Tissue factor-bearing microparticles are a link between acute promyelocytic leukemia cells and coagulation activation: a human subject study

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.

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.

Machine-Learning-Assisted Procoagulant Extracellular Vesicle Barcode Assay toward High-Performance Evaluation of Thrombosis-Induced Death Risk in Cancer Patients

Venous thromboembolism (VTE) is the most fatal complication in cancer patients. Unfortunately, the frequent misdiagnosis of VTE owing to the lack of accurate and efficient evaluation approaches may cause belated medical intervention and even sudden death. Herein, we present a rapid, easily operable, highly specific, and highly sensitive procoagulant extracellular vesicle barcode (PEVB) assay composed of TiO2 nanoflower (TiNFs) for visually evaluating VTE risk in cancer patients. TiNFs demonstrate rapid label-free EV capture capability by the synergetic effect of TiO2-phospholipids molecular interactions and topological interactions between TiNFs and EVs. From ordinary plasma samples, the PEVB assay can evaluate potential VTE risk by integrating TiNFs-based EV capture and in situ EV procoagulant ability test with machine-learning-assisted clinical data analysis. We demonstrate the feasibility of this PEVB assay in VTE risk evaluation by screening 167 cancer patients, as well as the high specificity (97.1%) and high sensitivity (96.8%), fully exceeding the nonspecific and posterior traditional VTE test. Together, we proposed a TiNFs platform allowing for highly accurate and timely diagnosis of VTE in cancer patients.

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.

Tissue factor activates the coagulation cascade in mouse models of acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is associated with a high risk of bleeding and thrombosis. APL patients have an activated coagulation system, hyperfibrinolysis, and thrombocytopenia. APL cells express tissue factor (TF), a receptor and cofactor for factor VII/VIIa. This study had 2 goals. Firstly, we measured biomarkers of coagulation and fibrinolysis activation as well as platelet counts and bleeding in both mouse xenograft and allograft models of APL. Secondly, we determined the effect of inhibiting TF on the activation of coagulation in these models. We observed increased levels of plasma thrombin-antithrombin complexes (TAT), D-dimer, and plasmin-antiplasmin complexes, reduced platelet counts, and increased tail bleeding in both mouse models of APL. Fibrinogen levels decreased in the xenograft model but not in the allograft model. In contrast, the red blood cell count decreased in the allograft model but not in the xenograft model. Inhibition of APL-derived human TF with an anti-human TF monoclonal antibody reduced the level of TAT, increased platelet count, and normalized tail bleeding in a xenograft model. Inhibition of all sources of TF (APL cells and host cells) in the allograft model with a rat anti-mouse TF monoclonal antibody decreased the levels of TAT but did not affect the platelet count. Our study demonstrates that TF plays a central role in the activation of coagulation in both the xenograft and allograft mouse models of APL. These APL mouse models can be used to investigate the mechanisms of coagulopathy and thrombocytopenia in APL.

Value of the FDP/FIB ratio in predicting early severe bleeding events in patients with newly diagnosed acute promyelocytic leukemia

Severe bleeding is the leading cause of early death in patients with newly diagnosed acute promyelocytic leukemia (APL). However, there are no means for hemorrhagic risk stratification in APL. This study aimed to identify optimized predictors of severe bleeding events related to APL. A total of 109 consecutive patients with newly diagnosed APL from January 2015 to April 2022 were retrospectively investigated. A systematic review of computer-based patient medical records was conducted to obtain clinical date, including baseline characteristics, routine blood examination findings, coagulation and fibrinolysis indexes, and bleeding events. Among the 109 patients, 89 were classified into the no-severe bleeding group, while 20 had severe bleeding. Compared with the patients with no severe bleeding, the patients with severe bleeding had significantly higher circulating leukemic cell percentages, disseminated intravascular coagulation (DIC) scores, D-dimer (D-D) levels, and fibrin degradation product (FDP) levels. They also had lower fibrinogen (FIB) levels and a longer prothrombin time. Multivariate analysis revealed that the circulating leukemic cell percentage (OR = 1.040, CI = 1.008-1.072, P = 0.012), FIB level (OR = 0.101, CI = 0.011-0.896, P = 0.040), and FDP level (OR = 1.012, CI = 1.000-1.024, P = 0.047) were independent risk factors for severe bleeding. FDP/FIB, D-D/FIB, and seven meaningful indicators in the single-factor analysis were included in the receiver operating characteristic (ROC) curve analysis. The results showed that FDP/FIB was the best indicator for predicting severe bleeding related to newly diagnosed APL. The area under the ROC curve of FDP/FIB was 0.915, and the best cutoff value was 61.77, with 100% sensitivity and 74.2% specificity. Statistical analysis showed a higher incidence of severe bleeding and higher DIC scores when FDP/FIB was >61.77 in APL patients. FDP/FIB has obvious advantages in predicting the degree of bleeding associated with primary promyelocytic leukemia; the greater the FDP/FIB value, the more severe the bleeding. The risk of severe bleeding was the highest when FDP/FIB > 61.77.

Platelet-Acute Leukemia Interactions

Acute leukemia (AL) is a hematological malignancy with high morbidity and mortality that is caused by abnormal hematopoietic stem cells. AL can change the parameters, quality, and function of platelets through numerous mechanisms, resulting in bleeding and even death in AL patients. Hence, AL patients are often clinically treated using normal platelet transfusion. However, studies have found that platelets can also affect AL cells. This review discusses the changes occurring in platelet count, mean platelet volume, platelet distribution width, reticulated platelets, platelet membrane glycoprotein, platelet aggregation, and activation in AL patients, the causes of these changes, and the possible significance of these changes for patient prognosis. The effects of platelets on the proliferation and drug resistance of AL cells are also discussed.

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 tissue factor-positive extracellular vesicles and their association with thrombosis in different diseases

Tissue factor (TF) is a procoagulant protein released from activated host cells, such as monocytes, and tumor cells on extracellular vesicles (EVs). TF + EVs are observed in the circulation of patients with various types of diseases. In this review, we will summarize the association between TF + EVs and activation of coagulation and survival in different types of diseases, including cancer, sepsis, and infections with different viruses, such as human immunodeficiency virus (HIV), influenza A virus (IAV), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We will also discuss the source of TF + EVs in various diseases. EVTF activity is associated with thrombosis in pancreatic cancer patients and coronavirus disease 2019 patients (COVID-19) and with disseminated intravascular coagulation in cancer patients. EVTF activity is also associated with worse survival in patients with cancer and COVID-19. Monocytes are the major sources of TF + EVs in sepsis, and viral infections, such as HIV, Ebola virus, and SARS-CoV-2. In contrast, alveolar epithelial cells are the major source of TF + EVs in bronchoalveolar lavage fluid in COVID-19 and influenza A patients. These studies indicate that EVTF activity could be used as a biomarker to identify patients that have an increased risk of coagulopathy and mortality.