Coagulation biomarkers and prediction of venous thromboembolism and survival in small cell lung cancer: A sub-study of RASTEN - A randomized trial with low molecular weight heparin

Circulating Blood Biomarkers and Risk of Venous Thromboembolism in Cancer Patients: A Systematic Review and Meta-Analysis

BACKGROUND

 Cancer patients have an increased risk of venous thromboembolism (VTE). Currently, the availability of highly discriminatory prediction models for VTE in cancer patients is limited. The implementation of biomarkers in prediction models might lead to refined VTE risk prediction. In this systematic review and meta-analysis, we aimed to evaluate candidate biomarkers and their association with cancer-associated VTE.

METHODS

 We searched Medline, EMBASE, and Cochrane Central for studies that evaluated biomarkers in adult cancer patients from inception to September 2022. We included studies reporting on VTE after a cancer diagnosis with biomarker measurements performed at a defined time point. Median/mean differences (for continuous measures) and odds ratios (for dichotomous measures) with 95% confidence intervals were estimated and pooled using random-effects models.

RESULTS

 We included 113 studies in the systematic review. Of these, 50 studies were included in the meta-analysis. We identified two biomarkers at cancer diagnosis (factor VIII and time to peak thrombin), three biomarkers pre-chemotherapy (D-dimer, fibrinogen, and mean platelet volume), and one biomarker preoperatively (platelet count) that had significant median or mean differences. Additionally, we found that hemoglobin <100 g/L and white blood count >11 × 109/L were significantly associated with future VTE risk only when measured at cancer diagnosis. Pre-chemotherapy neutrophil-to-lymphocyte ratio ≥3 and preoperative platelet count ≥400 × 109/L were also found to be associated with future VTE risk.

CONCLUSION

 In conclusion, this study identified nine candidate blood biomarkers that may help in optimizing VTE prediction in cancer patients that should be further explored in future studies.

Thrombin Generation Markers as Predictors of Cancer-Associated Venous Thromboembolism: A Systematic Review

Venous thromboembolism (VTE) is a main contributor to morbidity and mortality in cancer patients. Biomarkers with the potential to predict cancer-associated VTE are continually sought. Of these, markers of thrombin generation present a likely option. The present systematic review examines the ability of three widely used biomarkers of thrombin generation: prothrombin fragment 1.2 (F1.2), thrombin-antithrombin complex (TAT), and ex vivo thrombin generation, to predict VTE in both solid and hematologic adult cancer patients. Relevant studies were identified in the PubMed and Embase databases, and the review conformed to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Each study was evaluated using the quality assessment tool from the National Heart, Lung, and Blood Institute. The review protocol was published on PROSPERO with identifier CRD42022362339. In total, 24 papers were included in the review: 11 reporting data on F1.2, 9 on TAT, and 12 on ex vivo thrombin generation. The quality ratings of the included studies varied from good (n = 13), fair (n = 8), to poor (n = 3) with a high heterogenicity. However, F1.2, TAT complex, and ex vivo thrombin generation were all found to be associated with the development of VTE. This association was most pronounced for F1.2. Furthermore, the determination of F1.2 was able to improve the precision of several established risk assessment scores. In conclusion, markers of thrombin generation were found to be elevated in cancer patients with VTE, and particularly, F1.2 was found to be a promising predictor of cancer-associated VTE.

Plasma tissue factor activity in lung cancer patients predicts venous thromboembolism and poor overall survival

Background

Biomarkers to identify lung cancer (LC) patients with high risk of venous thromboembolism (VTE) are needed.

Objectives

To evaluate the usefulness of plasma tissue factor activity (TFA) and D-dimer levels for the prediction of VTE and overall survival in patients with LC.

Methods

In a prospective multicenter observational cohort of consecutive LC patients, TFA and D-dimer levels were measured at diagnosis before any cancer treatment (V1) and between 8 and 12 weeks after diagnosis (V2).

Results

Among 302 patients, 38 (12.6%) experienced VTE within the first year after diagnosis. V1-TFA and V1-D-dimer levels were significantly (P = .02) higher in patients who presented VTE within 3 months than in patients without VTE: V1-TFA was 2.02 (25th-75th percentiles, 0.20-4.01) vs 0.49 (0.20-3.09) ng/mL and V1-D-dimer was 1.42 (0.64-4.40) vs 0.69 (0.39-1.53) μg/mL, respectively. Cutoffs of 1.92 ng/mL for TFA and 1.26 μg/mL for D-dimer could discriminate both groups of patients. In multivariate analysis, V1-TFA > 1.92 ng/mL was the only significant predictor of VTE risk at 1 year (hazard ratio, 2.10; 95% CI, 1.06-4.16; P = .03). V2-TFA, quantified in 251 patients, decreased significantly compared with V1-TFA (0.20 vs 0.56 ng/mL, P < .05), but a V2-TFA level > 0.77 ng/mL could predict VTE in the following 3 months. Median overall survival was worse for patients with V1-TFA > 1.92 ng/mL (14.6 vs 23.8 months) and V1-D-dimer > 1.26 μg/mL (13.8 vs 24 months, P < .001).

Conclusion

High plasma TFA levels are associated with the occurrence of VTE within the next 3 months after each visit (V1 or V2) and poor survival.

Cancer-Associated Thrombosis: Epidemiology, Pathophysiological Mechanisms, Treatment, and Risk Assessment

Cancer patients represent a growing population with drastically difficult care and a lowered quality of life, especially due to the heightened risk of vast complications. Thus, it is well established so far that one of the most prominent complications in individuals with cancer is venous thromboembolism. Since there are various improved methods for screening and diagnosing cancer and its complications, the incidence of cancer-associated thrombosis has been on the rise in recent years. Therefore, the high mortality and morbidity rates among these patients are not a surprise. Consequently, there is an excruciating need for understanding the mechanisms behind this complex process, as well as the imperative for adequate analysis and application of the most suitable steps for cancer-associated thrombosis prevention. There are various and numerous mechanisms offering potential answers to cancer-associated thrombosis, some of which have already been elucidated in various preclinical and clinical scenarios, yet further and more elaborate studies are crucial to understanding and preventing this complex and harsh clinical entity. This article elaborates on the growing incidence, mortality, morbidity, and risk factors of cancer-associated thrombosis while emphasizing the pathophysiological mechanisms in the light of various types of cancer in patients and summarizes the most novel therapy and prevention guidelines recommendations.

The Rise of Extracellular Vesicles as New Age Biomarkers in Cancer Diagnosis: Promises and Pitfalls

Cell-to-cell interactions in the intricate microenvironment of tissue have a significant impact on the progression of cancer at every stage. Both cancer cells and stromal cells are responsible for the secretion of soluble chemical compounds as well as membrane-encased components, which both influence and govern the cell-to-cell interactions within the micro-environment of tumor cells. These membrane structures are identified as extracellular vesicles (EVs), which include exosomes and microvesicles. These nanosized vesicles are made up of bilayered proteolipids and have dimensions ranging from 50 to 1000 nm. It has been speculated that extracellular vesicles that originate from cancer cells perform a variety of functions in the development and progression of cancer which may involve the transport of regulatory materials, such as oncogenic proteins between nearby cells and to distant biological locations. In addition, their level in the serum of cancer patients is noticeably higher than those of healthy controls. The release of extracellular vesicles into the extracellular space is a continual process in both healthy and diseased cells. These extracellular vesicles hold molecular signatures that are defining features of health as well as disease. And hence, the EVs present in biological fluids provide unparalleled and noninvasive access to the necessary molecular details about the health status of the cells. Recent discoveries about these complex extracellular organelles have accelerated the discovery of cancer-specific biological markers as well as the development of unique diagnostic tools based on extracellular vesicles. In this mini-review, we aim to highlight the hopes and hypes associated with the applications of extracellular vesicles as biomarkers for cancer diagnosis.

Small cell lung cancer: circulating tumor cell lines and expression of mediators of angiogenesis and coagulation

Aim

Coagulation is frequently activated in cancer patients and has been correlated with an unfavorable prognosis. To evaluate whether a putative release of tissue factor (TF) by circulating tumor cells (CTCs) represents a target to impair the dissemination of small cell lung cancer (SCLC), the expression of relevant proteins in a panel of permanent SCLC and SCLC CTC cell lines that have been established at the Medical University of Vienna.

Methods

Five CTC and SCLC lines were analyzed using a TF enzyme-linked immunosorbent assay (ELISA) tests, RNA sequencing, and western blot arrays covering 55 angiogenic mediators. Furthermore, the influence of topotecan and epirubicin as well as hypoxia-like conditions on the expression of these mediators was investigated.

Results

The results demonstrate that the SCLC CTC cell lines express no significant amounts of active TF but thrombospondin-1 (TSP-1), urokinase-type plasminogen activator receptor (uPAR), vascular endothelial-derived growth factor (VEGF) and angiopoietin-2 in two cases. The major difference between the SCLC and SCLC CTC cell lines found was the loss of the expression of angiogenin in the blood-derived CTC lines. Topotecan and epirubicin decreased the expression of VEGF, whereas hypoxia-like conditions upregulated VEGF.

Conclusions

Active TF capable of triggering coagulation seems not to be expressed in SCLC CTC cell lines in significant levels and, thus, CTC-derived TF seems dispensable for dissemination. Nevertheless, all CTC lines form large spheroids, termed tumorospheres, which may become trapped in clots of the microvasculature and extravasate in this supportive microenvironment. The contribution of clotting to the protection and dissemination of CTCs in SCLC may be different from other solid tumors such as breast cancer.

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.

Role of extracellular vesicles in cancer-specific interactions between tumour cells and the vasculature

Cancer progression impacts and exploits the vascular system in several highly consequential ways. Among different types of vascular cells, blood cells and mediators that are engaged in these processes, endothelial cells are at the centre of the underlying circuitry, as crucial constituents of angiogenesis, angiocrine stimulation, non-angiogenic vascular growth, interactions with the coagulation system and other responses. Tumour-vascular interactions involve soluble factors, extracellular matrix molecules, cell-cell contacts, as well as extracellular vesicles (EVs) carrying assemblies of molecular effectors. Oncogenic mutations and transforming changes in the cancer cell genome, epigenome and signalling circuitry exert important and often cancer-specific influences upon pathways of tumour-vascular interactions, including the biogenesis, content, and biological activity of EVs and responses of cancer cells to them. Notably, EVs may carry and transfer bioactive, oncogenic macromolecules (oncoproteins, RNA, DNA) between tumour and vascular cells and thereby elicit unique functional changes and forms of vascular growth and remodeling. Cancer EVs influence the state of the vasculature both locally and systemically, as exemplified by cancer-associated thrombosis. EV-mediated communication pathways represent attractive targets for therapies aiming at modulation of the tumour-vascular interface (beyond angiogenesis) and could also be exploited for diagnostic purposes in cancer.

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.

Cancer-associated venous thromboembolism

Cancer-associated thrombosis (including venous thromboembolism (VTE) and arterial events) is highly consequential for patients with cancer and is associated with worsened survival. Despite substantial improvements in cancer treatment, the risk of VTE has increased in recent years; VTE rates additionally depend on the type of cancer (with pancreas, stomach and primary brain tumours having the highest risk) as well as on individual patient's and cancer treatment factors. Multiple cancer-specific mechanisms of VTE have been identified and can be classified as mechanisms in which the tumour expresses proteins that alter host systems, such as levels of platelets and leukocytes, and in which the tumour expresses procoagulant proteins released into the circulation that directly activate the coagulation cascade or platelets, such as tissue factor and podoplanin, respectively. As signs and symptoms of VTE may be non-specific, diagnosis requires clinical assessment, evaluation of pre-test probability, and objective diagnostic testing with ultrasonography or CT. Risk assessment tools have been validated to identify patients at risk of VTE. Primary prevention of VTE (thromboprophylaxis) has long been recommended in the inpatient and post-surgical settings, and is now an option in the outpatient setting for individuals with high-risk cancer. Anticoagulant therapy is the cornerstone of therapy, with low molecular weight heparin or newer options such as direct oral anticoagulants. Personalized treatment incorporating risk of bleeding and patient preferences is essential, especially as a diagnosis of VTE is often considered by patients even more distressing than their cancer diagnosis, and can severely affect the quality of life. Future research should focus on current knowledge gaps including optimizing risk assessment tools, biomarker discovery, next-generation anticoagulant development and implementation science.

Longitudinal Dynamics of Coagulation and Angiogenesis Markers in Cancer Patients During and After Chemotherapy

Hemostatic parameters have been investigated as molecular determinants of tumor progression. To analyze the dynamics of microparticle-associated tissue factor activity (MPTF), tissue factor antigen (TF-Ag), and angiopоietin-2 (ANG-2) in cancer patients before, during, and after active treatment and to explore their potential as biomarkers for metastatic occurrence and death. Blood for the analysis of MPTF, TF-Ag, ANG-2, and conventional hemostatic tests was sampled in 111 patients with various cancers at 4 consecutive visits: before first chemotherapy cycle, after 3 courses, at the sixth course, and 3 months after chemotherapy cessation. Patients were followed up until metastatic progression/death or the end of the study. MPTF did not change during chemotherapy, but increased significantly after treatment cessation. Total TF-Ag and ANG-2 decreased throughout active treatment. Significant drop of their levels was observed 3 months post therapy cessation. Progressive disease was significantly associated with higher pre-chemotherapy TF-Ag and fibrinogen. Elevated baseline levels of fibrinogen were associated with increased risk of shortened progression free survival. Cessation of chemotherapy is associated with significant change of hemostatic parameters. Pre-chemotherapy levels of TF-Ag and fibrinogen may be informative of disease state and prognosis.

Polyphosphate expression by cancer cell extracellular vesicles mediates binding of factor XII and contact activation

Cleaved HK is observed in many patients with cancer, suggesting activation of the contact system.

EVs from cancer cell lines or patients with cancer express polyphosphate, bind and activate FXII, and are prothrombotic.

Extracellular vesicles (EV) have been implicated in diverse biological processes, including intracellular communication, transport of nucleic acids, and regulation of vascular function. Levels of EVs are elevated in cancer, and studies suggest that EV may stimulate thrombosis in patients with cancer through expression of tissue factor. However, limited data also implicate EV in the activation of the contact pathway of coagulation through activation of factor XII (FXII) to FXIIa. To better define the ability of EV to initiate contact activation, we compared the ability of EV derived from different cancer cell lines to activate FXII. EV from all cell lines activated FXII, with those derived from pancreatic and lung cancer cell lines demonstrating the most potent activity. Concordant with the activation of FXII, EV induced the cleavage of high molecular weight kininogen (HK) to cleaved kininogen. We also observed that EVs from patients with cancer stimulated FXII activation and HK cleavage. To define the mechanisms of FXII activation by EV, EV were treated with calf intestinal alkaline phosphatase or Escherichia coli exopolyphosphatase to degrade polyphosphate; this treatment blocked binding of FXII to EVs and the ability of EV to mediate FXII activation. In vivo, EV induced pulmonary thrombosis in wild-type mice, with protection conferred by a deficiency in FXII, HK, or prekallikrein. Moreover, pretreatment of EVs with calf intestinal alkaline phosphatase inhibited their prothrombotic effect. These results indicate that polyphosphate mediates the binding of contact factors to EV and that EV-associated polyphosphate may contribute to the prothrombotic effects of EV in cancer.

Hemostatic Biomarkers and Cancer Prognosis: Where Do We Stand?

Cancer patients are characterized by hypercoagulable state and an increased rate of thrombotic events, the most common being venous thromboembolism. Several hemostatic pathways that are significantly implicated in mechanisms of thromboembolic disease are also involved in growth, invasion, and metastatic spread of malignant cells as well in tumor-induced neo-angiogenesis. This close connection between cancer and the hemostatic system has prompted numerous studies on the role of alterations in the level plasma biomarkers of the different compartments of hemostasis in predicting cancer prognosis. In this review, we collect the results of several exemplificative studies that have evaluated clotting activation biomarkers in relation to different cancer outcomes with a final emphasis on current research and forthcoming directions in this field.

Tissue factor and its procoagulant activity on cancer-associated thromboembolism in pancreatic cancer

Pancreatic cancer frequently involves cancer-associated thromboembolism, which is strongly associated with poor prognosis. Tissue factor, a blood coagulation factor largely produced in cancer patients as a component of extracellular vesicles, plays a key role in the incidence of cancer-associated thromboembolism in patients with pancreatic cancer. However, no prospective studies have been published on the relationship between tissue factor and cancer-associated thromboembolism or patient clinical characteristics, including recent chemotherapy regimens. Thus, we aimed to address this in a Japanese cohort of 197 patients and 41 healthy volunteers. Plasma tissue factor levels were measured by ELISAs preevaluated by tissue factor specificity. Multivariable analysis was used to identify independent predictors of cancer-associated thromboembolism. We found that the cancer-associated thromboembolism rate in the patient cohort was 6.6% (4.6%, venous thromboembolism; 2.0%, arterial thromboembolism). Tissue factor levels of 100 pg/mL or higher at patient registration were predictive of cancer-associated thromboembolism, with positive and negative predictive values of 23.1% and 94.6%, respectively. Multivariable analysis showed that plasma tissue factor levels were an independent predictive factor for cancer-associated thromboembolism, with a risk ratio of 5.54 (95% confidence interval, 1.02-30.09). Unlike in healthy volunteers and patients without cancer-associated thromboembolism, tissue factor levels were highly correlated with extracellular vesicles' procoagulant activity in patients developing cancer-associated thromboembolism. Taken together, our data show that the tissue factor levels at patient registration were a predictive factor for cancer-associated thromboembolism in this cohort of patients with pancreatic cancer.

Implications and pitfalls for cancer diagnostics exploiting extracellular vesicles

Early detection of cancer in order to facilitate timely therapeutic interventions is an unsolved problem in today's clinical diagnostics. Tumors are detected so far mostly after pathological symptoms have emerged (usually already in progressed disease states), within preventive screenings, or occasionally as incidental finding. The emergence of extracellular vesicle (EV) analytics in combination with liquid biopsy sampling opened a plethora of new possibilities for the detection of tumors (and other diseases). This review gives an overview of the diversity of currently known EV species and the relevant cargo molecules representing potential biomarkers to detect, identify and characterize tumor cells. A number of molecules reported in recent years to be valuable targets for different aspects of cancer diagnostics, are presented. Furthermore, we discuss (technical) challenges and pitfalls related to the various potential applications (screening, diagnosis, prognosis, monitoring) of liquid biopsy based EV analytics, and give an outlook to possible future directions of this emerging field in oncology.

Tissue Factor and Extracellular Vesicles: Activation of Coagulation and Impact on Survival in Cancer

Simple Summary

The tissue factor (TF)-factor VIIa complex is the major physiological initiator of blood coagulation. Tumors express TF and release TF-positive extracellular vesicles (EVs) into the circulation, and this is associated with the activation of coagulation. Circulating levels of EVTF activity may be a useful biomarker to identify patients at risk for thrombosis. Tumor TF and TF-positive EVs are also associated with reduced survival.

Abstract

Tissue factor (TF) is a transmembrane glycoprotein that functions as a receptor for FVII/FVIIa and initiates the extrinsic coagulation pathway. Tumors and cancer cells express TF that can be released in the form of TF positive (TF+) extracellular vesicles (EVs). In this review, we summarize the studies of tumor TF and TF + EVs, and their association with activation of coagulation and survival in cancer patients. We also summarize the role of tumor-derived TF + EVs in venous thrombosis in mouse models. Levels of tumor TF and TF + EVs are associated with venous thromboembolism in pancreatic cancer patients. In addition, levels of EVTF activity are associated with disseminated intravascular coagulation in cancer patients. Furthermore, tumor-derived TF + EVs enhance venous thrombosis in mice. Tumor TF and TF + EVs are also associated with worse survival in cancer patients, particularly in pancreatic cancer patients. These studies indicate that EVTF activity could be used as a biomarker to identify pancreatic cancer patients at risk for venous thrombosis and cancer patients at risk for disseminated intravascular coagulation. EVTF activity may also be a useful prognostic biomarker in cancer patients.

Increased activity of procoagulant factors in patients with small cell lung cancer

Small cell lung cancer (SCLC) patients have augmented risk of developing venous thromboembolism, but the mechanisms triggering this burden on the coagulation system remain to be understood. Recently, cell-derived microparticles carrying procoagulant phospholipids (PPL) and tissue factor (TF) in their membrane have attracted attention as possible contributors to the thrombogenic processes in cancers. The aims of this study were to assess the coagulation activity of platelet-poor plasma from 38 SCLC patients and to provide a detailed procoagulant profiling of small and large extracellular vesicles (EVs) isolated from these patients at the time of diagnosis, during and after treatment compared to 20 healthy controls. Hypercoagulability testing was performed by thrombin generation (TG), procoagulant phospholipid (PPL), TF activity, Protein C, FVIII activity and cell-free deoxyribonucleic acid (cfDNA), a surrogate measure for neutrophil extracellular traps (NETs). Our results revealed a coagulation activity that is significantly increased in the plasma of SCLC patients when compared to age-related healthy controls, but no substantial changes in coagulation activity during treatment and at follow-up. Although EVs in the patients revealed an increased PPL and TF activity compared with the controls, the TG profiles of EVs added to a standard plasma were similar for patients and controls. Finally, we found no differences in the coagulation profile of patients who developed VTE to those who did not, i.e. the tests could not predict VTE. In conclusion, we found that SCLC patients display an overall increased coagulation activity at time of diagnosis and during the disease, which may contribute to their higher risk of VTE.

Plasminogen activator inhibitor 1 and venous thrombosis in pancreatic cancer

Pancreatic cancer patients have a high risk of venous thromboembolism (VTE). Plasminogen activator inhibitor 1 (PAI-1) inhibits plasminogen activators and increases the risk of thrombosis. PAI-1 is expressed by pancreatic tumors and human pancreatic cell lines. However, to date, there are no studies analyzing the association of active PAI-1 and VTE in pancreatic cancer patients. We investigated the association of active PAI-1 in plasma and VTE in pancreatic cancer patients. In addition, we determined if the presence of human pancreatic tumors expressing PAI-1 impairs venous thrombus resolution in mice. Plasma levels of active PAI-1 in patients with pancreatic cancer and mice bearing human tumors were determined by enzyme-linked immunosorbent assay. We measured PAI-1 expression in 5 different human pancreatic cancer cell lines and found that PANC-1 cells expressed the highest level. PANC-1 tumors were grown in nude mice. Venous thrombosis was induced by complete ligation of the inferior vena cava (IVC). Levels of active PAI-1 were independently associated with increased risk of VTE in patients with pancreatic cancer (subdistribution hazard ratio per doubling of levels: 1.39 [95% confidence interval, 1.09-1.78], P = .007). Mice bearing PANC-1 tumors had increased levels of both active human and active mouse PAI-1 and decreased levels of plasmin activity. Importantly, mice bearing PANC-1 tumors exhibited impaired venous thrombus resolution 8 days after IVC stasis compared with nontumor controls. Our results suggest that PAI-1 contributes to VTE in pancreatic cancer.

Inflammatory Biomarkers in the Short-Term Prognosis of Venous Thromboembolism: A Narrative Review

The relationship between inflammation and venous thrombosis is not well understood. An inflammatory response may be both the cause and consequence of venous thromboembolism (VTE). In fact, several risk factors of VTE modulate thrombosis through inflammatory markers. Acute pulmonary embolism (PE) is burdened by a remarkable mortality rate, up to 34% in severely ill patients presenting with hemodynamic instability. Initial mortality risk stratification is based on hemodynamic instability. Patients with a situation of hemodynamic stability require immediate further risk assessment based on clinical, imaging, and circulating biomarkers, as well as the presence of comorbidities. Some inflammatory biomarkers have shown potential usefulness in the risk stratification of patients with VTE, especially acute PE. C-reactive protein on admission is associated with 30-day mortality and bleeding in VTE patients. P-selectin is associated with right ventricle dysfunction in PE patients and might be associated with VTE recurrences and the extension of thrombosis. Tissue factor microparticles are associated with VTE recurrence in cancer-associated thrombosis. Other inflammatory biomarkers present scarce evidence (inflammatory cytokines, erythrocyte sedimentation rate, fibrinogen, leukocyte count). In this manuscript, we will review the prognostic role of different inflammatory biomarkers available both for clinical practice and research in VTE patients.

Levels of the cancer biomarker CA 19-9 are associated with thrombin generation in plasma from treatment-naïve pancreatic cancer patients

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is associated with a hypercoagulable state and high mortality. Increases in the plasma levels of tumor marker carbohydrate antigen (CA) 19-9 are used in diagnosis and follow-up but have also been reported to precede venous thromboembolism (VTE).

AIMS

We examined the association between CA 19-9 and thrombin generation (TG) in plasma from PDAC patients, as well as their association with coagulation biomarkers prior to pancreatic surgery. In addition, we determined the effect of commercial sources of CA 19-9 on TG.

METHODS

We collected plasma from 58 treatment-naïve PDAC patients without any signs of VTE. We measured levels of CA 19-9, FVIII, fibrinogen, D-dimer, antithrombin and extracellular vesicle (EV) tissue factor (TF) activity and TG using a Calibrated Automated Thrombogram (CAT). The effect of different commercial sources of CA 19-9 on TG in Standard Human Plasma (SHP) was also studied.

RESULTS

Patient plasma samples were divided into 4 preoperative groups based on the level of CA 19-9: none < 2, low = 3-200, high = 201-1000, and very high > 1000 U/mL. CA 19-9 levels were associated with several of the TG parameters, including endogenous thrombin potential, peak, and time to peak. CA 19-9 did not associate with any of the coagulation biomarkers. Spiking of SHP with CA 19-9 increased TG but this was decreased by an anti-TF antibody.

CONCLUSIONS

CA 19-9 was associated with TG in patients prior to any pancreatic cancer treatments or signs of VTE. Some commercial sources of CA 19-9 enhanced TG in SHP seemingly due to contaminating TF.

Primary prophylaxis for venous thromboembolism in ambulatory cancer patients receiving chemotherapy

BACKGROUND

Venous thromboembolism (VTE) often complicates the clinical course of cancer. The risk is further increased by chemotherapy, but the trade-off between safety and efficacy of primary thromboprophylaxis in cancer patients treated with chemotherapy is uncertain. This is the third update of a review first published in February 2012.

OBJECTIVES

To assess the efficacy and safety of primary thromboprophylaxis for VTE in ambulatory cancer patients receiving chemotherapy compared with placebo or no thromboprophylaxis, or an active control intervention.

SEARCH METHODS

For this update, the Cochrane Vascular Information Specialist searched the Cochrane Vascular, CENTRAL, MEDLINE, Embase and CINAHL databases and World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov trials registers to 3 August 2020. We also searched the reference lists of identified studies and contacted content experts and trialists for relevant references.

SELECTION CRITERIA

Randomised controlled trials comparing any oral or parenteral anticoagulant or mechanical intervention to no thromboprophylaxis or placebo, or comparing two different anticoagulants.

DATA COLLECTION AND ANALYSIS

We extracted data on risk of bias, participant characteristics, interventions, and outcomes including symptomatic VTE and major bleeding as the primary effectiveness and safety outcomes, respectively. We applied GRADE to assess the certainty of evidence.

MAIN RESULTS

We identified six additional randomised controlled trials (3326 participants) for this update, bringing the included study total to 32 (15,678 participants), all evaluating pharmacological interventions and performed mainly in people with locally advanced or metastatic cancer. The certainty of the evidence ranged from high to very low across the different outcomes and comparisons. The main limiting factors were imprecision and risk of bias. Thromboprophylaxis with direct oral anticoagulants (direct factor Xa inhibitors apixaban and rivaroxaban) may decrease the incidence of symptomatic VTE (risk ratio (RR) 0.43, 95% confidence interval (CI) 0.18 to 1.06; 3 studies, 1526 participants; low-certainty evidence); and probably increases the risk of major bleeding compared with placebo (RR 1.74, 95% CI 0.82 to 3.68; 3 studies, 1494 participants; moderate-certainty evidence). When compared with no thromboprophylaxis, low-molecular-weight heparin (LMWH) reduced the incidence of symptomatic VTE (RR 0.62, 95% CI 0.46 to 0.83; 11 studies, 3931 participants; high-certainty evidence); and probably increased the risk of major bleeding events (RR 1.63, 95% CI 1.12 to 2.35; 15 studies, 7282 participants; moderate-certainty evidence). In participants with multiple myeloma, LMWH resulted in lower symptomatic VTE compared with the vitamin K antagonist warfarin (RR 0.33, 95% CI 0.14 to 0.83; 1 study, 439 participants; high-certainty evidence), while LMWH probably lowers symptomatic VTE more than aspirin (RR 0.51, 95% CI 0.22 to 1.17; 2 studies, 781 participants; moderate-certainty evidence). Major bleeding was observed in none of the participants with multiple myeloma treated with LMWH or warfarin and in less than 1% of those treated with aspirin. Only one study evaluated unfractionated heparin against no thromboprophylaxis, but did not report on VTE or major bleeding. When compared with placebo or no thromboprophylaxis, warfarin may importantly reduce symptomatic VTE (RR 0.15, 95% CI 0.02 to 1.20; 1 study, 311 participants; low-certainty evidence) and may result in a large increase in major bleeding (RR 3.82, 95% CI 0.97 to 15.04; 4 studies, 994 participants; low-certainty evidence). One study evaluated antithrombin versus no antithrombin in children. This study did not report on symptomatic VTE but did report any VTE (symptomatic and incidental VTE). The effect of antithrombin on any VTE and major bleeding is uncertain (any VTE: RR 0.84, 95% CI 0.41 to 1.73; major bleeding: RR 0.78, 95% CI 0.03 to 18.57; 1 study, 85 participants; very low-certainty evidence).

AUTHORS' CONCLUSIONS

In ambulatory cancer patients, primary thromboprophylaxis with direct factor Xa inhibitors may reduce the incidence of symptomatic VTE (low-certainty evidence) and probably increases the risk of major bleeding (moderate-certainty evidence) when compared with placebo. LMWH decreases the incidence of symptomatic VTE (high-certainty evidence), but increases the risk of major bleeding (moderate-certainty evidence) when compared with placebo or no thromboprophylaxis. Evidence for the use of thromboprophylaxis with anticoagulants other than direct factor Xa inhibitors and LMWH is limited. More studies are warranted to evaluate the efficacy and safety of primary prophylaxis in specific types of chemotherapeutic agents and types of cancer, such as gastrointestinal or genitourinary cancer.

Cancer cell-derived tissue factor-positive extracellular vesicles: biomarkers of thrombosis and survival

PURPOSE OF REVIEW

Tissue factor (TF) is released from cancer cells and tumors in the form of extracellular vesicles (EVs). This review summarizes our current knowledge of the mechanisms of release of TF-positive EVs (TF+EVs) from cancer cells and the effect of these TF+EVs on cultured endothelial cells. In addition, we will summarize the contribution of TF+EVs to thrombosis in mice, and the association between plasma EVTF activity and venous thrombosis as well as survival of cancer patients.

RECENT FINDINGS

The release of TF+EVs from cancer cells is regulated by multiple factors, including hypoxia, epithelial-mesenchymal transition, and various intracellular signaling pathways. Cancer cell-derived, TF+EVs confer procoagulant activity to endothelial cells and induce the expression of adhesion proteins and IL-8. In addition, they contribute to thrombosis by directly activating the coagulation system and by generating thrombin that activates platelets in mouse models. Finally, there is an association between EVTF activity and venous thrombosis in pancreatic cancer patients as well as mortality in cancer patients.

SUMMARY

Cancer cell-derived TF+EVs bind to and activate endothelial cells. In addition, they serve as biomarkers of survival of cancer patients and venous thrombosis in pancreatic cancer patients.

Do we need prophylactic anticoagulation in ambulatory patients with lung cancer? A review

Venous thromboembolism is a common complication of malignancy. Lung cancer is considered one of the most thrombogenic cancer types. Primary thromboprophylaxis is not currently recommended for all ambulatory patients with active cancer. In the present narrative review we aim to summarize recent data on the safety and efficacy of primary thromboprophylaxis as well as on venous thromboembolism risk assessment, focusing on ambulatory patients with lung cancer. A potential benefit from prophylactic anticoagulation with low molecular weight heparins in terms of venous thromboembolism risk reduction and increased overall survival in patients with lung cancer, without a significant increase in bleeding risk, has been reported in several studies. Recent studies also reveal promising results of direct oral anticoagulants regarding their efficacy as primary thromboprophylaxis in patients with cancer, including those with lung cancer. However, the use of different study methodologies and the heterogeneity of study populations among the trials limit the extraction of definite results. More randomized, controlled trials, restricted to a well-characterized population of patients with lung cancer, are greatly anticipated. The use of risk assessment tools for stratification of venous thromboembolic risk is warranted. The development of an accurate and practical risk assessment model for patients with lung cancer represents an unmet need.

Novel Aspects of Extracellular Vesicles as Mediators of Cancer-Associated Thrombosis

The establishment of prothrombotic states during cancer progression is well reported but the precise mechanisms underlying this process remain elusive. A number of studies have implicated the presence of the clotting initiator protein, tissue factor (TF), in circulating tumor-derived extracellular vesicles (EVs) with thrombotic manifestations in certain cancer types. Tumor cells, as well as tumor-derived EVs, may activate and promote platelet aggregation by TF-dependent and independent pathways. Cancer cells and their secreted EVs may also facilitate the formation of neutrophil extracellular traps (NETs), which may contribute to thrombus development. Alternatively, the presence of polyphosphate (polyP) in tumor-derived EVs may promote thrombosis through a TF-independent route. We conclude that the contribution of EVs to cancer coagulopathy is quite complex, in which one or more mechanisms may take place in a certain cancer type. In this context, strategies that could attenuate the crosstalk between the proposed pro-hemostatic routes could potentially reduce cancer-associated thrombosis.

Biology and Role of Extracellular Vesicles (EVs) in the Pathogenesis of Thrombosis

Extracellular vesicles (EVs) are well-established mediators of cell-to-cell communication. EVs can be released by every cell type and they can be classified into three major groups according to their biogenesis, dimension, density, and predominant protein markers: exosomes, microvesicles, and apoptotic bodies. During their formation, EVs associate with specific cargo from their parental cell that can include RNAs, free fatty acids, surface receptors, and proteins. The biological function of EVs is to maintain cellular and tissue homeostasis by transferring critical biological cargos to distal or neighboring recipient cells. On the other hand, their role in intercellular communication may also contribute to the pathogenesis of several diseases, including thrombosis. More recently, their physiological and biochemical properties have suggested their use as a therapeutic tool in tissue regeneration as well as a novel option for drug delivery. In this review, we will summarize the impact of EVs released from blood and vascular cells in arterial and venous thrombosis, describing the mechanisms by which EVs affect thrombosis and their potential clinical applications.

Future Options of Molecular-Targeted Therapy in Small Cell Lung Cancer

Lung cancer is the leading cause of cancer-related deaths worldwide. With a focus on histology, there are two major subtypes: Non-small cell lung cancer (NSCLC) (the more frequent subtype), and small cell lung cancer (SCLC) (the more aggressive one). Even though SCLC, in general, is a chemosensitive malignancy, relapses following induction therapy are frequent. The standard of care treatment of SCLC consists of platinum-based chemotherapy in combination with etoposide that is subsequently enhanced by PD-L1-inhibiting atezolizumab in the extensive-stage disease, as the addition of immune-checkpoint inhibition yielded improved overall survival. Although there are promising molecular pathways with potential therapeutic impacts, targeted therapies are still not an integral part of routine treatment. Against this background, we evaluated current literature for potential new molecular candidates such as surface markers (e.g., DLL3, TROP-2 or CD56), apoptotic factors (e.g., BCL-2, BET), genetic alterations (e.g., CREBBP, NOTCH or PTEN) or vascular markers (e.g., VEGF, FGFR1 or CD13). Apart from these factors, the application of so-called 'poly-(ADP)-ribose polymerases' (PARP) inhibitors can influence tumor repair mechanisms and thus offer new perspectives for future treatment. Another promising therapeutic concept is the inhibition of 'enhancer of zeste homolog 2' (EZH2) in the loss of function of tumor suppressors or amplification of (proto-) oncogenes. Considering the poor prognosis of SCLC patients, new molecular pathways require further investigation to augment our therapeutic armamentarium in the future.

Measurement of tissue factor activity in extracellular vesicles from human plasma samples

Tissue factor (TF) is the cellular receptor for plasma factor (F) VII/FVIIa and triggers blood coagulation. Extracellular vesicles (EVs) are small membrane vesicles that are released from activated cells and tumor cells. Different cell types, including activated monocytes and tumors cells release TF-positive EVs into the circulation. We developed an assay to measure levels of TF activity in EVs isolated from human plasma samples. We and others have used this assay to demonstrate increased levels of EV TF activity in a variety of diseases associated with thrombosis, including cancer. These studies suggest that EV TF can be used as a biomarker of thrombotic risk. The strength of this laboratory assay is that it is relatively sensitive and specific. However, the limitations of the assay are that it is labor intensive and the coefficient of variation is too high for it to be used as a clinical assay.