Effects of all-trans retinoic acid or chemotherapy on the molecular regulation of systemic blood coagulation and fibrinolysis in patients with acute promyelocytic leukemia

Biomarkers of bleeding and venous thromboembolism in patients with acute leukemia

BACKGROUND

Coagulopathy and associated bleeding and deep vein thrombosis (DVT) are major causes of morbidity and mortality in patients with acute leukemia. The underlying mechanisms of these complications have not been fully elucidated.

OBJECTIVES

To evaluate the associations between biomarker levels and bleeding and DVT in acute leukemia patients.

METHODS

We examined plasma levels of activators, inhibitors, and biomarkers of the coagulation and fibrinolytic pathways in patients aged ≥18 years with newly diagnosed acute leukemia compared with those of normal controls. Multivariable regression models were used to examine the association of biomarkers with bleeding and DVT in acute leukemia patients. The study included 358 patients with acute leukemia (29 with acute promyelocytic leukemia [APL], 253 with non-APL acute myeloid leukemia, and 76 with acute lymphoblastic leukemia) and 30 normal controls.

RESULTS

Patients with acute leukemia had higher levels of extracellular vesicle tissue factor (EVTF) activity, phosphatidylserine-positive extracellular vesicles, plasminogen activator inhibitor-1, plasmin-antiplasmin complexes, and cell-free DNA and lower levels of citrullinated histone H3-DNA complexes compared with normal controls. APL patients had the highest levels of EVTF activity and the lowest levels of tissue plasminogen activator among acute leukemia patients. There were 41 bleeding and 23 DVT events in acute leukemia patients. High EVTF activity was associated with increased risk of bleeding (subdistribution hazard ratio, 2.30; 95% CI, 0.99-5.31), whereas high levels of plasminogen activator inhibitor-1 were associated with increased risk of DVT (subdistribution hazard ratio, 3.00; 95% CI, 0.95-9.47) in these patients.

CONCLUSION

Our study shows alterations in several biomarkers in acute leukemia and identifies biomarkers associated with risk of bleeding and DVT.

Dysregulated hemostasis in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is associated with a high incidence of early death, which occurs within 30 days of diagnosis. The major cause of early death in APL is severe bleeding, particularly intracranial bleeding. Although APL is known to be associated with activation of coagulation, hyperfibrinolysis, and thrombocytopenia, the precise mechanisms that cause bleeding have not yet been elucidated. I propose that a combination of four pathways may contribute to bleeding in APL: (1) tissue factor, (2) the urokinase plasminogen activator/urokinase plasminogen activator receptor, (3) the annexin A2/S100A100/tissue plasminogen activator, and (4) the podoplanin/C-type lectin-like receptor 2. A better understanding of these pathways will identify new biomarkers to determine which APL patients are at high risk of bleeding and allow the development of new treatments for APL-associated bleeding.

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.

Impaired fibrinolysis and increased clot strength are potential risk factors for thrombosis in lymphoma

Thrombosis and bleeding are significant contributors to morbidity and mortality in patients with hematological cancer, and the impact of altered fibrinolysis on bleeding and thrombosis risk is poorly understood. In this prospective cohort study, we investigated the dynamics of fibrinolysis in patients with hematological cancer. Fibrinolysis was investigated before treatment and 3 months after treatment initiation. A dynamic clot formation and lysis assay was performed beyond the measurement of plasminogen activator inhibitor 1, tissue- and urokinase-type plasminogen activators (tPA and uPA), plasmin-antiplasmin complexes (PAP), α-2-antiplasmin activity, and plasminogen activity. Clot initiation, clot propagation, and clot strength were assessed using rotational thromboelastometry. A total of 79 patients were enrolled. Patients with lymphoma displayed impaired fibrinolysis with prolonged 50% clot lysis time compared with healthy controls (P = .048). They also displayed decreased clot strength at follow-up compared with at diagnosis (P = .001). A patient with amyloid light-chain amyloidosis having overt bleeding at diagnosis displayed hyperfibrinolysis, indicated by a reduced 50% clot lysis time, α-2-antiplasmin activity, and plasminogen activity, and elevated tPA and uPA. A patient with acute promyelocytic leukemia also displayed marked hyperfibrinolysis with very high PAP, indicating extreme plasmin generation, and clot formation was not measurable, probably because of the extremely fast fibrinolysis. Fibrinolysis returned to normal after treatment in both patients. In conclusion, patients with lymphoma showed signs of impaired fibrinolysis and increased clot strength, whereas hyperfibrinolysis was seen in patients with acute promyelocytic leukemia and light-chain amyloidosis. Thus, investigating fibrinolysis in patients with hematological cancer could have diagnostic value.

Biomarkers of bleeding and venous thromboembolism in patients with acute leukemia

Background

Coagulopathy and associated bleeding and venous thromboembolism (VTE) are major causes of morbidity and mortality in patients with acute leukemia. The underlying mechanisms of these complications have not been fully elucidated.

Objectives

To evaluate the associations between biomarker levels and bleeding and VTE in acute leukemia patients.

Patients/Method

We examined plasma levels of activators, inhibitors and biomarkers of the coagulation and fibrinolytic pathways in patients ≥18 years with newly diagnosed acute leukemia compared to healthy controls. Multivariable regression models were used to examine the association of biomarkers with bleeding and VTE in acute leukemia patients. The study included 358 patients with acute leukemia (29 acute promyelocytic leukemia [APL], 253 non-APL acute myeloid leukemia [AML] and 76 acute lymphoblastic leukemia [ALL]), and 30 healthy controls.

Results

Patients with acute leukemia had higher levels of extracellular vesicle (EV) tissue factor (TF) activity, phosphatidylserine-positive EVs, plasminogen activator inhibitor-1 (PAI-1), plasmin-antiplasmin complexes, cell-free DNA and lower levels of citrullinated histone H3-DNA complexes compared to healthy controls. APL patients had the highest levels of EVTF activity and the lowest levels of tissue plasminogen activator among the acute leukemia patients. There were 41 bleeding and 37 VTE events in acute leukemia patients. High EVTF activity was associated with increased risk of bleeding (sHR 2.30, 95%CI 0.99-5.31) whereas high PAI-1 was associated with increased risk of VTE (sHR 3.79, 95%CI 1.40-10.28) in these patients.

Conclusions

Our study shows alterations in several biomarkers in acute leukemia and identifies biomarkers associated with risk of bleeding and VTE.

The Coagulopathy of Acute Promyelocytic Leukemia: An Updated Review of Pathophysiology, Risk Stratification, and Clinical Management

Acute promyelocytic leukemia (APL) has a well-established mechanism and a long-term prognosis that exceeds that of any other acute leukemia. These improving outcomes are due, in part, to all-trans retinoic acid (ATRA) and arsenic trioxide (ATO), two targeted and highly active agents in this disease. However, there remains a considerable morbidity and mortality risk in APL secondary to clinically significant hemorrhagic and/or thrombotic events. Prevention and treatment of these coagulopathic complications remain significant impediments to further progress in optimizing outcomes for patients with APL. Moreover, the relative rarity of APL hinders adequately powered randomized controlled trials for evaluating APL coagulopathy management strategies. This review draws from peer-reviewed works falling between initial descriptions of APL in 1957 and work published prior to January 2023 and provides an updated overview of the pathophysiology of hemorrhagic and thrombotic complications in APL, outlines risk stratification parameters, and compiles current clinical best practices. An improved understanding of the pathophysiologic mechanisms driving hemorrhage and thrombosis along with the completion of well-designed trials of management strategies will assist clinicians in developing interventions that mitigate these devastating complications in an otherwise largely curable disease.

The Tissue Factor Pathway in Cancer: Overview and Role of Heparan Sulfate Proteoglycans

Historically, the only focus on tissue factor (TF) in clinical pathophysiology has been on its function as the initiation of the extrinsic coagulation cascade. This obsolete vessel-wall TF dogma is now being challenged by the findings that TF circulates throughout the body as a soluble form, a cell-associated protein, and a binding microparticle. Furthermore, it has been observed that TF is expressed by various cell types, including T-lymphocytes and platelets, and that certain pathological situations, such as chronic and acute inflammatory states, and cancer, may increase its expression and activity. Transmembrane G protein-coupled protease-activated receptors can be proteolytically cleaved by the TF:FVIIa complex that develops when TF binds to Factor VII (PARs). The TF:FVIIa complex can activate integrins, receptor tyrosine kinases (RTKs), and PARs in addition to PARs. Cancer cells use these signaling pathways to promote cell division, angiogenesis, metastasis, and the maintenance of cancer stem-like cells. Proteoglycans play a crucial role in the biochemical and mechanical properties of the cellular extracellular matrix, where they control cellular behavior via interacting with transmembrane receptors. For TFPI.fXa complexes, heparan sulfate proteoglycans (HSPGs) may serve as the primary receptor for uptake and degradation. The regulation of TF expression, TF signaling mechanisms, their pathogenic effects, and their therapeutic targeting in cancer are all covered in detail here.

Highly Efficient Cardiac Differentiation and Maintenance by Thrombin-Coagulated Fibrin Hydrogels Enriched with Decellularized Porcine Heart Extracellular Matrix

Biochemical and biophysical properties instruct cardiac tissue morphogenesis. Here, we are reporting on a blend of cardiac decellularized extracellular matrix (dECM) from porcine ventricular tissue and fibrinogen that is suitable for investigations employing an in vitro 3D cardiac cell culture model. Rapid and specific coagulation with thrombin facilitates the gentle inclusion of cells while avoiding sedimentation during formation of the dECM-fibrin composite. Our investigations revealed enhanced cardiogenic differentiation in the H9c2 myoblast cells when using the system in a co-culture with Nor-10 fibroblasts. Further enhancement of differentiation efficiency was achieved by 3D embedding of rat neonatal cardiomyocytes in the 3D system. Calcium imaging and analysis of beating motion both indicate that the dECM-fibrin composite significantly enhances recovery, frequency, synchrony, and the maintenance of spontaneous beating, as compared to various controls including Matrigel, pure fibrin and collagen I as well as a fibrin-collagen I blend.

Association between retinol intake and periodontal health in US adults

BACKGROUND

Inflammation and oxidative stress are two hallmarks of periodontitis. Retinol is an antioxidant and suppresses expression of pro-inflammatory factors. However, the evidence for an association between retinol intake and periodontitis is limited. Thus, the aim of this study is to assess the association between retinol intake and periodontal health.

METHODS

Data used in this cross-sectional study from the National Health and Nutrition Examination Survey (NHANES) 2009-2014 (n = 9081). Dietary intake of retinol was measured based on two 24-h dietary recall interviews. The category of periodontitis was defined by the CDC/AAP according to clinical periodontal parameters. Univariate and multivariate logistic regression analyses were applied to investigate the relationship between retinol intake and the risk of periodontitis.

RESULTS

Compared with the lowest tertile, individuals in the highest tertile of retinol intake were less likely to be periodontitis (OR_tertile3vs1 = 0.79, 95% CI: 0.65-0.96). The association was still significant in populations who were less than 60 years old (OR_tertile3vs1 = 0.80, 95% CI: 0.65-0.97), non-Hispanic black (OR_tertile3vs1 = 0.62, 95% CI: 0.42-0.94), PI ≤ 1.3 (OR_tertile3vs1 = 0.72, 95% CI: 0.55-0.93), 1.3 < PI ≤ 3.5 (OR_tertile3vs1 = 0.70, 95% CI: 0.55-0.89), non-smoker (OR_tertile3vs1 = 0.63, 95% CI: 0.48-0.81), obesity (OR_tertile3vs1 = 0.68, 95% CI: 0.49-0.94) and who had not diabetes mellitus (OR_tertile3vs1 = 0.79, 95% CI: 0.65-0.95) or had hypertension (OR_tertile3vs1 = 0.63, 95% CI: 0.47-0.84).

CONCLUSION

Retinol intake is inversely associated with poor periodontal health in US adults.

Coagulopathy in Patients with Low/Intermediate Risk Acute Promyelocytic Leukemia treated with First Line Arsenic Trioxide in Combination with All-Trans Retinoic Acid: A Monocentric Experience

No abstract  

Effect of Therapeutically Related Drugs on Coagulation-Anticoagulation Balance in Acute Promyelocytic Leukemia

Acute promyelocytic leukemia (APL) usually presents with a series of coagulation-anticoagulation disturbance. Early administration of All-trans retinoic acid (ATRA) can reduce the risk of bleeding, but the potential for thrombosis needs to be addressed in some cases. The role of arsenic agent in correcting coagulation disorder remains to be studied, but oral arsenic agent shows potential advantages in coagulation recovery compared with intravenous agent, and chemotherapy can aggravate the progress of coagulation disease. In addition to early application of ATRA, avoiding invasive procedures and transfusion support can reduce the risk of bleeding. Whether the administration of heparin, thrombomodulin, recombinant factor VIIa or antifibrinolytics reduces the risk of bleeding and thrombosis associated with APL remains to be further explored, and their routine use outside of clinical trials is not recommended. This article reviews the effects of related drugs on coagulation-anticoagulation balance in APL patients.

Tyrosol, at the Concentration Found in Maltese Extra Virgin Olive Oil, Induces HL-60 Differentiation towards the Monocyte lineage

Tyrosol is a phenolic found in extra virgin olive oil (EVOO). In a Maltese monocultivar EVOO, it was present at a concentration of 9.23 ppm. The HL-60 acute myeloid leukaemia cell line, which can be differentiated to both monocytes and neutrophils, was exposed to tyrosol at this concentration and analysed for evidence of differentiation and effects of cytotoxicity. The polyphenol induced a 1.93-fold increase in cellular oxidative activity (p-value 0.044) and enhanced surface expression of CD11b and CD14. This indicates that tyrosol induces monocytic-like differentiation. An RNA-seq analysis confirmed the upregulation of monocyte genes and the loss of neutrophil genes concomitant with the bi-potential promyelocyte precursor moving down the monocytic pathway. A cell cycle analysis showed an accumulation of cells in the Sub G0/G1 phase following tyrosol exposure for 5 days, which coincided with an increase in apoptotic and necrotic markers. This indicates differentiation followed by cell death, unlike the positive monocyte differentiation control PMA. This selective cytotoxic effect following differentiation indicates therapeutic potential against leukaemia.

Coagulopathy in Acute Promyelocytic Leukemia: Can We Go Beyond Supportive Care?

Acute promyelocytic leukemia (APL) is characterized by frequent complications due to a distinct coagulopathy. While advances in treatments have improved long-term survival, hemorrhagic and thrombotic complications remain the most common causes of death and morbidity. Improved understanding of the mechanisms of the coagulopathy associated with APL may lead to therapeutic interventions to mitigate the risk of hemorrhage and thrombosis.

Hemorrhage in acute promyelocytic leukemia: Can it be predicted and prevented?

Hemorrhagic death is the leading cause of treatment failure in acute promyelocytic leukemia (APL). Our ability to identify patients at greatest risk of hemorrhage, and to actively prevent hemorrhage, remains limited. Nevertheless, some data is available to guide contemporary clinical practice and future investigation. Circulating disease burden, best represented by the peripheral WBC / blast count, is the most consistent predictor of major and fatal bleeding risk. In contrast, laboratory markers of disseminated intravascular coagulation (DIC) appear to be poor predictors. A number of interventions have been posited to reduce bleeding risk. Prompt initiation of all-trans retinoic acid (ATRA), avoidance of invasive procedures, transfusion support, and cytoreduction all have theoretical merit. Though they lack strong evidence to support their benefit with respect to bleeding, they are associated with limited risks, and are therefore advisable. Low-dose therapeutic heparin and antifibrinolytics have not shown the ability to positively modify bleeding risk, and heparin has been associated with harm. Thrombomodulin has shown promise in limited retrospective studies however further prospective data are needed. rFVIIa may have a role in cases of life-threatening bleeding however evidence is largely anecdotal. Additional studies evaluating the above interventions, and investigating other potential interventions are needed.

Deluging Thrombosis: An Unusual Presentation of Acute Promyelocytic Leukemia

Acute promyelocytic leukemia (APML) patients are prone to thrombosis. However, thrombosis at presentation is rare in APML. Our patient presented with thrombosis and cytopenia, and the clinical diagnosis was of paroxysmal nocturnal hemoglobinuria. However, subsequent peripheral blood smear and bone marrow study confirmed the diagnosis of APML. The patient was successfully managed with anticoagulation, arsenic trioxide, and all-trans retinoic acid.

Analysis of the role of thrombomodulin in all-trans retinoic acid treatment of coagulation disorders in cancer patients

BACKGROUND

Clinical studies have shown that all-trans retinoic acid (RA), which is often used in treatment of cancer patients, improves hemostatic parameters and bleeding complications such as disseminated intravascular coagulation (DIC). However, the mechanisms underlying this improvement have yet to be elucidated. In vitro studies have reported that RA upregulates thrombomodulin (TM) expression on the endothelial cell surface. The objective of this study was to investigate how and to what extent the TM concentration changes after RA treatment in cancer patients, and how this variation influences the blood coagulation cascade.

RESULTS

In this study, we introduced an ordinary differential equation (ODE) model of gene expression for the RA-induced upregulation of TM concentration. Coupling the gene expression model with a two-compartment pharmacokinetic model of RA, we obtained the time-dependent changes in TM and thrombomodulin-mRNA (TMR) concentrations following oral administration of RA. Our results indicated that the TM concentration reached its peak level almost 14 h after taking a single oral dose (110 [Formula: see text]) of RA. Continuous treatment with RA resulted in oscillatory expression of TM on the endothelial cell surface. We then coupled the gene expression model with a mechanistic model of the coagulation cascade, and showed that the elevated levels of TM over the course of RA therapy with a single daily oral dose (110 [Formula: see text]) of RA, reduced the peak thrombin levels and endogenous thrombin potential (ETP) up to 50 and 49%, respectively. We showed that progressive reductions in plasma levels of RA, observed in continuous RA therapy with a once-daily oral dose (110 [Formula: see text]) of RA, did not affect TM-mediated reduction of thrombin generation significantly. This finding prompts the hypothesis that continuous RA treatment has more consistent therapeutic effects on coagulation disorders than on cancer.

CONCLUSIONS

Our results indicate that the oscillatory upregulation of TM expression on the endothelial cells over the course of RA therapy could potentially contribute to the treatment of coagulation abnormalities in cancer patients. Further studies on the impacts of RA therapy on the procoagulant activity of cancer cells are needed to better elucidate the mechanisms by which RA therapy improves hemostatic abnormalities in cancer.

Predictive factors of fatal bleeding in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is associated with a profound coagulopathy. Based on retrospective assessments, several potential risk factors for hemorrhagic morbidity and mortality have emerged. Several studies have shown elevated white blood cell (WBC) count at presentation to be a robust predictor of bleeding events. Other clinical and laboratory parameters have been evaluated with variable association with hemorrhagic morbidity or mortality. These include ECOG performance status, age, morphological subtype, platelet count, peripheral blood blast count, ethnicity, body mass index, prothrombin time, activated partial thromboplastin time, lactate dehydrogenase, d-dimers, creatinine and fibrinogen levels. Unfortunately, most of those assessments were based on a small patient sample and the results have been at times contradictory in terms of which parameters are independent predictors. More recently, two large retrospective studies have reported on the issue. They included data from several international trials of chemotherapy for APL, one on adults and the other focused on the pediatric population. Importantly, both analyses found that WBC count at presentation is the main predictor of early hemorrhagic death and early thrombo-hemorrhagic death, respectively. Much remains to be done if the rate of induction mortality in APL is going to be reduced significantly. One approach would be to incorporate the known risk factors for early hemorrhagic death into a risk stratification system and devise personalized transfusion interventions to meet an individual patient's risk, which could be evaluated in future randomized trials.

Single cell coagulomes as constituents of the oncogene-driven coagulant phenotype in brain tumours

Molecular profiling of human cancers revealed a startling diversity in disease-causing mechanisms superseding histological and anatomical commonalities. The emerging molecular subtypes and disease entities are often driven by distinct oncogenic pathways and their effectors, including those acting extracellularly on the vascular and coagulation systems. Indeed, several oncogenic mutations such as those affecting protein-coding genes (RAS, EGFR, PTEN, TP53) and non-coding RNA (microRNA) regulate multiple effectors of the coagulation system (coagulome), including tissue factor, protease activated receptors, clotting factors, mediators of platelet function and fibrinolysis. This is exemplified by differential coagulome profiles in the molecular subtypes of glioblastoma, medulloblastoma and other human tumours. There is mounting clinical evidence that the mutational status of cancer driver genes such as KRAS or IDH1 may influence the risk of venous thromboembolism in patients with colorectal, lung or brain cancers. Notably, single cell sequencing in glioblastoma revealed a remarkable intra-tumoural heterogeneity of cancer cell populations with regard to their individual coagulomes, suggesting a combinatorial and dynamic nature of the global pro-thrombotic phenotype. We suggest that the cellular complexity of specific cancers may define their mechanisms of interactions with the coagulation system, and the risks of thrombosis. Thus, more biologically- based, disease-specific and personalized approaches may be needed to diagnose and manage cancer-related thrombosis.

Mechanisms and management of coagulopathy in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is a subtype of leukemia which is associated with unique and distinctive coagulopathy. In the absence of treatment it is rapidly fatal and even after initiation of therapy the major cause of early mortality is related to hemorrhagic complications. The coagulopathy can be exacerbated with the start of treatment. In the absence of early hemorrhage related deaths the probability of cure exceeds 90% in low and intermediate risk patients and 80% even in high risk patients, highlighting the importance of understanding the pathophysiology of this complication and instituting prompt and appropriate management strategies. The coagulopathy in APL is complex and results from a combination of thrombocytopenia, disseminated intravascular coagulation and hyperfibronlysis. Recently the effect of all-trans retinioc acid (ATRA) induced ETosis on exacerbating coagulopathy in the first few days after starting therapy with this agent raises the potential for potentially novel strategies to reduce the risk of hemorrhage. Currently management is mainly related to rapid initiation of therapy with ATRA along with appropriate and adequate replacement of blood products to correct the coagulopathy. There is limited role for the use of low dose anti-coagulants and anti-fibrinolytic agents in the initial management of this disease. There is limited data on the use of rFVIIa or the use of global tests of hemostasis in the management of this condition.

Characteristics of fibrinolytic disorders in acute promyelocytic leukemia

OBJECTIVES

Catastrophic hemorrhage remains the main cause of acute promyelocytic leukemia (APL) treatment failure. This study was aimed to study the pathogenesis of coagulopathy in patients with APL.

METHODS

Multiple procoagulant and profibrinolytic parameters in plasma and peripheral leukocytes from 24 patients with newly diagnosed APL accompanied by coagulopathy before and after arsenic trioxide (ATO) treatment were evaluated.

RESULTS

Prior to the treatment, the patients had elevated D-dimer and decreased fibrinogen levels. Plasma urokinase-type plasminogen activator receptor (uPAR) and plasmin-ɑ₂ antiplasmin complexes (PAP) levels, plasmin (Pn) activity, and cell surface levels of urokinase-type plasminogen activator (uPA) and tissue-type plasminogen activator (tPA) were significantly higher; plasma plasminogen activator inhibitor-1 (PAI-1) levels and plasminogen (Pg) activity were significantly decreased; plasma plasminogen activator (PA) activity, uPA and tPA levels; and cell surface levels of uPAR and annexin II were not significantly different from levels in the control group. During ATO treatment, both patients' plasma PA activity and uPAR on leukocytes gradually increased, annexin II on leukocytes increased initially and decreased afterwards, and tPA and uPA on leukocytes remained consistently higher in the patients than in the controls. Other parameters gradually tended toward normal values.

CONCLUSIONS

In APL, activated coagulation system activated fibrinolytic system, and increased uPAR levels could contribute to the hyperfibrinolysis. Annexin II might not be involved in the coagulopathy.

Malignant transformation in melanocytes is associated with increased production of procoagulant microvesicles

Shedding of microvesicles (MVs) by cancer cells is implicated in a variety of biological effects, including the establishment of cancer-associated hypercoagulable states. However, the mechanisms underlying malignant transformation and the acquisition of procoagulant properties by tumour-derived MVs are poorly understood. Here we investigated the procoagulant and prothrombotic properties of MVs produced by a melanocyte-derived cell line (melan-a) as compared to its tumourigenic melanoma counterpart Tm1. Tumour cells exhibit a two-fold higher rate of MVs production as compared to melan-a. Melanoma MVs display greater procoagulant activity and elevated levels of the clotting initiator protein tissue factor (TF). On the other hand, tumour- and melanocyte- derived MVs expose similar levels of the procoagulant lipid phosphatidylserine, displaying identical abilities to support thrombin generation by the prothrombinase complex. By using an arterial thrombosis model, we observed that melanoma- but not melanocyte-derived MVs strongly accelerate thrombus formation in a TF-dependent manner, and accumulate at the site of vascular injury. Analysis of plasma obtained from melanoma-bearing mice showed the presence of MVs with a similar procoagulant pattern as compared to Tm1 MVs produced in vitro. Remarkably, flow-cytometric analysis demonstrated that 60% of ex vivo MVs are TF-positive and carry the melanoma-associated antigen, demonstrating its tumour origin. Altogether our data suggest that malignant transformation in melanocytes increases the production of procoagulant MVs, which may contribute for a variety of coagulation- related protumoural responses.

A Revised Fibrinogen Cutoff Value in the Chinese Disseminated Intravascular Coagulation Scoring System May Provide a Better Prognostic Value for Hematological Malignancies

To retrospectively validate the prognostic value of the latest Chinese disseminated intravascular coagulation (DIC) scoring system (CDSS) in hematological malignancies, 260 patients with confirmed hematological malignancies and suspected DIC in West China Hospital between 2011 and 2015 were included in this study. We evaluated via univariate and multivariate analyses the diagnostic biomarkers, and the cutoff levels used in the CDSS, except those for fibrinogen, were found to be valid. In subgroup analyses, the value of fibrinogen was found to be mainly unfit for the acute promyelocytic leukemia group. Forty-six patients (17.7%) had elevated fibrinogen levels (>4 g/L) and tended to have a poor prognosis, and thus we redetermined the cutoff value of fibrinogen (<1 g/L or >4 g/L was defined as abnormal). As a result, all of the markers used in the CDSS had prognostic value (including for the promyelocytic leukemia group); meanwhile, this modification also resulted in a larger area under the receiver operating characteristic curve compared to the CDSS and the International Society on Thrombosis and Haemostasis score. We believe that, with regard to prognosis prediction, this cutoff value modification for fibrinogen is preferable for DIC patients with a tendency toward severe hypofibrinogenemia. However, a multicenter, prospective study is needed to validate this possibility.

Effect of ATRA and ATO on the expression of tissue factor in NB4 acute promyelocytic leukemia cells and regulatory function of the inflammatory cytokines TNF and IL-1β

The characteristic hemorrhages of acute promyelocytic leukemia (APL) are caused in part by the high expression of tissue factor (TF) on leukemic cells, which also produce TNF and IL-1β, proinflammatory cytokines known to increase TF in various cell types. Exposure of NB4 cells, an APL cell line, to all-trans retinoic acid (ATRA) or arsenic trioxide (ATO) rapidly and strongly reduced TF mRNA. Both drugs also reduced TNF mRNA, but later, and moreover increased IL-1β mRNA. The effect on procoagulant activity of cells and microparticles, as measured with calibrated automated thrombography, was delayed and only partial at 24 h. TNF and IL-1β inhibition reduced TF mRNA and activity only partially. Inhibition of the inflammatory signaling intermediate p38 reduced TF mRNA by one third but increased TNF and IL-1β mRNA. NF-κB inhibition reduced, within 1 h, TF and TNF mRNA but did not change IL-1β mRNA, and rapidly and markedly reduced cell survival, with procoagulant properties still being present. In conclusion, although we provide evidence that TNF, IL-1β, and their signaling intermediates have a regulatory function on TF expression by NB4 APL cells, the effect of ATRA and ATO on TF can only partially be accounted for by their impact on these cytokines.

Promyelocytic extracellular chromatin exacerbates coagulation and fibrinolysis in acute promyelocytic leukemia

Despite routine treatment of unselected acute promyelocytic leukemia (APL) with all-trans-retinoic acid (ATRA), early death because of hemorrhage remains unacceptably common, and the mechanism underlying this complication remains elusive. We have recently demonstrated that APL cells undergo a novel cell death program, termed ETosis, which involves release of extracellular chromatin. However, the role of promyelocytic extracellular chromatin in APL-associated coagulation remains unclear. Our objectives were to identify the novel role of ATRA-promoted extracellular chromatin in inducing a hypercoagulable and hyperfibrinolytic state in APL and to evaluate its interaction with fibrin and endothelial cells (ECs). Results from a series of coagulation assays have shown that promyelocytic extracellular chromatin increases thrombin and plasmin generation, causes a shortening of plasma clotting time of APL cells, and increases fibrin formation. DNase I but not anti-tissue factor antibody could inhibit these effects. Immunofluorescence staining showed that promyelocytic extracellular chromatin and phosphatidylserine on APL cells provide platforms for fibrin deposition and render clots more resistant to fibrinolysis. Additionally, coincubation assays revealed that promyelocytic extracellular chromatin is cytotoxic to ECs, converting them to a procoagulant phenotype. This cytotoxity was blocked by DNase I by 20% or activated protein C by 31%. Our current results thus delineate the pathogenic role of promyelocytic extracellular chromatin in APL coagulopathy. Furthermore, the remaining coagulation disturbance in high-risk APL patients after ATRA administration may be treatable by intrinsic pathway inhibition via accelerating extracellular chromatin degradation.

Recurrent Arterial Thrombosis as a Presenting Feature of a Variant M3-Acute Promyelocytic Leukemia

Acute limb ischemia (ALI) is a common vascular emergency. Hematologic malignancies are commonly associated with derangement of normal hemostasis and thrombo-hemorrhagic symptoms during the course of the disease are common. However, ALI as an initial presenting feature of acute leukemia is rare. Due to the rarity of this presentation, there is a scarcity of prospective randomized data to optimally guide the management of these patients. Current knowledge is mainly based on isolated cases. We report our experience managing a patient who presented with ALI and was found to have occult leukemia. A review of all cases with ALI as a presenting feature of acute leukemia is also presented.

Synthesis of minoxidil conjugates and their evaluation as HL-60 differentiation agents

Activation of minoxidil (MNX) with N,N'-carbonyldiimidazole and coupling with natural polyamines (PAs) and commercially available aliphatic or aromatic amines provided a series of new conjugates which were evaluated for their ability to induce differentiation to HL-60 acute myeloid leukemia cancer cells, using a modified NBTZ reduction test. Although neither MNX nor 4,4'-methylenedianiline (MDA) or 2,7-diaminofluorene (DAF), alone or in combination, had any effect, the MNX-spermine (SPM) conjugate (11) and the conjugates 7 and 8 of MNX with MDA and DAF exhibited a differentiation-inducing effect at a concentration of 10 μM without being toxic on proliferating human peripheral blood mononuclear cells.

PML-RARa modulates the vascular signature of extracellular vesicles released by acute promyelocytic leukemia cells

Oncogenic transformation is believed to impact the vascular phenotype and microenvironment in cancer, at least in part, through mechanisms involving extracellular vesicles (EVs). We explored these questions in the context of acute promyelocytic leukemia cells (NB4) expressing oncogenic fusion protein, PML-RARa and exquisitely sensitive to its clinically used antagonist, the all-trans retinoic acid (ATRA). We report that NB4 cells produce considerable numbers of EVs, which are readily taken up by cultured endothelial cells triggering their increased survival. NB4 EVs contain PML-RARa transcript, but no detectable protein, which is also absent in endothelial cells upon the vesicle uptake, thereby precluding an active intercellular trafficking of this oncogene in this setting. ATRA treatment changes the emission profile of NB4-related EVs resulting in preponderance of smaller vesicles, an effect that occurs in parallel with the onset of cellular differentiation. ATRA also increases IL-8 mRNA and protein content in NB4 cells and their EVs, while decreasing the levels of VEGF and tissue factor (TF). Endothelial cell uptake of NB4-derived EVs renders these cells more TF-positive and procoagulant, and this effect is diminished by pre-treatment of EV donor cells with ATRA. Profiling angiogenesis-related transcripts in intact and ATRA-treated APL cells and their EVs reveals multiple differences attributable to cellular responses and EV molecular packaging. These observations point to the potential significance of changes in the angiogenic signature and activity associated with EVs released from tumor cells subjected to targeted therapy.

Weaving a two-dimensional fishing net from titanoniobate nanosheets embedded with Fe₃O₄ nanocrystals for highly efficient capture and isotope labeling of phosphopeptides

Qualitative and quantitative characterization of phosphopeptides by means of mass spectrometry (MS) is the main goal of MS-based phosphoproteomics, but suffers from their low abundance in the large haystack of various biological molecules. Herein, we introduce two-dimensional (2D) metal oxides to tackle this biological separation issue. A nanocomposite composed of titanoniobate nanosheets embedded with Fe₃O₄ nanocrystals (Fe₃O₄-TiNbNS) is constructed via a facile cation-exchange approach, and adopted for the capture and isotope labeling of phosphopeptides. In this nanoarchitecture, the 2D titanoniobate nanosheets offer enlarged surface area and a spacious microenvironment for capturing phosphopeptides, while the Fe₃O₄ nanocrystals not only incorporate a magnetic response into the composite but, more importantly, also disrupt the restacking process between the titanoniobate nanosheets and thus preserve a greater specific surface for binding phosphopeptides. Owing to the extended active surface, abundant Lewis acid sites and excellent magnetic controllability, Fe₃O₄-TiNbNS demonstrates superior sensitivity, selectivity and capacity over homogeneous bulk metal oxides, layered oxides, and even restacked nanosheets in phosphopeptide enrichment, and further allows in situ isotope labeling to quantify aberrantly-regulated phosphopeptides from sera of leukemia patients. This composite nanosheet greatly contributes to the MS analysis of phosphopeptides and gives inspiration in the pursuit of 2D structured materials for separation of other biological molecules of interests.

Oncogenes and the coagulation system--forces that modulate dormant and aggressive states in cancer

Cancers arise and progress genetically amidst profound perturbations of the microenvironmental and systemic homeostasis. This includes the coagulation system, which is a part of the vascular milieu (niche) that remains under the control of molecular events occurring within the cancer cell genome. Thus, activation of several prototypic oncogenic pathways, such as RAS, EGFR, HER2, MET, SHH and loss of tumor suppressors (PTEN, TP53) alter the expression, activity and vesicular release of coagulation effectors, as exemplified by tissue factor (TF). The cancer-specific determinants of coagulopathy are also illustrated by the emerging link between the expression profiles of coagulation-related genes (coagulome) in glioblastoma multiforme (GBM), medulloblastoma (MB) and possibly other cancers and molecular subtypes of these respective tumors. The state of the coagulome is consequential for growth, metastasis and angiogenesis of established tumors, but could potentially also affect dormant cancer cells. For example, TF expression may trigger awakening of dormant glioma cells in mice in a manner involving recruitment of vascular and inflammatory cells, and resulting in lasting changes in the cancer cell genome and epigenome. Thus, coagulation system effectors could act as both targets and (indirect) inducers of genetic tumor progression, and a better understanding of this link may hold new diagnostic and therapeutic opportunities.

Brain neoplasms and coagulation-lessons from heterogeneity

The coagulation system constitutes an important facet of the unique vascular microenvironment in which primary and metastatic brain tumors evolve and progress. While brain tumor cells express tissue factor (TF) and other effectors of the coagulation system (coagulome), their propensity to induce local and peripheral thrombosis is highly diverse, most dramatic in the case of glioblastoma multiforme (GBM), and less obvious in pediatric tumors. While the immediate medical needs often frame the discussion on current clinical challenges, the coagulation pathway may contribute to brain tumor progression through subtle, context-dependent, and non-coagulant effects, such as induction of inflammation, angiogenesis, or by responding to iatrogenic insults (e.g. surgery). In this regard, the emerging molecular diversity of brain tumor suptypes (e.g. in glioma and medulloblastoma) highlights the link between oncogenic pathways and the tumor repertoire of coagulation system regulators (coagulome). This relationship may influence the mechanisms of spontaneous and therapeutically provoked tumor cell interactions with the coagulation system as a whole. Indeed, oncogenes (EGFR, MET) and tumor suppressors (PTEN, TP53) may alter the expression, activity, and vesicular release of tissue factor (TF), and cause other changes. Conversely, the coagulant microenvironment may also influence the molecular evolution of brain tumor cells through selective and instructive cues. We suggest that effective targeting of the coagulation system in brain tumors should be explored through molecular stratification, stage-specific analysis, and more personalized approaches including thromboprophylaxis and adjuvant treatment aimed at improvement of patient survival.

Microparticles: new light shed on the understanding of venous thromboembolism

Microparticles are small membrane fragments shed primarily from blood and endothelial cells during either activation or apoptosis. There is mounting evidence suggesting that microparticles perform a large array of biological functions and contribute to various diseases. Of these disease processes, a significant link has been established between microparticles and venous thromboembolism. Advances in research on the role of microparticles in thrombosis have yielded crucial insights into possible mechanisms, diagnoses and therapeutic targets of venous thromboembolism. In this review, we discuss the definition and properties of microparticles and venous thromboembolism, provide a synopsis of the evidence detailing the contributions of microparticles to venous thromboembolism, and propose potential mechanisms, by which venous thromboembolism occurs. Moreover, we illustrate a possible role of microparticles in cancer-related venous thromboembolism.

Disseminated intravascular coagulation: testing and diagnosis

Abnormalities of the hemostatic system in patients with DIC result from the sum of vectors for hypercoagulation and hyperfibrinolysis. DIC is classified into hyperfibrinolysis, hypercoagulation, massive bleeding or nonsymptomatic types according to the balance of the two vectors. Both the antithrombin (AT) and protein C (PC) levels are significantly low in patients with septic DIC, and reduced amounts of AT and PC result in the lack of inhibition of thrombin and activated FVIII, respectively. Thrombin activates FVIII, while activated FVIII accelerates the coagulation pathway to generate thrombin; thus activation of the coagulation system persists. Three sets of diagnostic criteria have been established by the Japanese Ministry of Health, Labour and Welfare, International Society of Thrombosis and Haemostasis and Japanese Association for Acute Medicine, respectively. Although these three diagnostic criteria score hemostatic abnormalities using similar global coagulation tests, the sensitivity and/or specificity for death differ. Treatment with AT or activated PC may not improve the outcomes of patients with sepsis at the early stage, although they may improve the outcomes in those with DIC. Therefore, new diagnostic criteria for determining the appropriate time to initiate anticoagulant treatment are required.

Cerebral venous and sinus thrombosis in a patient with acute promyelocytic leukemia during all-trans retinoic acid induction treatment

Cerebral venous and sinus thrombosis is a rare cerebrovascular disorder, which seldom represents a complication of acute promyelocytic leukemia (APL). As a part of the coagulopathy of APL, thrombosis is a less recognized and underestimated life-threatening manifestation and is overshadowed by the more obvious bleeding complications. Here, we described a 28-year-old woman with APL who developed massive thrombosis of the cerebral sinuses while on induction treatment with all-trans retinoic acid. On the basis of this report, the potential pathogenic mechanisms and the diagnosis based on magnetic resonance imaging (MRI) combined with magnetic resonance venogram (MRV) are discussed. Early anticoagulant therapy contributed to the progressive dissolution of the thrombosis, as documented by MRI, with the complete disappearance of neurological signs without sequelae. Given the increasing recognition of thromboembolic events in APL, the use of prophylactic anticoagulation during induction therapy may need to be redefined.

How we prevent and treat differentiation syndrome in patients with acute promyelocytic leukemia

Differentiation syndrome (DS), formerly known as retinoic acid syndrome, is a relatively common and potentially severe complication seen in patients with acute promyelocytic leukemia treated with all-trans retinoic acid and/or arsenic trioxide. The full-blown syndrome consists of unexplained fever, weight gain, dyspnea with pulmonary infiltrates, pleuropericardial effusion, hypotension, and renal failure. Most measures currently used for management of DS have very little evidence-based support, and therefore, many remain controversial. Despite the lack of evidence supporting DS prophylaxis, several groups have adopted a preventive strategy with corticosteroids, especially for patients with leukocyte levels higher than from 5 to 10 × 10(9)/L. DS diagnosis should be suspected in the presence of any of the above-mentioned signs and symptoms, and preemptive treatment with dexamethasone should be started immediately. Other supportive measures can also be crucial for the correct management of DS, especially in those patients with life-threatening complications. Temporary discontinuation of all-trans retinoic acid or arsenic trioxide is indicated only for patients in very poor clinical condition or with severe renal or pulmonary dysfunction, sometimes requiring admission to the intensive care unit. Recognition of specific biomarkers and a better understanding of DS pathogenesis can be helpful for the development of specific therapies to counteract DS in a timely manner.

Thrombomodulin alfa treatment in patients with acute promyelocytic leukemia and disseminated intravascular coagulation: a retrospective analysis of an open-label, multicenter, post-marketing surveillance study cohort

INTRODUCTION

Patients with acute promyelocytic leukemia (APL) can develop disseminated intravascular coagulation (DIC) that results in life-threatening hemorrhagic complications. Studies regarding the safety and efficacy of thrombomodulin alfa (TM-α; recombinant human soluble thrombomodulin) in patients with APL and DIC are limited.

MATERIALS AND METHODS

A retrospective evaluation was performed on a cohort of 172 patients with APL from an open-label, multicenter, post-marketing surveillance study of TM-α.

RESULTS

Of the 172 patients, 31 were relapse/refractory APL patients, and 141 were newly diagnosed APL patients. Within the first 30 days, 24 patients (14.0%) died, and six of those deaths (3.5%) were due to hemorrhage. In total, 12 patients (7.0%) had severe hemorrhagic complications. Both the early death rate due to hemorrhage as well as the severe hemorrhage rate did not exceed those in some recent population-based studies of patients with APL. Forty-nine patients received TM-α prior to the initiation of antileukemic treatment, and one patient experienced hemorrhagic early death (ED), suggesting that early TM-α treatment appeared to result in a reduction in the hemorrhagic ED rate. Moreover, TM-α improved coagulopathy regardless of concomitant all-trans retinoic acid treatment.

CONCLUSIONS

This study confirmed the safety and efficacy of TM-α in daily clinical practice for patients with APL and DIC. TM-α appeared to reduce hemorrhagic early deaths due to DIC in patients with APL who were receiving antileukemic treatment.

Diagnosis and treatment of disseminated intravascular coagulation (DIC) according to four DIC guidelines

Disseminated intravascular coagulation (DIC) is categorized into bleeding, organ failure, massive bleeding, and non-symptomatic types according to the sum of vectors for hypercoagulation and hyperfibrinolysis. The British Committee for Standards in Haematology, Japanese Society of Thrombosis and Hemostasis, and the Italian Society for Thrombosis and Haemostasis published separate guidelines for DIC; however, there are several differences between these three sets of guidelines. Therefore, the International Society of Thrombosis and Haemostasis (ISTH) recently harmonized these differences and published the guidance of diagnosis and treatment for DIC. There are three different diagnostic criteria according to the Japanese Ministry Health, Labour and Welfare, ISTH, and Japanese Association of Acute Medicine. The first and second criteria can be used to diagnose the bleeding or massive bleeding types of DIC, while the third criteria cover organ failure and the massive bleeding type of DIC. Treatment of underlying conditions is recommended in three types of DIC, with the exception of massive bleeding. Blood transfusions are recommended in patients with the bleeding and massive bleeding types of DIC. Meanwhile, treatment with heparin is recommended in those with the non-symptomatic type of DIC. The administration of synthetic protease inhibitors and antifibrinolytic therapy is recommended in patients with the bleeding and massive bleeding types of DIC. Furthermore, the administration of natural protease inhibitors is recommended in patients with the organ failure type of DIC, while antifibrinolytic treatment is not. The diagnosis and treatment of DIC should be carried out in accordance with the type of DIC.

Guidance for diagnosis and treatment of DIC from harmonization of the recommendations from three guidelines

Three guidelines have recently been published for the diagnosis and treatment of disseminated intravascular coagulation (DIC) in adults. This communication seeks to harmonize the recommendations in these guidelines using a modified GRADE system. The scoring system for diagnosis of DIC using global coagulation tests is known to correlate with key clinical observations and outcomes (Moderate quality). The cornerstone of DIC treatment is the treatment of the underlying condition (Moderate quality). In general, transfusion of platelets or plasma (components) in patients with DIC should be reserved for patients who are bleeding (Low quality). Therapeutic doses of heparin should be considered in cases of DIC where clinical features of thrombosis predominate. Heparin is not recommended in those patients with a high risk of bleeding, (Moderate quality). However, prophylactic doses of unfractionated heparin or low molecular we ight heparin is recommended in critically ill and non-bleeding patients with DIC for prevention of venous thromboembolism (Moderate to High quality). Although further prospective evidence from randomized controlled trials is required, administration of antithrombin or recombinant thrombomodulin may be considered in certain patients with DIC. In general, patients with DIC should not be treated with antifibrinolytic agents (Low quality). However those who present with severe bleeding, that is characterized by a markedly hyperfibrinolytic state such as leukemia (Low quality) and trauma (Moderate quality), may be treated with antifibrinolytic agents. © 2013 International Society on Thrombosis and Haemostasis.

Acute promyelocytic leukemia-associated thrombosis

Patients with acute promyelocytic leukemia (APL) are prone to both bleeding and thrombosis. The bleeding complications are well known. In contrast, APL-associated thrombosis is relatively underappreciated. We aimed to explore the issue of APL-associated thrombosis events. In the past 20 years, 127 cases with APL were found in our hospital database. We collected their coagulation laboratory profiles, including leukemia burdens, white blood cell and platelet counts, prothrombin time, activated partial thromboplastin time, fibrinogen levels, and disseminated intravascular coagulation scores. Data were compared between patients with or without thrombosis. Clinical outcomes and potential risk factors were obtained for analysis. Ten cases with APL-associated thrombosis were found. The incidence of thrombosis was 7.9% in our cohort. Five patients had cerebral infarction, 5 had catheter-related thrombosis and 1 had acute myocardial infarction. No laboratory data were associated with clinical thrombosis. Three patients died during the induction phase but thrombosis was not the direct cause of death for any of them. We conclude that patients with APL are susceptible to thrombosis in addition to bleeding. Laboratory coagulation parameters did not predict thrombosis in our series. Ischemic stroke and catheter-related thrombosis were the most common events in our Taiwanese cohort. Such a thrombosis pattern is unique and worth further investigation.

Genetic pathways linking hemostasis and cancer

Oncogenic events impact interactions of cancer cells with their surroundings. Amongst the most consequential, in this regard, is the influence on angiogenesis, inflammation and hemostasis. Indeed, mutant oncogenes (EGFR, HER2, RAS, MET, PML-RARα) are known to alter the expression of angiogenic and pro-inflammatory factors, as well as change the cancer cell coagulome, including the levels of tissue factor (TF) and other mediators (PAI-1, COX2). Accompanying losses of tumour suppressor genes (PTEN, p53), and changes in microRNA (miR-19b, miR-520) facilitate these effects. Transforming genes may also trigger ectopic production of coagulation factors (e.g. FVII) by cancer cells and their release and properties of procoagulant microparticles (MPs). By deregulating protease activated receptors (PAR1/2) oncogenes may also change tumour cell responses to coagulation factor signalling. These changes act in concert with microenvironmental factors (hypoxia), stress responses (therapy) and differentiation programs, including epithelial-to-mesechymal transitions (EMT) and through tumour initiating cell (TIC) compartment. In so doing, the coagulation system influences early (initiation, angiogenesis), intermediate (growth, invasion) and late stages (metastasis, relapse) of cancer progression. In fact, TF may act as a molecular switch that controls the transition between dormant, latent and progressive/metastatic disease. TIC-like cells may play a role in these effects, as they express TF and PAR-1/2, and respond to stimulation with their agonists. As major human malignancies (e.g. glioblastoma) are increasingly recognized to consist of a spectrum of molecularly distinct disease subtypes driven by specific genetic pathways, so too may their patterns of interaction differ with the coagulation system. A better understanding of these linkages may be a source of new diagnostic, prognostic and therapeutic opportunities.

Thrombosis in hematologic malignancies: risks and consequences

SUMMARY Thrombotic complications in hematologic malignancies have been found to be high among the various forms of cancer. Thrombosis not only increases the morbidity, but also has an adverse impact on survival. The pathogenesis among the different forms of hematologic malignancies is reviewed in this article. The thrombogenicity of the individual malignant cells, the tumor burden, treatment modalities and presence of comorbidities are among the major risk factors. These factors vary with the acute leukemias, lymphomas, multiple myeloma and myeloproliferative neoplasms. The thrombogenetic factors in the more common hematologic malignancies are discussed. Results of recent randomized controlled clinical trials are beginning to provide data for meaningful therapeutic guidelines on thromboprophylaxis. They also enable the clinician to assess the risk factors in each individual patient. More clinical trials are needed to provide better risk stratification and to devise risk-adapted treatment regimens.

Bleeding and thrombosis in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) has evolved from being a deadly to a highly curable disease, due to targeted molecular therapy with all-trans retinoic acid (ATRA). As a result, the incidence of early hemorrhagic deaths for which APL is notorious has reduced to 5-10% as reported in clinical trials. These results are not replicated outside of clinical trials as is evident from recent population-based registries. High incidence of early hemorrhagic deaths remains the greatest contributor to treatment failure in this otherwise curable leukemia. Additionally, thrombosis is now being increasingly recognized in APL patients and may be associated with ATRA usage.

Monoclonal antibodies against receptor-induced binding sites detect cell-bound plasminogen in blood

Binding of Glu-plasminogen (the native, circulating form of the zymogen) to cells results in enhancement of its activation. Cell-associated plasmin proteolytic activity is a key component of physiologic and pathologic processes requiring extracellular matrix degradation. Recently, we developed antiplasminogen mAbs that recognize receptor-induced binding sites (RIBS) in Glu-plasminogen and, therefore, preferentially react with cell-associated Glu-plasminogen in the presence of soluble Glu-plasminogen. Here we have used FACS with a representative antiplasminogen receptor-induced binding site mAb, mAb49, to examine whether plasminogen associates with peripheral blood cells in blood. Plasminogen binding to neutrophils, monocytes, B-lymphocytes, T-lymphocytes, and platelets was clearly detected. Treatment of whole blood with lipopolysaccharide or 12-0 tetradecanoylphorbol-13-acetate up-regulated plasminogen binding to neutrophils and in vivo treatment with all-trans retinoic acid decreased plasminogen binding to acute promyelocytic leukemia blasts. Our results demonstrate that mAb49 can be used to monitor cell-bound plasminogen in blood under both normal and pathologic conditions.