Abstract: We used the thrombin generation assay to evaluate the hypercoagulable state according to JAK2(V617F) mutational status in patients with Essential Thrombocythemia (ET), and Polycythemia Vera (PV). Thrombin generation was determined in the presence and absence of activated protein C (APC), and APC-resistance was expressed as normalized APC sensitivity ratio (nAPCsr). Tissue factor pathway inhibitor (TFPI), total and free protein S (PS), FII, FV and neutrophil elastase were measured in plasma; CD11b was measured on neutrophils. Compared to normal control subjects, patients had a lower endogenous thrombin potential (ETP) in the absence of APC, but had a higher ETP in the presence of APC, showing the occurrence of APC-resistance. The nAPCsr values significantly increased in JAK2(V617F) carriers compared to non carriers, and were highest in JAK2(V617F) homozygous patients. FII, FV, free-PS, and TFPI levels were reduced in patients, and mainly in JAK2(V617F) carriers. Multiple regression analysis indicated the low free PS level as major determinant of the increased nAPCsr. Elastase was significantly increased in patients and was inversely correlated with free PS. In conclusion, these data indicate the occurrence of acquired APC-resistance in ET and PV patients, likely due to a reduction in free-PS levels. The APC resistant phenotype is influenced by the JAK2(V617F) mutational load, as shown by the more pronounced APC-resistance in homozygous subjects.

Abstract: 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.

Abstract: Malignancy is an acquired thrombophilic condition that significantly increases the risk of thrombosis. Both venous and arterial thromboembolisms are recognized complications in patients with cancer. In addition, clotting activation may have a role in tumor progression. The pathogenesis of thrombophilia in cancer is multifactorial; however, an important role is attributed to the tumor cell capacity to interact with and activate the host hemostatic system. Recently, new strategies to prevent and cure thrombosis in cancer have become available, thus improving the management of thrombotic complications in the malignant disease. An antineoplastic effect of anticoagulant agents has also been suggested. Both heparins and vitamin K antagonists have been tested in this context. Heparins have been more extensively studied. Recently, the results of prospective, randomized clinical trials to evaluate the effect of low-molecular-weight heparin on cancer survival have created new interest in this area. The published data are promising and provide new information in the research knowledge in this field. The potential anticancer activity of heparins is supported by data from in vitro and experimental studies.

Abstract: 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.

Abstract: 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.

Abstract: Recombinant human G-CSF (rHuG-CSF) is used for hematopoietic progenitor cells (HPC) mobilization and collection. Activation of polymorphonuclear leukocytes (PMN) is present during rHuG-CSF treatment and is associated with endothelial cell dysfunction and hypercoagulation. We evaluated whether PMN activation by rHuG-CSF may alter the blood oxidative status and subsequently affect the vascular cell function. Fourteen healthy individuals received rHuG-CSF for HPC harvesting. Blood was drawn before starting rHuG-CSF (T0), on the last day of rHuG-CSF (T1) and 1 week after stopping rHuG-CSF (T2). Levels of CD11b, myeloperoxidase (MPO), hydroperoxides, nitric oxide (NO), and soluble endothelium (sES), leukocyte (sLS), and platelet (sPS) selectins were measured. During rHuG-CSF, CD11b, MPO and hydroperoxides significantly increased, while NO levels significantly decreased, compared with T0. At T2 all these markers returned to baseline values. Significant increments of all selectins were observed during rHuG-CSF. At T2 sES and sEP significantly decreased back to pre-treatment values, whereas sLS remained significantly high. These data show that rHuG-CSF induces a transient inflammatory status characterized by circulating activated PMN, which release reactive oxygen species and intracellular proteases, promoting the onset of an abnormal oxidative status. This process may modify the hemostatic balance towards a pro-thrombotic state.

Abstract: The evidence of the important two-way clinical correlation between cancer and venous thromboembolism (VTE) dates back to Trousseau's time. Over time it has been established that cancer patients not only exhibit a higher risk of developing VTE when compared with noncancer patients, but also that VTE, especially in its idiopathic presentation, sometimes acts as an epiphenomenon of a hidden cancer, offering possible chances for anticipated diagnosis of the pathology. Research has contributed greatly to the progression of this field through the identification of VTE risk factors in this setting, and through the assessment of the most adequate thromboprophylaxis and treatment modalities as well as secondary prophylaxis management. Anticoagulant drugs appear to be an attractive strategy in cancer treatment because there is growing evidence for their possible benefits in terms of cancer prognosis and patient survival.

Abstract: 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.

Abstract: Thrombotic complications are frequently observed in patients with polycythemia vera (PV) and essential thrombocythemia (ET). Abnormalities of red blood cells and platelets arising from the clonal rearrangement of hematopoietic cells have been considered, although causal relationships between any of these specific abnormalities and thrombosis have not been clearly established. The involvement of neutrophils and macrophages, which participate in thrombosis and hemostasis, has been insufficiently explored in PV and ET. Persistent activation of circulating neutrophils was recently demonstrated in ET and PV patients, in parallel with an increase in plasma concentrations of endothelial damage-derived and prothrombotic substances. Other studies have explored whether the augmentation of adhesion of neutrophils may affect neutrophil/platelet interaction since a significant increase in circulating neutrophil/platelet aggregates is found in ET and PV. This review summarizes the current knowledge of the pathogenesis of thrombosis in PV and ET, with emphasis on the role of neutrophils in hemostasis and their possible involvement in the mechanisms of the acquired thrombophilia of these patients. Available data suggest that these hemostatic markers deserve to be included in prospective clinical studies aimed at identifying their predictive role in the vascular complications of patients with ET and PV.

Abstract: 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.

Abstract: Defibrotide (DF), a polydeoxyribonucleotide with antithrombotic properties, has recently proven effective in patients with severe hepatic veno-occlusive disease (VOD), a life-threatening complication of high-dose chemo/radiotherapy regimens for stem cell transplantation. To understand the mechanism of its beneficial effect, we studied the impact of DF on the expression of tissue factor (TF) and fibrinolytic proteins (PAI-1 and t-PA) on endothelial cells. The in vitro response to DF of two types of human endothelial cells (ECs) of different origins, that is from macrovascular (HUVEC) and microvascular (HMEC-1 cell line) beds, was evaluated in the presence or absence of a proinflammatory stimulus (ie bacterial endotoxin, LPS). The results show that DF was able to significantly reduce the LPS-induced TF expression by HMEC-1, and less prominently by HUVEC. In addition, DF importantly influenced the fibrinolytic properties of both HMEC-1 and HUVEC. Specifically, it dose-dependently counteracted the LPS-induced increase in PAI-1 levels and decrease in t-PA activity expression. It also significantly incremented t-PA antigen in resting EC. Decreasing the procoagulant activity and increasing the fibrinolytic potential of EC favors an anticoagulant phenotype of the endothelium, which may protect from fibrin deposition and vascular occlusion.

Abstract: 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.

Abstract:

Abstract: To evaluate whether all-trans-retinoic acid (ATRA) is able to modulate the hemostatic system in patients with solid tumors, we studied patients with locally advanced breast cancer who were enrolled in a Phase Ib study of ATRA +/- Tamoxifen (Tam). In this study, two groups of 15 patients/each were treated for 21 days before operation with ATRA at three doses (15, 45, or 75 mg/m(2)/day on alternate days) given alone (group 1) or in combination with Tam (group 2). One additional group received Tam alone. Plasma samples were evaluated for hypercoagulation markers (FVIIa, F1+2, TAT, D-dimer), fibrinolysis proteins (t-PA, PAI-1), and coagulation inhibitors (protein C, AT). At baseline, cancer patients had FVIIa, F1+2, TAT, and PAI-1 significantly greater than control subjects. During treatment, in the patients given ATRA alone, hypercoagulation markers appeared unmodified. Instead, subjects given Tam alone had a significant elevation of FVIIa, F1+2, and TAT versus baseline. However, in the ATRA + Tam groups, hypercoagulation markers were decreased compared with Tam alone. These results suggest that in selected conditions, pre-operative ATRA may modulate the hypercoagulable state of breast cancer patients.

Abstract: Thrombohemorrhagic complications are a major cause of morbidity and mortality in patients with essential thrombocythemia (ET) and polycythemia vera (PV). The pathogenesis of these complications is not completely clarified. Several studies have described abnormalities of red blood cells and platelets in these patients. However, no studies are available on changes in the polymorphonuclear leukocytes (PMNs), which can play an important role in the activation of the hemostatic system. In patients with ET (n = 37) and PV (n = 34), a series of PMN activation parameters (PMN membrane CD11b and leukocyte alkaline phosphatase [LAP] antigen expression, cellular elastase content, plasma elastase, and myeloperoxidase levels) was evaluated simultaneously with the levels of plasma markers of endothelial damage (thrombomodulin and von Willebrand factor antigen) and hypercoagulation (thrombin-antithrombin complex, prothrombin fragment 1 + 2, and D-dimer). The results show the occurrence of PMN activation in both groups of patients compared with a control group of healthy subjects. An increase in CD11b and LAP expression by PMN membrane was observed, together with a significant increase in cellular elastase content, plasma elastase, and myeloperoxidase levels. In addition, patients had high plasma levels of endothelial and hypercoagulation markers compared with controls. For the first time, these data show that in ET and PV, 2 hematologic conditions that place patients at increased risk for thrombosis, an in vivo leukocyte activation occurs and is associated with laboratory signs of endothelium and coagulation system activation. (Blood. 2000;96:4261-4266)

Abstract: Granulocyte colony-stimulating factor (G-CSF) enhances neutrophil functions in vitro and in vivo. It is known that neutrophil-derived products can alter the hemostatic balance. To understand whether polymorphonuclear leukocyte (PMN) activation, measured as PMN degranulation and phenotypical change, may be associated to hemostatic alterations in vivo, we have studied the effect of recombinant human G-CSF (rHuG-CSF) administration on leukocyte parameters and hemostatic variables in healthy donors of hematopoietic progenitor cells (HPCs). Twenty-six consecutive healthy donors receiving 10 micrograms/kg/d rHuG-CSF subcutaneously for 5 to 7 days to mobilize HPCs for allogeneic transplants were included in the study. All of them responded to rHuG-CSF with a significant white blood cell count increase. Blood samples were drawn before therapy on days 2 and 5 and 1 week after stopping rHuG-CSF treatment. The following parameters were evaluated: (1) PMN activation parameters, ie, surface CD11b/CD18 antigen expression, plasma elastase antigen levels and cellular elastase activity; (2) plasma markers of endothelium activation, ie, thrombomodulin (TM) and von Willebrand factor (vWF) antigens; (3) plasma markers of blood coagulation activation, ie, F1+2, TAT complex, D-dimer; and (4) mononuclear cell (MNC) procoagulant activity (PCA) expression. The results show that, after starting rHuG-CSF, an in vivo PMN activation occurred, as demonstrated by the significant increment of surface CD11b/CD18 and plasma elastase antigen levels. Moreover, PMN cellular elastase activity, which was significantly increased at 1 day of treatment, returned to baseline at day 5 to 6, in correspondence with the elastase antigen peak in the circulation. This change was accompanied by a parallel significant increase in plasma levels of the two endothelial and the three coagulation markers. The PCA generated in vitro by unstimulated MNC isolated from rHuG-CSF-treated subjects was not different from that of control cells from untreated subjects. However, endotoxin-stimulated MNC isolated from on-treatment individuals produced significantly more PCA compared with both baseline and control samples. All of the parameters were decreased or normal 1 week after stopping treatment. These data show that rHuG-CSF induces PMN activation and transiently affects some hemostatic variables in healthy HPC donor subjects. The clinical significance of these findings remains to be established.

Abstract: Acetylsalicylic acid (ASA) is currently recommended as an antithrombotic for patients with essential thrombocythemia (ET) who are at an increased risk of thrombotic events. However, ASA is also associated with an increased risk of bleeding in these patients as compared to the risk of bleeding in other patients treated with ASA. Recent data suggest that while ASA inhibits platelet thromboxane A2 (TxA2) synthesis in all individuals, ASA has little effect or inhibits the lipoxygenase pathway (i.e., 12-hydroxyeicosatetranoic acid or 12-HETE synthesis) in some individuals, and enhances 12-HETE synthesis in others. These differential effects are associated with a pronounced prolongation of the bleeding time vs. no prolongation of the bleeding time, respectively, i.e., in ASA responders and ASA nonresponders, respectively. To determine if the increased risk of ASA-induced bleeding seen in ET patients is associated with an effect on 12-HETE synthesis, we compared the relative effects of ASA on the bleeding time, platelet TxA2 and 12-HETE synthesis, and platelet aggregation and adhesion in ET patients and healthy volunteers. ASA (300 mg, taken orally) prolonged the bleeding time in 82% of the ET patients but only 27% of the healthy volunteers although platelet TxA2 synthesis and ADP- and collagen-induced aggregation were inhibited significantly in both groups. In contrast, platelet 12-HETE synthesis was unchanged and platelet adhesion was decreased in those patients and volunteers whose bleeding times were prolonged by ASA, whereas platelet 12-HETE synthesis was increased significantly and platelet adhesion was unaffected in those patients and volunteers whose bleeding times were not prolonged, and in some cases shortened by ASA. These results confirm previous data that demonstrate that ASA has different effects on platelet 12-HETE synthesis and platelet adhesion in different individuals, i.e., inhibitory or no effect in ASA responders (in whom ASA prolonged bleeding) vs. enhancing effects in ASA nonresponders (in whom ASA did not prolong bleeding). These results also indicate that there is a greater percentage of ASA responders in patients with ET than that seen in the general population, a difference that is associated with an effect of ASA on the lipoxygenase pathway. This may explain the increased bleeding side effects seen in the ET patient population.

Abstract: All-trans-retinoic acid (ATRA) downregulates the expression of two cellular procoagulants, tissue factor (TF) and cancer procoagulant (CP), in human promyelocytic leukemia cells. To evaluate whether or not changes of the procoagulant activities (PCAs) may share mechanisms with the ATRA-induced cyto-differentiation process, we have characterized the effect of ATRA on the TF and CP expression by NB4 cells, an ATRA maturation-inducible cell line, and two NB4-derived cell lines resistant to ATRA-induced maturation, the NB4. 306 and NB4.007/6 cells. Next, we evaluated the effect on the PCAs of the NB4 parental cells of three synthetic retinoid analogues, ie: AM580 (selective for the retinoic acid receptor [RAR] alpha), capable to induce the granulocytic differentiation of NB4 cells; and CD2019 (selective for RARbeta) and CD437 (selective for RARgamma), both lacking this capability. Cells were treated with either ATRA or the analogues (10(-6) to 10(-8) mol/L) for 96 hours. The effect on cell differentiation was evaluated by morphologic changes, cell proliferation, nitro blue tetrazolium reduction assay, and flow cytometry analysis of the CD33 and CD11b surface-antigen expression. PCA was first measured in 20 mmol/L Veronal Buffer cell extracts by the one-stage clotting assay of normal and FVII-deficient plasmas. Further TF and CP have been characterized and quantified in cell-sample preparations by chromogenic and immunological assays. In the first series of experiments, ATRA downregulates both TF and CP in NB4 parental cells, as expected. However, in the differentiation-resistant cell lines, it induced a significant loss of TF but had little or no effect on CP. In a second series of experiments, in the NB4 parental cells, the RARalpha agonist (AM580) induced cell maturation and reduced 91% CP expression, whereas CD437 and CD2019 had no cyto-differentiating effects and did not affect CP levels. On the other hand, in the same cells the TF expression was reduced by ATRA and AM580, but also by the RARbeta agonist CD2019, which did not induce cell maturation. These data indicate that in NB4 cells, ATRA modulation of CP occurs in parallel with signs of cell differentiation, while the regulation of TF appears to be at least in part independent from these processes, and involves both alpha and beta nuclear retinoid receptors.

Abstract: Pulmonary distress symptoms and thrombotic complications are side-effects of all-trans-retinoic acid (ATRA) therapy for remission induction in acute promyelocytic leukaemia (APL). The ATRA-induced increase of leukaemic cell adhesive molecules may be responsible. To explore this we used a functional assay to study the effect of ATRA treatment on the adhesion of blast cells to cultured human endothelial cells (EC), endothelial cell matrix (ECM), and interleukin 1beta-activated EC (IL1 + EC). NB4 cells, a maturation-inducible human promyelocytic leukaemia cell line, were treated with 1 microM ATRA or the vehicle (control), labelled with 51Cr and tested in the adhesion assay. ATRA increased NB4 adhesion to EC (P<0.01), ECM (P<0.001) and IL1 + EC (P=n.s.). An inhibition study with anti-EC adhesion receptors MoAbs indicated that anti-E-selectin, anti-VCAM-1 and anti-ICAM-1 effectively inhibited cell adhesion to IL1 + EC (18+/-7%, 45 +/-6.9% and 29+/-6% inhibition, respectively) and to unstimulated EC. Preincubation of ATRA-treated NB4 cells with MoAbs anti-VLA4 and anti-LFA1, the VCAM-1 and ICAM-1 counter-receptors respectively, resulted in a significant inhibition of adhesion. Cytofluorimetric analysis of the NB4 cell membrane molecules confirmed the increase under ATRA of VLA4, LFA1, MAC1 and ICAM-1. Therefore ATRA increases NB4 cell adhesion to the endothelium and the subendothelial matrix. These findings parallel the increment of NB4 surface adhesive molecules, among which VLA4 and LFA1 appear to play an important part. These mechanisms may contribute to the complications of ATRA therapy in APL.

Abstract: Therapy with all-trans-retinoic acid (ATRA) can rapidly improve the coagulopathy of acute promyelocytic leukemia (APL). This study was designed to evaluate whether the APL cell line NB4 induces the procoagulant activity (PCA) of human endothelial cells (ECs) in vitro, and whether this property is modified after ATRA-induced NB4 maturation. EC monolayers were incubated for 4 hours at 37 degrees C with the conditioned media (CM) of NB4 treated with 1 mumol/L ATRA (ATRA-NB4-CM) or the vehicle (control-NB4-CM). EC lysates were tested for PCA. ATRA-NB4-CM induced significantly more PCA:tissue factor (TF) than control-NB4-CM (P < .01). To identify the cause of TF induction, interleukin (IL)-1 beta antigen levels were measured in CM samples. ATRA-NB4-CM contained significantly more IL-1 beta than control-NB4-CM. EC PCA was significantly inhibited by an anti-IL-1 beta antibody. The addition to the media of 10 mumol/L ATRA counteracted the EC TF expression induced by NB4-CM. These data indicate that ATRA increases the promyelocyte-induced EC TF, partly through increased IL-1 beta production. However, ATRA can protect the endothelium from the procoagulant stimulus of leukemic cells.

Abstract: In basal conditions, NB4 and HL-60, two acute promyelocytic leukemia cell lines, express high levels of tumor necrosis factor (TNF-alpha) mRNA, whereas they do not synthesize appreciable amounts of the transcripts coding for interleukin-1 beta (IL-1 beta) or interleukin-8 (IL-8). Upon granulocytic differentiation with all-trans retinoic acid (ATRA) or the combination of ATRA and granulocyte-colony-stimulating factor (G-CSF), significant amounts of IL-1 beta and IL-8 mRNAs accumulated in both cell types. These changes in mRNA levels were parallelled by the increased secretion of the two cytokines. Dexamethasone (DEX) had no effect on the induction of IL-1 beta mRNA, while it enhanced the G-CSF-, ATRA- and (ATRA+G-CSF) dependent secretion of the cytokine. In combination with ATRA and G-CSF, the corticosteroid increased the expression of leukocyte alkaline phosphatase, a late marker of granulocytic differentiation.

Abstract: Acute promyelocytic leukemia (APL) cells express different types of procoagulant activity (PCA), including tissue factor (TF), and cancer procoagulant (CP). The aim of this study was to investigate whether the NB4 cell line, the first ever isolated human APL line, with the typical t(15;17) chromosomal balance translocation, possess CP as well as the cells freshly isolated from APL patients. Secondly, since the NB4 line is maturation inducible by all-trans-retinoic acid (ATRA), we wanted to verify whether CP, if present, was affected by ATRA treatment. The NB4 cells were able to shorten the recalcification assay of normal human plasma (total PCA). To distinguish CP in the assay for clotting activity, two criteria were used, the independence from factor VII to trigger blood coagulation and the sensitivity to cysteine proteinase inhibitors. Forty-seven per cent of total PCA of cell extracts was found to be FVII-independent PCA. A similar proportion of FVII-independent activity (42%) was detected in the cell serum-free supernatants. The activity was significantly decreased by cysteine proteinase inhibitors, including HgCl2, lodoacetic acid and Z-Ala-AlaCHN2. Additionally CP was directly identified and quantified by an immunocapture enzyme assay. The mean +/- SD concentration of CP detected by this assay in the NB4 cells, before any treatment, was 1.89 +/- 0.5 microgram/mg protein. Treatment of NB4 cells with 10(-6) M ATRA for 5 days significantly decreased the expression of CP, which became virtually undetectable by the clotting assay, and was 64% less than the untreated control by the immunocapture enzyme assay. This study provides the first evidence that the human promyelocytic cell line NB4 possess CP. The expression of this procoagulant is modulated by ATRA.

Abstract: Platelet adhesion to collagen under flow conditions was studied in 18 patients with lupus anticoagulant, seven of which showed a prolonged bleeding time in the presence of a normal platelet count. The effect of patient plasma, IgG and purified anticardiolipin antibodies on platelet adhesion was also examined. We found a significant reduction of platelet adhesion in patients with lupus anticoagulant, which was more evident in patients with prolonged bleeding time. This platelet adhesion defect could be attributed to a plasma factor. In fact, patients' platelets regained normal adhesion when mixed with normal plasma, whereas controls' platelets showed abnormal adhesion in the presence of patient plasma. A causative role of antiphospholipid antibodies was demonstrated in experiments using purified immunoglobulins and anticardiolipin antibodies.