To Tissue Factor Research Articles

Evaluation of Clinical Risk Factors and Thrombosis-Related Biomarkers in Newly Diagnosed Patients with Multiple Myeloma at Risk for Cancer-Associated Thrombosis. the Observational Roadmat-CAT-MM Study

Background: Hypercoagulability is a common blood alteration in newly diagnosed chemotherapy naïve patients with multiple myeloma. Multiple myeloma (MM) figures among malignancies that significantly increase the risk of venous thromboembolism (VTE). The rate of VTE is higher at the time of diagnosis and during the first months following initiation of first line therapy; approximately 10% of newly diagnosed MM (NDMM) will develop a VTE. Despite adequate thromboprophylaxis as per guidelines, the risk of residual VTE is not eliminated and remains as high as 12%. The optimization of VTE prevention in patients with MM is an unmet need. The exact mechanism of the increased risk of VTE is not yet fully understood. The identification of the procoagulant potential of cancer cells, which is related principally to tissue factor (TF) expression, attracts particular interest. Aim: We conducted a longitudinal prospective observational study, to explore the relationship of MM with cellular and plasma hypercoagulability as well as tissue factor positive microparticles, aiming to identify the most relevant biomarkers, which could be used in a Risk Assessment Model (RAM) for VTE in combination with clinical risk factors. Methods: Newly diagnosed patients (182) with multiple myeloma (NDMM) were prospectively enrolled. Patients were followed up for 12 months and the primary end-point was symptomatic objectively confirmed VTE. Patients were risk stratified and received thromboprophylaxis (none, aspirin on low molecular weight heparin (LMWH) based on previously published recommendations by the IMWG and EMN. Prior to treatment initiation and thromboprophylaxis initiation baseline biomarkers were obtained: Thrombin generation (TGT) in citrated PPP was assessed with the Thrombogram-Thrombinoscope® assay using PPP-reagent® 5 pm TF by Diagnostica Stago. The levels of P-Selectin and heparanase in plasma were measured with ELISA Kit (Cusabio Biotech and R&D Systems respectively). The procoagulant phospholipids clotting time was measured with STA-Procoag-PPL®, Levels of Factor VIIa were measured by Staclot VIIa-rTF®, D-Dimers (DDi) by Liatest D-Di (Diagnostica Stago, France), and Tissue Factor activity (TFa) by specific clotting based home test. TF expression MPC-derived microparticles (MPC-dMPs) were detected using a Zymuphen MP-TF activity kit (Hyphen BioMed, Neuville sur Oise, France). These were compared against values in a population of healthy individuals (n=30). Results: The distribution of patients enrolled in the study is as follows: Median age was 67 years (36-86) and 52% of the population was male. Median time to follow up was 7 months (1-12 months). The control group (30 healthy individuals). The overall rate of symptomatic VTE during follow-up was 11.5% (n = 21 patients). Eleven out of 21 events (52%) occurred within 3 months from treatment initiation. Six of these patients did not receive any thromboprophylaxis; six patients were on aspirin at the time of the event and three were on LMWH.At inclusion, patients showed significantly increased levels of TFa, FVIIa, D-Dimers and FM, and significantly shorter Procoag-PPL® as compared to the group of healthy individuals. Levels of P-selectin and TM were significantly lower in patients as compared to healthy individuals. The levels of heparanase were not significantly different in the group of patients as compared to the healthy individuals. Overall thrombin generation was attenuated in patients compared to healthy individuals. Lag-time and ttPeak were significantly increased and Peak, MRI, and ETP were significantly lower as compared to the control group, MP-TF activity measured in NDMM significantly increased 1.46± 0.38 pg/mL compared to control subjects 0.19 ± 0.05 pg/mL (Table 1). Multivariate logistic regression analysis demonstrated that ETP, Procoag-PPL® and MP-TF were independently associated with VTE occurrence. (Table 2) Conclusion: The prospective ROADMAP-CAT-MM study demonstrates the presence of pronounced cellular hypercoagulability in newly diagnosed chemotherapy naïve patients with MM characterized by decreased Procoag-PPL® clotting time, enhanced endothelial cell activation, and exhausted thrombin generation. The Procoag-PPL clotting time and the ETP and MP-TF were found to be independently associated with the risk of VTE and can be prospectively incorporated into a RAM for VTE in MM.

Tissue factor targeting peptide enhances nanoparticle binding and delivery of a synthetic specialized pro-resolving lipid mediator to injured arteries

BackgroundSpecialized pro-resolving lipid mediators (SPM) such as resolvin D1 (RvD1) attenuate inflammation and exhibit vasculo-protective properties. MethodsWe investigated poly-lactic-co-glycolic acid (PLGA)-based nanoparticles (NP), containing a peptide targeted to tissue factor (TF) for delivery of 17R-RvD1 and a synthetic analog 17-R/S-benzo-RvD1 (benzo-RvD1) using in vitro and in vivo models of acute vascular injury. NPs were characterized in vitro by size, drug loading, drug release, TF binding, and vascular smooth muscle cell migration assays. NPs were also characterized in a rat model of carotid angioplasty. ResultsPLGA NPs based on a 75/25 lactic to glycolic acid ratio demonstrated optimal loading (507.3 pg 17R-RvD1/mg NP; P = ns) and release of RvD1 (153.1 pg 17R-RvD1/mg NP; P < .05). NPs incorporating the targeting peptide adhered to immobilized TF with greater avidity than NPs with scrambled peptide (50 nM: 41.6 ± 0.52 vs 32.66 ± 0.34; 100 nM: 35.67 ± 0.95 vs 23.5 ± 0.39; P < .05). NPs loaded with 17R-RvD1 resulted in a trend toward blunted vascular smooth muscle cell migration in a scratch assay. In a rat model of carotid angioplasty, 16-fold more NPs were present after treatment with TF-targeted NPs compared with scrambled NPs (P < .01), with a corresponding trend toward higher tissue levels of 17R-RvD1 (P = .06). Benzo-RvD1 was also detectable in arteries treated with targeted NP delivery and accumulated at 10 times higher levels than NP loaded with 17R-RvD1. There was a trend toward decreased CD45 immunostaining in vessels treated with NP containing benzo-RvD1 (0.76 ± 0.38 cells/mm2 vs 122.1 ± 22.26 cells/mm2; P = .06). There were no significant differences in early arterial inflammatory and cytokine gene expression by reverse transcription-polymerase chain reaction. ConclusionsTF-targeting peptides enhanced NP-mediated delivery of SPM to injured artery. TF-targeted delivery of SPMs may be a promising therapeutic approach to attenuate the vascular injury response.

Inhibition of protein disulfide isomerase with PACMA-31 regulates monocyte tissue factor through transcriptional and posttranscriptional mechanisms

IntroductionProtein disulfide isomerase (PDI) contributes to tissue factor (TF) regulation in monocytes. While bacitracin and quercetin-3-rutinoside mitigate myeloid TF production, the effect of PACMA-31, a more specific PDI inhibitor with distinct pharmacologic properties, remains unclear. Materials and methodsLipopolysaccharide (LPS) stimulation of peripheral blood mononuclear cells (PBMCs) or citrate-anticoagulated whole blood was carried out in the presence of PACMA-31 or DMSO vehicle before monocytes were analyzed for TF expression, including antigen, procoagulant activity (PCA) and mRNA, release of IL-6 and TNFα, and LPS-induced signaling pathways. ResultsWhile PACMA-31 alone had no effect, coincubation with LPS and PACMA-31 (25 μM) enhanced LPS-induced monocyte TF production in whole blood. The effect was at least partially regulated on the transcriptional level and could not be explained by increased phosphatidylserine membrane exposure. In contrast, the same PACMA-31 concentrations were cytotoxic in isolated PBMCs. A lower dose of PACMA-31, however, restored the stimulating effect by enhancing IκB-NFκB signaling that also increased the release of IL-6 and TNFα. The protease-activated receptor 2 (PAR2) inhibitor ENMD547 but not TF antibody 10H10 or factor Xa inhibitor rivaroxaban prevented the stimulatory effect of PACMA-31 on inflammatory monocytes. In sharp contrast, short time incubation of LPS-stimulated PBMCs with 25 μM PACMA-31 was non-cytotoxic and significantly inhibited cellular TF PCA but not surface antigen expression. ConclusionsPACMA-31 regulates monocyte TF in a concentration-dependent manner by opposing transcriptional and posttranscriptional mechanisms. While low concentrations of PACMA-31 augment monocyte TF production by amplifying LPS-dependent PAR2 signaling, high concentrations convert monocyte TF into its non-coagulant state.

Major bleeding during oral anticoagulant therapy associated with factor V activation by factor Xa

ObjectivePlasma thrombin generation (TG) provides important information on coagulation status; however, current TG output parameters do not predict major bleeding of patients on anticoagulants. We recently reported that factor V (FV) activation by factor X (FX)a contributes importantly to the initiation phase of TG. Here we investigated how this pathway varies in the normal population and whether FXa‐mediated activation of FV is associated with major bleeding in patients on anticoagulant therapy. ApproachWe employed TIX‐5, a specific inhibitor of FV activation by FXa, to estimate the contribution of FXa‐mediated FV activation to tissue factor (TF)–initiated TG. ResultsWe show that the contribution of this pathway to plasma TG varies considerably in the normal population, as measured by the time needed to form the first traces of thrombin (TG lag time; mean prolongation by TIX‐5 40%, range 0%–116%). Comparing patients on vitamin K antagonists (VKA) of the BLEED study (263 patients with and 538 patients without major bleeding), showed a marked prolongation in the median TG lag time in the presence of TIX‐5 in cases (12.83 versus 11.00 minutes, P = 0.0030), while the TG lag time without TIX‐5 only showed a minor although significant difference (5.83 vs. 5.67 minutes, P = 0.0198). The TIX‐5 sensitivity (lag time + TIX‐5/lag time + vehicle) in the upper quartile was associated with a 1.62‐fold (95% confidence interval 1.04–2.52) increased risk of major bleeding compared to the lowest quartile. ConclusionA greater dependence on FXa‐mediated activation of FV of TG is associated with increased risk of major bleeding during VKA therapy.

930TiP innovaTV 207: New dosing cohort in the open label phase II study of tisotumab vedotin in solid tumors

Tisotumab vedotin (TV) is an investigational antibody-drug conjugate directed to Tissue Factor (TF). In the phase I/II innovaTV 201 and phase II innovaTV 204 studies, TV demonstrated encouraging antitumor activity with a manageable safety profile in patients (pts) with multiple TF-expressing tumor types. The innovaTV 207 trial is a global, open label, multicenter phase II trial assessing the safety, tolerability, and activity of TV in solid tumors known to express TF. This abstract presents the addition of Part C, testing TV in squamous non-small cell lung cancer (NSCLC) and squamous cell carcinoma of the head and neck (SCCHN).

Multi\u2010omics analysis reveals the interaction between the complement system and the coagulation cascade in the development of endometriosis

Endometriosis (EMS) is a disease that shows immune dysfunction and chronic inflammation characteristics, suggesting a role of complement system in its pathophysiology. To find out the hub genes and pathways involved in the pathogenesis of EMs, three raw microarray datasets were recruited from the Gene Expression Omnibus database (GEO). Then, a series of bioinformatics technologies including gene ontology (GO), Hallmark pathway enrichment, protein–protein interaction (PPI) network and gene co-expression correlation analysis were performed to identify hub genes. The hub genes were further verified by the Real-time quantitative polymerase chain reaction (RT-PCR) and Western Blot (WB). We identified 129 differentially expressed genes (DEGs) in EMs, of which 78 were up-regulated and 51 were down-regulated. Through GO functional enrichment analysis, we found that the DEGs are mainly enriched in cell adhesion, extracellular matrix remodeling, chemokine regulation, angiogenesis regulation, epithelial cell proliferation, et al. In Hallmark pathway enrichment analysis, coagulation pathway showed great significance and the terms in which included the central complement factors. Moreover, the genes were dominating in PPI network. Combined co-expression analysis with experimental verification, we found that the up-regulated expression of complement (C1S, C1QA, C1R, and C3) was positively related to tissue factor (TF) in EMs. In this study, we discovered the over expression complement and the positive correlation between complement and TF in EMs, which suggested that interaction of complement and coagulation system may play a role within the pathophysiology of EMS.

A modified clot-based assay to measure negatively charged procoagulant phospholipids

Growing evidence supports a role for extracellular vesicles (EVs) in haemostasis and thrombosis due to exposure of negatively charged procoagulant phospholipids (PPL). Current commercial PPL-dependent clotting assays use chemically phospholipid depleted plasma to measure PPL activity. The purpose of our study was to modify the PPL assay by substituting the chemically phospholipid depleted plasma with PPL depleted plasma obtained by ultracentrifugation This in order to get readily access to a sensitive and reliable assay to measure PPL activity in human plasma and cell supernatants. The performance of the assay was tested, including the influence of individual coagulation factors and postprandial lipoproteins and compared to a commercial PPL assay (STA-Procoag-PPL). The two PPL assays displayed similar sensitivity to exogenously added standardized phospholipids. The PPL activity measured by the modified assay strongly correlates with the results from the commercial assay. The intraday- and between-days coefficients of variation ranged from 2–4% depending on the PPL activity in the sample. The modified PPL assay was insensitive to postprandial lipoprotein levels in plasma, as well as to tissue factor (TF) positive EVs from stimulated whole blood. Our findings showed that the modified assay performed equal to the comparator, and was insensitive to postprandial lipoproteins and TF+ EVs.

Conformational Plasticity-Rigidity Axis of the Coagulation Factor VII Zymogen Elucidated by Atomistic Simulations of the N-Terminally Truncated Factor VIIa Protease Domain.

The vast majority of coagulation factor VII (FVII), a trypsin-like protease, circulates as the inactive zymogen. Activated FVII (FVIIa) is formed upon proteolytic activation of FVII, where it remains in a zymogen-like state and it is fully activated only when bound to tissue factor (TF). The catalytic domains of trypsin-like proteases adopt strikingly similar structures in their fully active forms. However, the dynamics and structures of the available corresponding zymogens reveal remarkable conformational plasticity of the protease domain prior to activation in many cases. Exactly how ligands and cofactors modulate the conformational dynamics and function of these proteases is not entirely understood. Here, we employ atomistic simulations of FVIIa (and variants hereof, including a TF-independent variant and N-terminally truncated variants) to provide fundamental insights with atomistic resolution into the plasticity-rigidity interplay of the protease domain conformations that appears to govern the functional response to proteolytic and allosteric activation. We argue that these findings are relevant to the FVII zymogen, whose structure has remained elusive despite substantial efforts. Our results shed light on the nature of FVII and demonstrate how conformational dynamics has played a crucial role in the evolutionary adaptation of regulatory mechanisms that were not present in the ancestral trypsin. Exploiting this knowledge could lead to engineering of protease variants for use as next-generation hemostatic therapeutics.

EGFP-EGF1-conjugated poly (lactic-co-glycolic acid) nanoparticles as a carrier for the delivery of CCR2\u2212 shRNA to atherosclerotic macrophage in vitro

Reducing macrophage recruitment by silencing chemokine (C–C motif) receptor 2 (CCR2) expression is a promising therapeutic approach against atherosclerosis. However the transfection of macrophages with siRNA is often technically challenging. EGFP-EGF1-conjugated poly (lactic-co-glycolic acid) (PLGA) nanoparticles (ENPs) have a specific affinity to tissue factor (TF). In this study, the feasibility of ENPs as a carrier for target delivery of CCR2-shRNA to atherosclerotic cellular models of macrophages was investigated. Coumarin-6 loaded ENPs were synthesized using a double-emulsion method. Fluorescence microscopy and flow cytometry assay were taken to examine the uptake of Coumarin-6 loaded ENPs in the cellular model. Then a sequence of shRNA specific to CCR2 mRNA was constructed and encapsulated into ENPs. Target delivery of CCR2-shRNA to atherosclerotic cellular models of macrophages in vitro were evaluated. Results showed more uptake of ENPs by the cellular model than common PLGA nanoparticles. CCR2-shRNA loaded ENPs effectively silenced CCR2 gene in the atherosclerotic macrophages and exhibited a favorable cytotoxic profile to cultured cells. With their low cytotoxicity and efficient drug delivery, ENP could be a useful carrier for target delivery of CCR2-shRNA to inflammatory monocytes/macrophages for the therapy against atherosclerosis.

Modelization of Blood-Borne Hypercoagulability in Myeloma: A Tissue-Factor-Bearing Microparticle-Driven Process.

Introduction Hypercoagulability is a common blood alteration in newly diagnosed chemotherapy naïve patients with multiple myeloma. The identification of the procoagulant potential of cancer cells, which is principally related to tissue factor (TF) expression, attracts particular interest. The mechanisms by which myeloma plasma cells (MPCs) activate blood coagulation have been poorly investigated. Aim To identify the principal actors related with MPCs that boost thrombin generation (TG). Methods TF and annexin V expression by MPCs and MPC-derived microparticles (MPC-dMPs) was analyzed by flow cytometry. TF activity (TFa) and TF gene expression were also determined. TG in the presence of MPCs or MPC-dMPs was assessed with the calibrated automated thrombogram assay (CAT) in normal human PPP and in plasma depleted of factor VII or XII. TG was also assessed in plasma spiked with MPCs and MPC-dMPs. Results MPC-dMPs expressed approximately twofold higher levels of TF as compared with MPCs. The TFa expressed by MPC-dMPs was significantly higher compared with that expressed by MPCs. MPCs and MPC-dMPs enhanced TG of human plasma. TG was significantly higher with MPC-dMPs compared with MPCs. Conclusion MPCs indirectly induce blood-borne hypercoagulability through the release of MPC-dMPs rich in TF. Since MPCs, expressing low TFa, represent a weak procoagulant stimulus, the hypercoagulability at the microenvironment could be the resultant of MPC-dMPs rich in TF.

EGFP-EGF1-conjugated poly(lactic-co-glycolic acid) nanoparticles, a new diagnostic tool and drug carrier for atherosclerosis.

BackgroundEGFP-EGF1-conjugated poly(lactic-co-glycolic acid) (PLGA) nanoparticle (ENP) has a specific affinity to tissue factor (TF). The aim of this study was to investigate the target delivery of ENP to plaques and its uptake in a mouse model of atherosclerosis in vivo and in vitro.Materials and methodsCoumarin-6- and 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindotricarbo cyanine iodide (DiR)-loaded ENPs were synthesized using a double-emulsion method. Mouse vascular smooth muscle cells (VSMCs) were induced with MCP-1 to obtain an increased TF expression. Fluorescence microscopy and flow cytometry assay were performed to examine the uptake of coumarin-6-loaded ENPs in cellular models. An animal model of atherosclerosis was established with an ApoE (−/−) mouse fed with continuous high-fat diets for 14 weeks. DiR-loaded ENPs (DiR-ENPs) were injected via the caudal vein. The distribution of DiR-ENPs was examined through organ imaging and confocal laser scanning microscopy.ResultsResults indicated TFs were highly expressed in the cellular model. The uptake of coumarin-6-loaded ENPs was significantly higher than that of common PLGA nanoparticles. Thickening of intima and lipid deposition in the aorta could be observed in atherosclerosis mouse models. Confocal laser scanning microscopy organ imaging showed ENPs accumulated in vessels with atherosclerotic plaques, which coincided with high expressions of TF.ConclusionThis study showed that EGFP-EGF1-conjugated PLGA nanoparticles could be effectively delivered to atherosclerotic plaques in vivo and taken up by VSMCs with high TF expressions in vitro. Thus, it could be a promising carrier for targeted therapy of atherosclerosis.

Protein disulfide isomerase enhances tissue factor-dependent thrombin generation

Protein disulfide isomerase (PDI) plays an important role in fibrin generation in vivo, but the underlying mechanism remains largely unknown. In this study, using thrombin generation assay (TGA), we investigated whether PDI contributes to tissue factor (TF)-mediated thrombin generation. Human peripheral blood mononuclear cells (PBMCs) were treated with 100 ng/ml lipopolysaccharide (LPS), the expression of TF on cell surface was analyzed by flow cytometry. After incubation with an inhibitory anti-TF antibody, recombinant PDI protein or a PDI inhibitor PACMA31, LPS-stimulated human PBMCs were incubated with human plasma, and thrombin generation was assessed by Ceveron Alpha TGA and a fluorescent thrombin substrate. Bone marrow mononuclear cells isolated from PDI-knockout and wild-type mice were stimulated by LPS, followed by measurement of thrombin generation. LPS stimulation increased expression of TF on PBMCs, and thrombin generation. Inhibitory anti-TF antibody almost completely suppressed thrombin generation of LPS-stimulated PBMCs, suggesting that thrombin generation was TF-dependent. Recombinant PDI protein increased thrombin generation, while PACMA31 attenuated thrombin generation. Compared with control cells, PDI-deficient marrow mononuclear cells had less capacity in thrombin generation. Taken together, these data suggest that PDI enhances TF-dependent thrombin generation.

Factor Xa and VIIa inhibition by tissue factor pathway inhibitor is prevented by a monoclonal antibody to its Kunitz‐1 domain

Background Initiation of coagulation is induced by binding of activated factor VII (FVIIa) to tissue factor (TF) and activation of factor X (FX) in a process regulated by tissue factor pathway inhibitor (TFPI). TFPI contains three Kunitz-type protease inhibitor domains (K1-K3), of which K1 and K2 block the active sites of FVIIa and FXa, respectively. Objective To produce a monoclonal antibody (mAb) directed towards K1, to characterize the binding epitope, and to study its effect on TFPI inhibition. Methods A monoclonal antibody, mAb2F22, was raised against the N-terminal TFPI(1-79) fragment. Binding data were obtained by surface plasmon resonance analysis. The Fab-fragment of mAb2F22, Fab2F22, was expressed and the structure of its complex with TFPI(1-79) determined by X-ray crystallography. Effects of mAb2F22 on TFPI inhibition were measured in buffer- and plasma-based systems. Results mAb2F22 bound exclusively to K1 of TFPI (KD ~1 nm) and not to K2. The crystal structure of Fab2F22/TFPI (1-79) mapped an epitope on K1 including seven residues upstream of the domain. TFPI inhibition of TF/FVIIa amidolytic activity was neutralized by mAb2F22, although the binding epitope on K1 did not include the P1 residue. Binding of mAb2F22 to K1 blocked TFPI inhibition of the FXa amidolytic activity and normalized hemostasis in hemophilia human A-like plasma and whole blood. Conclusion mAb2F22 blocked TFPI inhibition of both FVIIa and FXa activities and mapped a FXa exosite for binding to K1. It reversed TFPI feedback inhibition of TF/FVIIa-induced coagulation and restored clot formation in FVIII-neutralized human plasma and blood.

In vitro characterization of MOD‐5014, a novel long‐acting carboxy‐terminal peptide (CTP)‐modified activated FVII

Recombinant FVIIa (rFVIIa) is an effective treatment for haemophilia through frequent administration. However, the short half-life of rFVIIa decreases its prophylactic ability to reduce bleeding. Carboxy-terminal peptide (CTP)-modified FVIIa (MOD-5014) is a long-acting rFVIIa developed for on-demand treatment of haemophilia using either an intravenous or subcutaneous injection with the aim of less frequent administrations, as well as for prophylactic use. The comprehensive evaluation of the activity MOD-5014 vs commercially available rhFVIIa, as well as their interaction with cofactors and inhibitors. The in vitro characterization included clotting activity, affinity by surface plasmon resonance, cleavage of synthetic substrates, thrombin generation (TG) and rotation thromboelastometry. Reduced specific activity was obtained for MOD-5014 compared to rhFVIIa, while both compounds demonstrated comparable affinity to tissue factor (TF). MOD-5014 showed reduced TG when spiked at a similar concentration as rhFVIIa, suggesting that an increased concentration might be needed in a clinical setting to provide initial haemostatic effect. MOD-5014 demonstrated a slightly lower affinity for binding to activated platelets and slightly lower proteolytic activity on the platelet surface, possibly as the fusion of CTP has the potential to sterically hinder binding to both the platelet membrane and to protein substrates. Both compounds showed a similar dose-dependent stimulatory effect on clot formation, and both showed a similar deactivation pattern following incubation with TF pathway inhibitor (TFPI), antithrombin and heparin. The comparable in vitro activity of MOD-5014 and rhFVIIa paves the way for in vivo pharmacology evaluations of MOD-5014 in preparation for clinical studies.

Site-Specific 64Cu Labeling of the Serine Protease, Active Site Inhibited Factor Seven Azide (FVIIai-N3), Using Copper Free Click Chemistry.

A method for site-specific radiolabeling of the serine protease active site inhibited factor seven (FVIIai) with 64Cu has been applied using a biorthogonal click reaction. FVIIai binds to tissue factor (TF), a trans-membrane protein involved in hemostasis, angiogenesis, proliferation, cell migration, and survival of cancer cells. First a single azide moiety was introduced in the active site of this 50 kDa protease. Then a NOTA moiety was introduced via a strain promoted azide-alkyne reaction and the corresponding conjugate was labeled with 64Cu. Binding to TF and the stability was evaluated in vitro. TF targeting capability of the radiolabeled conjugate was tested in vivo by positron emission tomography (PET) imaging in pancreatic human xenograft cancer mouse models with various TF expressions. The conjugate showed good stability (>91% at 16 h), an immunoreactivity of 93.5%, and a mean tumor uptake of 2.1 ± 0.2%ID/g at 15 h post injection. In conclusion, FVIIai was radiolabeled with 64Cu in single well-defined position of the protein. This method can be utilized to prepare conjugates from serine proteases with the label at a specific position.

Analysis of factor XIa, factor IXa and tissue factor activity in burn patients

IntroductionAn elevated procoagulant activity observed in trauma patients is, in part, related to tissue factor (TF) located on blood cells and microparticles. However, analysis of trauma patient plasma indicates that there are other contributor(s) to the procoagulant activity. We hypothesize that factor (F)XIa and FIXa are responsible for an additional procoagulant activity in burn patients. MethodsMultiple time-point plasma samples from 56 burn patients (total number of samples was 471; up to 20 time-points/patient collected in 3 weeks following admission) were evaluated in a thrombin generation assay using inhibitory antibodies to TF, FIXa and FXIa. ResultsDue to the limited volume of some samples, not all were analyzed for all three proteins. At admission, 10 of 53 patients (19%) had active TF, 53 of 55 (96%) had FXIa and 48 of 55 (87%) had FIXa in their plasma. 34 patients of 56 enrolled (61%) showed TF activity at one or more time-points. All patients had FXIa and 96% had FIXa at one or more time-points. Overall, TF was observed in 99 of 455 samples analyzed (22%), FXIa in 424 of 471 (90%) and FIXa in 244 of 471 (52%). The concentration of TF was relatively low and varied between 0 and 2.1pM, whereas that of FXIa was higher, exceeding 100pM in some samples. The majority of samples with FIXa had it at sub-nanomolar concentrations. No TF, FXIa and FIXa activity was detected in plasma from healthy individuals. ConclusionsFor the first time reported, the majority of plasma samples from burn patients have active FXIa and FIXa, with a significant fraction of them having active TF. The concentration of all three proteins varies in a wide range.

In vivo quantification of ultrasound targeted microbubbles to enhance cancer assessment.

Contrast-enhanced ultrasound with targeted microbubble contrast agents is an emerging technique for imaging biological processes at the molecular level. The accumulation of targeted microbubbles at tissue sites overexpressing specific molecular markers increases the backscattered signal for noninvasive evaluations of diseases. The aim of this preliminary study was to combine molecular imaging with an in vivo contrast agent quantification to support the early diagnosis of the pathology and to enhance the assessment of neoplastic tissues. Tumor growth was induced by subcutaneous injection of prostate cancer cells in four rats. Microbubbles targeted to tissue factor (TF) were administered. A vascularized region located in proximity to the tumor and centered around the focus depth was analyzed in each animal. The backscattered signals (i.e. the radio-frequency data) were acquired during two different perfusion conditions to evaluate the contribution of attached microbubbles. After image generation by means of a multi-pulse contrast-enhanced technique, a nonlinear regression method based on the support vector machine was employed to estimate the contrast agent concentrations in cubic voxels (1-mm side length). The number of attached microbubbles per mm(3) was estimated based on a multi-dimensional vector of features extracted from the processed radio-frequency signals. A significant correlation (p < 0.05) between the size of the tumors and the estimated microbubble concentration was found, thus opening the possibility for combining molecular imaging and contrast agent concentration mapping to refine pathology evaluation. Copyright © 2016 John Wiley & Sons, Ltd.

Procoagulant microparticles promote coagulation in a factor XI‐dependent manner in human endotoxemia

Essentials The procoagulant effects of microparticles (MPs) on coagulation in endotoxemia are not known. MPs from endotoxemia volunteers were evaluated for procoagulant activity in a plasma milieu. MPs from endotoxemia volunteers shortened clotting times and enhanced thrombin generation. MP procoagulant effects were mediated in a factor XI-dependent manner. Background Human endotoxemia is characterized by acute inflammation and activation of coagulation, as well as increased numbers of circulating microparticles (MPs). Whether these MPs directly promote coagulation and through which pathway their actions are mediated, however, has not been fully explored. Objectives In this study, we aimed to further characterize endotoxin-induced MPs and their procoagulant properties using several approaches. Methods Enumeration and characterization of MPs were performed using a new-generation flow cytometer. Relative contributions of the extrinsic and intrinsic pathways in MP-mediated procoagulant activity were assessed using plasmas deficient in factor (F) VII or FXI or with blocking antibodies to tissue factor (TF) or FXIa. Results Total MPs and platelet MPs were significantly elevated in plasma at 6 h after infusion of endotoxin in healthy human subjects. MPs isolated from plasma following endotoxin infusion also demonstrated increased TF activity in a reconstituted buffer system. When added to recalcified platelet-poor plasma, these MPs also promoted coagulation, as judged by a decreased clotting time with shortening of the lag time and time to peak thrombin using calibrated automated thrombography (CAT). However, the use of FVII-deficient plasma or blocking antibody to TF did not inhibit these procoagulant effects. In contrast, plasma clotting time was prolonged in FXI-deficient plasma and a blocking antibody to FXIa inhibited all MP-mediated parameters in the CAT assay. Conclusions The initiation of coagulation by cellular TF in endotoxemia is in contrast to (and presumably complemented by) the intrinsic pathway-mediated procoagulant effects of circulating MPs.

PO-49 - Bone microinfarction and microcirculation thrombosis; is it a possible mechanism for bone pain among cancer patients?

The blood supply of the bone and bone marrow are interconnected through a network of vessels. Arteries penetrating the bone flow into the marrow cavity while blood from marrow sinuses and veins leave the tissue via the bone. The current study was designed to search for thrombosis in the small blood vessels of bone and bone marrow. Bone biopsies of 40 patients were studied using specific staining to fibrin with martin scarlet blue (MSB) and by immune-staining to tissue factor (TF), TF pathway inhibitor and heparanase that is a pro-angiogenic and pro-coagulant protein. Biopsies included: ten cases of bone metastasis from carcinoma origin, ten cases of avascular necrosis (AVN) of femur head and ten cases of osteoarthrosis of femur head. Ten cases with diffuse large cell lymphoma without bone or bone marrow involvement were the control group. Vessels density was higher in the bone and bone marrow of metastasis, AVN and osteoarthrosis biopsies compared to controls (P<0.001). Thrombi were documented in the bone and bone marrow of metastasis (5/10), AVN (6/10) and osteoarthrosis (6/10) biopsies and were absent in the controls. Staining of TF, TFPI and heparanase were more prominent, mainly in the blood vessels, in the biopsies of metastasis, AVN and osteoarthrosis compared to controls. The present study demonstrates for the first time thrombosis in the microcirculation of bone and bone marrow that can potentially contribute to patients bone pain. Increased level of TF and heparanase may contribute to the procoagulant and pro-angiogenic state. Intervention with anticoagulant drugs to prevent bone pain should be further evaluated.

Inactivation of factor VIIa by antithrombin in vitro, ex vivo and in vivo: role of tissue factor and endothelial cell protein C receptor.

Recent studies have suggested that antithrombin (AT) could act as a significant physiologic regulator of FVIIa. However, in vitro studies showed that AT could inhibit FVIIa effectively only when it was bound to tissue factor (TF). Circulating blood is known to contain only traces of TF, at best. FVIIa also binds endothelial cell protein C receptor (EPCR), but the role of EPCR on FVIIa inactivation by AT is unknown. The present study was designed to investigate the role of TF and EPCR in inactivation of FVIIa by AT in vivo. Low human TF mice (low TF, ∼1% expression of the mouse TF level) and high human TF mice (HTF, ∼100% of the mouse TF level) were injected with human rFVIIa (120 µg kg−1 body weight) via the tail vein. At varying time intervals following rFVIIa administration, blood was collected to measure FVIIa-AT complex and rFVIIa antigen levels in the plasma. Despite the large difference in TF expression in the mice, HTF mice generated only 40–50% more of FVIIa-AT complex as compared to low TF mice. Increasing the concentration of TF in vivo in HTF mice by LPS injection increased the levels of FVIIa-AT complexes by about 25%. No significant differences were found in FVIIa-AT levels among wild-type, EPCR-deficient, and EPCR-overexpressing mice. The levels of FVIIa-AT complex formed in vitro and ex vivo were much lower than that was found in vivo. In summary, our results suggest that traces of TF that may be present in circulating blood or extravascular TF that is transiently exposed during normal vessel damage contributes to inactivation of FVIIa by AT in circulation. However, TF’s role in AT inactivation of FVIIa appears to be minor and other factor(s) present in plasma, on blood cells or vascular endothelium may play a predominant role in this process.