Circulating microparticles of glial origin and tissue factor bearing in high-grade glioma: a potential prothrombotic role

Initiation of combined antiretroviral therapy confers suboptimal beneficial effects on neurovascular function in people with HIV

Introduction

Due to advances in combined anti-retroviral treatment (cART), there is an increased burden of age-related cerebrovascular disease (CBVD), in people living with HIV (PWH). The underlying CNS injury can be assessed by measuring cerebral blood flow (CBF) and cerebrovascular reactivity (CVR).

Methods

35 treatment-naïve PWH and 53 HIV negative controls (HC) were enrolled in this study. Study participants underwent T1-weighted anatomical, pseudo-continuous arterial spin labeling, and resting-state functional MRI to obtain measures of CBF and CVR prior to starting cART treatment and at two-time points (12 weeks and 2 years) post-cART initiation. Controls were scanned at the baseline and 2-year visits. We also measured plasma levels of microparticles of endothelial and glial origin and well-known endothelial inflammation markers, ICAM-1 and VCAM-1, to assess HIV-associated endothelial inflammation and the interaction of these peripheral markers with brain neurovascular function.

Results

HIV infection was found to be associated with reduced CVR and increased levels of endothelial and glial microparticles (MPs) prior to initiation of cART. Further, CVR correlated negatively with peripheral MP levels in PWH.

Discussion

Our results suggest that while cART treatment has a beneficial effect on the neurovascular function after initiation, these benefits are suboptimal over time.

Temozolomide and Lomustine Induce Tissue Factor Expression and Procoagulant Activity in Glioblastoma Cells In Vitro

Glioblastoma (GBM) patients have one of the highest risks of venous thromboembolism (VTE), which is even further increased upon treatment with chemotherapy. Tissue factor (TF) is the initiator of the extrinsic coagulation pathway and expressed by GBM cells. In this study, we aimed to examine the effect of routinely used chemotherapeutic agents Temozolomide (TMZ) and Lomustine (LOM) on TF procoagulant activity and expression in GBM cells in vitro. Three human GBM cell lines (U-251, U-87, U-118) were exposed to 100 µM TMZ or 30 µM LOM for 72 h. TF procoagulant activity was assessed via an FXa generation assay and TF gene and protein expression through qPCR and Western blotting. The externalization of phosphatidylserine (PS) was studied using Annexin V flow cytometry. Treatment with TMZ and LOM resulted in increased procoagulant activity in all cell lines. Furthermore, both agents induced procoagulant activity in the supernatant and tumor-cell-secreted extracellular vesicles. In line, TF gene and protein expression were increased upon TMZ and LOM treatment. Additionally, PS externalization and induction of inflammatory-associated genes were observed. Overall, the chemotherapeutic modalities TMZ and LOM induced procoagulant activity and increased TF gene and protein expression in all GBM cell lines tested, which may contribute to the increased VTE risk observed in GBM patients undergoing chemotherapy.

Targeted DNA sequencing to identify genetic aberrations in glioblastoma that underlie venous thromboembolism; a cohort study

BACKGROUND AND OBJECTIVES

Patients with glioblastoma have a high risk of developing venous thromboembolism (VTE). However, the role of underlying genetic risk factors remains largely unknown. Therefore, the aim of this study was to discover whether genetic aberrations in glioblastoma associate with VTE risk.

METHODS

In this cohort study, all consecutive patients diagnosed with glioblastoma in two Dutch hospitals between February 2017 and August 2020 were included. Targeted DNA next-generation sequencing of all glioblastomas was performed for diagnostic purposes and included mutational status of the genes ATRX, BRAF, CIC, FUBP1, H3F3A, IDH1, IDH2, PIK3CA, PTEN and TP53 and amplification/gain or deletion of BRAF, CDKN2A, EGFR, NOTCH1 and PTEN. The primary outcome was VTE within three months before glioblastoma diagnosis until two years after. Cumulative incidences were determined using competing risk analysis adjusting for mortality. Univariable Cox regression analysis was performed to determine hazard ratios.

RESULTS

From 324 patients with glioblastoma, 25 were diagnosed with VTE. Patients with a CDKN2A deletion had a 12-month adjusted cumulative incidence of VTE of 12.5 % (95%CI: 7.3-19.3) compared with 5.4 % (95%CI: 2.6-9.6) in patients with CDKN2A wildtype (p = 0.020), corresponding to a HR of 2.53 (95%CI: 1.12-5.73, p = 0.026). No significant associations were found between any of the other investigated genes and VTE.

CONCLUSION

This study suggests a potential role for CDKN2A deletion in glioblastoma-related VTE. Therefore, once independently validated, CDKN2A mutational status may be a promising predictor to identify glioblastoma patients at high risk for VTE, who may benefit from thromboprophylaxis.

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 Small Extracellular Vesicles Profiling and Thrombin Generation as Potential Markers of Thrombotic Risk in Glioma Patients

Introduction

Patients with glioma (GM) are at a high risk of venous thromboembolism (VTE). The role of microvesiculation in the cancer-associated thrombosis mechanisms has been previously demonstrated. This study aimed to evaluate the relative abundance of extracellular vesicles (EVs) and thrombin generation (TG) in combination with standard laboratory tests in patients with newly diagnosed GM as potential prognostic markers in VTE.

Materials and Methods

In the present study, 11 patients with newly diagnosed GM and 10 healthy volunteers were analyzed. EVs were counted and their cellular origin was determined (CytoFlex B4-R2-V2, Beckman Coulter, United States), as well as thrombin generation test (TGT) (Diagnostica Stago SAS, France) was performed.

Results

In patients with GM, the relative abundance of the CD41 + EVs (platelet-derived)—and CD105 + EVs (endothelial-derived) was significantly higher than in the control group (44.3 [40.5; 52.4] vs. 27.2 [22.9; 31.0]%, p = 0.002, and 5.4 [4.8; 7.8] vs. 1.9 [1.5; 2.8]%, p = 0.0003, respectively). The D-dimer level was higher in patients with GM compared with the control group (0.46 [0.38; 1.85] vs. 0.36 [0.27; 0.40] μg/ml FEU, p = 0.03, respectively). There was a trend toward an increase in the peak thrombin and velocity index (VI) in the GM group (p = 0.06). During the follow-up period, two patients (18%) developed thrombosis, had tumor sizes of more than 5 cm, thrombocytopenia, increased VI, and D-dimer.

Conclusion

Analysis of platelet-derived EVs, platelet count, and TGT in combination with D-dimer assessment could improve the stratification of patients prone to VTE, which needs to be confirmed in a larger sample.

Investigation of glial fibrillary acidic protein (GFAP) in body fluids as a potential biomarker for glioma: a systematic review and meta-analysis

INTRODUCTION

Liquid biopsies are promising diagnostic tools for glioma. In this quantitative systematic review, we investigate whether the detection of intermediate filaments (IF) in body fluids can be used as a tool for glioma diagnosis and prognosis.

MATERIALS AND METHODS

We included all studies in which IF-levels were determined in patients with glioma and healthy controls. Of the 28 identified eligible studies, 12 focused on levels of GFAP in serum (sGFAP) and were included for metadata analysis.

RESULTS

In all studies combined, 62.7% of all grade IV patients had detectable levels of sGFAP compared to 12.7% of healthy controls. sGFAP did not surpass the limit of detection in lower grade patients or healthy controls, but sGFAP was significantly elevated in grade IV glioma (0.12 ng/mL (0.06 - 0.18), P < 0.001) and showed an average median difference of 0.15 ng/mL (0.04 - 0.25, P < 0.01) compared to healthy controls. sGFAP levels were linked to tumour volume, but not to patient outcome.

CONCLUSION

The presence of sGFAP is indicative of grade IV glioma, but additional studies are necessary to fully determine the usefulness of GFAP in body fluids as a tool for grade IV glioma diagnosis and follow-up.

Systemic coagulation is activated in patients with meningioma and glioblastoma

PURPOSE

Up to 30% of patients with glioblastoma (GBM) develop venous thromboembolism (VTE) over the course of the disease. Although not as high, the risk for VTE is also increased in patients with meningioma. Direct measurement of peak thrombin generation (TG) allows quantitative assessment of systemic coagulation activation in patients with GBM and meningioma. Our aim was to determine the extent of systemic coagulation activation induced by brain tumors, to measure the shift between pre- and post-operative peak TG in patients with GBM, and to assess the relationship between pre-surgical peak TG and pre-operative brain tumor volume on imaging.

METHODS

Pre- and post-surgical plasma samples were obtained from successive patients with GBM and once from patients with meningioma and healthy age- and sex-matched blood donor controls. TG was measured using the calibrated automated thrombogram (CAT) assay, and tumor volumes were measured in pre-surgical MRI scans.

RESULTS

Pre-surgical peak TG was higher in patients with GBM than in controls (288.6 ± 54.1 nM vs 187.1 ± 41.7 nM, respectively, P < 0.001), and, in the nine patients with GBM and paired data available, peak TG was significantly reduced after surgery (323 ± 38 nM vs 265 ± 52 nM, respectively, P = 0.007). Similarly, subjects with meningioma demonstrated higher peak TG compared to controls (242.2 ± 54.9 nM vs 177.7 ± 57.0 nM, respectively, P < 0.001). There was no association between peak TG and pre-operative tumor volume or overall survival.

CONCLUSION

Our results indicate that systemic coagulation activation occurs with both meningioma and GBM, but to a greater degree in the latter. Preoperative peak TG did not correlate with tumor volume, but removal of GBM caused a significant decrease in coagulation activation.

Glioblastoma cell populations with distinct oncogenic programs release podoplanin as procoagulant extracellular vesicles

Vascular anomalies, including local and peripheral thrombosis, are a hallmark of glioblastoma (GBM) and an aftermath of deregulation of the cancer cell genome and epigenome. Although the molecular effectors of these changes are poorly understood, the upregulation of podoplanin (PDPN) by cancer cells has recently been linked to an increased risk for venous thromboembolism (VTE) in GBM patients. Therefore, regulation of this platelet-activating protein by transforming events in cancer cells is of considerable interest. We used single-cell and bulk transcriptome data mining, as well as cellular and xenograft models in mice, to analyze the nature of cells expressing PDPN, as well as their impact on the activation of the coagulation system and platelets. We report that PDPN is expressed by distinct (mesenchymal) GBM cell subpopulations and downregulated by oncogenic mutations of EGFR and IDH1 genes, along with changes in chromatin modifications (enhancer of zeste homolog 2) and DNA methylation. Glioma cells exteriorize their PDPN and/or tissue factor (TF) as cargo of exosome-like extracellular vesicles (EVs) shed from cells in vitro and in vivo. Injection of glioma-derived podoplanin carrying extracelluar vesicles (PDPN-EVs) activates platelets, whereas tissue factor carrying extracellular vesicles (TF-EVs) activate the clotting cascade. Similarly, an increase in platelet activation (platelet factor 4) or coagulation (D-dimer) markers occurs in mice harboring the corresponding glioma xenografts expressing PDPN or TF, respectively. Coexpression of PDPN and TF by GBM cells cooperatively affects tumor microthrombosis. Thus, in GBM, distinct cellular subsets drive multiple facets of cancer-associated thrombosis and may represent targets for phenotype- and cell type-based diagnosis and antithrombotic intervention.

Plasma levels of extracellular vesicles and the risk of post-operative pulmonary embolism in patients with primary brain tumors: a prospective study

Primary brain tumors are associated with an increased risk of pulmonary embolism (PE), particularly in the early post-operative period. The pathophysiological mechanisms of PE are poorly understood. This study aims to describe prospectively extracellular vesicles (EVs) levels and investigate whether or not their variations allow to identify patients at increased risk of post-operative PE. Consecutive meningioma or glioma patients candidate to tumor resection were included in the study if a pulmonary perfusion scan (Q-scan) performed before surgery ruled out PE. EVs derived from platelets (CD41⁺) or endothelial cells (CD144⁺), tissue factor-bearing EVs (CD142⁺) and their procoagulant subtype (annexin V⁺) were analyzed by flow cytometry before surgery (T0), within 24 h (T1), two (T2) and seven days (T7) after surgery. Q-scan was repeated at T2. Ninety-three patients with meningioma, 59 with glioma and 76 healthy controls were included in the study. CD142⁺ and annexin V⁺/CD142⁺ EVs were increased at T0 in meningioma and glioma patients compared to healthy controls. Twenty-nine meningioma (32%) and 16 glioma patients (27%) developed PE at T2. EVs levels were similar in meningioma patients with or without PE, whereas annexin V⁺ and annexin V⁺/CD142⁺ EVs were significantly higher at T1 and T2 in glioma patients with PE than in those without. Procoagulant EVs, particularly annexin V⁺/CD142⁺, increase after surgery and are more prevalent in glioma patients who developed PE after surgery than in those who did not.

Cancer and thrombosis: new insights to an old problem

Venous thromboembolism (VTE) is a common complication in patients with cancer and portends a poor prognosis. Our understanding of the underlying pathophysiology of VTE in cancer has advanced since Trousseau first described hypercoagulability in patients with malignancy and Virchow described his famous triad of thrombosis formation. Malignancy itself induces a thrombophilic state by increasing the risk of venous stasis, endothelial injury and an imbalance of pro and anti-thrombotic factors leading to a hypercoaguable state. Additional insults to this thrombotic balance are introduced by patient-specific, treatment related and tumor-specific factors. The importance of understanding the factors associated with increased thrombosis in cancer is paramount in order to adequately identify patients who will benefit from thromboprophylaxis.

A new hybrid immunocapture bioassay with improved reproducibility to measure tissue factor-dependent procoagulant activity of microvesicles from body fluids

BACKGROUND

The procoagulant activity of tissue factor-bearing microvesicles (MV-TF) has been associated with the risk of developing venous thrombosis in cancer patients. However, MV-TF assays are limited either by i) a lack of specificity, ii) a low sensitivity, or iii) a lack of repeatability when high-speed centrifugation (HS-C) is used to isolate MV. Therefore, our objective was to develop a new hybrid "capture-bioassay" with improved reproducibility combining MV immunocapture from biofluids and measurement of their TF activity.

MATERIALS AND METHODS

Factor Xa generation and flow cytometry assays were used to evaluate IMS beads performance, and to select the most effective capture antibodies. The analytical performance between IMS-based and HS-C-based assays was evaluated with various models of plasma samples (from LPS-activated blood, spiked with tumoral MV, or with saliva MV) and different biofluids (buffer, plasma, saliva, and pleural fluid).

RESULTS

Combining both CD29 and CD59 antibodies on IMS beads was as efficient as HS-C to isolate plasmatic PS+ MV. The IMS-based strategy gave significantly higher levels of MV-TF activity than HS-C in tumor MV spiked buffer, and both pleural fluids and saliva samples. Surprisingly, lower TF values were measured in plasma due to TFPI (TF pathway inhibitor) non-specifically adsorbed onto beads. This was overcome by adding a TFPI-blocking antibody. After optimization, the new IMS-based assay significantly improved reproducibility of MV-TF bioassay versus the HS-C-based assay without losing specificity and sensitivity. In addition, this approach could identify the cellular origin of MV-TF in various biological fluids.

CONCLUSION

Compared to HS-C, the IMS-based measurement of MV-TF activity in body fluids improves reproducibility and makes the assay compatible with clinical practice. It can facilitate future automation.

Blood Biomarkers of Glioma in Response Assessment Including Pseudoprogression and Other Treatment Effects: A Systematic Review

Imaging-based monitoring of disease burden in glioma patients is frequently confounded by treatment effects. Circulating biomarkers could theoretically augment imaging-based response monitoring. This systematic review aimed to present and evaluate evidence for differential expression and diagnostic accuracy of circulating biomarkers with respect to outcomes of tumor response, progression, stable disease, and treatment effects (pseudoprogression, radionecrosis, pseudoresponse, and pseudolesions) in patients undergoing treatment for World Health Organization grades II-IV diffuse astrocytic and oligodendroglial tumors. MEDLINE, EMBASE, Web Of Science, and SCOPUS databases were searched until August 18, 2019, for observational or diagnostic studies on multiple circulating biomarker types: extracellular vesicles, circulating nucleic acids, circulating tumor cells, circulating proteins, and metabolites, angiogenesis related cells, immune cells, and other cell lines. Methodological quality of included studies was assessed using an adapted Quality Assessment of Diagnostic Accuracy Studies-2 tool, and level of evidence (IA-IVD) for individual biomarkers was evaluated using an adapted framework from the National Comprehensive Cancer Network guidelines on evaluating tumor marker utility. Of 13,202 unique records, 58 studies met the inclusion criteria. One hundred thirty-three distinct biomarkers were identified in a total of 1,853 patients across various treatment modalities. Fifteen markers for response, progression, or stable disease and five markers for pseudoprogression or radionecrosis reached level IB. No biomarkers reached level IA. Only five studies contained data for diagnostic accuracy measures. Overall methodological quality of included studies was low. While extensive data on biomarker dysregulation in varying response categories were reported, no biomarkers ready for clinical application were identified. Further assay refinement and evaluation in larger cohorts with diagnostic accuracy study designs are required. PROSPERO Registration: CRD42018110658.

Tissue factor procoagulant activity in the tumor cell lines and plasma of dogs with various malignant tumors

Hypercoagulability is a common paraneoplastic complication in dogs with various malignant tumors. Importantly, tissue factor procoagulant activity (TF-PCA) induced by TF-bearing microparticles (TF-MPs) is associated with hypercoagulability in human patients with cancer. However, TF-PCA in tumor cells and the association between circulating TF-MPs and hypercoagulability in dogs with malignant tumors remain poorly understood. Therefore, the present study was conducted to evaluate the TF-PCA in various types of canine tumor cell lines and plasma in dogs with malignant tumors. Mammary gland tumor, hemangiosarcoma, and malignant melanoma cell lines, but not lymphoma cell lines, expressed TF on their surfaces and showed cellular surface and MP-associated TF-PCA. The plasma TF-PCA was elevated in some dogs that naturally developed such tumors. No significant difference was observed in plasma TF-PCA between the disseminated intravascular coagulation (DIC) group (median: 43.40; range: 3.47-85.19; n=5) and non-DIC group (median: 7.73; range: 1.70-16.13; n=12). However, plasma TF-PCA was remarkably elevated in three of five dogs with DIC. To the best of our knowledge, this is the first study to evaluate plasma TF-PCA in dogs with malignant tumors. Further studies must be conducted to determine the cellular origin of TF-MPs and the efficacy of plasma TF-PCA as a biomarker of DIC in dogs with malignant tumors.

Increasing the sensitivity of the human microvesicle tissue factor activity assay

INTRODUCTION

The TF-FVIIa complex is the primary activator of coagulation. Elevated levels of microvesicle (MV) bearing tissue factor (TF)-dependent procoagulant activity are detectable in patients with an increased risk of thrombosis. Several methods have been described to measure MV TF activity but they are hampered by limited sensitivity and specificity. The aim of this work was to increase the sensitivity of the MV TF activity assay (called Chapel Hill assay).

MATERIAL AND METHODS

Improvements of the MV TF activity assay included i/ speed and time of centrifugation, ii/ use of a more potent inhibitory anti-TF antibody iii/ use of FVII and a fluorogenic substrate to increase specificity.

RESULTS

The specificity of the MV TF activity assay was demonstrated by the absence of activity on MV derived from a knock-out-TF cell line using an anti-human TF monoclonal antibody called SBTF-1, which shows a higher TF inhibitory effect than the anti-human TF monoclonal antibody called HTF-1. Experiments using blood from healthy individuals, stimulated or not by LPS, or plasma spiked with 3 different levels of MV, demonstrated that the new assay was more sensitive and this allowed detection of MV TF activity in platelet free plasma (PFP) samples from healthy individuals. However, the assay was limited by an inter-assay variability, mainly due to the centrifugation step.

CONCLUSIONS

We have improved the sensitivity of the MV TF activity assay without losing specificity. This new assay could be used to evaluate levels of TF-positive MV as a potential biomarker of thrombotic risk in patients.

Roles of Extracellular Vesicles in High-Grade Gliomas: Tiny Particles with Outsized Influence

High-grade gliomas, particularly glioblastomas (grade IV), are devastating diseases with dismal prognoses; afflicted patients seldom live longer than 15 months, and their quality of life suffers immensely. Our current standard-of-care therapy has remained essentially unchanged for almost 15 years, with little new therapeutic progress. We desperately need a better biologic understanding of these complicated tumors in a complicated organ. One area of rejuvenated study relates to extracellular vesicles (EVs)-membrane-enclosed nano- or microsized particles that originate from the endosomal system or are shed from the plasma membrane. EVs contribute to tumor heterogeneity (including the maintenance of glioma stem cells or their differentiation), the impacts of hypoxia (angiogenesis and coagulopathies), interactions amid the tumor microenvironment (concerning the survival of astrocytes, neurons, endothelial cells, blood vessels, the blood-brain barrier, and the ensuing inflammation), and influences on the immune system (both stimulatory and suppressive). This article reviews glioma EVs and the ways that EVs manifest themselves as autocrine, paracrine, and endocrine factors in proximal and distal intra- and intercellular communications. The reader should note that there is much controversy, and indeed confusion, in the field over the exact roles for EVs in many biological processes, and we will engage some of these difficulties herein.

Importance of GFAP isoform-specific analyses in astrocytoma

Gliomas are a heterogenous group of malignant primary brain tumors that arise from glia cells or their progenitors and rely on accurate diagnosis for prognosis and treatment strategies. Although recent developments in the molecular biology of glioma have improved diagnosis, classical histological methods and biomarkers are still being used. The glial fibrillary acidic protein (GFAP) is a classical marker of astrocytoma, both in clinical and experimental settings. GFAP is used to determine glial differentiation, which is associated with a less malignant tumor. However, since GFAP is not only expressed by mature astrocytes but also by radial glia during development and neural stem cells in the adult brain, we hypothesized that GFAP expression in astrocytoma might not be a direct indication of glial differentiation and a less malignant phenotype. Therefore, we here review all existing literature from 1972 up to 2018 on GFAP expression in astrocytoma patient material to revisit GFAP as a marker of lower grade, more differentiated astrocytoma. We conclude that GFAP is heterogeneously expressed in astrocytoma, which most likely masks a consistent correlation of GFAP expression to astrocytoma malignancy grade. The GFAP positive cell population contains cells with differences in morphology, function, and differentiation state showing that GFAP is not merely a marker of less malignant and more differentiated astrocytoma. We suggest that discriminating between the GFAP isoforms GFAPδ and GFAPα will improve the accuracy of assessing the differentiation state of astrocytoma in clinical and experimental settings and will benefit glioma classification.

Cancer-Associated Thrombosis in Cirrhotic Patients with Hepatocellular Carcinoma

It is common knowledge that cancer patients are more prone to develop venous thromboembolic complications (VTE). It is therefore not surprising that patients with hepatocellular carcinoma (HCC) present with a significant risk of VTE, with the portal vein being the most frequent site (PVT). However, patients with HCC are peculiar as both cancer and liver cirrhosis are conditions that can perturb the hemostatic balance towards a prothrombotic state. Because HCC-related hypercoagulability is not clarified at all, the aim of the present review is to summarize the currently available knowledge on epidemiology and pathogenesis of non-malignant thrombotic complications in patients with liver cirrhosis and HCC. They are at increased risk to develop both PVT and non-splanchnic VTE, indicating that both local and systemic factors can foster the development of site-specific thrombosis. Recent studies have suggested multiple and often interrelated mechanisms through which HCC can tip the hemostatic balance of liver cirrhosis towards hypercoagulability. Described mechanisms include increased fibrinogen concentration/polymerization, thrombocytosis, and release of tissue factor-expressing extracellular vesicles. Currently, there are no specific guidelines on the use of thromboprophylaxis in this unique population. There is the urgent need of prospective studies assessing which patients have the highest prothrombotic profile and would therefore benefit from early thromboprophylaxis.

Platelet activation parameters and platelet-leucocyte-conjugate formation in glioblastoma multiforme patients

Patients with glioblastoma multiforme (GBM) suffer from an increased incidence of vascular thrombotic events. However, key influencing factors of the primary hemostasis have not been characterized in GBM patients to date. Thus, the present study determines the activation level of circulating platelets in GBM patients, in-vitro reactivity to agonist-induced platelet stimulation and the formation of circulating platelet-leucocyte conjugates as well as the plasma levels of the proinflammatory lipid mediator sphingosine-1-phosphate (S1P). The endogenous thrombin potential (ETP) was determined as global marker for hemostasis. The 21 GBM patients and 21 gender and age matched healthy individuals enrolled in this study did not differ in mean total platelet count. Basal surface expression of platelet CD63 determined by flow cytometry was significantly increased in GBM patients compared to controls as was observed for the concentration of soluble P-selectin in the plasma of GBM patients. While the ETP was not affected, the immunomodulatory lipid S1P was significantly decreased in peripheral blood in GBM. Interestingly, monocyte expression of PSGL-1 (CD162) was decreased in GBM patient blood, possibly explaining the rather decreased formation of platelet-monocyte conjugates. Our study reveals an increased CD63 expression and P-selectin expression/ secretion of circulating platelets in GBM patients. In parallel a down-modulated PSGL-1 expression in circulating monocytes and a trend towards a decreased formation of heterotypic platelet-monocyte conjugates in GBM patients was seen. Whether this and the observed decreased plasma level of the immunomodulatory S1P reflects a systemic anti-inflammatory status needs to be addressed in future studies.

Tissue Factor-bearing MPs and the risk of venous thrombosis in cancer patients: A meta-analysis

Cancer patients with Tissue Factor (TF)-bearing MPs have been presented association with increased risk of venous thromboembolism (VTE), but results of these studies have not been consistent. We aimed to conduct a meta-analysis to assess the relationship between TF-bearing MPs and risk of VTE in patients with cancer. PubMed, Web of Science and EMBASE Databases were systematically retrieved up to1^th June 2017. Two case-control studies and four cohort studies met the entry requirements in this analysis. The summary odd ratio (OR) were estimated by a random effect model. The overall OR was 1.76 (95% CI: 1.21-2.56, I² = 62.0%). The OR of case-control studies was 3.41 (95% CI: 1.45-8.02, I² = 0.0%) and that of cohort studies was1.53 (95% CI: 1.05-2.24, I² = 66.1%). The association between TF-bearing MPs and the risk of VTE in cancer patients was found in this meta-analysis. Publication bias testing and sensitivity subgroup analysis suggested that results of this meta-analysis were robustness. In conclusion, TF-bearing MPs were associated with increased risk of VTE in patients with cancer. Whereas, more well-designed studies and more comprehensive adjustments for confounders in further studies are warranted to affirm the association.

Cancer-associated pathways and biomarkers of venous thrombosis

Cancer patients have an increased risk of venous thromboembolism (VTE). In this review, we summarize common and cancer type-specific pathways of VTE in cancer patients. Increased levels of leukocytes, platelets, and tissue factor-positive (TF⁺) microvesicles (MVs) are all potential factors that alone or in combination increase cancer-associated thrombosis. Patients with lung or colorectal cancer often exhibit leukocytosis. Neutrophils could increase VTE in cancer patients by releasing neutrophil extracellular traps whereas monocytes may express TF. Thrombocytosis is often observed in gastrointestinal, lung, breast, and ovarian cancer and this could decrease the threshold required for VTE. Soluble P-selectin has been identified as a biomarker of cancer-associated thrombosis in a general cancer population and may reflect activation of the endothelium. P-selectin expression by the endothelium may enhance VTE by increasing the recruitment of leukocytes. Studies in patients with pancreatic or brain cancer suggest that elevated levels of PAI-1 may contribute to VTE. Although elevated levels of TF⁺ MVs have been observed in patients with different types of cancer, an association between TF⁺ MVs and VTE has been observed only in pancreatic cancer. Podoplanin expression is associated with VTE in patients with brain cancer and may activate platelets. Future studies should measure multiple biomarkers in each cancer type to determine whether combinations of biomarkers can be used as predictors of VTE. A better understanding of the pathways that increase VTE in cancer patients may lead to the development of new therapies to reduce the morbidity and mortality associated with thrombosis.

Modulating thrombotic diathesis in hereditary thrombophilia and antiphospholipid antibody syndrome: a role for circulating microparticles?

Over the past decades, there have been great advances in the understanding of the pathogenesis of venous thromboembolism (VTE) in patients with inherited and acquired thrombophilia [mainly antiphospholipid antibody syndrome (APS)]. However, a number of questions remain unanswered. Prognostic markers capable of estimating the individual VTE risk would be of great use. Microparticles (MPs) are sub-micron membrane vesicles constitutively released from the surface of cells after cellular activation and apoptosis. The effects of MPs on thrombogenesis include the exposure of phopshatidylserine and the expression of tissue factor and MPs have been described in clinical studies as possible diagnostic and prognostic biomarkers for VTE. This review will provide a novel perspective on the current knowledge and research trends on the possible role of MPs in hereditary thrombophilia and APS. Basically, the published data show that circulating MPs may contribute to the development of VTE in thrombophilic carriers, both in mild and severe states. Moreover, the presence of endothelial-MPs and platelet-MPs has been described in antiphospholipid syndrome and seems to be directly linked to antiphospholipid antibodies and not to other underlying autoimmune disorders or the thrombotic event itself. In conclusion, circulating MPs may constitute an epiphenomenon of thrombophilia itself and could be up-regulated in acute particular conditions, promoting a global prothrombotic state up to the threshold of the clinical relevant thrombotic event.

Recent Progress in Research on the Pathogenesis of Pulmonary Thromboembolism: An Old Story with New Perspectives

Pulmonary thromboembolism (PTE) is part of a larger clinicopathological entity, venous thromboembolism. It is also a complex, multifactorial disorder divided into four major disease processes including venous thrombosis, thrombus in transit, acute pulmonary embolism, and pulmonary circulation reconstruction. Even when treated, some patients develop chronic thromboembolic pulmonary hypertension. PTE is also a common fatal type of pulmonary vascular disease worldwide, but earlier studies primarily focused on the pathological changes in the blood component of the disease. With contemporary advances in molecular and cellular biology, people are becoming increasingly aware of coagulation pathways, the function of vascular smooth muscle cells, microparticles, and the inflammatory pathways that play key roles in PTE. Combined hypoxia and immune research has revealed that PTE should be regarded as a class of complex diseases caused by multiple factors involving the vascular microenvironment and vascular cell dysfunction.

Biological basis of personalized anticoagulation in cancer: oncogene and oncomir networks as putative regulators of coagulopathy

Activation of stromal response pathways in cancer is increasingly viewed as both a local and systemic extension of molecular alterations driving malignant transformation. Rather than reflecting passive and unspecific responses to anatomical abnormalities, the coagulation system is a target of oncogenic deregulation, impacting the role of clotting and fibrinolytic proteins, and integrating hemostasis, inflammation, angiogenesis and cellular growth effects in cancer. These processes signify, but do not depend on, the clinically manifest coagulopathy and thrombosis. In this regard, the role of driver mutations affecting oncoprotein coding genes such as RAS, EGFR or MET and tumour suppressors (PTEN, TP53) are well described as regulators of tissue factor (TF), protease activated receptors (PAR-1/2) and ectopic coagulation factors (FVII). Indeed, in both adult and pediatric brain tumours the expression patterns of coagulation and angiogenesis regulators (coagulome and angiome, respectively) reflect the molecular subtypes of the underlying diseases (glioblastoma or medulloblastoma) as defined by their oncogenic classifiers and clinical course. This emerging understanding is still poorly established in relation to the transforming effects of non-coding genes, including those responsible for the expression of microRNA (miR). Indeed, several miRs have been recently found to regulate TF and other effectors. We recently documented that in the context of the aggressive embryonal tumour with multilayered rosettes (ETMR) the oncogenic driver miR (miR-520g) suppresses the expression of TF and correlates with hypocoagulant tumour characteristics. Unlike in adult cancers, the growth of pediatric embryonal brain tumour cells as spheres (to maintain stem cell properties) results in upregulation of miR-520g and downregulation of TF expression and activity. We postulate that oncogenic protein and miR coding genes form alternative pathways of coagulation system regulation in different tumour settings, a property necessitating more personalised and biologically-based approaches to anticoagulation.

Mutant IDH1 and thrombosis in gliomas

Mutant isocitrate dehydrogenase 1 (IDH1) is common in gliomas, and produces D-2-hydroxyglutarate (D-2-HG). The full effects of IDH1 mutations on glioma biology and tumor microenvironment are unknown. We analyzed a discovery cohort of 169 World Health Organization (WHO) grade II-IV gliomas, followed by a validation cohort of 148 cases, for IDH1 mutations, intratumoral microthrombi, and venous thromboemboli (VTE). 430 gliomas from The Cancer Genome Atlas were analyzed for mRNAs associated with coagulation, and 95 gliomas in a tissue microarray were assessed for tissue factor (TF) protein. In vitro and in vivo assays evaluated platelet aggregation and clotting time in the presence of mutant IDH1 or D-2-HG. VTE occurred in 26-30 % of patients with wild-type IDH1 gliomas, but not in patients with mutant IDH1 gliomas (0 %). IDH1 mutation status was the most powerful predictive marker for VTE, independent of variables such as GBM diagnosis and prolonged hospital stay. Microthrombi were far less common within mutant IDH1 gliomas regardless of WHO grade (85-90 % in wild-type versus 2-6 % in mutant), and were an independent predictor of IDH1 wild-type status. Among all 35 coagulation-associated genes, F3 mRNA, encoding TF, showed the strongest inverse relationship with IDH1 mutations. Mutant IDH1 gliomas had F3 gene promoter hypermethylation, with lower TF protein expression. D-2-HG rapidly inhibited platelet aggregation and blood clotting via a novel calcium-dependent, methylation-independent mechanism. Mutant IDH1 glioma engraftment in mice significantly prolonged bleeding time. Our data suggest that mutant IDH1 has potent antithrombotic activity within gliomas and throughout the peripheral circulation. These findings have implications for the pathologic evaluation of gliomas, the effect of altered isocitrate metabolism on tumor microenvironment, and risk assessment of glioma patients for VTE.

Microparticles as biomarkers of venous thromboembolic events

Microparticles (MPs) are small (0.1–1.0 μm) membrane vesicles constitutively released from the surface of cells after activation and apoptosis. The clinical research on MPs is hampered by the limitations of the currently available detection methods. A correlation between MPs and venous thromboembolism (VTE) has been observed. The effects of MPs on thrombogenesis involve the exposure of phosphatidylserine, the vehiculation of tissue factor, and MP-induced intercellular cross-talk between inflammation and coagulation. This review will focus on the potential role of plasma MPs as biomarkers in detecting acute unprovoked VTE, predicting VTE occurrence in high-risk situations (mainly cancer), and ultimately, we will discuss currently available studies on the prognostic role of MPs to guide primary and secondary VTE prevention protocols.

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.

Role of exosomes and microvesicles in hypoxia-associated tumour development and cardiovascular disease

Exosomes and microvesicles, collectively referred to as extracellular vesicles (EVs), can transfer complex biological information and induce a diverse signalling response in recipient cells with potential relevance in a wide array of pathological conditions. Tissue hypoxia constitutes a stress-associated phenotype that is central to the malignant state of aggressive tumours as well as to ischaemic tissue in cardiovascular disorders. The adaptive response to hypoxic stress is largely dependent on intercellular communication in which EVs, and cellular exchange of EV cargo molecules, have recently been implicated. The results of numerous studies indicate that hypoxia-dependent shaping of the molecular profile of EVs may mediate the biological response to hypoxia. EVs have been shown to induce tumour angiogenesis and hypercoagulation as well as tissue remodelling and protective effects in ischaemic cardiovascular conditions. Recent findings report increased levels of circulating EVs in patients with hypoxia-associated disorders such as myocardial infarction, stroke and pre-eclampsia, indicating a role of EVs as biomarkers in these pathophysiological states. Here, we discuss the intriguing role of EVs in tumour development and cardiovascular disease, focusing on the paracrine transfer of the hypoxic response to neighbouring cells and to distant cells at the systemic level, with wide implications for biomarker discovery and therapeutic intervention.

Microparticles That Form Immune Complexes as Modulatory Structures in Autoimmune Responses

Microparticles (MPs) are induced during apoptosis, cell activation, and even “spontaneous” release. Initially MPs were considered to be inert cellular products with no biological function. However, an extensive research and functional characterization have shown that the molecular composition and the effects of MPs depend upon the cellular background and the mechanism inducing them. They possess a wide spectrum of biological effects on intercellular communication by transferring different molecules able to modulate other cells. MPs interact with their target cells through different mechanisms: membrane fusion, macropinocytosis, and receptor-mediated endocytosis. However, when MPs remain in the extracellular milieu, they undergo modifications such as citrullination, glycosylation, and partial proteolysis, among others, becoming a source of neoantigens. In rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), reports indicated elevated levels of MPs with different composition, content, and effects compared with those isolated from healthy individuals. MPs can also form immune complexes amplifying the proinflammatory response and tissue damage. Their early detection and characterization could facilitate an appropriate diagnosis optimizing the pharmacological strategies, in different diseases including cancer, infection, and autoimmunity. This review focuses on the current knowledge about MPs and their involvement in the immunopathogenesis of SLE and RA.

Heparin in malignant glioma: review of preclinical studies and clinical results

Glioblastoma multiforme (GBM) is the most common primary brain tumor that is invariably lethal. Novel treatments are desperately needed. In various cancers, heparin and its low molecular weight derivatives (LMWHs), commonly used for the prevention and treatment of thrombosis, have shown therapeutic potential. Here we systematically review preclinical and clinical studies of heparin and LMWHs as anti-tumor agents in GBM. Even though the number of studies is limited, there is suggestive evidence that heparin may have various effects on GBM. These effects include the inhibition of tumor growth and angiogenesis in vitro and in vivo, and the blocking of uptake of extracellular vesicles. However, heparin can also block the uptake of (potential) anti-tumor agents. Clinical studies suggest a non-significant trend of prolonged survival of LMWH treated GBM patients, with some evidence of increased major bleedings. Heparin mimetics lacking anticoagulant effect are therefore a potential alternative to heparin/LMWH and are discussed as well.

Extracellular vesicles, tissue factor, cancer and thrombosis - discussion themes of the ISEV 2014 Educational Day

Although the association between cancer and venous thromboembolism (VTE) has long been known, the mechanisms are poorly understood. Circulating tissue factor–bearing extracellular vesicles have been proposed as a possible explanation for the increased risk of VTE observed in some types of cancer. The International Society for Extracellular Vesicles (ISEV) and International Society on Thrombosis and Haemostasis (ISTH) held a joint Educational Day in April 2014 to discuss the latest developments in this field. This review discusses the themes of that event and the ISEV 2014 meeting that followed.

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.

Pathophysiology of Trousseau's syndrome

Clinically relevant clotting abnormalities in cancer patients are referred to as Trousseau's syndrome. While thrombotic complications such as venous thromboembolism are most frequent in every day's practice, cancer patients may also experience severe bleeding symptoms due to complex systemic coagulopathies, including disseminated intravascular coagulation, haemolytic thrombotic microangiopathy, and hyperfibrinolysis. The pathophysiology of Trousseau's syndrome involves all aspects of Virchow's triad, but previous basic research has mainly focused on the cellular and molecular mechanisms underlying blood hypercoagulability in solid cancers and haematological malignancies. In this regard, over-expression of tissue factor (TF), the principal initiator of the extrinsic coagulation pathway, by primary tumour cells and increased shedding of TF-bearing plasma microparticles are critical to both thrombus formation and cancer progression. However, novel findings on intrinsic contact activation in vivo, such as the release of polyphosphates or DNA by activated platelets and neutrophils, respectively, have pointed to additional pathways in the complex pathophysiology of Trousseau's syndrome.

Membrane properties involved in calcium-stimulated microparticle release from the plasma membranes of S49 lymphoma cells

This study answered the question of whether biophysical mechanisms for microparticle shedding discovered in platelets and erythrocytes also apply to nucleated cells: cytoskeletal disruption, potassium efflux, transbilayer phospholipid migration, and membrane disordering. The calcium ionophore, ionomycin, disrupted the actin cytoskeleton of S49 lymphoma cells and produced rapid release of microparticles. This release was significantly inhibited by interventions that impaired calcium-activated potassium current. Microparticle release was also greatly reduced in a lymphocyte cell line deficient in the expression of scramblase, the enzyme responsible for calcium-stimulated dismantling of the normal phospholipid transbilayer asymmetry. Rescue of the scrambling function at high ionophore concentration also resulted in enhanced particle shedding. The effect of membrane physical properties was addressed by varying the experimental temperature (32–42°C). A significant positive trend in the rate of microparticle release as a function of temperature was observed. Fluorescence experiments with trimethylammonium diphenylhexatriene and Patman revealed significant decrease in the level of apparent membrane order along that temperature range. These results demonstrated that biophysical mechanisms involved in microparticle release from platelets and erythrocytes apply also to lymphocytes.

Tumor-derived tissue factor-positive microparticles and venous thrombosis in cancer patients

Patients with cancer have an increased risk for venous thrombosis. Interestingly, different cancer types have different rates of thrombosis, with pancreatic cancer having one of the highest rates. However, the mechanisms responsible for the increase in venous thrombosis in patients with cancer are not understood. Tissue factor (TF) is a transmembrane receptor and primary initiator of blood coagulation. Tumor cells express TF and spontaneously release TF-positive microparticles (MPs) into the blood. MPs are small membrane vesicles that are highly procoagulant. It has been proposed that these circulating tumor-derived, TF-positive MPs may explain the increased rates of venous thrombosis seen in patients with cancer. In animal models, increased levels of tumor-derived, TF-positive MPs are associated with activation of coagulation. Moreover, these MPs bind to sites of vascular injury and enhance thrombosis. We and others have found that patients with cancer have elevated levels of circulating TF-positive MPs. These MPs are derived from tumors because they express tumor markers and are decreased by tumor resection. Importantly, several studies have shown that increased levels of TF-positive MPs correlate with venous thrombosis in patients with cancer. Taken together, these results suggest that TF-positive MPs may be a useful biomarker to identify patients with cancer who are at high risk for thrombosis.