Mohamed Hatmi

Clinical studies with anticoagulants to improve survival in cancer patients.

Cancer is linked with hypercoagulability and risk of thrombosis and this close association was recognized by Armand Trousseau in 1865. The relation between cancer and blood coagulation is reciprocal: cancer induces a hypercoagulable state and predisposes to thrombosis and activation of platelets, blood coagulation and fibrinolysis interfere with tumor cell biology, tumor growth, angiogenesis and metastatic process. In the present article, we analyze the clinical trials which assessed the influence of anticoagulant treatment on the survival of patients with cancer. The available data show that low-molecular-weight heparins (LMWHs) tend to be more effective and safer than vitamin K antagonists (VKA) in improving survival in patients with cancer. The beneficial effect of anticoagulation with either LMWHs or VKA is not universal for all patients with cancer. There are some histological types of cancers which, at early stages, appear to be more sensitive than others to the effect of anticoagulant treatment. The available clinical trials, although limited, are encouraging for the beneficial effect of anticoagulant treatment on the survival of cancer patients. More clinical trials are needed, targeting groups of patients homogenous regarding the type of cancer, the stage of the disease and life expectancy. The forthcoming clinical trials have to address some issues regarding the optimal dose, the timing and the duration of treatment with LMWH in relation to chemotherapy or other anticancer therapies.

The influence of fibrin polymerization and platelet-mediated contractile forces on citrated whole blood thromboelastography profile

Thromboelastography analysis providing a global assessment of coagulation is gaining new interest in clinical practice. MinimalTF triggered whole blood thromboelastography provides a valuable tool for studying the kinetics of clot formation (expressed by the parameters R, K and alpha-angle) and the physical characteristics of the clot, such as its firmness and the elastic modulus shear (expressed by the parameters maximal amplitude MA and G). We studied the influence of fibrin polymerization and platelet functional status on each parameter of thromboelastographic trace obtained by minimalTF activation inWB by employing increasing concentrations of a fibrin polymerization inhibitors (the tetrapeptide Gly-Pro-Arg-Pro-OH.AcOH; Pefabloc-FG) and an inhibitor of actin polymerization (Cytochalasin D). Pefabloc-FG at concentrations higher than 5 mg/ml prolonged the R and K times and decreased the alpha-angle in a concentration-dependent manner but it did not modify MA and G parameters. At the concentration of 5 mg/ml, Pefabloc-FG completely inhibited clot formation. Cytochalasin D had no effect on R time but decreased the alpha-angle, MA and G parameters by reaching a plateau at the concentration of 5 microM. The effect of cytochalasin D was more pronounced on MA and G than on the alpha-angle. A combination of both Pefabloc-FG (0.5 mg/ml) and cytochalasin D (50 microM) significantly decreased alpha-angle compared to control as well as their single effect. However, G value was dramatically reduced in the presence of cytochalasin D exposure, without any additional effect when both inhibitors were combined. This study confirms the importance of fibrin polymerisation on the kinetics of thrombus formation and demonstrates the close association between the quality of the thrombus and the functional status of platelets. Normal platelet contractile forces are of major importance for the maximum amplitude of TEG which is related to the strength and elastic modulus of the thrombus.

Antiplatelet effect of once- or twice-daily aspirin dosage in stable coronary artery disease patients with diabetes

The aim of this pilot study was to compare the effect of two different regimens of aspirin dosage on platelet of coronary artery disease (CAD) diabetic patients. Twenty-five CAD diabetic patients were included. Initially, all patients received aspirin 100xa0mg/day for 10xa0days. At day 10, aspirin antiplatelet effect was determined by measuring the collagen/epinephrine closure time (CT) 2xa0h after the last aspirin dosage and the next morning at 8 a.m.. The aspirin regimen was modified to 100xa0mg twice daily for patients showing a non-optimal platelet-inhibitory effect (CTxa0<xa0298xa0s at 8 a.m.). Persistent high platelet reactivity (HPR) was defined by a CTxa0<xa0160xa0s. During the 100xa0mg/day aspirin regimen, the prevalence of HPR at 8 a.m. was 48%, and only 7 patients (28%) had showed an optimal platelet-inhibitory effect. Bridging to the twice-daily regimen, the HPR was significantly reduced (pxa0=xa00.025), and the optimal platelet-inhibitory effect was reached for 3 other patients. Our results showed that 100xa0mg aspirin twice-daily dosing rather than a once-daily dose significantly improves the aspirin effect on platelet of CAD diabetic patients. However, large prospective studies were needed to confirm whether this strategy will be clinically relevant and safe.

Tissue factor over-expression by human pancreatic cancer cells BXPC3 is related to higher prothrombotic potential as compared to breast cancer cells MCF7

Cancer histology influences the risk of venous thromboembolism and tissue factor (TF) is the key molecule in cancer-induced hypercoagulability. We investigated the relation between TF expression by pancreatic and breast cancer cells (BXPC3 and MCF7 respectively) and their capacity to trigger in vitro thrombin generation in normal human plasma. Flow cytometry and Western blot analysis for TF expression were performed using murine IgG1 monoclonal antibody against human TF. Real-time PCR for TFmRNA was also performed. Activity of TF expressed by cancer cells was measured with a specific chromogenic assay. Thrombin generation in PPP was assessed using calibrated automated thrombogram. Cancer cells were added to platelet poor plasma from healthy volunteers. In separate experiments cells were incubated with the anti-TF antibody at concentration that completely neutralized the activity of recombinant human TF on thrombin generation. BXPC3 cells expressed significantly higher amounts of functional TF as compared to MCF7 cells. Incubation of BXPC3 and MCF7 cells with PPP resulted in acceleration of the initiation phase of thrombin generation. BXPC3 cells manifested higher procoagulant potential than MCF7 cells. The incubation of BXPC3 or MCF7 cells with the anti-TF monoclonal antibody which resulted in reversal of their effect on thrombin generation. The present study establishes a link between the amount of TF expressed by cancer cells with their procoagulant activity. Both studied types of cancer cells trigger thrombin generation but they have different procoagulant potential. The procoagulant activity of BXPC3 and MCF7 cells is related to the amount of TF expressed. Kinetic parameters of thrombogram are the most relevant for the detection of the TF-dependent procoagulant activity of cancer cells. TF expression is one of the mechanisms by which cancer cells manifest their procoagulant potential but it is not the unique one. The present experimental model will allow the characterization the procoagulant fingerprint of cell lines from the same or different histological types of cancer.

Differential inhibition of thrombin generation by vitamin K antagonists alone and associated with low-molecular-weight heparin

Vitamin K antagonists (VKA) treatment starts with co-administration of low-molecular-weight heparin (LMWH). The anticoagulation induced by the two drugs is still not well determined. In the present study we used thrombin generation assay to evaluate the hypo-coagulation induced by treatment with VKA and by the combination of VKA with LMWH. Tissue factor triggered thrombin generation in platelet-poor plasma was assessed in samples from 15 healthy volunteers, 97 samples from patients treated with VKA and 41 samples from patients receiving enoxaparin and VKA. Patients were classified according to international normalised ratio (INR) level (<2, 2-3 and >3). In plasma samples from patients treated with VKA having INR 2-3 the inhibition of thrombin generation reached 50% compared to controls. In samples with INR>3 this inhibition was 80%. In samples from patients receiving both LMWH and VKA, thrombin generation was significantly decreased compared to the controls and VKA group. In samples with an INR 2-3 obtained from patients treated with LMWH and VKA, the inhibition of thrombin generation was similar to that observed in samples with an INR>3 obtained from VKA treated patients. Thrombin generation assay is sensitive to detect the global the anticoagulant effect produced by the association of LMWH and VKA. For equal INR dual anticoagulant treatment induces significantly more profound inhibition of thrombin generation compared to treatment with VKA alone. The clinical relevance of this observation merits to be studied in prospective studies in patients with defined indications of anticoagulant therapy.

Lobectomy and postoperative thromboprophylaxis with enoxaparin improve blood hypercoagulability in patients with localized primary lung adenocarcinoma

BACKGROUNDnPatients with lung adenocarcinoma undergoing surgery are in high risk for VTE and receive routine post-operative thromboprophylaxis with LWMH.nnnAIMnWe investigated markers of hypercoagulability in patients with primary localized adenocarcinoma and the modifications induced by lobectomy and postoperative administration of enoxaparin.nnnMATERIALS AND METHODSnPatients suffering from localised primary lung adenocarcinoma (n=15) scheduled for lobectomy were studied. The control group consisted of 15 healthy age and sex-matched individuals. Blood was collected before anaesthesia induction and after surgery, at several intervals until the 7th post-operative day. Samples were assessed for thrombin generation, phosphatidylserin expressing platelet derived microparticles expressing (Pd-MP/PS(+)), tissue factor activity (TFa), FVIIa and TFPI levels, procoagulant phospholipid dependent clotting time and anti-Xa activity.nnnRESULTSnAt baseline, patients showed increased thrombin generation and Pd-MP/PS(+). After lobectomy thrombin generation significantly decreased. Administration of enoxaparin attenuated thrombin generation. In about 50% of samples collected post-operatively an increase of thrombin generation occurred despite the presence of the expected anti-Xa activity in plasma. At the 7th post-operative day, 3 out of 15 patients showed a significant increase of thrombin generation.nnnCONCLUSIONnIn patients with localized lung adenocarcinoma, hypercoagulability is characterized by high thrombin generation and increased concentration of Pd-MP/PS(+). Tumor mass resection is related with attenuation of thrombin generation, which is inhibited by postoperative thromboprophylaxis with enoxaparin. The response to enoxaparin is not predicted by the concentration of the anti-Xa activity in plasma. The assessment of thrombin generation during prophylaxis with enoxaparin allows to identify patients with high residual plasma hypercoagulability.

Platelet glycoprotein IIIa (platelet antigen 1/platelet antigen 2) polymorphism and 1-year outcome in patients with stable coronary artery disease.

Platelet glycoprotein IIb/IIIa is a membrane receptor which plays a key role in coronary artery disease and thrombotic events. However, there is a considerable controversy regarding the clinical impact of glycoprotein IIIa platelet antigen 1 (PlA1)/platelet antigen 2 (PlA2) polymorphism as a risk factor for myocardial infarction. To evaluate the association between glycoprotein IIIa PlA1/PlA2 polymorphism and 1-year cardiovascular events occurrence in aspirin-treated patients with stable coronary artery disease. We prospectively included 188 postacute coronary syndrome patients (183 men) aged 59 ± 10 years and receiving aspirin (250 mg/day). The clinical outcome at 1 year was the composite end point of nonfatal myocardial infarction, stroke, recurrent unstable angina or cardiac death. Genotyping for PlA1/PlA2 polymorphism was conducted using PCR and restriction fragment length polymorphism analysis. The genotype distribution of glycoprotein IIIa PlA1/PlA2 polymorphism was PlA1/PlA1, 55.3%; PlA1/PlA2, 39.3% and PlA2/PlA2, 4%. Incidence of composite end point in homozygous PlA1/PlA1 carriers was significantly higher than in PlA2/PlA2 and PlA1/PlA2 patients [14.4 vs. 3.6% odds ratio 4.5 (1.2–16.6, 95% confidence interval); P = 0.012]. Multivariate analysis identified three strong predictive factors of cardiac death: age more than 65 years [odds ratio = 6.8, (1.4–34, 95% confidence interval); P = 0.018], ventricular ejection fraction less than 50% [odds ratio = 8.6, (1.7–42.6, 95% confidence interval); P = 0.008] and homozygous PlA1/PlA1 genotype [odds ratio = 8.8, (1.0–78.6, 95% confidence interval); P = 0.014]. Our results demonstrated that glycoprotein IIIa PlA1/PlA1 genotype carriers have a significantly increased risks of acute vascular ischemic events associated with a poor prognosis at 1 year. These postacute coronary syndrome patients might require an optimized secondary antithrombotic prophylaxis strategy.

Effect of Low Molecular Weight Heparins and Fondaparinux Upon Thrombin Generation Triggered by Human Pancreatic Cancer Cells BXPC3

Low molecular weight heparins (LMWHs) and fondaparinux are widely used for prophylaxis and treatment of venous thromboembolic disease in cancer patients. However, the optimization of the antithrombotic treatment especially in patients with adenocarcinoma of the pancreas is a challenging issue. The understanding of the mechanism of action of the LMWHs and fondaparinux in cancer-induced hypercoagulability might help to optimize antithrombotic treatment. To this aim, we investigated the influence of BXPC3 pancreas adenocarcinoma cells on the antithrombotic activity of LMWHs and fondaparinux. Thrombin generation (TG) in normal platelet poor (PPP) and platelet rich plasma (PRP) spiked with clinically relevant concentrations of dalteparin, enoxaparin, nadroparin tinzaparin and fondaparinux was assessed with the Calibrated Automated Thrombogram assay. BXPC3 (5 cells/μl) were added to plasma. The mean rate index (MRI) of the propagation phase of TG and the endogenous thrombin potential (ETP) were analyzed. The IC50 of the studied compounds were determined and compared on the basis of anti-Xa and anti-IIa equivalent units. We demonstrate that the specific antithrombin (AT)-dependent anti-Xa activity of LMWHs and fondaparinux almost selectively inhibits the propagation phase of TG. The synergy between the anti-Xa and anti-IIa activities of LMWHs rather than the selective inhibition of FXa warrants abrogation of TG. The mean molecular weight and anti-Xa/anti-IIa ratio of the AT-dependent agents cannot predict the alteration of their capacity to inhibit TG. Tinzaparin was the most potent inhibitor of TG than the other LMWHs. Enoxaparin was more potent than nadroparin and dalteparin.

The Cyclooxygenase-1 C50T Polymorphism Is Not Associated with Aspirin Responsiveness Status in Stable Coronary Artery Disease in Tunisian Patients

In this study, we evaluate the relationships between aspirin nonresponsiveness and the cyclooxygenase-1 (Cox-1) gene C50T polymorphism in stable coronary artery disease (CAD) in Tunisian patients. One hundred twenty-five stable CAD patients were included. The Cox-1 gene C50T polymorphism was determined by the polymerase chain reaction/restriction fragment length polymorphism method. Aspirin response was evaluated by measuring the collagen epinephrine closer time and the urinary dehydro-thromboxane B2 excretion. According to the collagen epinephrine closer time values, the frequency of the -50T allele was not significantly different in bad responders when compared with good responders (36.8% vs. 15.7%; p=0.1). Similarly, the presence of the -50T mutant allele was not statistically different comparing bad and good responders according to the urinary 11-dehydro-thromboxane B2 excretion concentration (60% vs. 40%; p=0.43). Our study did not demonstrate any association between the Cox-1 gene C50T polymorphism and aspirin nonresponsiveness status in stable CAD patients.

L’exploration fonctionnelle plaquettaire : intérêts en pratique clinique

Platelets play a pivotal role in the regulation of both thrombosis and haemostasis. Functional testing of platelet response has been exclusively used in the diagnosis and management of bleeding disorders. Recent advances of light transmission aggregometry and development of more useful devices have demonstrated the clinical utility to enlarge platelet function testing in patients with cardiovascular disease. The ex vivo measurement of residual platelet response seems, with some assays, predictive of adverse clinical events. Still a debate, it represents an emerging area of interest for both the clinician and the basic scientist. Heparin-induced thrombocytopenia diagnosis is also difficult and a functional assay is now available for an easier and rapid method to rule out such a life-threatening situation. This review article will describe the available methods of measuring platelet response and will discuss both the limitations and emerging data supporting the role of platelet function studies in clinical practice.