Tissue Factor Antigen Levels Research Articles

Abstract 609: Heterozygous Tissue Factor Deficiency Protects Against Factor VII Activation And Consumption In A Murine Endotoxemia Model

Background: At least 1 in 25,000 humans carry F3 null alleles predicted to cause heterozygous tissue factor (TF) deficiency. Mice with heterozygous TF deficiency ( F3 +/- ) exhibit increased bleeding times and reduced thrombus formation in some models, and are protected against lethal thrombosis in penetrant thrombophilia. TF supports the activation of factor VII (FVII) in vitro , an effect that is evident in vivo in the extreme case of low-TF mice expressing ~1% of basal TF levels. Aim: To determine the impact of heterozygous TF deficiency on FVII activation in vivo . Methods: Citrated plasma was isolated via inferior vena cava blood draw from F3 +/- and wildtype littermate mice at 10-11 weeks of age. To induce coagulation activation through endotoxemia, mice were challenged with intraperitoneal injection of 8 mg/kg LPS for 6 hours. Plasma TF was determined by ELISA. FVII and FVIIa levels were measured by FVII activity and Staclot VIIa-rTF clotting assays, respectively. n≥10 mice in all experiments. Results: F3 +/- mice have significantly reduced plasma TF antigen levels compared to wildtype littermate controls under basal conditions (6.5 pg/mL vs 11.6 pg/mL, p<0.001), differences that persist following endotoxemic challenge (9.9 pg/mL vs 14.8 pg/mL, p<0.001). At baseline, F3 +/- mice had similar circulating levels of zymogen FVII and FVIIa compared to controls. However, the levels of FVIIa correlated with FVII activity levels in F3 +/- mice (r 2 =0.66, p=0.003), whereas no correlation between FVIIa and FVII activity levels was observed in controls (r 2 =0.17, p=0.23). During endotoxemia, F3 +/- mice maintained significantly higher total FVII (85.6% vs 66.1%, p<0.05) and FVIIa (52.9% vs 35.4%, p<0.05) as compared to controls. Conclusions: FVII and FVIIa levels are unaffected by heterozygous TF deficiency in healthy mice, but FVIIa levels are dependent on the amount of FVII when TF is limiting. When TF expression and coagulation activation are augmented as during endotoxemic challenge, F3 +/- mice are protected against aberrant FVII activation and consumption. These studies suggest that human genetic variation influencing TF dosage could influence FVII activation and disease outcomes.

Tissue Factor (TF) Is Upregulated in Tumor-Bearing Mice Treated with Immune Checkpoint Inhibitor (ICI)

Introduction: Venous thromboembolism (VTE) is an important adverse event associated with immune checkpoint inhibitors (ICI) in cancer patients (12-15% annual rate). We have developed a murine model of venous thrombosis associated with ICI therapy (referred to as ICI-CAT). We found that mice bearing CT26 colon carcinoma treated with ICI developed larger thrombi following IVC occlusion compared with mice treated with IgG. ICI did not increase thrombus weight in mice without tumors. Tissue factor (TF) plays an important role in cancer-associated thrombosis (CAT) in patients treated with conventional therapies, and TF+ extracellular vesicles (EV) were associated with the development of VTE in pancreatic cancer. However, little is known about the impact of ICI on TF expression in patients treated with ICI. To address the underlying mechanism of ICI-associated thrombosis (IAT), we have examined the expression of TF in tumor and immune cells, as well as circulating EV, in our murine CT26 model. Methods: A syngeneic colon carcinoma model (CT26) in BALB/c mice was utilized to evaluate ICI-CAT following inferior vena cava ligation (stasis). Tumor tissue was analyzed for TF expression by immunoblotting using an anti-TF antibody (ab189483, Abcam). Tumor tissue was also dissociated, and TF-positive cells were assessed by flow cytometry analysis with CD45+ and CD45- gating using antibodies for CD11b, Ly6C, Ly6G (BioLegend), and TF (R&D). EV were isolated from platelet poor plasma from ICI or control IgG-treated mice by centrifugation (20,000 x g). Procoagulant activity of EV TF was measured using a chromogenic substrate to detect FXa generation following incubation of EV with FVIIa in the presence or absence of an anti-TF antibody. Results: Treatment of tumor-bearing mice with ICI markedly induced TF expression in tumors (Fig. A, Leftupper). Furthermore, levels of EV TF antigen (Fig. A, Left bottom) and EV TF activity (Fig. A, Right) were increased in mice treated with ICI. To explore the cellular origin of TF, we performed flow cytometry with dissociated tumor cells. A greater percentage of TF-positive cells in both the CD45+ (37.8%) and CD45- (74.6%) populations were detected in tumors from ICI treated mice compared to those treated with control IgG (27.9% and 49.8%, respectively), suggesting both tumor and tumor-infiltrating immune cells contribute to the larger thrombi observed in ICI-treated mice (Fig. B). Further analysis of CD45+ TF+ cells by CD11b gating (data not shown) revealed that a TF expression in a monocyte population (CD11b+ Ly6C+) was increased 3-fold by ICI (46.6%) compared to control IgG (14.2%) (Fig. C). We also found that TF expression was increased in cultured CT26 cells in response to interferon-g, but not in response to anti-PD-1 and anti-CTLA-4 antibodies, suggesting that ICIs do not directly upregulate TF and that more complex cellular interactions and inflammatory changes may be involved. Conclusions: ICI treatment of tumor-bearing mice results in increased tumor TF expression and EV TF expression. TF was also upregulated in immune cells in the tumor microenvironment after ICI treatment, including both tumor/stromal cells (CD45-), and tumor-associated monocytes and neutrophils (CD45+). These results suggest that multiple underlying mechanisms and diverse cellular expression underlie TF expression in this model, and that these processes many contribute to the larger thrombi observed in ICI-treated mice. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Measurement of tissue factor-positive extracellular vesicles in plasma: strengths and weaknesses of current methods.

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. 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. 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.

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.

Alterations in Sphingomyelin Metabolism Influences Tissue Factor Procoagulant Activity and the Release of TF-Positive Microvesicles

Tissue factor (TF), an integral membrane glycoprotein, is a cofactor for coagulation factor VIIa (FVIIa) and primary cellular initiator of the coagulation. Upon vascular injury or in disease conditions, blood comes in contact with TF, and the formation of TF-FVIIa complex initiates activation of the coagulation cascade. While TF is critical for the maintenance of hemostasis, aberrant expression of TF activity could lead to thrombotic disorders. Typically, most of TF on cell surfaces exist in a cryptic, coagulant inactive state, and an "activation" step (decryption) is essential for the transformation of cryptic TF to prothrombotic TF. Our recent studies showed that sphingomyelin (SM) in the outer leaflet of the plasma membrane is responsible for maintaining TF in an encrypted state in resting cells. The hydrolysis of SM, by either bacterial sphingomyelinase (bSMase) or acid-sphingomyelinase (ASMase) translocated from lysosomes to the outer leaflet in response to ATP, LPS or cytokine stimulation, increased TF activity on intact cells without altering TF protein levels. SM hydrolysis also led to the release of TF+ microvesicles (MVs). Inhibition of ASMase by functional inhibitors blocked LPS-induced TF procoagulant activity without impairing LPS-induced TF antigen levels in both in vitro and in vivo model systems. SM levels in the plasma membrane are regulated primarily by SM synthesizing enzymes, such as sphingomyelin synthases (SMS) 1 and 2 or SM hydrolyzing enzymes, such as ASMase and neutral SMases (nSMase). Many disease conditions, including diabetes, ischemia/hypoxia, and cancer, alter SM metabolism by altering the activities of the above enzymes. These diseases are also known to have increased thrombotic risk. To investigate the importance of SM metabolism in regulating TF procoagulant activity through TF encryption and decryption, we either overexpressed or silenced the enzymes involved in SM metabolism and determined their effect on TF procoagulant activity on intact cells and the release of TF+ MVs. Human monocyte-derived macrophages (MDMs) or human embilical vein endothelial cells (HUVEC) were chosen as cell model systems. In the first set of experiments, MDMs were transfected with adenovirus encoding SMS1, SMS2, or both to overexpress SMS. Analysis of SM levels in the outer leaflet by confocal microscopy and flow cytometry using SM specific binding protein (lysenin) revealed that overexpression of SMS1 or SMS2 increased SM levels in the outer leaflet. Measurement of TF activity on intact cells showed that overexpression of either SMS1 or SMS2 reduced both basal TF activity and the extent of increased TF activity following ATP or bSMase treatment. Overexpression of SMS1 or SMS2 also decreased the release of TF+ MVs. Overexpression of SMS1 or SMS2 had no significant effect on TF antigen levels. In the next set of experiments, MDMS were transfected with control scrambled RNA (scRNA) or siRNA specific for ASMase, nSMase1, nSMase2, or nSMase3. As expected from our earlier studies, ASMase silencing attenuated both basal and ATP-induced increased TF activity in MDMs. In case of nSMases, the knock-down of nSMase2 or nSMase3, but not nSMase1, reduced basal TF activity as well as ATP-induced TF decryption in MDMs. Analysis of SM levels in the outer leaflet showed that silencing of ASMase, nSMase2, or nSMase3 enhanced the SM content. The knock-down of either ASMase or nSMases did not affect TF antigen levels. In additional studies, HUVECs were transfected with control scRNA or siRNA specific for nSMase1, nSMAse2, or nSMase3. Forty eight hour post-transfection, HUVECs were stimulated with TNFα (10 ng/ml) plus IL-1β (10 ng/ml) for 6 h to induce TF expression. Analysis of cell surface TF activity showed that silencing nSMase2 or nSMase3, but not nSMase1, attenuated TNFα+IL-1β-induced TF procoagulant activity without decreasing TNFα+IL-1β-induced TF antigen levels. Overall, our data support the hypothesis that alterations in SM metabolism regulate TF procoagulant activity through encryption and decryption. Disclosures Rao: Takeda: Research Funding.

Markers of Coagulation and Angiogenesis Can Serve As Surrogate Biomarkers for Disease Activity and Survival in Cancer Patients

Based on observations of the link between hemostatic system and malignancy it is plausible to consider that plasma coagulation factors could serve as easily accessible markers for detection of malignant state and monitoring of cancer patients. Therefore, we hypothesized that tissue factor (TF), angiopoietin-2 (Ang-2) and soluble urokinase plasminogen activator receptor (suPAR) might perform as diagnostic and predictive biomarkers for the presence of malignancy as well as for the development of cancer-related events: metastatic progression and death.To analyze their performance TF-associated microparticle activity (MPTF), tissue factor antigen (TFAg), Ang-2 and suPAR were determined in 128 cancer patients with various cancer types receiving chemotherapy by sequential measurements (up to four times) at prespecified time points incorporated into interim and end-of-treatment analysis. MPTF activity was measured with Zymuphen MPTF kit, TFAg, suPAR and ANG-2 were quantitated by ELISA. Patients were followed up for progression free survival (PFS) from therapy initiation until occurrence of a combined event defined as either metastatic progression or death. In order to determine the predictive ability of hemostatic biomarkers for a PFS event Log-rank (Mantel-Cox) test was applied. ROC analysis was used to determine the cut off values for detection of an event, cut off values were transformed into binary variables and Kaplan-Meier curves were constructed. Cox regression analysis was applied to explore quantitatively the effect on the risk of progression.Results: Cut off values for the occurrence of an event were MPTF < 0.5 pg/ml (AUC 0.591), TFAg (√ pg/ml) > 8.28 (AUC 0.603), Ang-2 > 302.3 pg/ml (AUC 0.615) and suPAR (√ pg/ml) > 2.83. Shortened PFS was associated with decreased MPTF procoagulant activity and elevated plasma levels of TFAg, Ang-2, suPAR. As significant predictors for PFS were determined only TFAg (RR 4.57, p=0.038), Ang-2 (RR 2.138, p=0.031) and suPAR (RR 2.238, p=0.049).Conclusion: TFAg, Ang-2 and suPAR might be identified as significant adverse predictors of metastatic progression or death in cancer patients and risk is increased with elevated plasma levels. DisclosuresNo relevant conflicts of interest to declare.

The role of mononuclear cell tissue factor and inflammatory cytokines in patients with chronic thromboembolic pulmonary hypertension.

Thrombosis and inflammation are two major factors underlying chronic thromboembolic pulmonary hypertension (CTEPH). Tissue factor (TF), C-reactive protein (CRP), tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein 1 (MCP-1) may play critical roles in the process of CTEPH thrombosis and pulmonary vascular remodeling. Ten patients with a confirmed diagnosis of CTEPH, 20 patients with acute pulmonary thromboembolism and 15 patients with other types of pulmonary hypertension were enrolled in this study, along with 20 healthy subjects as the control group. The immunoturbidimetric method was used to determine the plasma content of CRP. The plasma levels of TNF-α, MCP-1, and TF antigen were measured by an enzyme-linked immunosorbent assay, and TF activity was measured by the chromogenic substrate method. Percoll density gradient centrifugation was used to separate peripheral blood mononuclear cells from plasma. The level of monocyte TF mRNA was examined by reverse transcriptase-polymerase chain reaction. The correlations between all indices described above were analyzed. In CTEPH patients, the expression of CRP, TNF-α, and MCP-1 was significantly higher than that in controls (P < 0.05). The levels of TF activity, TF antigen, and TF mRNA in monocyte cells were increased in CTEPH patients when compared with control subjects, but only the TF antigen and TF mRNA levels were significantly different (P < 0.05). In CTEPH patients, levels of CRP, MCP-1, and TNF-α significantly correlated with the level of TF antigen in plasma. TF gene expression was increased in patients with CTEPH, suggesting that blood-borne TF mainly comes from mononuclear cells. TF expression significantly correlated with levels of CRP, TNF-α and MCP-1. These factors may play an important role in the development of CTEPH via the inflammation–coagulation–thrombosis cycle.

Procoagulant and proinflammatory effects of red blood cells on lipopolysaccharide‐stimulated monocytes

We aimed to evaluate the mechanisms underlying the effects of red blood cells (RBCs) on the reactivity of monocytes to lipopolysaccharide (LPS) stimulation. Measurements of tissue factor (TF) antigen and activity were performed on freshly isolated white blood cells (WBCs)/platelets resuspended in heparinized plasma, as well as cultured monocytic cells. In a dose-dependent manner, RBCs significantly enhanced LPS-induced TF activity and antigen levels in blood monocytes; potentiation of TF activity by both human and murine RBCs did not require the presence of neutrophils and/or platelets. We also measured the levels of monocyte chemotactic protein-1 (MCP-1), the key proinflammatory chemokine that binds to duffy antigen receptor for chemokines (DARC) on RBC surface, in plasma and RBC lysates after the incubation of RBCs with WBC/platelets; at the concentrations corresponding to normal blood counts, RBCs exerted a significant influence on the free plasma levels of MCP-1, with about two-thirds of detectable MCP-1 post-LPS stimulation being associated with RBCs. Critically, DARC-deficient murine RBCs failed to enhance LPS-induced TF activity, confirming the mechanistic significance of RBC-DARC. Our study reports a novel mechanism by which RBCs promote procoagulant and proinflammatory sequelae of WBC exposure to LPS, likely mediated by RBC-DARC in the microenvironment(s) that bring monocytes and RBCs in close proximity.

Lung cancer chemotherapy agents increase procoagulant activity via protein disulfide isomerase-dependent tissue factor decryption.

Lung cancer patients undergoing chemotherapy have an elevated risk for thrombosis. However, the mechanisms by which chemotherapy agents increase the risk for thrombosis remains unclear. The aim of this study was to determine the mechanism(s) by which lung cancer chemotherapy agents cisplatin, carboplatin, gemcitabine, and paclitaxel elicit increased tissue factor activity on endothelial cells, A549 cells, and monocytes. Tissue factor activity, tissue factor antigen, and phosphatidylserine exposure were measured on chemotherapy-treated human umbilical vein endothelial cells (HUVEC), A549 cells, and monocytes. Cell surface protein disulfide isomerase (PDI) and cell surface free thiol levels were measured on HUVEC and A549 non-small cell lung carcinoma cells. Treatment of HUVECs, A549 cells, and monocytes with lung cancer chemotherapy significantly increased cell surface tissue factor activity. However, elevated tissue factor antigen levels were observed only on cisplatin-treated and gemcitabine-treated monocytes. Cell surface levels of phosphatidylserine were increased on HUVEC and monocytes treated with cisplatin/gemcitabine combination therapy. Chemotherapy also resulted in increased cell surface levels of PDI and reduced cell surface free thiol levels. Glutathione treatment and PDI inhibition, but not phosphatidylserine inhibition, attenuated tissue factor activity. Furthermore, increased tissue factor activity was reversed by reducing cysteines with dithiothreitol. These studies are the first to demonstrate that lung cancer chemotherapy agents increase procoagulant activity on endothelial cells and A549 cells by tissue factor decryption through a disulfide bond formation in a PDI-dependent mechanism.

Abstract 580: Lung Cancer Chemotherapy Agents Increase Procoagulant Activity via Protein Disulfide Isomerase-Dependent Tissue Factor Decryption

Background: Lung cancer patients undergoing chemotherapy have an elevated risk for thrombosis. However, the mechanisms by which chemotherapy agents increase the risk for thrombosis remains unclear. Objectives: To determine the mechanism(s) by which lung cancer chemotherapy agents cisplatin, carboplatin, gemcitabine, and paclitaxel elicit increased tissue factor (TF) activity on endothelial cells, A549 cells, and monocytes. Methods: TF activity, TF antigen, and phosphatidylserine exposure were measured on chemotherapy-treated human umbilical vein endothelial cells (HUVEC), A549 cells, and monocytes. Cell surface protein disulfide isomerase (PDI) and cell surface free-thiol levels were measured on HUVEC and A549 non-small cell lung carcinoma cells. Results: Treatment of HUVECs, A549 cells, and monocytes with lung cancer chemotherapy significantly increased cell surface TF activity. However, elevated TF antigen levels were observed only on cisplatin- and gemcitabine-treated monocytes. Cell surface levels of phosphatidylserine were increased on HUVEC and monocytes treated with cisplatin/gemcitabine combination therapy. Chemotherapy also resulted in increased cell surface levels of PDI and reduced cell surface free thiol levels. Glutathione treatment and PDI inhibition, but not phosphatidylserine inhibition attenuated TF activity. Furthermore, increased TF activity was reversed by reducing cysteines with dithiothreitol. Conclusions: These studies are the first to demonstrate that lung cancer chemotherapy agents increase procoagulant activity on endothelial cells, blood monocytes, and A549 cells by TF decryption through a disulfide bond formation in a PDI-dependent mechanism.

Phospholipid‐dependent procoagulant activity is highly expressed by circulating microparticles in patients with essential thrombocythemia

This study evaluates the functional procoagulant features of plasma microparticle (MP) to explore the MP contribution to the hypercoagulable state of patients with essential thrombocythemia (ET). Platelet-free plasma samples were obtained from 73 ET patients (37 positive for the JAK2V617F mutation) and 72 control subjects. The calibrated automated thrombogram (CAT) was performed in plasma samples to determine thrombin generation of MP-associated tissue factor (TF) and procoagulant phospholipid (PPL) activity, and the STA Procoag PPL assay to measure MP-PPL activity only. Both thrombin generation and PPL procoagulant activities were found significantly elevated in ET patients compared to controls, and were associated to significantly higher levels of TF antigen and FVIIa/AT complex. Thrombin generation was significantly greater in JAK2-V617F positive compared to JAK2-V617F negative patients and normal subjects. Significant correlations were found between the PPL-assay and the different parameters of the CAT assay. No difference was seen between the thrombosis and no thrombosis group. Prospective studies are needed to test whether MP-associated thrombin generation and procoagulant activity may predict for thrombosis in these patients.

Thrombotic Biomarker Profiling Of Plasma Samples From Patients Undergoing Bypass Surgery Using Protein Chip Array

IntroductionCardiovascular bypass surgical procedures, such as the coronary bypass procedure (CAP), patients are exposed to large doses of heparin and protamine sulfate. There is a high prevalence of anti-heparin platelet factor-4 antibodies in these patients. Although a fraction of these patients develop HIT syndrome, the role of circulating anti-heparin platelet factor-4 antibodies is not clear. Some of these patients may be at a high risk for post-surgical thrombotic complications. Such thrombogenic mediators as the microparticle and tissue factor, may also be up regulated in these patients. Inflammatory processes may also contribute to the overall post-thrombotic complications. The relevance of thrombotic mediators and inflammatory processes remains to be further explored in these patients. Recently protein chip array approach using SELDI/TOF mass spectrometry methods have been employed to identify the unique biomarker in various diseases. The purpose of this study was to determine the protein chip array profile and quantification of various mediators of thrombotic activation in patients who have undergone bypass surgery. Materials & MethodsPlasma samples from 79 patients were collected immediately prior to and two weeks after the CAP. Protein chip array profiling was carried out on a SELDI/TOF mass spectrometric method (PCS4000, BioRad, Richmond, CA) employing a gold chip array in the molecular weight range of 3000-150,000. The intensity of unique peaks was also calculated in terms of relative intensities. Microparticles were measured using a functional method (Hyphen Biomedical, France) and tissue factor antigen levels were measured using an ELISA method. The anti-heparin platelet factor-4 antibodies were also measured using a commercially available ELISA method (Genprobe, Wisconsin). ResultsOf the 79 patients, 20 showed a unique biomarker peak around 11-12kDa in the pre-op samples, which was absent from normal controls. 77 of the patients showed this unique biomarker peak at one week, whereas only 48 patients exhibited at two weeks after surgery. The relative intensity of the 11.6kDa biomarker was much higher at one week (6-fold) and was decreased at two weeks (3-fold). In addition to this unique peak, other biomarker peaks were noted at 15.1 and 15.8kDa. However, these peaks were not changed at different time points. In comparison to the normal, the microparticle levels were higher at the baseline sample (10.1±3.2nM) and increased to 19.3±6.1 and 24.5±8.1nM. Similarly, the tissue factor levels were increased at three weeks' time period. The anti-heparin platelet factor-4 titer rose 28% from the baseline at week one and 33% at week two. ConclusionsThe results on the biomarker profile are consistent to the earlier finding, where the presence of a unique biomarker in the range of 11-12kDa have been reported in patients with high prevalence of anti-heparin platelet factor-4 antibody. The increased level of microparticles and tissue factor at post-surgical periods of one week and two weeks suggest endogenous activation of thrombogenic mechanisms, which appears proportional to the up regulation of the anti-heparin platelet factor-4 antibodies. Thus, this data indicates that the non-functional anti-heparin platelet factor-4 antibodies may result in the activation of cellular processes leading to thrombogenesis. Further characterization of the unique biomarkers identified in these patients may be useful in understanding of the pathogenesis of inflammatory processes and their relevance to thrombogenesis in CABG patients. Clinical ImplicationsThese results indicate that the nonfunctional anti-heparin platelet factor 4 antibodies are capable of mediating inflammatory and thrombotic responses without symptomatic thrombocytopenia. Therefore, the measurement of these antibodies along with inflammatory and thrombogenic mediators may be helpful in the diagnostic and prognostic management of these patients. Disclosures:No relevant conflicts of interest to declare.

Tumour expresion of tissue factor and tissue factor pathway inhibitor in ovarian cancer- relationship with venous thrombosis risk

Ovarian cancer is known to display a particular association with venous thromboembolism (VTE) with reports up to 42% of patients developing thromboembolic complications. Tissue Factor (TF) and its inhibitor Tissue Factor Pathway Inhibitor (TFPI) have been implicated in VTE risk in cancer. The aim of this study was to measure tumour derived TF and TFPI and to investigate their potential role in VTE in ovarian cancer patients. TF and TFPI mRNA expression was measured using TaqMan real time PCR in 99 ovarian tumour samples. Nineteen cases complicated by VTE were matched to 19 cases without VTE. TF and TFPI protein levels were measured using ELISA and immunohistochemistry was used to localize TF expression. The role of TF expression on overall survival was also determined. TF mRNA and protein expression was increased in tumours from patients with clear cell carcinoma (p<0.001). TF protein expression was also increased in endometroid carcinoma (P<0.01) compared with benign tumours. TFPI mRNA expression was increased in clear cell carcinoma (P<0.01). TF mRNA and antigen level was increased in malignant tumours of patients who developed VTE compared with matched malignant õtumours of patients who remained thrombosis free (P<0.01). There was no difference in TFPI expression between the two groups. TF expression in ovarian cancer is significantly higher in patients who develop VTE. TF expression was increased in clear cell ovarian cancer and endometroid cancer and this may explain the higher risk of VTE in these subgroups. TF derived from these tumours may be the trigger for VTE in ovarian cancer.

4-Hydroxy-2-Nonenal Enhances Tissue Factor Activity in Human Monocytic Cells via p38 Mitogen-Activated Protein Kinase Activation-Dependent Phosphatidylserine Exposure

4-hydroxy-2-nonenal (HNE) is one of the major aldehydes formed during lipid peroxidation and is believed to play a role in the pathogenesis of atherosclerosis. The objective of the present study is to investigate the effect of HNE on tissue factor (TF) procoagulant activity expressed on cell surfaces. TF activity and antigen levels on intact cells were measured using factor Xa generation and TF monoclonal antibody binding assays, respectively. Exposure of phosphatidylserine on the cell surface was analyzed using thrombin generation assay or by binding of a fluorescent dye-conjugated annexin V. 2',7'-dichlorodihydrofluorescein diacetate was used to detect the generation of reactive oxygen species. Our data showed that HNE increased the procoagulant activity of unperturbed THP-1 cells that express traces of TF antigen, but had no effect on unperturbed endothelial cells that express no measurable TF antigen. HNE increased TF procoagulant activity but not TF antigen of both activated monocytic and endothelial cells. HNE treatment generated reactive oxygen species, activated p38 mitogen-activated protein kinase, and increased the exposure of phosphatidylserine at the outer leaflet in THP-1 cells. Treatment of THP-1 cells with an antioxidant, N-acetyl cysteine, suppressed the above HNE-induced responses and negated the HNE-mediated increase in TF activity. Blockade of p38 mitogen-activated protein kinase activation inhibited HNE-induced phosphatidylserine exposure and increased TF activity. HNE increases TF coagulant activity in monocytic cells through a novel mechanism involving p38 mitogen-activated protein kinase activation that leads to enhanced phosphatidylserine exposure at the cell surface.

Physiological levels of blood coagulation factors IX and X control coagulation kinetics in an in vitro model of circulating tissue factor

Thrombosis significantly contributes to cancer morbidity and mortality. The mechanism behind thrombosis in cancer may be circulating tissue factor (TF), as levels of circulating TF are associated with thrombosis. However, circulating TF antigen level alone has failed to predict thrombosis in patients with cancer. We hypothesize that coagulation factor levels regulate the kinetics of circulating TF-induced thrombosis. Coagulation kinetics were measured as a function of individual coagulation factor levels and TF particle concentration. Clotting times increased when pooled plasma was mixed at or above a ratio of 4:6 with PBS. Clotting times increased when pooled plasma was mixed at or above a ratio of 8:2 with factor VII-depleted plasma, 7:3 with factor IX- or factor X-depleted plasmas, or 2:8 with factor II-, V- or VIII-depleted plasmas. Addition of coagulation factors VII, X, IX, V and II to depleted plasmas shortened clotting and enzyme initiation times, and increased enzyme generation rates in a concentration-dependent manner. Only additions of factors IX and X from low-normal to high-normal levels shortened clotting times and increased enzyme generation rates. Our results demonstrate that coagulation kinetics for TF particles are controlled by factor IX and X levels within the normal physiological range. We hypothesize that individual patient factor IX and X levels may be prognostic for susceptibility to circulating TF-induced thrombosis.

Lung Cancer Chemotherapy Agents Increase Procoagulant Activity In Vitro and In Vivo

Abstract 35 Introduction:Cancer patients have an elevated risk for thrombosis, with venous thromboembolism (VTE) being the second leading cause of death in cancer patients. The risk of VTE is further increased in patients undergoing standard chemotherapy. However, the mechanism(s) by which chemotherapy increases the risk for thrombosis in lung cancer patients is not well understood. Previous studies have shown that treatment of endothelial cells with chemotherapy agents (such as cisplatin, gemcitabine, and paclitaxel) promotes coagulation through an increase in tissue factor (TF) procoagulant activity. Objective:The purpose of this study was to determine in vitro and in vivo procoagulant effects of anti-lung cancer therapy agents cisplatin, carboplatin, paclitaxel, gemcitabine and bevacizumab. We studied the effects of these agents individually as well as in combinations (cisplatin/gemcitabine and carboplatin/paclitaxel) on cell surface TF activity, TF antigen levels, and phosphatidylserine (PS) exposure levels. We also examined the effects of lung cancer chemotherapy agents on thrombin generation in healthy mice. Methods:Human umbilical vein endothelial cells (HUVECs), blood monocytes, and A549 cells were treated for 24 hours with clinically relevant concentrations of chemotherapy agents alone as well as in combination. Cell surface TF activity was measured by factor Xa (FXa) generation in the presence or absence of factor VIIa and CaCl2 on drug-treated cells. To demonstrate that FXa generation was TF-dependent, Xa generation assays were performed on chemotherapy-treated cells incubated with a TF-inhibitory antibody. Cell surface TF antigen and PS levels were measured by flow cytometry. Healthy Balb/C mice received intraperitoneal injections of lung cancer chemotherapy agents alone or in combination. Blood was collected 24 hours post-chemotherapy by carotid artery cannulation. Plasma levels of thrombin-antithrombin (TAT) complex were measured by ELISA. Results:Treatment of all cell lines with single agent and combination chemotherapy significantly increased FXa generation on HUVEC, A459 cells and monocytes. To confirm that chemotherapy-induced FXa generation was TF dependent, FXa generation was repeated in the presence or absence of factor VIIa, an essential component of the extrinsic tenase complex. We also performed the FXa generation assay in the presence or absence of a TF inhibiting antibody HTF-1. Absence of factor VIIa as well as pre-incubation of cells with HTF-1 resulted in ablation of FXa generation, confirming that generation of FXa is due to cell surface TF activity. Through flow cytometry methods we determined that cell surface TF antigen levels remain unchanged on chemotherapy treated HUVEC and A459 cells. In contrast to HUVEC and A549 cells, monocytes treated with high-dose cisplatin alone or in combination with gemcitabine, expressed a significant increase in TF antigen levels. Measurement of cell surface PS exposure levels revealed a significant increase in PS levels only on HUVEC treated with high-dose cisplatin and gemcitabine combinations. However, inhibition of PS with Annexin V on HUVEC treated with high-dose cisplatin/gemcitabine combination did not decrease FXa generation. Furthermore, inhibition of protein disulfide isomerase (PDI) on A549 cells treated with cisplatin/gemcitabine combination but not carboplatin/paclitaxel combination resulted in moderately diminished levels of FXa. Our in vivo results demonstrated that treatment of healthy mice with bevacizumab, paclitaxel and carboplatin moderately increased plasma TAT levels in healthy mice. Conclusions:Our studies are the first to explore the effects of lung cancer chemotherapy agents on monocyte and A549 cell TF activity levels, as well as the first to investigate the mechanisms by which lung cancer agents may promote TF decryption on these cell lines. We are also the first to report in vivo increases in thrombin generation in response to treatment of healthy mice with anti-lung cancer agents. These studies reveal potential mechanisms by which lung cancer chemotherapy induce a hypercoagulable state. Disclosures:No relevant conflicts of interest to declare.

Leptin upregulates tissue factor expression in human breast cancer MCF-7 cells

IntroductionObesity is a risk factor for both cardiovascular disease and cancer development. Leptin, a cytokine produced by adipose tissue, controls different processes in peripheral tissues, including cancer development and thrombotic disorders in patients with a variety of clinical disorders. Tissue factor (TF), the trigger of blood clotting, is abundant in the adipose tissue.Since TF, often expressed by cancer cells, is considered a hallmark of cancer progression, we investigated whether leptin could modulate TF in the human metastatic breast carcinoma cell line MCF-7. Materials and MethodsMCF-7 cells were incubated with or without the different reagents at 37°C. At the end of incubation, cells were tested for procoagulant activity by a one-stage clotting assay, TF and TNF-α antigen levels and mRNA by ELISA and real-time RT-PCR, respectively. Leptin receptor was studied by FACS. ResultsBoth TF activity and antigen constitutively expressed by MCF-7 were significantly increased by leptin in a dose-dependent fashion. TF mRNA levels were also enhanced indicating that leptin exerts its effect at the transcription level. The effect of leptin was specific and required binding to its receptor (Ob-R), which was found on the surface of the cells, since antibodies against leptin and Ob-R completely prevented TF expression upregulation.In addition, leptin enhanced both TNF-α mRNA synthesis and secretion from MCF7. An anti-TNF-α MoAb completely abolished the leptin-induced TF expression. ConclusionsThese data support the hypothesis that leptin, by its upregulation of TF, possibly mediated by TNF-α synthesis, may contribute to processes underlying both cancer and vascular cell disorders.

Glycosylation of tissue factor is not essential for its transport or functions

Glycosylation plays an important role in protein function. The importance of glycosylation for tissue factor (TF) function is unclear. The aim of the present study is to investigate the importance of TF glycosylation in transport to the cell surface and its coagulant and signaling functions. Endothelial cells and peripheral blood mononuclear cells (PBMC) were treated with tunicamycin to inhibit N-linked glycosylation. Site-specific mutagenesis of one or more potential N-linked glycosylation sites in TF was used to generate TF mutants lacking glycans. TF expression at the cell surface was determined in binding assays using (125)I-FVIIa or (125)I-TF mAb and confocal microscopy. TF coagulant activity was measured by factor (F) Xa generation assay, and TF signaling function was assessed by measuring cleavage of protease activated receptor 2 (PAR2) and activation of p44/42 MAPK. Tunicamycin treatment reduced TF activity at the endothelial cell surface; however, this reduction was found to be the result of decreased TF protein production in tunicamycin-treated cells. Tunicamycin treatment had no significant effect on TF activity or antigen levels in PBMC. No significant differences were observed in TF protein expression and procoagulant activity among cells transfected to express either wild-type TF or TF mutants. A fully non-glycosylated TF is shown to bind FVIIa and interact with FX with the same efficiency as that of wild-type TF. Non-glycosylated TF is also capable of supporting FVIIa cleavage of PAR2 and PAR2-dependent p44/42 MAPK activation. Glycosylation is not essential for TF transport and coagulant or signaling functions.

E0448 A study of relation between tissue factor pathway and acute coronary syndrome

ObjectiveTo investigate the changes of plasma quantity of Tissue Factor (TF) and Tissue Factor Pathway Inhibitor (TFPI) in different type of Acute coronary syndrome (ACS) patients and the association between...

Weight-adjusted dalteparin for prevention of vascular thromboembolism in advanced pancreatic cancer patients decreases serum tissue factor and serum-mediated induction of cancer cell invasion

The aim of the present study was to assess the role of tissue factor and serum-induced cell invasion in patients with advanced pancreatic cancer (APC). A cohort of 39 patients with APC, without thrombosis, receiving chemotherapy, were entered in a randomized controlled trial (ISRCTN = 76464767) of thromboprevention with weight-adjusted dalteparin (WAD). A total of 19 patients received WAD, the remaining 20 acting as a control group. Serum from baseline and week 8 was analysed for circulating-tissue factor antigen using ELISA. Circulating-tissue factor antigen rose from 324 pg/ml, [interquartile range (IQR) 282-347 pg/ml] to 356 pg/ml, (IQR 319-431 pg/ml) in controls (C), and decreased in the dalteparin-treated group (D) from 336 pg/ml (IQR 281-346 pg/ml) to 303 pg/ml (IQR 274-339 pg/ml). The difference in median percentage change between D and C was statistically significant [-4.0 (D) vs. 4.7 (C); P = 0.005, n = 39]. Serum-induced cellular invasion of MIA-Paca-2 cells in response to patient serum was studied using a Boyden chamber assay in 30 patients (14 WAD and 16 C). The median percentage change between C and D was significant [+54.9 (C) vs. -21.9 (D) P = 0.025, n = 30]. There was a weak correlation between BB-tissue factor reduction and cellular invasion reduction (Spearman) [0.384 (P = 0.037, n = 30)]. APC patients treated with WAD have lower tissue factor antigen levels and attenuated induction of cellular invasion in their blood. These assays may provide useful markers to guide appropriate dalteparin (and other low-molecular weight heparin) dosing schedules to optimize anticancer effects of dalteparin in APC.