Procoagulant activity of extracellular vesicles as a potential biomarker for risk of thrombosis and DIC in patients with acute leukaemia

Clinical and biological advances of critical complications in acute myeloid leukemia

Managing acute myeloid leukemia (AML) and its critical complications requires understanding the complex interplay between disease biology, treatment strategies, and patient characteristics. Complications like sepsis, acute respiratory failure (ARF), hyperleukocytosis, coagulopathy, tumor lysis syndrome (TLS) and central nervous system (CNS) involvement present unique challenges needing precise evaluation and tailored interventions. Venetoclax-induced TLS and differentiation syndrome (DS) from IDH1/IDH2 or menin inhibitors highlight the need for ongoing research and innovative approaches. As the microbiological landscape evolves and new therapeutic agents emerge, adapting strategies to mitigate harmful pharmacological interactions is crucial. Advances in understanding the genetic profiles of patients with hyperleukocytosis contribute to better-targeted therapeutic strategies. Effective AML management relies on collaborative efforts from hematologists, specialized services, and intensive care units (ICUs). This review analyzes recent data on critical AML complications, identifies areas for further investigation, and proposes ways to advance clinical research and enhance patient care strategies.

Update on Tissue Factor Detection in Blood in 2024: A Narrative Review

Tissue factor (TF) is a transmembrane protein essential for hemostasis. Different forms of active TF circulate in the blood, either as a component of blood cells and extracellular vesicles (EVs) or as a soluble plasma protein. Accumulating experimental and clinical evidence suggests that TF plays an important role in thrombosis. Many in-house and commercially available assays have been developed to measure TF-dependent procoagulant activity or antigen in blood and have shown promising results for the prediction of disease outcomes or the occurrence of thrombosis events in diseases such as cancer or infectious coagulopathies. This review addresses the different assays that have been published for measuring circulating TF antigen and/or activity in whole blood, cell-free plasma, and EVs and discusses the main preanalytical and analytical parameters that impact results and their interpretation, highlighting their strengths and limitations. In the recent decade, EVTF assays have been significantly developed. Among them, functional assays that use a blocking anti-TF antibody or immunocapture to measure EVTF activity have higher specificity and sensitivity than antigen assays. However, there is still a high variability between assays. Standardization and automatization are prerequisites for the measurement of EVTF in clinical laboratories.

Thrombosis in Myeloid Malignancies: From CHIP to AML

The development of myeloid malignancies is a multi-step process starting from pre-malignant stages. Large-scale studies on clonal hematopoiesis of indeterminate potential (CHIP) identified this condition as a risk factor for developing hematologic malignancies, in particular myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). In parallel, CHIP was found to confer an enhanced thrombotic risk, in particular for cardiovascular diseases. In a similar fashion, in recent years, alongside their life-threatening features, increasing attention has been drawn toward thrombotic complications in myeloid malignancies. Thus, the purpose of this review is to gather a growing body of evidence on incidence, pathogenesis and clinical impact of thrombosis in myeloid malignancies at every step of malignant progression, from CHIP to AML.

EXTRACELLULAR VESICLES AS REGULATORS OF IMMUNE FUNCTION IN TRAUMATIC INJURIES AND SEPSIS

ABSTRACT

Despite advancements in critical care and resuscitation, traumatic injuries are one of the leading causes of death around the world and can bring about long-term disabilities in survivors. One of the primary causes of death for trauma patients are secondary phase complications that can develop weeks or months after the initial insult. These secondary complications typically occur because of systemic immune dysfunction that develops in response to injury, which can lead to immunosuppression, coagulopathy, multiple organ failure, unregulated inflammation, and potentially sepsis in patients. Recently, extracellular vesicles (EVs) have been identified as mediators of these processes because their levels are increased in circulation after traumatic injury and they encapsulate cargo that can aggravate these secondary complications. In this review, we will discuss the role of EVs in the posttrauma pathologies that arise after burn injuries, trauma to the central nervous system, and infection. In addition, we will examine the use of EVs as biomarkers for predicting late-stage trauma outcomes and as therapeutics for reversing the pathological processes that develop after trauma. Overall, EVs have emerged as critical mediators of trauma-associated pathology and their use as a therapeutic agent represents an exciting new field of biomedicine.

Thrombin generation assay: the present and the future

The need for a more precise test that replicates the in vivo hemostatic conditions is increasingly being recognized. Up to now, the thrombin generation assay (TGA) has become the most reliable approach to evaluate the status of coagulation activation. The clinical potential for the TGA is most promising in the prediction of venous thromboembolism recurrence. However, there is currently an urgent need for a standardized global test that can reliably detect, predict and monitor coagulation disorders in both clinical and experimental studies. We have recently modified the TGA to analyze not only tissue factor-driven coagulation, but the intrinsic coagulation pathway as well. In the present review, we discuss different TG tests, emphasizing the requirement for a better understanding of the evaluation of distinct coagulation pathways using this technique, as well as the standardization and clinical validation.

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 Extracellular Vesicles Are Strongly Associated With Cardiovascular Risk Markers

Background

Extracellular vesicles (EVs) are submicron membrane-bound vesicles released from various cells, which are emerging as a potential novel biomarker in cardiovascular diseases (CVDs) due to their procoagulatory and prothrombotic properties. However, there is little information about the relationships between circulating EVs and conventional and thrombogenic risk markers of CVDs.

Objective

To investigate the relationships between circulating EVs, conventional cardiovascular risk markers and thrombogenic markers in subjects with moderate risk of CVDs.

Design

Subjects (n = 40) aged 40-70 years with moderate risk of CVDs were recruited and assessed for body mass index, blood pressure and plasma lipid profile, as well as platelet aggregation, clot formation, thrombin generation and fibrinolysis. Numbers of circulating EVs were assessed by Nanoparticle Tracking Analysis and flow cytometry. A range of assays were used to assess the procoagulatory activity of plasma and circulating EVs.

Results

Circulating EV numbers were positively associated with body mass index, blood pressure, plasma triacylglycerol concentration and overall CVD risk. Higher circulating EV numbers were also associated with increased thrombin generation and enhanced clot formation, and EVs isolated from subjects with moderate CVD risk promoted thrombin generation ex vivo. Higher numbers of endothelial-derived EVs were associated with a greater tendency for clot lysis. Plasma triacylglycerol concentration and diastolic blood pressure independently predicted circulating EV numbers, and EV numbers independently predicted aspects of thrombin generation and clot formation and 10-year CVD risk.

Conclusion

Circulating EVs were strongly associated with both conventional and thrombogenic risk markers of CVDs, and also with overall CVD risk, highlighting a potentially important role for EVs in CVDs.

Prevention of venous thromboembolism in hematologic neoplasms: an expert consensus from SEHH-SETH

Venous thromboembolism (VTE) is a serious complication in hematologic neoplasms, so finding adequate prevention strategies is an urgent requirement. However, prospective studies with large enough cohorts are scarce, limiting the development of evidence-based thromboprophylaxis guidelines. The present position paper is addressed to all hematologists treating patients affected by hematologic neoplasms with the aim to provide clinicians with a useful tool for the prevention of VTE.

Extracellular vesicles in kidneys and their clinical potential in renal diseases

Extracellular vesicles (EVs), such as exosomes and microvesicles, are cell-derived lipid bilayer membrane particles, which deliver information from host cells to recipient cells. EVs are involved in various biological processes including the modulation of the immune response, cell-to-cell communications, thrombosis, and tissue regeneration. Different types of kidney cells are known to release EVs under physiologic as well as pathologic conditions, and recent studies have found that EVs have a pathophysiologic role in different renal diseases. Given the recent advancement in EV isolation and analysis techniques, many studies have shown the diagnostic and therapeutic potential of EVs in various renal diseases, such as acute kidney injury, polycystic kidney disease, chronic kidney disease, kidney transplantation, and renal cell carcinoma. This review updates recent clinical and experimental findings on the role of EVs in renal diseases and highlights the potential clinical applicability of EVs as novel diagnostics and therapeutics.

The "Vesicular Intelligence" Strategy of Blood Cancers

Blood cancers are a heterogeneous group of disorders including leukemia, multiple myeloma, and lymphoma. They may derive from the clonal evolution of the hemopoietic stem cell compartment or from the transformation of progenitors with immune potential. Extracellular vesicles (EVs) are membrane-bound nanovesicles which are released by cells into body fluids with a role in intercellular communication in physiology and pathology, including cancer. EV cargos are enriched in nucleic acids, proteins, and lipids, and these molecules can be delivered to target cells to influence their biological properties and modify surrounding or distant targets. In this review, we will describe the “smart strategy” on how blood cancer-derived EVs modulate tumor cell development and maintenance. Moreover, we will also depict the function of microenvironment-derived EVs in blood cancers and discuss how the interplay between tumor and microenvironment affects blood cancer cell growth and spreading, immune response, angiogenesis, thrombogenicity, and drug resistance. The potential of EVs as non-invasive biomarkers will be also discussed. Lastly, we discuss the clinical application viewpoint of EVs in blood cancers. Overall, blood cancers apply a ‘vesicular intelligence’ strategy to spread signals over their microenvironment, promoting the development and/or maintenance of the malignant clone.

A pilot study of procoagulant platelet extracellular vesicles and P-selectin increase during induction treatment in acute lymphoblastic leukaemia paediatric patients: two new biomarkers of thrombogenic risk?

In paediatric acute lymphoblastic leukaemia (ALL), focus has shifted towards preventing treatment-related complications, including venous thromboembolism, the cause of significant mortality and morbidity. To better understand thrombogenic mechanisms during induction treatment, we studied the number, origin and procoagulant activity of extracellular vesicles (EVs) and P-selectin level throughout the induction course in 24 paediatric patients. EVs were mainly of platelet origin. We observed a significant increase in EV number, in platelet EV number and P-selectin level throughout the induction course. There was a correlation between higher EV and platelet EV number, P-selectin level, higher platelet count and leucocyte count. We also observed a correlation between higher EV procoagulant activity and higher platelet count and leucocyte count and higher P-selectin level. Older age and T phenotype were associated with a higher EV procoagulant activity. Platelet EV generation may play a role in thrombogenic complications in ALL patients and could serve as a biomarker to identify patients with a high risk of thrombosis. As a marker of platelet activation, P-selectin may be another relevant marker with the advantage of being easier to analyse in clinical practice.

Extracellular Vesicles as an Efficient and Versatile System for Drug Delivery

Despite the recent advances in drug development, the majority of novel therapeutics have not been successfully translated into clinical applications. One of the major factors hindering their clinical translation is the lack of a safe, non-immunogenic delivery system with high target specificity upon systemic administration. In this respect, extracellular vesicles (EVs), as natural carriers of bioactive cargo, have emerged as a promising solution and can be further modified to improve their therapeutic efficacy. In this review, we provide an overview of the biogenesis pathways, biochemical features, and isolation methods of EVs with an emphasis on their many intrinsic properties that make them desirable as drug carriers. We then describe in detail the current advances in EV therapeutics, focusing on how EVs can be engineered to achieve improved target specificity, better circulation kinetics, and efficient encapsulation of therapeutic payloads. We also identify the challenges and obstacles ahead for clinical translation and provide an outlook on the future perspective of EV-based therapeutics.

Deciphering the messages carried by extracellular vesicles in hematological malignancies

Extracellular vesicles (EVs) are nanosized membrane-bound particles released from all living cells examined thus far. EVs can transfer information in the form of proteins, nucleic acids, and lipids from donor cells to recipient cells. Here we summarize recent advances in understanding the role(s) EVs play in hematological malignancies (HM) and outline potential prognostic and diagnostic strategies using EVs. EVs have been shown to promote proliferation and angiogenesis, and alter the bone marrow microenvironment to favour the growth and survival of diverse HM. They also promote evasion of anti-cancer immune responses and increase multi-drug resistance. Using knowledge of EV biology, including HM-specific packaging of cargo, EV based diagnostics and therapeutic approaches show substantial clinical promise. However, while EVs may represent a new paradigm to solve many of the challenges in treating and/or diagnosing HM, much work is needed before they can be used clinically to improve patient outcomes.

Extracellular vesicles and coagulation in blood from healthy humans revisited

Background: In 2001, we studied the presence and coagulant properties of “microparticles” in the blood of healthy humans. Since then, multiple improvements in detection, isolation and functional characterization of the now called “extracellular vesicles” (EVs) have been made, and shortcomings were identified. Aim: To revisit the presence and function of EVs in blood from healthy humans. Methods: Blood was collected from 20 healthy donors. EV-containing plasma was prepared according to new guidelines, and plasma was diluted to prevent swarm detection. Single EVs were measured by flow cytometry with known sensitivity of fluorescence and light scatter. The haemostatic properties of EVs were measured by thrombin-, fibrin-, and plasmin generation. Plasma concentrations of thrombin-antithrombin complexes and prothrombin fragment 1 + 2 were measured to assess the coagulation status in vivo. Results: Compared to 2001, the total concentrations of detected EVs increased from 190- to 264-fold. In contrast to 2001, however, EVs are non-coagulant which we show can be attributed to improvements in blood collection and plasma preparation. No relation is present between the plasma concentrations of EVs and either TAT or F1 + 2. Finally, we show that EVs support plasmin generation. Discussion: Improvements in blood collection, plasma preparation and detection of EVs reveal that results from earlier studies have to be interpreted with care. Compared to 2001, higher concentrations of EVs are detected in blood of healthy humans which promote fibrinolysis rather than coagulation.

Thrombin Generation and Cancer: Contributors and Consequences

The high occurrence of cancer-associated thrombosis is associated with elevated thrombin generation. Tumour cells increase the potential for thrombin generation both directly, through the expression and release of procoagulant factors, and indirectly, through signals that activate other cell types (including platelets, leukocytes and erythrocytes). Furthermore, cancer treatments can worsen these effects. Coagulation factors, including tissue factor, and inhibitors of coagulation are altered and extracellular vesicles (EVs), which can promote and support thrombin generation, are released by tumour and other cells. Some phosphatidylserine-expressing platelet subsets and platelet-derived EVs provide the surface required for the assembly of coagulation factors essential for thrombin generation in vivo. This review will explore the causes of increased thrombin production in cancer, and the availability and utility of tests and biomarkers. Increased thrombin production not only increases blood coagulation, but also promotes tumour growth and metastasis and as a consequence, thrombin and its contributors present opportunities for treatment of cancer-associated thrombosis and cancer itself.

Low extracellular vesicle-associated tissue factor activity in patients with persistent lupus anticoagulant and a history of thrombosis

Lupus anticoagulants (LA) are a heterogeneous group of antiphospholipid antibodies (aPLAs) that promote thrombosis. Tissue factor (TF)-bearing extracellular vesicles (EVs) might contribute to the prothrombotic state of patients with persistent LA and a history of thrombosis. To investigate if EV-associated TF activity is elevated in a well-defined group of LA-positive patients with a history of thrombosis in comparison to that of healthy controls. Adult patients (n = 94, median age 40.1 years, interquartile range (IQR) 29.9-53.4; 87% females) positive for LA and a history of thrombosis (78% venous thrombosis, 17% arterial thrombosis, 5% venous thrombosis and arterial thrombosis) and healthy age- and sex-matched controls (n = 30, median age 42.9 years, IQR 38.6-45.8, 77% females) were included in this study. EV-TF activity was determined with a factor Xa generation assay and anti-β2-glycoprotein (anti-β2GPI) and anticardiolipin (aCL) antibodies by enzyme-linked immunoassays. EV-TF activity did not differ between 94 LA-positive patients with a history of thrombosis (median 0.05 pg/mL, IQR 0.00-0.14) and 30 healthy controls (median 0.06, IQR 0.00-0.11, p = 0.7745). No correlation was found between EV-TF activity and lupus-sensitive activated partial thromboplastin time (aPTT-LA) (rho = 0.034), Rosner index (rho = - 0.056), anti-β2GPI IgG (rho = 0.05), anti-β2GPI IgM (rho = - 0.08), aCL IgG (rho = 0.12), and aCL IgM (rho = - 0.11) in LA-positive patients. We found low EV-TF activity levels in LA-positive patients and a history of thrombosis and no correlation with analyzed aPLAs. Our data indicate that circulating TF-bearing EVs do not contribute to the prothrombotic state of patients with LA.

Increased Risk of Thrombosis Associated with Peripherally Inserted Central Catheters Compared with Conventional Central Venous Catheters in Children with Leukemia

OBJECTIVE

To study the risk of catheter-associated thrombosis (CAT) between peripherally inserted central catheters (PICCs) and tunneled central venous catheters in children with leukemia.

STUDY DESIGN

We analyzed all PICCs and conventional tunneled catheters placed in patients aged <18 years and admitted to our institute for leukemia treatment between February 2008 and April 2014. Cases of symptomatic CAT were confirmed by ultrasound and treated with low-molecular-weight heparin.

RESULTS

During the study period, 157 PICCs and 138 conventional tunneled catheters were placed in 192 patients with leukemia. CAT incidence was 1.5% (n = 2) in the conventional tunneled catheter group and 10.2% (n = 16) in the PICC group. The OR for CAT occurrence after PICC vs conventional tunneled catheter placement was 5.6 (95% CI, 1.2-26.5).

CONCLUSION

Our results suggest that the use of PICCs in children with leukemia increases the risk of CAT in comparison with the use of conventional tunneled catheters. Further randomized controlled studies are needed to characterize this risk and to better define indications.

Circulating MicroRNAs as Biomarkers in Diffuse Large B-cell Lymphoma: A Pilot Prospective Longitudinal Clinical Study

Objectives:

Diffuse large B-cell lymphoma (DLBCL) is highly heterogeneous in terms of phenotype and treatment response in patients. These characteristics make the prognosis difficult to establish and hinder the use of new personalized treatments in clinical practice. In this context, there is currently a need to define new biomarkers enabling a better definition of DLBCL subtypes, prognosis evaluation, and an overview of the resistance to chemotherapeutics. The aim of this study was to evaluate the use of microRNAs found in plasma from patients with DLBCL as biomarkers of tumor evolution in these patients.

Method:

For this purpose, a plasma biobank was created with samples from patients with DLBCL. The evolution of the level of selected microRNAs during treatment has been studied. A total of 19 patients with DLBCL were included in this pilot mono-centered study and a total of 68 samples were analyzed.

Results:

The first step of this study was the selection of the microRNAs to be quantified in all the samples of the biobank and that could potentially be used as biomarkers. To this end, quantification of 377 microRNAs was performed on the plasma samples of 2 selected patients with DLBCL and 1 healthy donor with no history of cancer. Among the 377 microRNAs evaluated, 7 were selected and analyzed in the entire biobank.

Conclusions:

This study highlighted 5 circulating microRNAs whose plasma levels would be worth further investigating for the characterization of DLBCL evolution in patients. MiR-21 and miR-197 had a significant higher plasmatic level in patients with tumors unresponsive to treatment. With a higher plasma level in patients with complete remission, miR-19b, miR-20a, and miR-451 could enable to differentiate, at the remission review, patients with residual tumor, from patients with complete remission.

Laboratory biomarkers for venous thromboembolism risk in patients with hematologic malignancies: A review

INTRODUCTION

Despite high rates of venous thromboembolism (VTE) among patients with hematologic malignancies, few tools exist to assist providers in identifying those patients at highest risk for this potentially fatal complication. Laboratory biomarkers, such as d-dimer, have demonstrated utility in some clinical settings to distinguish patients at increased risk.

MATERIALS AND METHODS

We performed a systematic review of the literature utilizing search terms including "biomarker", "venous thromboembolism", "hematologic malignancy", "lymphoma", "myeloma" and "leukemia" in the Medline database. A total of 25 studies investigating laboratory biomarkers of increased thrombotic risk in the setting of hematologic malignancy were identified and included in this review.

RESULTS AND CONCLUSIONS

The most studied biomarkers, d-dimer and fibrinogen, demonstrated some degree of efficacy in identifying high-risk patients at levels >4.0 mg/L or <1.0 g/L respectively. Additional markers which demonstrated promise included thrombin generation, mean platelet volume, soluble VEGF, soluble P-selectin and extracellular vesicles. Other biomarkers reviewed, which did not consistently demonstrate significant associations with VTE included prothrombin fragments F1 + 2, factor VIII, protein C, protein S, von Willebrand antigen and activity, antithrombin, thrombin antithrombin complex, antiphospholopid antibody, plasminogen activator inhibitor, tissue factor pathway inhibitor and several variants associated with known hypercoagulable states (factor V Leiden, prothrombin gene variant, methylenetetrahydrofolate reductase variant). Data to support any of the biomarkers discussed here in routine clinical decision-making are currently lacking, but additional investigation in clinical studies, ideally in combination with clinical factors known to be associated with increased thrombotic risk, is warranted.

Thrombosis in adult patients with acute leukemia

PURPOSE OF REVIEW

Recent studies indicate that the risk of thrombosis in hematologic patients may be similar or even higher than that found in patients with solid tumors. However, available information about pathogenesis and incidence of thrombosis in acute leukemia is limited. This review focuses on mechanisms underlying thrombosis in acute leukemia and discusses recent literature data.

RECENT FINDINGS

In the last few years, proofs have been provided that leukemic cells release free prothrombotic products, such as micro-vesicles, tissue factors, circulating free DNA and RNA. Furthermore, leukemic blasts can activate the procoagulant population of platelets, which initiate and amplify coagulation, causing thrombosis. In addition to factors produced by acute leukemia itself, others concur to trigger thrombosis. Some drugs, infections and insertion of central venous catheter have been described to increase risk of thrombosis in patients with acute leukemia.

SUMMARY

Thrombosis represents a serious complication in patients affected by myeloid and lymphoid acute leukemia. A proper knowledge of its pathophysiology and of the predisposing risk factors may allow to implement strategies of prevention. Improving prevention of thrombosis appears a major goal in patients whose frequent conditions of thrombocytopenia impede an adequate delivery of anticoagulant therapy.

Eculizumab decreases the procoagulant activity of extracellular vesicles in paroxysmal nocturnal hemoglobinuria: A pilot prospective longitudinal clinical study

INTRODUCTION

Paroxysmal nocturnal hemoglobinuria (PNH) is a disease characterized by the susceptibility of blood cells to attack by the complement system, inducing extracellular vesicle (EV) production. Thromboembolism is the leading cause of death in this condition. Eculizumab, a humanized monoclonal antibody which inhibits the C5 protein of the complement, reduces the thrombotic risk in PNH.

MATERIALS AND METHOD

We conducted a pilot, prospective, open-label, longitudinal clinical study with six PNH patients treated with eculizumab. The aim was to measure, by flow cytometry, the EVs' production in the patients' platelet-free plasma (PFP) before and during the treatment. We also assessed the procoagulant activity in PFP using STA®-Procoag-PPL and thrombin generation assays (TGA). A high-sensitive version of TGA was also used to study the procoagulant profile induced by the EVs using EVs pelleted from PFP.

RESULTS

We observed a decrease in platelet EV count with eculizumab treatment (p<0.05). STA®-Procoag-PPL assay showed a decrease of the procoagulant profile induced by procoagulant phospholipids (PL) during treatment. These results were not confirmed by TGA on PFP, due to a lack of sensitivity. Thus, we used a high-sensitive version of TGA that enabled us to observe variation in the procoagulant profile induced by the EVs with eculizumab (p<0.05).

CONCLUSIONS

Eculizumab has an impact on the extent of EV production and on the procoagulant profile induced by the procoagulant PL and the EVs. One factor in the antithrombotic action of eculizumab is its ability to decrease EV production and the procoagulant profile induced by PL and EVs.