Utility of the Khorana and the new-Vienna CATS prediction scores in cancer patients of the HYPERCAN cohort.

BACKGROUND: Risk assessment models (RAMs) are relevant approaches to identify cancer outpatients at high risk of venous thromboembolism (VTE). Among the proposed RAMs, the Khorana (KRS) and the new-Vienna CATS risk scores have been externally validated in ambulatory patients with cancer. OBJECTIVES: To test KRS and new-Vienna CATS scores in 6-month VTE prediction and mortality in a large prospective cohort of metastatic cancer outpatients during chemotherapy. PATIENTS/METHODS: Newly diagnosed patients with metastatic non-small cell lung, colorectal, gastric, or breast cancers were analyzed (n = 1286). The cumulative incidence of objectively confirmed VTE was estimated with death as a competing risk and multivariate Fine and Gray regression. RESULTS: Within 6 months, 120 VTE events (9.7%) occurred. The KRS and the new-Vienna CATS scores showed comparable c-stat. Stratification by KRS provided VTE cumulative incidences of 6.2%, 11.4%, and 11.5% in the low-, intermediate-, and high-risk categories, respectively (p = ns), and of 8.5% vs. 11.8% (p = ns) in the low- vs. high-risk group by the single 2-point cut-off value stratification. Using a pre-defined 60-point cut-off by the new-Vienna CATS score, 6.6% and 12.2% cumulative incidences were obtained in the low- and high-risk groups, respectively (p < 0.001). Furthermore, having a KRS ≥2 = or a new-Vienna CATS score >60 points was also an independent risk factor for mortality. CONCLUSION: In our cohort, the 2 RAMs showed a comparable discriminating potential; however, after the application of cut-off values, the new-Vienna CATS score provided statistically significant stratification for VTE. Both RAMs proved to be effective in identifying patients at increased risk of mortality.

Increased platelet thrombus formation under flow conditions in whole blood from polycythaemia vera patients.

BACKGROUND: Polycythaemia vera is a myeloproliferative neoplasm characterised by a high incidence of thrombosis. The contribution of platelets, key players in haemostasis, in this setting is still unclear. So far, the majority of studies have been focussed on specific platelet abnormalities but not on their actual capacity to form thrombi. The aim of this study was to characterise, ex vivo under flow conditions, the capacity of platelets from patients with polycythaemia vera to adhere to collagen and induce thrombus formation. MATERIALS AND METHODS: Thirty-nine patients and 30 healthy controls were studied. Thrombus formation was induced by perfusing whole blood over a collagen-coated surface, in a parallel-plate flow chamber coupled to a fluorescent microscope. This dynamic system enables platelet adhesion and thrombus formation to be followed in real time and also allows measurements of the extent of the thrombus and platelet surface antigen expression. Laboratory data were analysed in the light of the patients' main haematological parameters and therapies. RESULTS: Platelet adhesion was significantly greater in patients than in control subjects. Patient thrombi were usually larger and more complex than those formed by control platelets. A significant positive correlation was found between platelet adhesion and both the haematocrit and red blood cell count. These parameters remained significantly correlated with platelet adhesion also after multivariable analysis adjusted for gender, age, therapy and JAK2V617F allele burden. Furthermore, subjects with a haematocrit >45% had significantly greater platelet adhesion than subjects with a haematocrit <45%. DISCUSSION: Our data indicate that increased platelet adhesion participates in the thrombotic diathesis of patients with polycythaemia vera, and that the haematocrit level can affect the adhesive and thrombus forming capacities of platelets.

Thrombin generation predicts early recurrence in breast cancer patients.

BACKGROUND: Cancer patients present with a hypercoagulable state often associated with poor disease prognosis. OBJECTIVES: This study aims to evaluate whether thrombin generation (TG), a global coagulation test, may be a useful tool to improve the identification of patients at high risk of early disease recurrence (ie, E-DR within 2 years) after breast cancer surgery. PATIENTS/METHODS: A cohort of 522 newly diagnosed patients with surgically resected high-risk breast cancer were enrolled in the ongoing prospective HYPERCAN study. TG potential was measured in plasma samples collected before starting systemic chemotherapy. Significant predictive hemostatic and clinic-pathological parameters were identified in the derivation cohort by Cox regression analysis. A risk prognostic score for E-DR was generated in the derivation and tested in the validation cohort. RESULTS: After a median observation period of 3.4 years, DR occurred in 51 patients, 28 of whom were E-DR. E-DR subjects presented with the highest TG values as compared to both late-DR (from 2 to 5 years) and no relapse subjects (P < .01). Multivariate analysis in the derivation cohort identified TG, mastectomy, triple negative and Luminal B HER2-neg molecular subtypes as significant independent predictors for E-DR, which were utilized to generate a risk assessment score. In the derivation and validation cohorts, E-DR rates were 2.3% and 0% in the low-risk, 10.1% and 6.3% in the intermediate-risk, and 18.2% and 16.7%, in the high-risk categories, respectively. CONCLUSIONS: Inclusion of TG in a risk-assessment model for E-DR significantly helps the identification of operated breast cancer patients at high risk of very early relapse.

Thrombotic biomarkers for risk prediction of malignant disease recurrence in patients with early stage breast cancer.

In cancer patients, hypercoagulability is a common finding. It has been associated with an increased risk of venous thromboembolism, but also to tumor proliferation and progression. In this prospective study of a large cohort of breast cancer patients, we aimed to evaluate whether pre-chemotherapy abnormalities in hemostatic biomarkers levels: (i) are associated with breast cancer-specific clinico-pathological features; and (ii) can predict for disease recurrence. D-dimer, fibrinogen, prothrombin fragment 1+2, and FVIIa/antithrombin levels were measured in 701 early-stage resected breast cancer patients candidate to adjuvant chemotherapy and prospectively enrolled in the HYPERCAN study. Significant prognostic parameters for disease recurrence were identified by Cox regression multivariate analysis and used for generating a risk assessment model. Pre-chemotherapy D-dimer, fibrinogen, and pro-thrombin fragment 1+2 levels were significantly associated with tumor size and lymph node metastasis. After 3.4 years of follow up, 71 patients experienced a recurrence. Cox multivariate analysis identified prothrombin fragment 1+2, tumor size, and Luminal B HER2-negative or triple negative molecular subtypes as independent risk factors for disease recurrence. Based on these variables, we generated a risk assessment model that significantly differentiated patients at low- and high-risk of recurrence (cumulative incidence: 6.2 vs 20.7%; Hazard Ratio=3.5; P<0.001). Our prospective clinical and laboratory data from the HYPERCAN study were crucial for generating a scoring model for assessing risk of disease recurrence in resected breast cancer patients, candidate to systemic chemotherapy. This finding stimulates future investigations addressing the role of plasma prothrombin fragment 1+2 in the management of breast cancer patients to provide the rationale for new therapeutic strategies. (The HYPERCAN study is registered at clinicaltrials.gov identifier 02622815).

Acute promyelocytic leukemia cell adhesion to vascular endothelium is reduced by heparins.

Adhesion of acute promyelocytic leukemia (APL) cells to endothelial cells (EC) is among the mechanisms of the APL-associated coagulopathy, responsible for early hemorrhagic deaths in affected patients. We compared the effects of dalteparin and enoxaparin, two low-molecular-weight heparins (LMWH), and unfractionated heparin (UFH), on APL NB4 adhesion to micro- (HMEC-1) and macro-vascular EC (HUVEC), in resting and interleukin-1ß (IL-1ß)-stimulated conditions. The heparin effect on EC adhesion molecule (ICAM-1, VCAM-1, E-selectin) expression was also assessed. In HMEC-1, dalteparin inhibited IL1ß-induced NB4 adhesion by 80%, enoxaparin by 52%, and UFH by 44%. Similar results were obtained in HUVEC. This was associated with a significant decrease of VCAM-1 and ICAM-1 expression. In conclusion, we show that LMWH significantly counteract APL cell adhesion to the vessel wall, by modulating EC adhesion molecule expression. This property of heparins may represent one approach for hampering excess clotting activation and microthrombi deposition in APL.

Mechanisms and risk factors of thrombosis in cancer.

The close relationship between cancer and thrombosis is known since more than a century. Venous thromboembolism (VTE) may be the first manifestation of an occult malignancy in an otherwise healthy individual. Cancer patients commonly present with abnormalities of laboratory coagulation tests, indicating an ongoing subclinical hypercoagulable condition. The results of laboratory tests demonstrate that a process of fibrin formation and removal parallels the development of malignancy, which is of particular interest since fibrin and other clotting products are important for both thrombogenesis and tumor progression. Besides general clinical risk factors (i.e. age, previous VTE, immobility, etc.), other factors typical of cancer can increase the thrombotic risk in these patients, including the type of cancer, advanced disease stage, and cancer therapies. In addition, biological factors, including tumor cell-specific prothrombotic properties and the host cell inflammatory response to the tumor, play a central role in the pathogenesis of cancer-associated thrombosis. Cancer cells produce and release procoagulant and fibrinolytic proteins, as well as inflammatory cytokines. In addition, they are capable of directly adhering to host cells (i.e. endothelial cells, monocytes, platelets, and neutrophils), thereby stimulating additional prothrombotic properties of the host effector cells. Tumor-shed procoagulant microparticles also contribute to the patient hypercoagulable state. Finally, the changes of stromal cells of the tumor 'niche' induced by tissue factor (TF) highlight new interactions between hemostasis and cancer. Of interest, most of these mechanisms, besides activating the hemostatic system, also promote tumor growth and metastasis, and are regulated by oncogenic events. Indeed, molecular studies demonstrate that oncogenes responsible for the cellular neoplastic transformation drive the programs of hemostatic protein expression and microparticle liberation by cancer tissues. Human and animal experimental models demonstrate that activation of cancer-associated prothrombotic mechanisms parallels the development of overt thrombotic syndromes in vivo.

Tissue Factor Expression on Platelet Surface during Preparation and Storage of Platelet Concentrates.

BACKGROUND: Tissue factor (TF), the main activator of blood coagulation, is expressed on platelet surface and, together with procoagulant phospholipids, contributes to the global coagulation potential of these blood components. The present study evaluated, for the first time, the expression of TF on platelet surface during preparation and storage of platelet concentrates (PC) for transfusional use. METHODS: Platelet TF was measured by flow cytometry in healthy donor whole blood (WB) and in pooled buffy-coat-derived PC on the day of preparation and up to 4 days of storage in parallel with classical markers of platelet activation, i.e., fibrinogen, P-selectin, and glycoprotein GPIIb. Data were analyzed according to donor age and blood ABO group. RESULTS: TF was detected on whole blood platelets and was found highest in O donors. Compared to whole blood, platelet surface TF was higher upon PC preparation and further increased during storage. The rise in TF levels positively correlated with the elevations of the other platelet markers. CONCLUSIONS: Our findings show that platelet surface TF is maintained in PC obtained by the pooled buffy coat method. Further studies are warranted to investigate a possible correlation between TF levels and the hemostatic response of the platelet transfusion recipient.

LMWH bemiparin and ULMWH RO-14 reduce the endothelial angiogenic features elicited by leukemia, lung cancer, or breast cancer cells.

Low-molecular-weight heparins (LMWH) are anticoagulant drugs that also possess antitumor properties. We evaluated whether "second generation" LMWH bemiparin and the Ultra-Low-MWH (ULMWH) RO-14 are able to inhibit in vitro the angiogenic response of microvascular endothelium stimulated by tumor-cell-conditioned media (TCM) from human leukemia, lung cancer, and breast cancer cells. Bemiparin and RO-14 dose dependently inhibited the increase of capillary-like tube formation (Matrigel-based assay) and endothelial migration (wound-healing assay) induced by TCM. Both drugs also inhibited angiogenic response elicited by purified VEGF and FGF-2. These findings support a possible role of these molecules as adjuvant drugs in cancer treatment.

Comparative assessment of low-molecular-weight heparins in cancer from the perspective of patient outcomes and survival.

Patients with cancer are at high risk of developing venous thromboembolism (VTE), including deep venous thrombosis and pulmonary embolism. Compared to non-cancer patients, VTE in cancer is more frequently associated with clinical consequences, including recurrent VTE, bleeding, and an increase in the risk of death. Low-molecular-weight heparins (LMWHs) are commonly recommended for the prevention and treatment of VTE in cancer patients because of their favorable risk-to-benefit profile. Indeed, compared with vitamin K antagonists, LMWHs are characterized by a reduced need for coagulation monitoring, few major bleeding episodes, and once-daily dosing, which make these drugs more suitable in the cancer setting. Guidelines have been published recently with the aim to improve the clinical outcomes in cancer patients at risk of VTE and its complications. Coagulation activation in cancer may have a role not only in thrombosis but also in tumor growth and dissemination. Hence, inhibition of fibrin formation has been considered a possible tool against the progression of malignant disease. Clinical studies show that anticoagulant drugs may have a beneficial effect on survival in cancer patients, with a major role for LMWHs. Recently a number of prospective randomized clinical trials to test LMWHs to improve cancer survival as a primary endpoint in cancer patients have been conducted. Although the results are controversial, the interest in this research area remains high.

Bemiparin in oncology.

An association between cancer and thrombosis has been recognized since 1865. It is considered to be a two-way association; cancer is associated with an increased risk of venous thromboembolism (VTE), whereas activation of the coagulation cascade enhances the proliferation, angiogenesis potential and metastasis of tumour cells. A sizeable proportion of VTE events in cancer patients undergoing major surgery occur after discharge from hospital, suggesting that extended thromboprophylaxis beyond the normal 7-10 days is warranted in these patients. Studies have demonstrated reduced incidences of VTE with extended thromboprophylaxis using low molecular weight heparins (LMWH) and guidelines recommend continuing thromboprophylaxis after discharge in patients who have undergone major cancer surgery, but the evidence is still considered limited and of low quality, and the recommendations have not been widely implemented in clinical practice. Extended prophylaxis with bemiparin was shown to reduce significantly the incidence of major VTE in patients undergoing major cancer surgery in the Cancer, Bemiparin and Surgery Evaluation study, providing further support for the routine use of extended thromboprophylaxis with LMWH in cancer patients. Heparins, particularly LMWH, in addition to preventing VTE in cancer patients, can block tumour cell growth, invasion, metastasis and angiogenesis. As with other LMWH, bemiparin and its ultra-low molecular weight derivative, RO-14, appear to be effective in preventing angiogenesis in in-vitro models. Recent clinical studies have demonstrated significant survival advantages when LMWH have been added to chemotherapy in cancer patients. This could be partly due, not only to the prevention of thromboembolic diseases in these patients, but also to 'direct' antineoplastic properties of LMWH. The survival benefits appeared greater in patients with limited cancer, especially limited small cell lung cancer. The Adjuvant Bemiparin in Small Cell Lung Cancer study is assessing the effect of bemiparin on survival in patients with limited small cell lung cancer, and although results are not yet available, preliminary data appear very promising.

Nitric oxide derivatives and soluble plasma selectins in patients with myeloproliferative neoplasms.

Essential thrombocythaemia (ET) and polycythaemia vera (PV) are characterised by a high incidence of thrombotic complications due to high-shear stress of the vessel wall, blood hyperviscosity and hypoxaemia, all factors responsible for chronic endothelial dysfunction and platelet and leukocyte activation. We evaluated the activation status of vascular cells in 18 consecutive ET and 14 PV patients by measuring the plasma levels of the nitric oxide derivatives (NOX) (i.e. nitrites and nitrates) and of soluble selectins of platelet (P-selectin), endothelial cell (P-selectin and E-selectin) and leukocyte (L-selectin) origin. The effect of hydroxyurea (HU) therapy on these parameters was also investigated. NOX were significantly (p<0.01) increased in ET patients treated with HU (11.5 +/- 2.6 nM) compared to non-HU treated ET (1.41 +/- 0.3 nM) and to controls (4.78 +/- 2.49 nM). Multivariate analysis confirmed HU therapy as an independent predictor of higher NOX levels in ET. In addition, NOX significantly correlated with haematocrit. Plasma P-selectin was significantly elevated in ET (350 +/- 40 ng/10(6) platelets) and PV (482 +/- 53 ng/10(6) platelets) patients compared to controls (120 +/- 8 ng/10(6) platelets). In PV, also E-selectin (23.8 +/- 4.2 ng/ml) was significantly increased compared to controls (11.2 +/- 1.1 ng/ml; p<0.01). P-selectin was significantly correlated to platelet (R=0.33; p=0.01) and leukocyte count (R=0.6; p=0.000), while E-selectin (R=0.34; p=.014) and sL-selectin (R=0.3; p=0.03) were correlated with leukocyte count only. In the multivariate analysis, NOX predicted increased levels of E-selectin in ET, but not in PV patients. Our data demonstrate that ET and PV are characterised by an altered pattern of soluble selectins and NOX. HU-mediated increase of NOX levels could represent an additional antithrombotic mechanism of this drug.

Endothelial capillary tube formation and cell proliferation induced by tumor cells are affected by low molecular weight heparins and unfractionated heparin.

BACKGROUND: Clinical studies suggest a survival advantage in cancer patients receiving low molecular weight heparin (LMWH). A suggested mechanism for this beneficial effect may reside in the antiangiogenic activity of heparins. OBJECTIVES: In this study we investigated whether two different LMWHs, i.e. enoxaparin and dalteparin, and unfractionated heparin (UFH), affect the angiogenic potential of human microvascular endothelial cells (HMEC-1) promoted by tumor cells. METHODS: HMEC-1 cells were incubated with tumor cell conditioned media (TCM) derived from human breast cancer and leukemic cells (i.e. MCF-7, MDA.MB.231, and NB4 cell lines) or recombinant cytokines (i.e. VEGF, FGF-2, TNF-alpha) +/-heparins. Capillary-like tube formation in Matrigel and cell proliferation were evaluated. RESULTS: All three TCM induced a significant (p<0.05) increase in total length of tubes formed by HMEC-1 in Matrigel. These increases were significantly counteracted (62 to 100% mean inhibition) by enoxaparin and dalteparin, but were significantly less affected by UFH. Similarly, the tube formation induced by standard VEGF, FGF-2, or TNF-alpha was 100% inhibited by enoxaparin, and 70-90% by dalteparin, whereas minor or no inhibition was observed with UFH. VEGF was the most active cytokine in TCM of both breast cancer and leukemic cells. EC proliferation was significantly increased by standard angiogenic factors, and slightly affected by breast cancer TCM (p=ns). The addition of heparins significantly counteracted the proliferative stimuli. CONCLUSIONS: These results support a major role for LMWH compared to UFH in inhibiting the proangiogenic effect exerted by tumor cells or purified angiogenic factors on microvascular endothelium.

V617F JAK-2 mutation in patients with essential thrombocythemia: relation to platelet, granulocyte, and plasma hemostatic and inflammatory molecules.

OBJECTIVE: This article evaluates patients with essential thrombocythemia (ET) to determine whether the V617F mutation in the JAK2 gene affects platelet hemostatic and adhesive molecules, platelet-polymorphonuclear leukocyte (PMN) interactions, and PMN-activation characteristics, as well as plasma hypercoagulation markers. PATIENTS AND METHODS: Thirty-seven ET patients with V617F JAK2 mutation and 38 wild-type, and 50 healthy controls were studied. RESULTS: Platelets from overall ET patients, compared to controls, expressed significantly higher membrane tissue factor (TF) and P-selectin (p < 0.01) and lower CD41 and CD42b (p < 0.01). TF appeared significantly higher in the V617F JAK2 carriers compared to wild-type, and total platelet TF antigen levels confirmed the same result. The presence of circulating platelet/PMN aggregates was significantly greater in the JAK2-mutation carriers than in the wild-type and controls (p < 0.05). PMN surface activation and inflammatory markers (i.e., CD14, TF, CD11b, and leukocyte alkaline phosphatase [LAP]) were all significantly higher in ET versus control subjects, with CD14 and LAP being the highest in the JAK2 mutation carriers. Finally, a significant increase in plasma hypercoagulation markers was found in ET patients, and the only difference for the V617F JAK2 carriers was higher plasma thrombomodulin levels (p < 0.01). Differences in white blood cell and PMN count, platelet TF, PMN CD14, and LAP, and plasma thrombomodulin remained significant after multivariate analysis. CONCLUSIONS: These results show that a correlation exists between the presence of V617F JAK2 mutation and selected hemostatic activation variables.

Differential effect of the low-molecular-weight heparin, dalteparin, and unfractionated heparin on microvascular endothelial cell hemostatic properties.

BACKGROUND AND OBJECTIVES: Heparins, including unfractionated heparin (UFH) and low-molecular-weight heparins (LMWH), are glycosaminoglycans that are largely used as anti-thrombotic drugs. While the mechanisms of their anticoagulant actions in blood have been extensively studied, their effects on the hemostatic properties of the endothelium are still under investigation. The aim of this study was to compare the antithrombotic effects of a LMWH, i.e. dalteparin, with UFH on both microvascular (human microvascular endothelial cells [HMEC-1]) and macrovascular (human umbilical vein endothelial cells [HUVEC]) endothelial cells. DESIGN AND METHODS: Endothelial cells were incubated with dalteparin or UFH and exposed to an inflammatory stimulus (i.e. lipopolysaccharide [LPS]). The following parameters were evaluated: tissue factor (TF procoagulant activity, antigen and mRNA), tissue factor pathway inhibitor (TFPI), and thrombomodulin (TM). RESULTS: In HMEC-1 and HUVEC, both heparins inhibited LPS-induced endothelial cell TF expression. However, in HMEC-1, dalteparin was significantly more effective than UFH. Both heparins increased TFPI antigen release in HMEC-1 and HUVEC. Dalteparin also reversed LPS-induced reduction of TM in HMEC-1, while UFH did not. INTERPRETATION AND CONCLUSIONS: These data show that both dalteparin and UFH suppress inflammatory-mediated TF expression and increase the anticoagulant properties of macro- and micro-vascular endothelial cells. However, dalteparin has significantly greater effects than UFH in the microvascular endothelium, a site that plays a central role in many processes involved in inflammation and thrombosis.

Leukocyte-platelet interaction in patients with essential thrombocythemia and polycythemia vera.

OBJECTIVE: Circulating polymorphonuclear leukocyte (PMN) activation occurs in patients with essential thrombocythemia (ET) and polycythemia vera (PV). We want to define whether this phenomenon plays a role in the formation of circulating PMN-platelet aggregates in these conditions. METHODS: In 80 patients (46 ET and 34 PV) and 50 control subjects, we conducted a flow cytometric analysis to evaluate the levels of PMN-platelet aggregates (defined as the percentage of CD11b-positive PMN coexpressing a platelet-specific marker, i.e., CD42b or CD62P) and the levels of activated PMN and activated platelets. In addition, the in vitro PMN-platelet aggregate formation in response to N-formyl-methionyl-leucyl-phenylalanine (f-MLP)-induced activation of PMN was studied. RESULTS: Significantly high PMN-platelet aggregates in ET and PV patients were found and were associated with increased PMN surface CD11b and surface platelet CD62P expression. In vitro f-MLP stimulation upregulated PMN-CD11b expression and simultaneously increased CD11b/CD42b and CD11b/CD62P aggregates, without affecting platelet surface antigens. In ET patients receiving aspirin, the increments in f-MLP-induced PMN-CD11b and in PMN-platelet aggregates were significantly lower versus ET subjects not treated with aspirin. CONCLUSION: Our data show that in ET and PV patients PMN activation plays an important role in increasing circulating PMN-platelet aggregates and suggest that aspirin treatment may decrease their formation.

Venous thromboembolism in oncology.

Thromboembolic events represent well-recognised complications of neoplastic disease contributing, in a significant manner, to the morbidity and mortality from cancer. The close relationship between the activation of blood coagulation and tumor growth is known since 1865, when Armand Trousseau first described the clinical association between primary or idiopathic venous thromboembolism and an underlying occult malignancy. However, only in the last decades significant advances in this field have been achieved, both on the comprehension of the complex interactions between the tumor and the hemostatic system, and on the prophylaxis and therapy of the thromboembolic manifestations in cancer patients.

All-trans retinoic acid modulates microvascular endothelial cell hemostatic properties.

BACKGROUND AND OBJECTIVES: All-trans retinoic acid (ATRA) is an anti-tumor agent capable of controlling the hypercoagulable state associated with malignancy. Among hemostasis-regulating functions, ATRA modulates the procoagulant and fibrinolytic properties of endothelial cells (EC) from large vessels (HUVEC). In this study we investigated whether ATRA may affect the same activities of EC derived from microvessels (HMEC-1 cell line). DESIGN AND METHODS: We studied the effects of ATRA on procoagulant (i.e. tissue factor, TF), fibrinolytic (i.e. tissue plasminogen activator and inhibitor, t-PA and PAI-1) and anticoagulant (i.e. thrombomodulin, TM) properties of HMEC-1, compared to HUVEC. The type of retinoic acid receptor (RAR) possibly involved was identified by using synthetic retinoid selective agonists or antagonists for RAR alpha, beta or gamma. The study was conducted with or without tumor necrosis factor (TNF)alpha to induce the expression of some endothelial hemostatic properties. RESULTS: ATRA significantly inhibited TNFalpha-induced TF expression in HMEC-1 as well as HUVEC. ATRA increased t-PA antigen without significantly affecting PAI-1 expression, and counteracted the TNFalpha-induced t-PA decrease in both types of EC. Accordingly, t-PA activity was significantly increased by ATRA, even in the presence of TNFalpha. Finally, ATRA upregulated TM, and prevented TNFalpha-induced TM downregulation. The study with selective RARs agonists and antagonists indicated that RARalpha played a major role in t-PA and TM modulation, whereas all three receptors were involved in TF downregulation. INTERPRETATION AND CONCLUSIONS: This study provides the first evidence that ATRA increases antithrombotic potential also in microvascular EC, a very relevant compartment for tumor- and/or antitumor therapy-associated vascular complications.

Clotting mechanisms and cancer: implications in thrombus formation and tumor progression.

Development of cancer is associated with activation of blood coagulation. The results of laboratory tests clearly demonstrate that fibrin formation and dissolution is continuously ongoing at different rates in these patients, who are at increased risk of secondary thrombosis. Notably, fibrin formation is also involved in the process of tumor spread and metastasis. The pathogenesis of the hemostatic disorders in cancer is complex and reflects the interaction of different mechanisms involving the activation of various hemostatic components, such as the coagulation and fibrinolytic systems, the vascular endothelium, leukocytes, and platelets. Tumor cells possess the capacity to interact with all of these components. Indeed they directly activate the coagulation cascade by producing their own procoagulant factors, or they can stimulate the prothrombotic properties of other blood cell components. Additional mechanisms of blood clotting activation are started by the initiation of antitumor therapies. In the last 10 years research studies have greatly improved our knowledge of tumor-promoted prothrombotic functions. Understanding the molecular basis of the underlying mechanisms may help to identify better-targeted strategies to prevent thromboembolism in cancer patients. Further, pharmacological modulation of malignant cell hemostatic properties may not only affect the tumor-associated thrombotic risk but may also leave open the possibility to interfere with the progression of the disease.