Predictive value of tissue factor bearing microparticles in cancer associated thrombosis

Targeting thiol isomerase activity with zafirlukast to treat ovarian cancer from the bench to clinic

Thiol isomerases, including PDI, ERp57, ERp5, and ERp72, play important and distinct roles in cancer progression, cancer cell signaling, and metastasis. We recently discovered that zafirlukast, an FDA-approved medication for asthma, is a pan-thiol isomerase inhibitor. Zafirlukast inhibited the growth of multiple cancer cell lines with an IC50 in the low micromolar range, while also inhibiting cellular thiol isomerase activity, EGFR activation, and downstream phosphorylation of Gab1. Zafirlukast also blocked the procoagulant activity of OVCAR8 cells by inhibiting tissue factor-dependent Factor Xa generation. In an ovarian cancer xenograft model, statistically significant differences in tumor size between control vs treated groups were observed by Day 18. Zafirlukast also significantly reduced the number and size of metastatic tumors found within the lungs of the mock-treated controls. When added to a chemotherapeutic regimen, zafirlukast significantly reduced growth, by 38% compared with the mice receiving only the chemotherapeutic treatment, and by 83% over untreated controls. Finally, we conducted a pilot clinical trial in women with tumor marker-only (CA-125) relapsed ovarian cancer, where the rate of rise of CA-125 was significantly reduced following treatment with zafirlukast, while no severe adverse events were reported. Thiol isomerase inhibition with zafirlukast represents a novel, well-tolerated therapeutic in the treatment of ovarian cancer.

Polyphosphate expression by cancer cell extracellular vesicles mediates binding of factor XII and contact activation

Cleaved HK is observed in many patients with cancer, suggesting activation of the contact system.

EVs from cancer cell lines or patients with cancer express polyphosphate, bind and activate FXII, and are prothrombotic.

Extracellular vesicles (EV) have been implicated in diverse biological processes, including intracellular communication, transport of nucleic acids, and regulation of vascular function. Levels of EVs are elevated in cancer, and studies suggest that EV may stimulate thrombosis in patients with cancer through expression of tissue factor. However, limited data also implicate EV in the activation of the contact pathway of coagulation through activation of factor XII (FXII) to FXIIa. To better define the ability of EV to initiate contact activation, we compared the ability of EV derived from different cancer cell lines to activate FXII. EV from all cell lines activated FXII, with those derived from pancreatic and lung cancer cell lines demonstrating the most potent activity. Concordant with the activation of FXII, EV induced the cleavage of high molecular weight kininogen (HK) to cleaved kininogen. We also observed that EVs from patients with cancer stimulated FXII activation and HK cleavage. To define the mechanisms of FXII activation by EV, EV were treated with calf intestinal alkaline phosphatase or Escherichia coli exopolyphosphatase to degrade polyphosphate; this treatment blocked binding of FXII to EVs and the ability of EV to mediate FXII activation. In vivo, EV induced pulmonary thrombosis in wild-type mice, with protection conferred by a deficiency in FXII, HK, or prekallikrein. Moreover, pretreatment of EVs with calf intestinal alkaline phosphatase inhibited their prothrombotic effect. These results indicate that polyphosphate mediates the binding of contact factors to EV and that EV-associated polyphosphate may contribute to the prothrombotic effects of EV in cancer.

Increased activity of procoagulant factors in patients with small cell lung cancer

Small cell lung cancer (SCLC) patients have augmented risk of developing venous thromboembolism, but the mechanisms triggering this burden on the coagulation system remain to be understood. Recently, cell-derived microparticles carrying procoagulant phospholipids (PPL) and tissue factor (TF) in their membrane have attracted attention as possible contributors to the thrombogenic processes in cancers. The aims of this study were to assess the coagulation activity of platelet-poor plasma from 38 SCLC patients and to provide a detailed procoagulant profiling of small and large extracellular vesicles (EVs) isolated from these patients at the time of diagnosis, during and after treatment compared to 20 healthy controls. Hypercoagulability testing was performed by thrombin generation (TG), procoagulant phospholipid (PPL), TF activity, Protein C, FVIII activity and cell-free deoxyribonucleic acid (cfDNA), a surrogate measure for neutrophil extracellular traps (NETs). Our results revealed a coagulation activity that is significantly increased in the plasma of SCLC patients when compared to age-related healthy controls, but no substantial changes in coagulation activity during treatment and at follow-up. Although EVs in the patients revealed an increased PPL and TF activity compared with the controls, the TG profiles of EVs added to a standard plasma were similar for patients and controls. Finally, we found no differences in the coagulation profile of patients who developed VTE to those who did not, i.e. the tests could not predict VTE. In conclusion, we found that SCLC patients display an overall increased coagulation activity at time of diagnosis and during the disease, which may contribute to their higher risk of VTE.

Platelet-Derived Procoagulant Microparticles as Blood-based Biomarker of Breast Cancer

Objective:

Breast cancer is the main cause of cancer death in women worldwide. Elevated plasma levels of circulating cell-derived microparticles (MPs) have been reported in various types of cancer, including breast cancer, with the ability to mediate inflammation and thrombosis. Microparticles are bioactive agents, and it has been suggested that MPs can be used as a diagnostic, prognostic, or therapeutic biomarker in various diseases. The aim of this study was to investigate the levels of platelet-derived MPs (PMPs) in breast cancer patients.

Materials and Methods:

In this case-control study, 30 patients with breast cancer and 20 normal subjects were sampled after obtaining written consent. MPs were isolated from blood samples by centrifugation technique. CD42b and annexin V markers were used respectively for counting PMPs and procoagulant MPs with flow cytometry.

Results:

Flow cytometry results showed that the number of PMPs and procoagulant annexin V positive MPs was significantly higher in the breast cancer patients than normal subjects (p<0.001). The number of the annexin V MPs differed significantly in patients with high tumor size (T2) compared to the patients with low tumor size (T1) and controls (p<0.001). Significant and positive correlations were found between PMP levels and tissue-based biomarkers, tumor grading, and distant metastasis (P<0.05). Tumor histological type did not correlate with the numbers of PMPs (p=0.065).

Conclusion:

Increased levels of PMPs and activity in terms of hemostasis and having a positive and significant relationship with tumor grading and metastasis may indicate the effective role of PMPs in the pathogenesis and prognosis of breast cancer.

Pathophysiology 1. Mechanisms of Thrombosis in Cancer Patients

Thrombosis is a major cause of morbidity and mortality in cancer patients. The pathogenesis of blood coagulation activation in oncological patients is complex and involves both clinical and biological factors. Abnormalities in one or more coagulation test are common in cancer patients, even without thrombotic manifestations, indicating an ongoing hypercoagulable condition. Moreover, venous thromboembolism (VTE) can be the first symptom of an occult malignancy in an otherwise healthy individual. The levels of laboratory markers of activation of blood coagulation parallel the development of malignancy, being the coagulant mechanisms important for both thrombogenesis and tumor progression. Besides general clinical risk factors for VTE, also disease-specific clinical factors, i.e., type and stage of the tumor, and anticancer therapies increase the thrombotic risk in these patients. Furthermore, biological factors, including the cancer cell-specific prothrombotic properties together with the host cell inflammatory response to the tumor, are relevant as well as unique players in the pathogenesis of the cancer-associated hypercoagulability. Cancer cells produce and release procoagulant and fibrinolytic proteins, inflammatory cytokines, and procoagulant microparticles. They also express adhesion molecules binding to the receptors of host vascular cells (i.e., endothelial cells, platelets, and leukocytes), thereby stimulating the prothrombotic properties of these normal cells, including the shed of cell-specific microparticles and neutrophil extracellular traps. Of interest, several genes responsible for the cellular neoplastic transformation drive the programs of hemostatic properties expressed by cancer tissues. A better understanding of such mechanisms will help the development of novel strategies to prevent and treat the Trousseau's syndrome (i.e., cancer-associated thrombosis).

Extracellular vesicles from human saliva promote hemostasis by delivering coagulant tissue factor to activated platelets

Essentials Human salivary extracellular vesicles (EVs) expose coagulant tissue factor (TF). Salivary EVs expose CD24, a ligand of P-selectin. CD24 and coagulant TF co-localize on salivary EVs. TF+ /CD24+ salivary EVs bind to activated platelets and trigger coagulation.

SUMMARY

Background Extracellular vesicles (EVs) from human saliva expose coagulant tissue factor (TF). Whether such TF-exposing EVs contribute to hemostasis, however, is unknown. Recently, in a mice model, tumor cell-derived EVs were shown to deliver coagulant TF to activated platelets at a site of vascular injury via interaction between P-selectin glycoprotein ligand-1 (PSGL-1) and P-selectin. Objectives We hypothesized that salivary EVs may deliver coagulant TF to activated platelets via interaction with P-selectin. Methods We investigated the presence of two ligands of P-selectin on salivary EVs, PSGL-1 and CD24. Results Salivary EVs expose CD24 but PSGL-1 was not detected. Immune depletion of CD24-exposing EVs completely abolished the TF-dependent coagulant activity of cell-free saliva, showing that coagulant TF and CD24 co-localize on salivary EVs. In a whole blood perfusion model, salivary EVs accumulated at the surface of activated platelets and promoted fibrin generation, which was abolished by an inhibitory antibody against human CD24. Conclusions A subset of EVs in human saliva expose coagulant TF and CD24, a ligand of P-selectin, suggesting that such EVs may facilitate hemostasis at a site of skin injury where the wound is licked in a reflex action.

Clinical significance of circulating microparticles for venous thrombo - embolism in cancer patients

Cancer patients have a four-to seven-fold increased risk to develop a venous thromboembolic event. Accumulating evidence from experimental and clinical studies indicates that microparticles (MPs), small procoagulant membrane vesicles that are defined by size and a negatively charged phosphatidylserine rich surface, play an important role in the pathogenesis of cancer-related venous thromboembolism (VTE). However, the clinical significance of MPs as a predictive biomarker for VTE in cancer patients has not been fully elucidated yet. This might be due to unresolved methodological problems and a lack of data from large prospective clinical studies that investigate the role of MPs in cancer-related VTE.

It is the aim of this review to give an overview on the most important characteristics of MPs and studies dealing with the role of MPs in cancer-related VTE. Also recent progresses, unresolved problems and future perspectives in this research field will be discussed. In the conclusion we will assess the clinical significance of MPs in cancer-related VTE.

Neutrophil extracellular traps are increased in cancer patients but does not associate with venous thrombosis

Background

A single center, prospective tissue-based study was conducted to investigate an association between neutrophil extracellular traps (NETs) and venous thromboembolic disease in patients with malignancy.

Methods

Plasma was collected from 65 patients in which 27 were cancer patients and 38 were age-matched non-cancer patients. Plasma NETs, circulating free DNA (cfDNA), DNase-1, endonuclease-G, endonuclease activity and thrombin-antithrombin III (TAT) complex levels was quantified. Laboratory values were also compared. Additionally, NETs detection and quantification was performed with fluorescent immunohistochemistry (IHC) in tissue-banked tumor sections and fresh human venous thrombus derived from cancer patients.

Results

Plasma samples from cancer patients contained higher levels of nucleosomes (P=0.0009) and cfDNA (P=0.0008) compared to the non-cancer group. Western blot analysis revealed significantly lower DNase-1 protein levels (P=0.016) that paralleled lower nuclease activity (P=0.03) in plasma samples from cancer patients compared to non-cancer patients. Thrombus tissue from cancer patients and tumor tissue from liver and lung cancer also showed marked levels of NETs. However, increased levels of NETs in cancer patients did not correlate with TAT complex activation or prevalence of venous thrombosis in cancer patients.

Conclusions

Further studies are warranted to determine the role of NETs as a procoagulant in human thrombosis.

Procoagulant microparticles derived from cancer cells have determinant role in the hypercoagulable state associated with cancer

Hypercoagulablity is a common alteration of blood coagulation in cancer patients. However, the procoagulant activity of cancer cells is not sufficient to induce hypercoagulability. The present study was aimed to identify the mechanism with which hypercoagulabilty is produced in the presence of cancer cells. We focused on the analysis of the procoagulant elements carried by cancer cell-derived microparticles (CaCe-dMP) and we evaluated the impact of microparticles associated with the cancer cells from which they stem on thrombin generation. CaCe-dMP from the cancer cells were isolated from the conditioned medium and analyzed for tissue factor (TF) and procoagulant phospholipid expression. Thrombin generation of normal plasma was assessed by the Thrombinoscope (CAT®) in the presence or absence of pancreas adeno-carcinoma cells (BXPC3) or breast cancer MCF7 cells supplemented with the respective CaCe-dMP. Both BXPC3 and MCF7 cells express abundant amounts of active TF. Phosphatidylserine was identified on the surface of CaCe-dMP, unlike the cancer cells themselves. The expression of TFa by the microparticles was significantly higher to that observed on the cancer cells. Culture of the cancer cells with their microparticles resulted in thrombin generation significantly higher as compared to the upper normal limit. In conclusion, cancer cells 'enrich' the microenvironment with procoagulant elements, especially procoagulant micro-particles which express TF and procoagulant phospholipids. The association of cancer cells with procoagulant microparticles is necessary for a state of hypercoagulability, at the level of the tumoral microenvironment. The intensity of the hypercoagulability depends on the histological type of the cancer cells.

Methodological Guidelines to Study Extracellular Vesicles

Owing to the relationship between extracellular vesicles (EVs) and physiological and pathological conditions, the interest in EVs is exponentially growing. EVs hold high hopes for novel diagnostic and translational discoveries. This review provides an expert-based update of recent advances in the methods to study EVs and summarizes currently accepted considerations and recommendations from sample collection to isolation, detection, and characterization of EVs. Common misconceptions and methodological pitfalls are highlighted. Although EVs are found in all body fluids, in this review, we will focus on EVs from human blood, not only our most complex but also the most interesting body fluid for cardiovascular research.

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.

Extracellular vesicles and blood diseases

Extracellular vesicles (EVs) are small membrane vesicles released from many different cell types by the exocytic budding of the plasma membrane in response to cellular activation or apoptosis. EVs disseminate various bioactive effectors originating from the parent cells and transfer functional RNA and protein between cells, enabling them to alter vascular function and induce biological responses involved in vascular homeostasis. Although most EVs in human blood originate from platelets, EVs are also released from leukocytes, erythrocytes, endothelial cells, smooth muscle cells, and cancer cells. EVs were initially thought to be small particles with procoagulant activity; however, they can also evoke cellular responses in the immediate microenvironments and transport microRNAs (miRNA) into target cells. In this review, we summarize the recent literature relevant to EVs, including a growing list of clinical disorders that are associated with elevated EV levels. These studies suggest that EVs play roles in various blood diseases.

Microparticles as Biomarkers of Blood Coagulation in Cancer

Cancer is associated with hypercoagulopathy and increased risk of thrombosis. This negatively influences patient morbidity and mortality. Cancer is also frequently complicated by the development of venous thromboembolism (VTE). Tumor-derived tissue factor (TF)-bearing microparticles (MPs) are associated with VTE events in malignancy. MPs are small membrane vesicles released from many different cell types by exocytic budding of the plasma membrane in response to cellular activation or apoptosis. MPs may also be involved in clinical diseases through expression of procoagulative phospholipids. The detection of TF-expressing MPs in cancer patients may be clinically useful. In lung and breast cancer patients, MPs induce metastasis and angiogenesis and may be indicators of vascular complications. Additionally, MPs in patients with various types of cancer possess adhesion proteins and bind target cells to promoting cancer progression or metastasis. Overexpression of TF by cancer cells is closely associated with tumor progression, and shedding of TF-expressing MPs by cancer cells correlates with the genetic status of cancer. Consequently, TF-expressing MPs represent important markers to consider in the prevention of and therapy for VTE complications in cancer patients.

Microparticle analysis in disorders of hemostasis and thrombosis

Microparticles (MPs) are submicron vesicles released from the plasma membrane of eukaryotic cells in response to activation or apoptosis. MPs are known to be involved in numerous biologic processes, including inflammation, the immune response, cancer metastasis, and angiogenesis. Their earliest recognized and most widely accepted role, however, is the ability to promote and support the process of blood coagulation. Consequently, there is ongoing interest in studying MPs in disorders of hemostasis and thrombosis. Both phosphatidylserine (PS) exposure and the presence of tissue factor (TF) in the MP membrane may account for their procoagulant properties, and elevated numbers of MPs in plasma have been reported in numerous prothrombotic conditions. To date, however, there are few data on true causality linking MPs to the genesis of thrombosis. A variety of methodologies have been employed to characterize and quantify MPs, although detection is challenging due to their submicron size. Flow cytometry (FCM) remains the most frequently utilized strategy for MP detection; however, it is associated with significant technological limitations. Additionally, preanalytical and analytical variables can influence the detection of MPs by FCM, rendering data interpretation difficult. Lack of methodologic standardization in MP analysis by FCM confounds the issue further, although efforts are currently underway to address this limitation. Moving forward, it will be important to address these technical challenges as a scientific community if we are to better understand the role that MPs play in disorders of hemostasis and thrombosis.

Circulating microparticles in patients with antiphospholipid antibodies: characterization and associations

The antiphospholipid syndrome is characterized by venous or arterial thrombosis and/or recurrent fetal loss in the presence of circulating antiphospholipid antibodies. These antibodies cause activation of endothelial and other cell types leading to the release of microparticles with procoagulant and pro-inflammatory properties. The aims of this study were to characterize the levels of endothelial cell, monocyte or platelet derived, and tissue factor-bearing microparticles in patients with antiphospholipid antibodies, to determine the association of circulating microparticles with anticardiolipin and anti-β2-glycoprotein antibodies, and to define the cellular origin of microparticles that express tissue factor. Microparticle content within citrated blood from 47 patients with antiphospholipid antibodies and 144 healthy controls was analyzed within 2hours of venipuncture. Levels of Annexin-V, CD105 and CD144 (endothelial derived), CD41 (platelet derived) and tissue factor positive microparticles were significantly higher in patients than controls. Though levels of CD14 (monocyte-derived) microparticles in patient plasma were not significantly increased, increased levels of CD14 and tissue factor positive microparticles were observed in patients. Levels of microparticles that stained for CD105 and CD144 showed a positive correlation with IgG (R=0.60, p=0.006) and IgM anti-beta2-glycoprotein I antibodies (R=0.58, p=0.006). The elevation of endothelial and platelet derived microparticles in patients with antiphospholipid antibodies and their correlation with anti-β2-glycoprotein I antibodies suggests a chronic state of vascular cell activation in these individuals and an important role for β2-glycoprotein I in development of the pro-thrombotic state associated with antiphospholipid antibodies.

Effect of tissue factor knockdown on the growth, invasion, chemoresistance and apoptosis of human gastric cancer cells

This study aimed to explore the role of tissue factor (TF) and evaluate its antitumor effects in the biological processes of gastric cancer cells using the application of RNA interference technology to silence TF in the SGC7901 gastric cancer cell line. Specific small interfering RNA (siRNA) designed for targeting human TF was transfected into SGC7901 cells. The expression levels of TF in the cells were detected by reverse transcription-polymerase chain reaction. Cell proliferation and chemosensitivity were measured by Cell Counting Kit-8. The metastatic potential of the SGC7901 cells was determined by Transwell experiments and wound-healing assays. Cell apoptosis was assessed by Annexin V-fluorescein isothiocyanate/propidium iodide double-staining method. The expression levels of TF mRNA were significantly reduced by the TF-siRNA in the SGC7901 cells, resulting in the suppression of cell proliferation, chemoresistance and invasion, and subsequently the induction of cell apoptosis. TF knockdown with siRNA inhibits the growth, invasion and chemoresistance and enhances the apoptosis of SGC7901 cells, providing a potential approach for gene therapy against human gastric cancer.

miR-20b regulates expression of proteinase-activated receptor-1 (PAR-1) thrombin receptor in melanoma cells

The proteinase-activated receptor 1 (PAR-1) plays a central role in melanoma progression and its expression level is believed to correlate with the degree of cancer invasiveness. Here, we show that PAR-1 is post-transcriptionally regulated by miR-20b microRNA in human melanoma cells. PAR-1 was found to be expressed in metastatic melanoma cells but was barely detectable in primary melanoma. By transducing primary melanoma cells with a lentivirus containing a 3'-UTR construct of PAR-1 mRNA, we could show that endogenous melanoma microRNAs interacted with PAR-1 3'-UTR and silenced a fused luciferase reporter. Transfection of an inhibitor against miR-20b into primary melanoma cells reversed this process. Finally, transfection of miR-20b mimic into metastatic melanoma cells caused downregulation of the luciferase reporter. We conclude that miR-20b regulates expression of melanoma PAR-1 receptor, which may explain the differential expression of PAR-1 observed in human melanoma.

Inhibition of tissue factor pathway inhibitor increases the sensitivity of thrombin generation assay to procoagulant microvesicles

Patients with cancer have a seven-fold to 10-fold increased risk of developing venous thromboembolism (VTE). Circulating microvesicles could be a predictive biomarker for VTE in cancer. Thrombin generation assay (TGA) is a useful technique to detect procoagulant activity of microvesicles. However, TGA suffers from a lack of sensitivity due to the presence of tissue factor pathway inhibitor (TFPI) in plasma. The aim of the study was to improve the sensitivity of TGA to tissue factor by limiting the interference of TFPI. Serial dilutions of MDA-MB231 cells were incubated for 45 min at 37°C to generate microvesicles. Samples were then centrifuged and supernatants that contain microvesicles were used for TGA. Normal pooled plasma was incubated with inhibitor of TFPI or was diluted twice to decrease plasma level of TFPI. Lagtime was used as a surrogate marker of TGA to detect procoagulant activity of microvesicles. Inhibition of TFPI decreased twice the cell concentration needed for a significant reduction of lagtime and decreased 2.4-fold the intraassay variability. Plasma dilution had no impact on the TGA sensitivity when TGA was triggered by microvesicles derived from MDA-MB-231. Thrombin generation is a very sensitive method to study the procoagulant activity of tissue factor bearing microvesicles. The sensitivity can be increased by inhibition of TFPI with specific monoclonal antibody against its Kunitz domain I. A two times plasma dilution is an interesting cheaper alternative to study the procoagulant activity of microvesicles by TGA with a good sensitivity, especially when low plasma quantities are available.

Pathophysiology and management of thrombosis in cancer: 150 years of progress

The association of thrombosis with cancer has been recognized since the middle of the nineteenth century. It remains a common and serious complication of the cancer itself, as well as chemotherapy. Thrombosis is the second leading cause of death in cancer patients, second only to the cancer itself. For many years the treatment options for managing thrombosis in cancer had been static, but the past decade has seen significant evolution in the management, with the clear superiority of low molecular weight heparin over warfarin for secondary prevention of thrombosis. This article will review the understanding and management of thrombosis in cancer.

Microparticles and microRNAs: new players in the complex field of coagulation

Atherosclerosis is a complex process that begins with endothelial dysfunction, and continues with several inflammatory processes leading, eventually, to plaque rupture and formation of arterial thrombus. Increased platelet reactivity and classical coagulation pathways are not the only players of the whole thrombotic process: microparticles (MPs), irregularly shaped small vesicles released from the plasma membrane after cell activation, apoptosis, or exposure to shear stress have been demonstrated to be involved in such a process. MicroRNAs (MiRs), small-non-coding single-strand RNAs acting as post-transcriptional modulator of target gene expression are expressed in the large majority of eukaryotes. MiRs are implicated in several phenomena: control of metabolism, control of cell-differentiation, control of cell-proliferation and control of cell-apoptosis, therefore contributing to physiologic and pathogenic processes in hematologic, genetic, infective and cardiac diseases. Microparticles operate as a delivery system of MiRs, playing an active and important role in processes such as coagulation and thrombosis. These novel findings also suggest MPs and, in particular MIRs, as possible and promising therapeutic targets.

Coagulation and metastasis: what does the experimental literature tell us?

Inhibition of coagulation greatly limits cancer metastasis in many experimental models. Cancer cells trigger coagulation, through expression of tissue factor or P-selectin ligands that have correlated with worse prognosis in human clinical studies. Cancer cells also affect coagulation through expression of thrombin and release of microparticles that augment coagulation. In the cancer-bearing host, coagulation facilitates tumour progression through release of platelet granule contents, inhibition of Natural Killer cells and recruitment of macrophages. We are revisiting this literature in the light of recent studies in which treatment of clinical cohorts with anticoagulant drugs led to diminished metastasis.

Biomolecular markers of cancer-associated thromboembolism

Venous thromboembolism (VTE; deep venous thrombosis and pulmonary embolism) is associated with a poor prognosis in most malignancies and is a major cause of death among cancer patients. Universal anticoagulation for primary thromboprophylaxis in the outpatient setting is precluded by potential bleeding complications, especially without sufficient evidence that all patients would benefit from such prophylaxis. Therefore, appropriately targeting cancer patients for thromboprophylaxis is key to reducing morbidity and perhaps mortality. Predictive biomarkers could aid in identifying patients at high risk for VTE. Possible biomarkers for VTE include C-reactive protein, platelet and leukocyte counts, D-dimer and prothrombin fragment 1+2, procoagulant factor VIII, tissue factor, and soluble P-selectin. Evidence is emerging to support the use of risk assessment models in selecting appropriate candidates for primary thromboprophylaxis in the cancer setting. Further studies are needed to optimize these models and determine utility in reducing morbidity and mortality from cancer-associated thromboembolism.

Thrombin generation assay and transmission electron microscopy: a useful combination to study tissue factor-bearing microvesicles

Introduction

Patients with cancer have a 7- to 10-fold increased risk of developing venous thromboembolism. Circulating microvesicles could be a useful predictive biomarker for venous thromboembolism in cancer. Validated and standardised techniques that could be used to determine the complete microvesicle phenotype are required.

Objectives

These were two-fold: a) to characterise tissue factor (TF)-bearing microvesicles released by cultured breast cancer cells MDA-MB-231 by flow cytometry (FCM), transmission electron microscopy (TEM) and thrombin generation assay (TGA); and b) to validate the sensitivity and variability intra/inter-assay of TGA as a useful method to study the procoagulant activity (PCA) of microvesicles.

Methods

Cultured breast cancer cells MDA-MB-231 were incubated for 45 minutes at 37°C. Samples were then centrifuged or not at 4,500 g for 15 minutes, and cells and MVs or MV-containing supernatants were used for TEM, FCM and TGA. In activity assays, microvesicles (i.e. cell-depleted supernatants) were incubated with anti-TF antibodies or with annexin V to assess the contribution of TF and phospholipids to the PCA. Alternatively, supernatants were filtered through 0.1, 0.22, 0.45 or 0.65 µm membranes and subjected to TGA.

Results

The majority of the PCA was associated with microvesicles smaller than 0.1 µm, and the mean microvesicle size estimated by TEM after 10,000 g centrifugation was 121±54 nm with a majority of vesicles between 100 and 200 nm. Microvesicles derived from 5,000 MDA-MB-231cells/ml were sufficient to significantly increase the thrombin generation of normal pooled plasma.

Conclusions

TEM, FCM and filtration coupled to TGA represent a useful combination to study the PCA of TF-bearing microvesicles, whatever their size. And it will be interesting to implement these techniques in patients.

Tumour and microparticle tissue factor expression and cancer thrombosis

Cancer is frequently complicated by venous thromboembolic events (VTE), which pose a significant health burden due to the associated high morbidity and mortality rates, yet the exact details of the pathophysiological mechanisms underlying their development are yet to be fully elucidated. Tissue factor (TF), the primary initiator of coagulation, is often overexpressed in malignancy and as such is a prime candidate in predicting the hypercoagulable state. Further exploration of this potential role has identified increases in the number of TF-expressing microparticles (MP) in the circulation of cancer patients, in particular in those known to have high incidences of thromboembolic complications. The risk of VTE in cancer is found to be further elevated by chemotherapy. Chemotherapy may, in eliciting cancer cell apoptosis, result in an increase in release of circulating procoagulant MP. We discuss a potential role of elevated tumour TF expression and increased circulating TF-positive MP in predicting VTE risk.

Microparticles in tumor progression

Microparticles (MP) are shed from the surface of activated or apoptotic blood cells and their levels in plasma reflect a balance between cell stimulation, proliferation, and death. MP production occurs through vesiculation of cell membranes, and involves cytoskeletal changes and a shift in the normal phospholipid asymmetry. The expression on the majority of MP of the anionic phosphatidylserine (PS) is responsible for the capacity of MP to support blood coagulation activation. In some cases, PS expression is also associated, in the same MP, with the presence of active Tissue Factor, the main activator of blood coagulation. Elevation in plasma levels of MP have been described in numerous clinical conditions, most of which also associated with an increased thrombotic risk. Particularly, MP have been found to be increased in both solid and hematological malignancies, including myeloproliferative neoplasms. A role of MP in tumor progression has been suggested by both in vitro and in vivo studies. Evidence exists that MP of platelet origin are the main players in this process, being rich in pro-angiogenic factors. The utility of measuring MP as a diagnostic and prognostic marker is currently a subject of intense investigation. The possibility to inhibit MP production by pharmacological interventions represents a future challenge.

Cancer cells induced to express mesenchymal phenotype release exosome-like extracellular vesicles carrying tissue factor

Aggressive epithelial cancer cells frequently adopt mesenchymal characteristics and exhibit aberrant interactions with their surroundings, including the vasculature. Whether the release/uptake of extracellular vesicles (EVs) plays a role during these processes has not been studied. EVs are heterogeneous membrane structures that originate either at the surface (microparticles), or within (exosomes) activated or transformed cells, and are involved in intercellular trafficking of bioactive molecules. Here, we show that epithelial cancer cells (A431, DLD-1) adopt mesenchymal features (epithelial-to-mesenchymal transition-like state) upon activation of epidermal growth factor receptor (EGFR) coupled with blockade of E-cadherin. This treatment leads to a coordinated loss of EGFR and tissue factor (TF) from the plasma membrane and coincides with a surge in emission of small, exosome-like EVs containing both receptors. TF (but not EGFR) is selectively up-regulated in EVs produced by mesenchymal-like cancer cells and can be transferred to cultured endothelial cells rendering them highly procoagulant. We postulate that epithelial-to-mesenchymal transition-like changes may alter cancer cell interactions with the vascular systems through altered vesiculation and TF shedding.

Phosphatidylethanolamine is externalized at the surface of microparticles

Microparticles (MPs) are membrane-bound vesicles shed normally or as a result of various (pathological) stimuli. MPs contain a wealth of bio-active macromolecules. Aminophospholipid phosphatidylserine (PS) is present on the surface of many MPs. As PS and phosphatidylethanolamine (PE) are related, yet distinct aminophospholipids, the purpose of this study was to systematically and directly assess PE exposure on MPs. We examined MPs from various human cellular sources (human breast cancer, endothelial, red and white blood cells) by flow cytometry using a PE-specific probe, duramycin, and two PS-specific probes, annexin V and lactadherin. PS and PE exposure percentage was comparable on vascular and blood cell-derived MPs (80-90% of MP-gated events). However, the percentage of malignant breast cancer MPs exposing PE (~90%) was significantly higher than PS (~50%). Thus, while PS and PE exposure can result from a general loss of membrane asymmetry, there may also be distinct mechanisms of PE and PS exposure on MPs that vary by cellular source.

Oncogenic extracellular vesicles in brain tumor progression

The brain is a frequent site of neoplastic growth, including both primary and metastatic tumors. The clinical intractability of many brain tumors and their distinct biology are implicitly linked to the unique microenvironment of the central nervous system (CNS) and cellular interactions within. Among the most intriguing forms of cellular interactions is that mediated by membrane-derived extracellular vesicles (EVs). Their biogenesis (vesiculation) and uptake by recipient cells serves as a unique mechanism of intercellular trafficking of complex biological messages including the exchange of molecules that cannot be released through classical secretory pathways, or that are prone to extracellular degradation. Tumor cells produce EVs containing molecular effectors of several cancer-related processes such as growth, invasion, drug resistance, angiogenesis, and coagulopathy. Notably, tumor-derived EVs (oncosomes) also contain oncogenic proteins, transcripts, DNA, and microRNA (miR). Uptake of this material may change properties of the recipient cells and impact the tumor microenvironment. Examples of transformation-related molecules found in the cargo of tumor-derived EVs include the oncogenic epidermal growth factor receptor (EGFRvIII), tumor suppressors (PTEN), and oncomirs (miR-520g). It is postulated that EVs circulating in blood or cerebrospinal fluid (CSF) of brain tumor patients may be used to decipher molecular features (mutations) of the underlying malignancy, reflect responses to therapy, or molecular subtypes of primary brain tumors [e.g., glioma or medulloblastoma (MB)]. It is possible that metastases to the brain may also emit EVs with clinically relevant oncogenic signatures. Thus, EVs emerge as a novel and functionally important vehicle of intercellular communication that can mediate multiple biological effects. In addition, they provide a unique platform to develop molecular biomarkers in brain malignancies.

Microparticle-associated tissue factor activity, venous thromboembolism and mortality in pancreatic, gastric, colorectal and brain cancer patients

BACKGROUND

Tissue factor (TF) expression by tumors contributes to tumor growth. Release of TF-positive microparticles (MPs) may contribute to venous thromboembolism (VTE).

OBJECTIVES

To conduct a prospective cohort study to determine whether elevated MP-associated TF (MP-TF) activity is predictive of VTE and mortality in four cancer types.

PATIENTS/METHODS

We determined MP-TF activity in pancreatic, gastric, colorectal and brain cancer patients. We used a chromogenic endpoint assay for all patients and also a chromogenic kinetic assay for patients with pancreatic and brain cancer.

RESULTS

During follow-up, 12/60 (20%) pancreatic, 6/43 (14%) gastric, 12/126 (10%) colorectal and 19/119 (16%) brain cancer patients developed VTE; 46/60 (77%), 30/43 (70%), 47/126 (37%) and 67/119 (56%), respectively, died. MP-TF activity levels were highest in pancreatic cancer. We did not find a statistically significant association of MP-TF activity with the risk of VTE in any of the four cancer types by using two statistical methods. An association of MP-TF activity with the risk of mortality was detected in pancreatic cancer with the endpoint assay (hazard ratio [HR] 1.8 and 95% confidence interval [CI] 1.4-2.3 per doubling of activity, P < 0.001) and the kinetic assay (HR 1.2, 95% CI 1.1-1.4, P < 0.001); adjustment for type of treatment was not performed. In pancreatic cancer, MP-TF activity correlated with D-dimer level (endpoint assay, r = 0.51; chromogenic assay, r = 0.48), and a correlation between assays (r = 0.61) was found.

CONCLUSION

MP-TF activity was not associated with future VTE in pancreatic, gastric, colorectal and brain cancer. However, we found a strong association of MP-TF activity with mortality in pancreatic cancer. MP-TF activity might be reflective of an aggressive pancreatic cancer phenotype.

Markers of inflammation and coagulation may be modulated by enteral feeding strategy

BACKGROUND

Although enteral nutrition (EN) is provided to most mechanically ventilated patients, the effect of specific feeding strategies on circulating markers of coagulation and inflammation is unknown.

METHODS

Markers of inflammation (tumor necrosis factor [TNF]-α, interleukin [IL]-1β, interferon [IFN]-γ, IL-6, IL-8, IL-10, IL-12) and coagulation (tissue factor [TF], plasminogen activator inhibitor-1) were measured at baseline (n = 185) and 6 days (n = 103) in mechanically ventilated intensive care unit patients enrolled in a randomized controlled study of trophic vs full-energy feeds to test the hypothesis that trophic enteral feeds would be associated with decreases in markers of inflammation and coagulation compared to full-energy feeds.

RESULTS

There were no differences in any of the biomarkers measured at day 6 between patients who were randomized to receive trophic feeds compared to full-energy feeds. However, TF levels decreased modestly in patients from baseline to day 6 in the trophic feeding group (343.3 vs 247.8 pg/mL, P = .061) but increased slightly in the full-calorie group (314.3 vs 331.8 pg/mL). Lower levels of TF at day 6 were associated with a lower mortality, and patients who died had increasing TF levels between days 0 and 6 (median increase of 39.7) compared to decreasing TF levels in patients who lived (median decrease of 95.0, P = .033).

CONCLUSIONS

EN strategy in critically ill patients with acute respiratory failure does not significantly modify inflammation and coagulation by day 6, but trophic feeds may have some modest effects in attenuating inflammation and coagulation.

Low molecular weight heparin downregulates tissue factor expression and activity by modulating growth factor receptor-mediated induction of nuclear factor-κB

Treatment of cancer patients with low molecular weight heparin (LMWH) appears to have beneficial effects. In this study, the influence of low molecular weight heparin (LMWH) on tissue factor (TF) expression and activity in five cell lines from various tissues was analysed and explored. Incubation of cells with LMWH (0-2000μg/ml) resulted in the downregulation of TF mRNA expression which was both LMWH concentration-dependent and time-dependent. Downregulation of TF was also measured as decreased cellular TF antigen and activity. Consistently, incubation of cells with LMWH suppressed the nuclear localisation and the transcriptional activity of NFκB. Decreased TF mRNA was largely achievable by incubating the cells with an NFκB inhibitor alone whilst incubation with betulinic acid to activate NFκB reversed the inhibitory influence of LMWH. Cells were also incubated with a range of concentrations of EGF (0-10ng/ml), bFGF (0-20ng/ml) or VEGF (0-4ng/ml) in the presence or absence of LMWH (200μg/ml) for 24h and TF antigen measured. Inclusion of LMWH reduced TF expression in response to EGF, bFGF or VEGF but TF expression was partially restored by increasing concentrations of the growth factors. We conclude that LMWH downregulates TF expression in vitro through a mechanism that involves interference with the function of growth factors which in turn is mediated through the downregulation of the transcriptional activity of NFκB. This mechanism may also explain some of the beneficial influences attributed to LMWH therapy in the treatment of cancer patients.

Variable plasma levels of Factor V Leiden correlate with circulating platelet microparticles in carriers of Factor V Leiden

INTRODUCTION

Inheritance of Factor V Leiden (FVL) is associated with an increased but variable level of risk for thrombosis. We have previously shown that FVL heterozygotes have elevated levels of circulating pro-coagulant microparticles (MP). Here we sought to determine if these subjects differed in their plasma levels of FVL and if this was related to MP concentrations and/or history of thrombosis.

MATERIALS AND METHODS

The Hemoclot Quanti. V-L clotting assay was used to specifically measure FVL in plasma samples from 44 known carriers (12M, 32F; aged 46±13years). Circulating MP were quantified by flow cytometry using fluorochrome conjugated antibodies to platelet (CD41a), leukocyte (CD45), and endothelial (CD62e) surface markers, and MP prothrombinase activity was determined by ELISA.

RESULTS

The cohort was found to have a mean FVL of 49.5±5.6% and this was positively correlated to the total number of circulating CD41a+MP (R=0.31, p=0.03) but not to other MP subsets or to MP prothrombinase activity. The amount of FVL relative to normal factor V (FVL/FV clotting ratio) was calculated and found to be highly variable, ranging from 0.37 to 0.69, and significantly correlated with a history of thrombosis (n=14; p=0.04).

CONCLUSIONS

This is the first study to investigate the relationship between varying levels of FVL and plasma derived MP. These results are consistent with our previous findings of an increase in MP levels in carriers of FVL as compared to controls, and suggest a role for FVL/FV ratio in predicting risk of thrombosis in carriers of FVL.

Microparticles in hemostasis and thrombosis

Blood contains microparticles (MPs) derived from a variety of cell types, including platelets, monocytes, and endothelial cells. In addition, tumors release MPs into the circulation. MPs are formed from membrane blebs that are released from the cell surface by proteolytic cleavage of the cytoskeleton. All MPs are procoagulant because they provide a membrane surface for the assembly of components of the coagulation protease cascade. Importantly, procoagulant activity is increased by the presence of anionic phospholipids, particularly phosphatidylserine (PS), and the procoagulant protein tissue factor (TF), which is the major cellular activator of the clotting cascade. High levels of platelet-derived PS(+) MPs are present in healthy individuals, whereas the number of TF(+), PS(+) MPs is undetectable or very low. However, levels of PS(+), TF(+) MPs are readily detected in a variety of diseases, and monocytes appear to be the primary cellular source. In cancer, PS(+), TF(+) MPs are derived from tumors and may serve as a useful biomarker to identify patients at risk for venous thrombosis. This review will summarize our current knowledge of the role of procoagulant MPs in hemostasis and thrombosis.

Small interference RNA targeting tissue factor inhibits human lung adenocarcinoma growth in vitro and in vivo

Background

The human coagulation trigger tissue factor (TF) is overexpressed in several types of cancer and involved in tumor growth, vascularization, and metastasis. To explore the role of TF in biological processes of lung adenocarcinoma, we used RNA interference (RNAi) technology to silence TF in a lung adenocarcinoma cell line A549 with high-level expression of TF and evaluate its antitumor effects in vitro and in vivo.

Methods

The specific small interfering RNA (siRNA) designed for targeting human TF was transfected into A549 cells. The expression of TF was detected by reverse transcription-PCR and Western blot. Cell proliferation was measured by MTT and clonogenic assays. Cell apoptosis was assessed by flow cytometry. The metastatic potential of A549 cells was determined by wound healing, the mobility and Matrigel invasion assays. Expressions of PI3K/Akt, Erk1/2, VEGF and MMP-2/-9 in transfected cells were detected by Western blot. In vivo, the effect of TF-siRNA on the growth of A549 lung adenocarcinoma xenografts in nude mice was investigated.

Results

TF -siRNA significantly reduced the expression of TF in the mRNA and protein levels. The down-regulation of TF in A549 cells resulted in the suppression of cell proliferation, invasion and metastasis and induced cell apoptosis in dose-dependent manner. Erk MAPK, PI3K/Akt pathways as well as VEGF and MMP-2/-9 expressions were inhibited in TF-siRNA transfected cells. Moreover, intratumoral injection of siRNA targeting TF suppressed the tumor growth of A549 cells in vivo model of lung adenocarcinoma.

Conclusions

Down-regulation of TF using siRNA could provide a potential approach for gene therapy against lung adenocarcinoma, and the antitumor effects may be associated with inhibition of Erk MAPK, PI3K/Akt pathways.

Effect of dibutyryl cyclic adenosine monophosphate on the gene expression of plasminogen activator inhibitor-1 and tissue factor in adipocytes

INTRODUCTION

Hypertrophic adipocytes in obese states express the elevated levels of plasminogen activator inhibitor-1 (PAI-1) and tissue factor (TF). An increase in the intracellular concentration of cyclic adenosine monophosphate (cAMP) promotes triglyceride hydrolysis and may improve dysregulation of adipocyte metabolism. Here, we investigate the effect of dibutyryl-cAMP (a phosphodiesterase-resistant analog of cAMP) on the gene expression of PAI-1 and TF in adipocytes.

MATERIALS AND METHODS

Differentiated 3T3-L1 adipocytes were treated with dibutyryl-cAMP and agents that would be expected to elevate intracellular cAMP, including cilostazol (a phosphodiesterase inhibitor with anti-platelet and vasodilatory properties), isoproterenol (a beta adrenergic agonist) and forskolin (an adenylyl cyclase activator). The levels of PAI-1 and TF mRNAs were measured using real-time quantitative reverse transcription-PCR.

RESULTS AND CONCLUSIONS

The treatment of adipocytes with dibutyryl-cAMP resulted in the inhibition of both lipid accumulation and TF gene expression. However, PAI-1 gene expression was slightly but significantly increased by dibutyryl-cAMP. On the other hand, cilostazol inhibited the expression of PAI-1 without affecting lipid accumulation. When the adipocytes were treated with cilostazol in combination with isoproterenol or forskolin, the inhibitory effect of cilostazol on PAI-1 gene expression was counteracted, thus suggesting that inhibition by cilostazol may not be the result of intracellular cAMP accumulation by phosphodiesterase inhibition. These results suggest the implication of cAMP in regulation of the gene expression of TF and PAI-1 in adipocytes. Our findings will serve as a useful basis for further research in therapy for obesity-associated thrombosis.

Coagulation update: what's new in hemostasis testing?

The current report provides a personal perspective summarising some interesting recent developments in hemostasis, as well as providing a brief glimpse into some possible imminent changes to come. We briefly review routine coagulation tests, and what changes may take place related to the new emerging anticoagulants. We also briefly review the old and new global tests of hemostasis, including thrombin generation and thromboelastography. Also briefly discussed within the diagnostics of bleeding and thrombotic disorders are the role of microparticles, the rise and fall of thrombophilia testing, the 'disappearance' of fibrinolysis pathway tests, and the absence of tests related to the endothelium, in part reflecting upon Virchow's triad.

Microvesicles as mediators of intercellular communication in cancer--the emerging science of cellular 'debris'

Cancer cells emit a heterogeneous mixture of vesicular, organelle-like structures (microvesicles, MVs) into their surroundings including blood and body fluids. MVs are generated via diverse biological mechanisms triggered by pathways involved in oncogenic transformation, microenvironmental stimulation, cellular activation, stress, or death. Vesiculation events occur either at the plasma membrane (ectosomes, shed vesicles) or within endosomal structures (exosomes). MVs are increasingly recognized as mediators of intercellular communication due to their capacity to merge with and transfer a repertoire of bioactive molecular content (cargo) to recipient cells. Such processes may occur both locally and systemically, contributing to the formation of microenvironmental fields and niches. The bioactive cargo of MVs may include growth factors and their receptors, proteases, adhesion molecules, signalling molecules, as well as DNA, mRNA, and microRNA (miRs) sequences. Tumour cells emit large quantities of MVs containing procoagulant, growth regulatory and oncogenic cargo (oncosomes), which can be transferred throughout the cancer cell population and to non-transformed stromal cells, endothelial cells and possibly to the inflammatory infiltrates (oncogenic field effect). These events likely impact tumour invasion, angiogenesis, metastasis, drug resistance, and cancer stem cell hierarchy. Ongoing studies explore the molecular mechanisms and mediators of MV-based intercellular communication (cancer vesiculome) with the hope of using this information as a possible source of therapeutic targets and disease biomarkers in cancer.

Tissue factor-bearing microparticles and thrombus formation

Blood microparticles are vesicular structures with a diameter of 100 to 1000 nm that are present in the blood of normal subjects and in patients with various diseases. These microparticles are derived from cells that circulate in the blood and cells associated with the blood vessel wall. Microparticle membranes retain the protein receptors of their parent cells and may retain RNAs and other cytosolic content. On the basis of surface protein expression, microparticles are known to be derived from platelets, granulocytes, monocytes, endothelial cells, smooth muscle cells, and tumor cells. Only a subpopulation of these microparticles expresses tissue factor.