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

Lethal pulmonary thromboembolism in mice induced by intravenous human umbilical cord mesenchymal stem cell-derived large extracellular vesicles in a dose- and tissue factor-dependent manner

Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have obvious advantages over MSC therapy. But the strong procoagulant properties of MSC-EVs pose a potential risk of thromboembolism, an issue that remains insufficiently explored. In this study, we systematically investigated the procoagulant activity of large EVs derived from human umbilical cord MSCs (UC-EVs) both in vitro and in vivo. UC-EVs were isolated from cell culture supernatants. Mice were injected with UC-EVs (0.125, 0.25, 0.5, 1, 2, 4 μg/g body weight) in 100 μL PBS via the tail vein. Behavior and mortality were monitored for 30 min after injection. We showed that these UC-EVs activated coagulation in a dose- and tissue factor-dependent manner. UC-EVs-induced coagulation in vitro could be inhibited by addition of tissue factor pathway inhibitor. Notably, intravenous administration of high doses of the UC-EVs (1 μg/g body weight or higher) led to rapid mortality due to multiple thrombus formations in lung tissue, platelets, and fibrinogen depletion, and prolonged prothrombin and activated partial thromboplastin times. Importantly, we demonstrated that pulmonary thromboembolism induced by the UC-EVs could be prevented by either reducing the infusion rate or by pre-injection of heparin, a known anticoagulant. In conclusion, this study elucidates the procoagulant characteristics and mechanisms of large UC-EVs, details the associated coagulation risk during intravenous delivery, sets a safe upper limit for intravenous dose, and offers effective strategies to prevent such mortal risks when high doses of large UC-EVs are needed for optimal therapeutic effects, with implications for the development and application of large UC-EV-based as well as other MSC-EV-based therapies.

Tissue factor positive microparticles as a biomarker for increased risk of breast cancer-associated thrombosis: a mini review

PURPOSE OF REVIEW

Cancer-associated thrombosis (CAT), such as venous thromboembolism (VTE), is a frequent complication in cancer patients, resulting in poor prognosis. Breast cancer is not highly thrombogenic but is highly prevalent, resulting in increased VTE cases. Many cancers express tissue factor (TF), a glycoprotein that triggers coagulation. The cancer cells were shown to express and release substantial amounts of TF-positive microparticles (MPTF), associated with a prothrombotic state. This narrative review evaluated the current use of the procoagulant MPTF as a biomarker for thrombosis risk in breast cancer.

RECENT FINDINGS

Tumors of epithelial origin with elevated TF expression have been associated with increased VTE incidence. Thus, studies have affirmed the use of MPTF biomarkers for VTE risk in many cancers. Patients with metastatic breast cancer and CAT were found to exhibit elevated procoagulant microparticles in vitro, due to TF expression. The silencing of TF was associated with decreased microparticle release in breast carcinoma cell lines, associated with decreased coagulation.

SUMMARY

CAT is a multifactorial condition, with several various underlying diseases. It is proposed that MPTF may be an effective biomarker for thrombosis risk in breast cancer patients but requires a more systemic evaluation utilizing standardized quantification methods.

High concentration of the plasma microparticles for venous thromboembolism associated with lung cancer

BACKGROUND

Limited biomarkers are used for predicting risk of venous thromboembolism (VTE) associated with cancer. Circulating microparticles (MPs), especially tissue factor- positive microparticles (TF + MPs), play an important role in the development of cancer-associated VTE. This study investigated the predictive value of plasma MPs and TF + MPs for VTE in lung cancer.

METHODS

A case-control study was performed using the Beijing Chao-Yang Hospital Lung Cancer Registry. Cases had VTE occurring 3 months before or after a diagnosis of lung cancer. Controls were patients with lung cancer without VTE matched for age, histology and stage. The proportion of MPs and TF + MPs was evaluated by light-scatter-based flow cytometry.

RESULTS

Between January 2012 and December 2015, 30 cases with VTE and 60 controls without VTE were included. The proportion of MPs and TF + MPs was significantly more elevated in patients with VTE than in those without VTE (P < 0.05 for both). By multivariate logistic regression analysis, MPs (OR 1.153; 95% CI 1.068-1.245; P < 0.001) and adenocarcinoma (OR 3.223; 95% CI 1.062-9.782; P = 0.039) were significantly associated with VTE. The sensitivity of the proportion of MPs in diagnosing VTE was 93.3%, and the specificity was 70.0%. The sensitivity of the proportion of TF + MPs in diagnosing VTE was 66.7%, and the specificity was 88.3%. The area under the receiver operating characteristic curves for the diagnostic of the proportion of MPs and TF + MPs values were 0.836 (95% CI 0.750-0.922, P < 0.001) and 0.828 (95% CI 0.736-0.920, P < 0.001) respectively.

CONCLUSION

The elevated proportion of MPs and TF + MPs might help predict VTE associated with lung cancer.

Tissue factor activity on microvesicles from cancer patients

PURPOSE

The expression of active tissue factor (TF) on the surface of microvesicles (MVs) is essential for the activation of the coagulation system and transduction of the signaling pathways in cancer cells. In its use as a biomarker for cancer-associated venous thromboembolism (VTE), TF has shown high expression variability. As a contribution to this discussion, we present a study investigating plasma samples from patients with various progressive tumors at high risk for VTE.

METHODS

Based on our previous study uncovering microvesicles (MVs), the larger ectosome-like extracellular vesicles (EV), as the major source of TF activity in EV preparations, we now determined TF activity on enriched MVs isolated from plasma of cancer patients and compared it with that on MVs from healthy individuals.

RESULTS

We found considerably higher amounts of MVs as well as higher levels of MV-bound TF activities in the plasma of cancer patients. We also show that preparations from plasma of cancer patients have the potency to induce ERK phosphorylation in a human tumor cell line through proteinase-activated receptor two (PAR2) activation.

CONCLUSION

We suggest that MVs instead of whole EV preparations, and TF activity rather than its antigenic quantification should be used in clinical studies for identifying patients with progressive tumors at high risk for VTE.

Associations between Peripheral Thromboembolic Vascular Disease and Androgen Deprivation Therapy in Asian Prostate Cancer Patients

This study aimed to investigate the risks of thromboembolic vascular disease following androgen deprivation therapy (ADT) administered to prostate cancer (PCa) patients. A total of 24,464 men with newly diagnosed PCa during 2000–2008 were recruited through a longitudinal health insurance database in Taiwan. All PCa patients were stratified into two: ADT and non-ADT groups. Patients with ADT treatment were grouped into three: surgical castration, chemical castration, and anti-androgen alone. The risks of pulmonary embolism (PE), peripheral arterial occlusion disease (PAOD), and deep vein thrombosis (DVT) were assessed in multiple Cox proportional-hazards regression with time-dependent covariates. During the 12-year follow-up period, incidence rates per 1000 person-years in ADT and non-ADT groups were 2.87 and 1.62 for DVT, 1.00 and 0.52 for PE, and 1.03 and 0.70 for PAOD, respectively. The DVT and PE risks were significantly increased in patients receiving combined androgen blockade (CAB) compared with the counterpart ADT non-recipients. After adjusting for potential risk factors, PCa patients receiving CAB had the highest PE risk (HR = 3.11), followed by DVT risk (HR = 2.53). The DVT risk remained elevated throughout the entire duration of chemical castration. However, high PE risk was observed in patients with ≤720-day treatment duration. No association was found between ADT and PAOD risks. Overall, the risks of PE and DVT were considerably heightened in Asian men subjected to CAB for PCa, whereas PAOD risk was unrelated to such treatments.

Promising biomarkers for the prediction of catheter-related venous thromboembolism in hospitalized children: An exploratory study

BACKGROUND

Pediatric venous thromboembolism (VTE) has increased over the past 10 years, with central venous catheters (CVC) being the strongest risk factor. Current tools are not sufficient to predict VTE risk. The utility of biomarkers in predicting CVC-related VTE has been minimally explored. Our objective is to determine the utility of microparticles (MPs), factor VIII (FVIII) activity, and thrombin generation (TG) in prospectively predicting VTE occurrence in hospitalized children with CVCs.

PROCEDURE

In this nested case-control pilot study, consecutive hospitalized children needing CVC placement (1 month to 21 years) were enrolled. Venous samples were collected prior to or within 24 h of CVC placement. MPs were measured using factor Xa initiated clot-based assay. FVIII was measured using a one-stage clot-based assay. TG was measured using calibrated automated thrombogram.

RESULTS

There were three CVC-related VTE events (7%) in our cohort of 42 subjects. Xa clotting time (XaCT) ratio was lower (0.68 ± 0.07 vs 0.95 ± 0.21, P = .4), while FVIII (461 ± 120 vs 267 ± 130, P = .02), peak thrombin (418 ± 89 vs 211 ± 101, P = .001), endogenous thrombin potential (ETP) (1828 ± 485 vs 1282 ± 394, P = .03), and velocity index (VI) (182 ± 28 vs 75 ± 53, P = .001) were higher in subjects with CVC-related VTE compared to those without CVC-related VTE. Sensitivity/specificity analysis revealed optimal cutoff values for XaCT ratio (0.75), FVIII (370), ETP (1680), peak (315), and VI (130), with receiver operating characteristic area under the curve values >0.9.

CONCLUSION

MPs, FVIII, and TG can potentially predict pediatric CVC-related VTE in a prospective fashion. Stratification according to VTE risk may aid in guiding preventative efforts in future studies.

Anticoagulation Strategies in Patients With Cancer: JACC Review Topic of the Week

Patients with active cancer are at an increased risk of arterial and venous thromboembolism (VTE) and bleeding events. Historically, in patients with cancer, low molecular weight heparins have been preferred for treatment of VTE, whereas warfarin has been the standard anticoagulant for stroke prevention in patients with atrial fibrillation (AF). More recently, direct oral anticoagulants (DOACs) have been demonstrated to reduce the risk of venous and arterial thromboembolism in large randomized clinical trials of patients with VTE and AF, respectively, thus providing an attractive oral dosing option that does not require routine laboratory monitoring. In this review, we summarize available clinical trial data and guideline recommendations, and outline a practical approach to anticoagulation management of VTE and AF in cancer.

Heterogeneity of microvesicles from cancer cell lines under inflammatory stimulation with TNF-α

Microvesicles (MVs) represent a subgroup of extracellular vesicles (EVs) emerging from various cells by blebbing of their outer membrane. Therefore, they share features such as membrane composition and antigenicity with their parental cells. Released by many immune and tumor cells, MVs act as intercellular messengers, account for horizontal gene transfer and can activate the coagulation system. With the aim to investigate their relevance for tumor cell biology, we characterized MVs released by human tumor cell lines of various origins in the absence or presence of TNF-α. After stimulation, we used the combination of low and high-speed centrifugation to enrich MVs from cell culture supernatants. We analyzed the presentation of phosphatidylserine (PS) and tissue factor (TF) activity on the cell surface and investigated their potency to induce tumor cell migration. In all tumor cell lines, TNF-α stimulation enhanced the release of MVs. While the expression of PS was universally increased, an elevated activity of procoagulant TF could be detected on MVs from lung, pancreatic, and colon carcinoma, but not from breast and ovarian cancer cell lines. Functionally, TNF-α stimulation significantly increased the potency of MVs to induce tumor cell migration. In conclusion, inflammatory conditions promote the release of MVs with increased procoagulant activity from tumor cell lines in vitro. PS-containing and TF-expressing MVs may account for systemic activation of the coagulation system as seen in cancer patients and, since they induce tumor cell migration, they may serve as biomarkers for tumor progression.

Adipose-derived mesenchymal stem cells release microvesicles with procoagulant activity

Extracellular vesicles are produced by a number of different cell types, among them mesenchymal stromal/stem cells (MSC) of different sources. It has been shown that extracellular vesicles of MSC exert similar therapeutic effects as the cells themselves. Here, we isolated and characterized extracellular vesicles produced by adipose-derived MSC (adMSC) in vitro upon stimulation with the proinflammatory substances lipopolysaccharide (LPS) and tumor necrosis factor (TNF). We found that the number of vesicles produced by adMSC does not change upon stimulation of the cells with LPS and TNF. Furthermore, adMSC-derived extracellular vesicles exert procoagulant activity independent of previous stimulation with LPS or TNF. We found evidence that the vesicles induce coagulation via both the intrinsic and the extrinsic pathway of coagulation.

The coagulome and the oncomir: impact of cancer-associated haemostatic dysregulation on the risk of metastasis

Patients with cancer are at high risk of both thromboembolic and haemorrhagic events during the course of their disease. The pathogenesis of haemostatic dysfunction in cancer is complex and involves the interplay of multiple factors. There is growing evidence that interactions between malignancies and the coagulation system are not random but can represent coordinated and clinically-significant adaptations that enhance tumour cell survival, proliferation and metastatic potential. A detailed understanding of the interactions between the haemostatic systems and the pathophysiology of metastasis may not only provide insight into strategies that could potentially reduce the incidence of thrombohaemorrhagic events and complications, but could also help design strategies that are capable of modifying tumour biology, progression and metastatic potential in ways that could enhance anticancer therapies and thereby improve overall survival.

Platelets in cancer and thrombosis

Platelets are the smallest circulating blood cells and their major function is the maintenance of haemostasis. They do not have a nucleus, but instead a multitude of granules that contain molecules important for several physiological processes. These granules can be released after platelet activation and thereby platelets take part in haemostasis, wound repair or immunological processes. Furthermore, platelets are also involved in the pathophysiology of several diseases, including cancer. Platelets can support various steps of cancer development and progression by promoting tumour growth, angiogenesis and metastasis. Moreover, platelets contribute to the hypercoagulable state frequently observed in cancer patients, leading to an increased risk of venous thromboembolism (VTE). In previous studies a high platelet count was repeatedly found to be associated with an elevated risk of VTE and a worse prognosis in patients with cancer.

The aim of this review is to give an overview of the most important alterations of platelet physiology in cancer patients and how these alterations may influence cancer disease and contribute to cancer-associated 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.

Thrombosis in cancer patients: etiology, incidence, and management

Venous thromboembolism (VTE) is the second most common cause of mortality in cancer patients. The mechanisms of cancer-associated thrombosis (CAT), much like cancer itself, are multi-factorial and incompletely understood. Cancer type, stage, tumor-derived factors and genetics all affect CAT risk. Furthermore, cancer therapies as well as the indwelling vascular devices through which these therapies are delivered can increase the risk for CAT. In this review, we summarize mechanisms of hypercoagulability in cancer patients, patterns of thrombosis associated with cancer, current guidelines for the diagnosis and management of CAT, and important considerations regarding the placement of implantable vascular devices in the care of cancer patients with VTE.

Tissue factor expressed by microparticles is associated with mortality but not with thrombosis in cancer patients

A prothrombotic state is one of the hallmarks of malignancy and a major contributor to morbidity and mortality in cancer patients. Tissue factor (TF) is often overexpressed in malignancy and is a prime candidate in predicting the hypercoagulable state. Moreover, increased number of TF-exposing microparticles (MPs) in cancer patients may contribute to venous thromboembolism (VTE). We have conducted a prospective cohort study to determine whether elevated TF antigen, TF activity and TF associated to MPs (MPs-TF) are predictive of VTE and mortality in cancer patients. The studied population consisted of 252 cancer patients and 36 healthy controls. TF antigen and activity and MPs-TF were determined by ELISA and chromogenic assays. During a median follow-up of 10 months, 40 thrombotic events were recorded in 34 patients (13.5%), and 73 patients (28.9%) died. TF antigen and activity were significantly higher in patients than in controls (p<0.01) mainly in patients with advanced stages, whereas no differences were observed for TF activity of isolated MPs. We did not find a statistically significant association of TF variables with the risk of VTE. Multivariate analysis adjusting for age, sex, type of cancer and other confounding variables showed that TF activity (p<0.01) and MPs-TF activity (p<0.05) were independently associated with mortality. In conclusion, while TF variables were not associated with future VTE in cancer patients, we found a strong association of TF and MPs-TF activity with mortality, thus suggesting they might be good prognostic markers in cancer patients.

Endothelium-derived microparticles from chronically thromboembolic pulmonary hypertensive patients facilitate endothelial angiogenesis

Background

Increased circulating levels of endoglin⁺ endothelial microparticles (EMPs) have been identified in several cardiovascular disorders, related to severity. Endoglin is an auxilary receptor for transforming growth factor β (TGF-β) important in the regulation of vascular structure.

Results

We quantified the number of microparticles in plasma of six patients with chronic thromboembolic pulmonary hypertension (CTEPH) and age- and sex-matched pulmonary embolic (PE) and healthy controls and investigated the role of microparticle endoglin in the regulation of pulmonary endothelial function in vitro. Results show significantly increased levels of endoglin⁺ EMPs in CTEPH plasma, compared to healthy and disease controls. Co-culture of human pulmonary endothelial cells with CTEPH microparticles increased intracellular levels of endoglin and enhanced TGF-β-induced angiogenesis and Smad1,5,8 phosphorylation in cells, without affecting BMPRII expression. In an in vitro model, we generated endothelium-derived MPs with enforced membrane localization of endoglin. Co-culture of these MPs with endothelial cells increased cellular endoglin content, improved cell survival and stimulated angiogenesis in a manner similar to the effects induced by overexpressed protein.

Conclusions

Increased generation of endoglin⁺ EMPs in CTEPH is likely to represent a protective mechanism supporting endothelial cell survival and angiogenesis, set to counteract the effects of vascular occlusion and endothelial damage.

Electronic supplementary material

The online version of this article (doi:10.1186/s12929-016-0224-9) contains supplementary material, which is available to authorized users.

A phase I clinical trial of bavituximab and paclitaxel in patients with HER2 negative metastatic breast cancer

Bavituximab is a chimeric monoclonal antibody that targets phosphatidylserine (PS). PS is externalized on cells in the tumor microenvironment when exposed to hypoxia and/or other physiological stressors. On attaching to PS, bavituximab is thought to promote antitumor immunity through its effects on PS receptors in monocytes, and myeloid-derived suppressor cells, as well as trigger antitumor effects by inducing an antibody-dependent cellular cytotoxicity on tumor-associated endothelial cells. We conducted a phase I clinical trial of bavituximab in combination with paclitaxel in patients with HER2-negative metastatic breast cancer. Patients were treated with weekly paclitaxel (80 mg/m² for 3/4 weeks) and weekly bavituximab (3 mg/kg for 4/4 weeks). Correlative studies included the measurement of circulating microparticles, endothelial cells, and apoptotic tumor cells by flow cytometry. Fourteen patients with metastatic breast cancer were enrolled; all were evaluable for toxicity and 13 were evaluable for response. Treatment resulted in an overall response rate (RR) of 85% with a median progression-free survival (PFS) of 7.3 months. Bone pain, fatigue, headache, and neutropenia were the most common adverse effects. Infusion-related reactions were the most common adverse event related to bavituximab therapy. Correlative studies showed an increase in the PS-expressing apoptotic circulating tumor cells in response to bavituximab, but not with paclitaxel. No changes in the number of circulating endothelial cells or apoptotic endothelial cells were observed with therapy. Platelet and monocyte-derived microparticles decreased after initiation of bavituximab. Bavituximab in combination with paclitaxel is well tolerated for treatment of patients with metastatic breast cancer with promising results observed in terms of clinical RRs and PFS. The toxicity profile of bavituximab is notable for manageable infusion-related reactions with no evidence for increased thrombogenicity. Recent preclinical data suggest that bavituximab can also promote antitumor immune activity that should be explored in future clinical trials.

VTE risk assessment in cancer. Who needs prophylaxis and who does not?

Venous thromboembolism (VTE) in patients with cancer is associated with an increased morbidity and mortality, and its prevention is of major clinical importance. However, the VTE rates in the cancer population vary between 0.5% - 20%, depending on cancer-, treatment- and patient-related factors. The most important contributors to VTE risk are the tumor entity, stage and certain anti-cancer treatments. Cancer surgery represents a strong risk factor for VTE, and medical oncology patients are at increased risk of developing VTE, especially when receiving chemotherapy or immunomodulatory drugs. Also biomarkers have been investigated for their usefulness to predict risk of VTE (e.g. elevated leukocyte and platelet counts, soluble P-selectin, D-dimer, etc.). In order to identify cancer patients at high risk of VTE and to improve risk stratification, risk assessment models have been developed, which contain both clinical parameters and biomarkers. While primary thromboprophylaxis with low-molecular-weight-heparin (LMWH) is recommended postoperatively for a period of up to 4 weeks after major cancer surgery, the evidence is less clear for medical oncology patients. Thromboprophylaxis in hospitalized medical oncology patients is advocated, and is based on results of randomized controlled trials which evaluated the efficacy and safety of LMWH for prevention of VTE in hospitalized medically ill patients. In recent trials the benefit of primary thromboprophylaxis in cancer patients receiving chemotherapy in the ambulatory setting has been investigated. However, at the present stage primary thromboprophylaxis for prevention of VTE in these patients is still a matter of debate and cannot be recommended for all cancer outpatients.

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.

Flamethrowers: blood cells and cancer thrombosis risk

Cancer patients are at an increased risk of venous thromboembolism. The clotting system is activated in most cancer patients, which is reflected by specific parameters such as an increased thrombin generation and elevated D-dimer levels. Blood cells, especially WBCs and platelets, play an important role in this activation process. Neutrophils and monocytes are subpopulations of WBCs that increase the thrombotic potential by different mechanisms. Neutrophils are activated by tumor cells and can release DNA, generating highly thrombogenic neutrophil extracellular traps. Monocytes are able to synthesize and express significant quantities of procoagulant tissue factor on their surfaces upon activation. An increased risk of VTE has been found in patients with solid tumors and elevated platelet count and in those with high-grade gliomas and low platelet count. Small circulating membrane vesicles, also called microparticles (MPs), which largely derive from platelets, contribute to the procoagulant potential. Specifically, procoagulant MPs could play a role in tumor-associated thrombosis in pancreatic cancer. Interventional studies are under way that are investigating the benefits of thromboprophylaxis in patients identified to be at high risk of VTE through risk-scoring models that include blood count parameters. The “flames” thrown by blood cells, such as neutrophil extracellular traps and MPs, although exciting, still have to be investigated for their usefulness in the clinical setting.

Flamethrowers: blood cells and cancer thrombosis risk

Cancer patients are at an increased risk of venous thromboembolism. The clotting system is activated in most cancer patients, which is reflected by specific parameters such as an increased thrombin generation and elevated D-dimer levels. Blood cells, especially WBCs and platelets, play an important role in this activation process. Neutrophils and monocytes are subpopulations of WBCs that increase the thrombotic potential by different mechanisms. Neutrophils are activated by tumor cells and can release DNA, generating highly thrombogenic neutrophil extracellular traps. Monocytes are able to synthesize and express significant quantities of procoagulant tissue factor on their surfaces upon activation. An increased risk of VTE has been found in patients with solid tumors and elevated platelet count and in those with high-grade gliomas and low platelet count. Small circulating membrane vesicles, also called microparticles (MPs), which largely derive from platelets, contribute to the procoagulant potential. Specifically, procoagulant MPs could play a role in tumor-associated thrombosis in pancreatic cancer. Interventional studies are under way that are investigating the benefits of thromboprophylaxis in patients identified to be at high risk of VTE through risk-scoring models that include blood count parameters. The "flames" thrown by blood cells, such as neutrophil extracellular traps and MPs, although exciting, still have to be investigated for their usefulness in the clinical setting.

Biomarkers predictive of venous thromboembolism in patients with newly diagnosed high-grade gliomas

BACKGROUND

High-grade gliomas (HGGs) are among the most prothrombotic of malignancies.

METHODS

We performed a prospective study to investigate 11 potential biomarkers for prediction of venous thromboembolism (VTE) in newly diagnosed HGG patients who had undergone a neurosurgical intervention. In addition, we tested 2 VTE risk assessment models (RAMs). The strongest predictors of VTE, which were identified by statistical forward selection, were used for the first RAM. The parameters used for the second RAM were both predictive of VTE and available in routine clinical practice.

RESULTS

One hundred forty-one HGG patients were included in this study, and 24 (17%) of them developed VTE during follow-up. An association with the risk of future VTE was found for the following parameters: leukocyte count, platelet count, sP-selectin, prothrombin-fragment 1 + 2, FVIII activity, and D-dimer. The first RAM included low platelet count (<25th percentile of the study population) and elevated sP-selectin (≥75th percentile). The cumulative VTE probability after 12 months was 9.7% for score 0 (n = 76), 18.9% for score 1 (n = 59), and 83.3% for score 2 (n = 6). The second RAM included low platelet count (<25th percentile), elevated leukocyte count, and elevated D-dimer (≥75th percentile). The probability of VTE was 3.3% for score 0 (n = 63), 23.0% for score 1 (n = 53), and 37.7% for score 2 (n = 22) or score 3 (n = 3).

CONCLUSIONS

We identified biomarkers suitable for assessing the VTE risk in newly diagnosed HGG patients. The application of 2 RAMs allowed identification of patients at high risk of developing VTE. We could also define patients at low risk of VTE, who would most probably not benefit from extended primary thromboprophylaxis.

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.

Biomarkers for prediction of venous thromboembolism in cancer

Cancer patients are at increased risk of deep vein thrombosis and pulmonary embolism. The incidence among different groups of cancer patients varies considerably depending on clinical factors, the most important being tumor entity and stage. Biomarkers have been specifically investigated for their capacity of predicting venous thromboembolism (VTE) during the course of disease. Parameters of blood count analysis (elevated leukocyte and platelet count and decreased hemoglobin) have turned out to be useful in risk prediction. Associations between elevated levels and future VTE have been found for d-dimer, prothrombin fragment 1+2, and soluble P-selectin and also for clotting factor VIII and the thrombin generation potential. The results for tissue factor-bearing microparticles are heterogeneous: an association with occurrence of VTE in pancreatic cancer might be present, whereas in other cancer entities, such as glioblastoma, colorectal, or gastric carcinoma, this could not be confirmed. Risk assessment models were developed that include clinical and laboratory markers. In the high-risk categories, patient groups with up to a >20% VTE rate within 6 months can be identified. A further improvement in risk stratification would allow better identification of patients for primary VTE prevention using indirect or novel direct anticoagulants.

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.