources of TF + EVs in sepsis, and viral infections, such as HIV, Ebola virus, and SARS-CoV-2. In contrast, alveolar epithelial cells are the major source of TF + EVs in bronchoalveolar lavage fluid in COVID-19 and influenza A patients. These studies indicate that EVTF activity could be used as a biomarker to identify patients that have an increased risk of coagulopathy and mortality.

Tissue factor and its procoagulant activity on cancer-associated thromboembolism in pancreatic cancer: Comment by Mackman et al

The Quantikine® ELISA detects tissue factor in cell lysates and culture supernatants containing extracellular vesicles from tissue factor-expressing cell lines but does not detect low levels of tissue factor antigen in plasma.

Authors' reply to the Letter to the Editor: Tissue factor and its procoagulant activity on cancer-associated thromboembolism in pancreatic cancer

Tissue factor-procoagulant activity (TF-PCA) on cells is modified by multiple molecular mechanisms of encryption and decryption. The risk of thrombosis is higher for patients with a high tissue factor antigen level at registration as this enables patient's blood more PCA-high status before the onset of cancer-associated thromboembolism (CAT). ELISA, including the Quantikine assay with validation as performed in our study, can contribute to more precise prediction of CAT.

Podoplanin promotes tumor growth, platelet aggregation, and venous thrombosis in murine models of ovarian cancer

BACKGROUND

Podoplanin (PDPN) is a sialylated membrane glycoprotein that binds to C-type lectin-like receptor 2 on platelets resulting in platelet activation. PDPN is expressed on lymphatic endothelial cells, perivascular fibroblasts/pericytes, cancer cells, cancer-associated fibroblasts, and tumor stromal cells. PDPN's expression on malignant epithelial cells plays a role in metastasis. Furthermore, the expression of PDPN in brain tumors (high-grade gliomas) was found to correlate with an increased risk of venous thrombosis.

OBJECTIVE

We examined the expression of PDPN and its role in tumor progression and venous thrombosis in ovarian cancer.

METHODS

We used mouse models of ovarian cancer and venous thrombosis.

RESULTS

Ovarian cancer cells express PDPN and release PDPN-rich extracellular vesicles (EVs), and cisplatin and topotecan (chemotherapies commonly used in ovarian cancer) increase the expression of podoplanin in cancer cells. The expression of PDPN in ovarian cancer cells promotes tumor growth in a murine model of ovarian cancer and that knockdown of PDPN gene expression results in smaller primary tumors. Both PDPN-expressing ovarian cancer cells and their EVs cause platelet aggregation. In a mouse model of venous thrombosis, PDPN-expressing EVs released from HeyA8 ovarian cancer cells produce more frequent thrombosis than PDPN-negative EVs derived from PDPN-knockdown HeyA8 cells. Blood clots induced by PDPN-positive EVs contain more platelets than those in blood clots induced by PDPN-negative EVs.

CONCLUSIONS

In summary, our findings demonstrate that the expression of PDPN by ovarian cancer cells promotes tumor growth and venous thrombosis in mice.

Hemostatic Biomarkers and Cancer Prognosis: Where Do We Stand?

Cancer patients are characterized by hypercoagulable state and an increased rate of thrombotic events, the most common being venous thromboembolism. Several hemostatic pathways that are significantly implicated in mechanisms of thromboembolic disease are also involved in growth, invasion, and metastatic spread of malignant cells as well in tumor-induced neo-angiogenesis. This close connection between cancer and the hemostatic system has prompted numerous studies on the role of alterations in the level plasma biomarkers of the different compartments of hemostasis in predicting cancer prognosis. In this review, we collect the results of several exemplificative studies that have evaluated clotting activation biomarkers in relation to different cancer outcomes with a final emphasis on current research and forthcoming directions in this field.

Tissue factor and its procoagulant activity on cancer-associated thromboembolism in pancreatic cancer

Pancreatic cancer frequently involves cancer-associated thromboembolism, which is strongly associated with poor prognosis. Tissue factor, a blood coagulation factor largely produced in cancer patients as a component of extracellular vesicles, plays a key role in the incidence of cancer-associated thromboembolism in patients with pancreatic cancer. However, no prospective studies have been published on the relationship between tissue factor and cancer-associated thromboembolism or patient clinical characteristics, including recent chemotherapy regimens. Thus, we aimed to address this in a Japanese cohort of 197 patients and 41 healthy volunteers. Plasma tissue factor levels were measured by ELISAs preevaluated by tissue factor specificity. Multivariable analysis was used to identify independent predictors of cancer-associated thromboembolism. We found that the cancer-associated thromboembolism rate in the patient cohort was 6.6% (4.6%, venous thromboembolism; 2.0%, arterial thromboembolism). Tissue factor levels of 100 pg/mL or higher at patient registration were predictive of cancer-associated thromboembolism, with positive and negative predictive values of 23.1% and 94.6%, respectively. Multivariable analysis showed that plasma tissue factor levels were an independent predictive factor for cancer-associated thromboembolism, with a risk ratio of 5.54 (95% confidence interval, 1.02-30.09). Unlike in healthy volunteers and patients without cancer-associated thromboembolism, tissue factor levels were highly correlated with extracellular vesicles' procoagulant activity in patients developing cancer-associated thromboembolism. Taken together, our data show that the tissue factor levels at patient registration were a predictive factor for cancer-associated thromboembolism in this cohort of patients with pancreatic cancer.

Tissue Factor and Extracellular Vesicles: Activation of Coagulation and Impact on Survival in Cancer

Simple Summary

The tissue factor (TF)-factor VIIa complex is the major physiological initiator of blood coagulation. Tumors express TF and release TF-positive extracellular vesicles (EVs) into the circulation, and this is associated with the activation of coagulation. Circulating levels of EVTF activity may be a useful biomarker to identify patients at risk for thrombosis. Tumor TF and TF-positive EVs are also associated with reduced survival.

Abstract

Tissue factor (TF) is a transmembrane glycoprotein that functions as a receptor for FVII/FVIIa and initiates the extrinsic coagulation pathway. Tumors and cancer cells express TF that can be released in the form of TF positive (TF+) extracellular vesicles (EVs). In this review, we summarize the studies of tumor TF and TF + EVs, and their association with activation of coagulation and survival in cancer patients. We also summarize the role of tumor-derived TF + EVs in venous thrombosis in mouse models. Levels of tumor TF and TF + EVs are associated with venous thromboembolism in pancreatic cancer patients. In addition, levels of EVTF activity are associated with disseminated intravascular coagulation in cancer patients. Furthermore, tumor-derived TF + EVs enhance venous thrombosis in mice. Tumor TF and TF + EVs are also associated with worse survival in cancer patients, particularly in pancreatic cancer patients. These studies indicate that EVTF activity could be used as a biomarker to identify pancreatic cancer patients at risk for venous thrombosis and cancer patients at risk for disseminated intravascular coagulation. EVTF activity may also be a useful prognostic biomarker in cancer patients.

Prognostic value of circulating markers of neutrophil activation, neutrophil extracellular traps, coagulation and fibrinolysis in patients with terminal cancer

Predicting survival accurately in patients with advanced cancer is important in guiding interventions and planning future care. Objective tools are therefore needed. Blood biomarkers are appealing due to their rapid measurement and objective nature. Thrombosis is a common complication in cancer. Recent data indicate that tumor-induced neutrophil extracellular traps (NETs) are pro-thrombotic. We therefore performed a comprehensive investigation of circulating markers of neutrophil activation, NET formation, coagulation and fibrinolysis in 106 patients with terminal cancer. We found that neutrophil activation and NET markers were prognostic in terminal cancer patients. Interestingly, markers of coagulation and fibrinolysis did not have a prognostic value in this patient group, and there were weak or no correlations between these markers and markers of neutrophil activation and NETs. This suggest that NETs are linked to a poor prognosis through pathways independent of coagulation. Additional studies are needed to determine the utility of circulating neutrophil activation and NET markers, alone or in concert with established clinical parameters, as objective and reliable prognostic tools in advanced cancer.

Novel Aspects of Extracellular Vesicles as Mediators of Cancer-Associated Thrombosis

The establishment of prothrombotic states during cancer progression is well reported but the precise mechanisms underlying this process remain elusive. A number of studies have implicated the presence of the clotting initiator protein, tissue factor (TF), in circulating tumor-derived extracellular vesicles (EVs) with thrombotic manifestations in certain cancer types. Tumor cells, as well as tumor-derived EVs, may activate and promote platelet aggregation by TF-dependent and independent pathways. Cancer cells and their secreted EVs may also facilitate the formation of neutrophil extracellular traps (NETs), which may contribute to thrombus development. Alternatively, the presence of polyphosphate (polyP) in tumor-derived EVs may promote thrombosis through a TF-independent route. We conclude that the contribution of EVs to cancer coagulopathy is quite complex, in which one or more mechanisms may take place in a certain cancer type. In this context, strategies that could attenuate the crosstalk between the proposed pro-hemostatic routes could potentially reduce cancer-associated thrombosis.

Detecting ovarian cancer using extracellular vesicles: progress and possibilities

Ovarian cancer (OC) is the deadliest gynecological malignancy. Most patients are diagnosed when they are already in the later stages of the disease. Earlier detection of OC dramatically improves the overall survival, but this is rarely achieved as there is a lack of clinically implemented biomarkers of early disease. Extracellular vesicles (EVs) are small cell-derived vesicles that have been extensively studied in recent years. They contribute to various aspects of cancer pathology, including tumor growth, angiogenesis and metastasis. EVs are released from all cell types and the macromolecular cargo they carry reflects the content of the cells from which they were derived. Cancer cells release EVs with altered cargo into biofluids, and so, they represent an excellent potential source of novel biomarkers for the disease. In this review, we describe the latest developments in EVs as potential biomarkers for earlier detection of OC. The field is still relatively young, but many studies have shown that EVs and the cargo they carry, including miRNAs and proteins, can be used to detect OC. They could also give insights into the stage of the disease and predict the likely therapeutic outcome. There remain many challenges to the use of EVs as biomarkers, but, through ongoing research and innovation in this exciting field, there is great potential for the development of diagnostic assays in the clinic that could improve patient outcome.

Measurement of tissue factor activity in extracellular vesicles from human plasma samples

Tissue factor (TF) is the cellular receptor for plasma factor (F) VII/FVIIa and triggers blood coagulation. Extracellular vesicles (EVs) are small membrane vesicles that are released from activated cells and tumor cells. Different cell types, including activated monocytes and tumors cells release TF-positive EVs into the circulation. We developed an assay to measure levels of TF activity in EVs isolated from human plasma samples. We and others have used this assay to demonstrate increased levels of EV TF activity in a variety of diseases associated with thrombosis, including cancer. These studies suggest that EV TF can be used as a biomarker of thrombotic risk. The strength of this laboratory assay is that it is relatively sensitive and specific. However, the limitations of the assay are that it is labor intensive and the coefficient of variation is too high for it to be used as a clinical assay.

Hemostatic biomarkers in cancer progression

Malignant disease is characterized by a hemostatic imbalance, usually shifted towards a procoagulant direction, and a high incidence of thrombotic complications. The mechanisms of hemostasis that are critically involved in thrombosis are also implicated in tumor progression, angiogenesis, and metastatic spread. As there is a close relationship between cancer and the clotting system, circulating biomarkers of activation of various hemostasis compartments (i.e. coagulation, fibrinolysis, platelets, endothelium, and other blood cells) have been extensively studied to predict cancer outcomes along with predicting the thrombotic risk. In this review, we will summarize the results of published studies and will focus on ongoing research and future directions of clotting activation bioproducts as biomarkers of cancer disease and progression.

Expression of tissue factor in human cervical carcinoma tissue

The present study aimed to investigate tissue factor (TF) expression in cervical cancer and explore its association with disease progression. A total of 258 cervical cancer tissues and their adjacent normal tissues were collected between September 2014 and September 2016. TF expression was detected in the tissue samples by immunohistochemistry and western blot analysis. Associations between the expression of TF and clinical stage, differentiation status and metastasis of cancer cells were examined. The mean immunohistochemistry score of TF expression in cervical cancer tissues was 2.86±1.76, which was significantly increased compared with the adjacent normal tissues (0.28±0.45). The expression of TF was also significantly associated with the clinical stage, lymph node metastasis and distant metastasis of cancer cells. Immunohistochemistry staining and western blot analysis demonstrated that TF expression in cervical cancer tissues significantly increased as the clinical stage increased. TF expression in tumor tissues from patients with lymph node metastasis was significantly increased compared with samples from patients without lymph node metastasis. TF expression was also significantly increased in patients with distant metastasis compared with those without. In conclusion, TF is highly expressed in cervical cancer tissues and high expression of TF may enhance the invasion and metastasis of cervical cancer cells.

Extracellular vesicles exposing tissue factor for the prediction of venous thromboembolism in patients with cancer: A prospective cohort study

INTRODUCTION

The procoagulant activity of extracellular vesicles (EV) exposing tissue factor (TF) is a promising biomarker for venous thromboembolism (VTE) in cancer patients. We evaluated an in-house EV-TF activity assay (the fibrin generation test) for the prediction of cancer-associated VTE. We also compared the results with the fibrin generation tests to an EV-TF-dependent factor Xa generation assay in samples from pancreatic cancer patients.

MATERIALS AND METHODS

Data collected in a multinational, prospective cohort study were used. Patients with various types of advanced cancer were enrolled if chemotherapy was scheduled or started in the previous 3 months. Patients were followed for 6 months for the occurrence of VTE. The fibrin generation test was performed at baseline to measure EV-TF procoagulant activity.

RESULTS

The fibrin generation test was performed in 648 patients with advanced cancer. The mean age was 62 years; 58% had distant metastasis. Forty patients (6.1%) developed VTE. Overall, a high fibrin generation test result was associated with a two-fold increased risk for VTE (HR 2.0; 95%-CI, 1.1-3.6). The association was stronger in patients with pancreatic cancer (HR 4.1; 95%-CI, 0.91-19) than in those with other tumor types (HR 1.5; 95%-CI, 0.72-3.1). Correlation between the FGT and the TF-dependent factor Xa generation assay in patients with pancreatic cancer was poor (Spearman's R = 0.35).

CONCLUSION

This study shows that a high EV-TF procoagulant activity as measured by the fibrin generation test is associated with an increased risk of VTE in cancer patients, in particular in those with pancreatic cancer. Future studies should aim to further improve the feasibility and accuracy of EV-TF activity assays.

Tumor-derived exosomes in ovarian cancer - liquid biopsies for early detection and real-time monitoring of cancer progression

Ovarian cancer usually has a poor prognosis because it predominantly presents as high stage disease. New approaches are required to develop more effective early detection strategies and real-time treatment response monitoring. Nano-sized extracellular vesicles (EVs, including exosomes) may provide an approach to enrich tumor biomarker detection and address this clinical need. Exosomes are membranous extracellular vesicles of approximately 100 nm in diameter that have potential to be used as biomarkers and therapeutic delivery tools for ovarian cancer. Exosomal content (proteins and miRNA) is often parent cell specific thus providing an insight or "fingerprint" of the intracellular environment. Furthermore, exosomes can aid cell-cell communication and have the ability to modify target cells by transferring their content. Additionally, via the capacity to evade the immune system and remain stable over long periods in circulation, exosomes have potential as natural drug agents. This review examines the potential role of exosomes in diagnosis, drug delivery and real-time monitoring in ovarian cancer.

Clinical significance of plasma D-dimer in ovarian cancer: A meta-analysis

BACKGROUND

D-dimer has been widely used for the diagnosis and prognosis of ovarian cancer, but there is still controversy on its prediction value of ovarian cancer.

OBJECTIVES

To explore the clinical significance of plasma D-dimer level on ovarian cancer systematically.

METHODS

Using PubMed, Cochrane Library, and Web of Science libraries, all the relevant studies for the diagnostic and prognostic value of plasma D-dimer for ovarian cancer and the relationship between elevated D-dimer level and venous thromboembolism (VTE) risk of ovarian cancer were searched till May 30, 2016. Standardized mean difference (SMD), odds ratio (OR), hazard ratio (HR), and 95% confidence interval (CI) were appropriately pooled.

RESULTS

A total of 15 eligible studies involving a total of 1437 cancer patients were included. No significant association was found between high D-dimer level and overall survival of patients with ovarian cancer (HR 1.32, 95% CI: 0.90-1.95, P  =  .044). However, subgroup analysis indicated that the sample sizes could explain the heterogeneity between studies. And elevated D-dimer could predict increased risk of mortality when the sample sizes were >100 (HR 1.800, 95% CI: 1.283-2.523, P  =  .845). Besides, plasma D-dimer level was significantly higher in malignant ovarian cancer patients compared with benign controls (SMD 0.774, 95% CI: 0.597-0.951, P  =  .39), higher in advanced ovarian cancer patients (International Federation of Gynecology and Obstetrics [FIGO] classification III and IV) than in early stage ovarian cancer patients (FIGO classification I and II, SMD 0.611, 95% CI: 0.373-0.849, P  =  .442). And high D-dimer level indicated high VTE risk (OR 4.068, 95% CI: 2.423-6.829, P  =  .629) of ovarian cancer patients.

CONCLUSION

The plasma D-dimer level in ovarian cancer patients can predict the changes that correlated with disease progression and the VTE risk. But its predictive value for the prognosis of ovarian cancer was significantly dependent on the sample sizes. More well-designed studies with large sample sizes are needed to validate and update the findings of present study.

Evaluation of venous thrombosis and tissue factor in epithelial ovarian cancer

OBJECTIVE

Ovarian clear cell carcinoma (OCCC) and high grade serous ovarian cancer (HGSOC) are associated with the highest risk of VTE among patients with epithelial ovarian cancer (EOC). Tissue factor (TF) is a transmembrane glycoprotein which can trigger thrombosis. We sought to evaluate if there is an association between VTE and tumor expression of tissue factor (TF), plasma TF, and microvesicle TF (MV TF) activity in this high-risk population.

METHODS

We performed a case-control study of OCCC and HGSOC patients with and without VTE. 105 patients who underwent surgery at a tertiary care center between January 1995 and October 2013 were included. Plasma TF was measured with an enzyme-linked immunosorbent assay. A TF-dependent Factor Xa generation assay was used to measure MV TF activity. Immunohistochemical (IHC) analysis was performed to evaluate tumor expression of TF.

RESULTS

35 women with OCCC or HGSOC diagnosed with VTE within 9months of surgery were included in the case group. Those with VTE had a worse OS, p<0.0001, with a greater than three-fold increase in risk of death, HR 3.33 (CI 1.75-6.35). There was no significant difference in median plasma TF level or MV TF activity level between patients with and without VTE. OCCC patients had greater expression of TF in their tumors than patients with HGSOC, p<0.0001.

CONCLUSIONS

TFMV activity and plasma TF level were not predictive of VTE in this patient population. Given the extensive expression of TF in OCCC tumors, it is unlikely IHC expression will be useful in risk stratification for VTE in this population.

Potential Coagulation Factor-Driven Pro-Inflammatory Responses in Ovarian Cancer Tissues Associated with Insufficient O₂ and Plasma Supply

Tissue factor (TF) is a cell surface receptor for coagulation factor VII (fVII). The TF-activated fVII (fVIIa) complex is an essential initiator of the extrinsic blood coagulation process. Interactions between cancer cells and immune cells via coagulation factors and adhesion molecules can promote progression of cancer, including epithelial ovarian cancer (EOC). This process is not necessarily advantageous, as tumor tissues generally undergo hypoxia due to aberrant vasculature, followed by reduced access to plasma components such as coagulation factors. However, hypoxia can activate TF expression. Expression of fVII, intercellular adhesion molecule-1 (ICAM-1), and multiple pro-inflammatory cytokines can be synergistically induced in EOC cells in response to hypoxia along with serum deprivation. Thus, pro-inflammatory responses associated with the TF-fVIIa-ICAM-1 interaction are expected within hypoxic tissues. Tumor tissue consists of multiple components such as stromal cells, interstitial fluid, albumin, and other micro-factors such as proton and metal ions. These factors, together with metabolism reprogramming in response to hypoxia and followed by functional modification of TF, may contribute to coagulation factor-driven inflammatory responses in EOC tissues. The aim of this review was to describe potential coagulation factor-driven inflammatory responses in hypoxic EOC tissues. Arguments were extended to clinical issues targeting this characteristic tumor environment.

Reciprocal links between venous thromboembolism, coagulation factors and ovarian cancer progression

Ovarian cancer is the most lethal gynecological malignancy, which is due to late presentation. Treating advanced stage ovarian cancer is difficult, and tumor recurrence and chemoresistance frequently occur. In addition, early detection remains a major challenge as there are no early warning signs and no appropriate biomarkers. To reduce mortality rates of ovarian cancer patients, novel drug targets and biomarkers are needed. We postulate that hemostatic keyplayers are of importance when combatting ovarian cancer. The majority of ovarian cancer patients have abnormal hemostatic blood serum marker levels, which indicate an activated coagulation system. This makes patients more prone to experiencing venous thromboembolism (VTE), and the occurrence of VTE in ovarian cancer patients adversely affects survival. Coagulation activation also promotes tumor progression as it influences tumor biology at several stages and the decreased survival rates associated with ovarian cancer-associated thrombosis are more likely due to cancer metastasis rather than to fatal thromboembolic events. In this review, we will discuss; (1) Population studies that address the bidirectional relationship between VTE and ovarian cancer, and the most important risk factors involved; (2) The mechanisms of coagulation factors and platelets that are critically involved in the development of VTE, and the progression of ovarian cancer; (3) Roles and future directions of coagulation factors in ovarian cancer therapy, and in diagnosis and prognosis of ovarian cancer as biomarkers.