New insights into the pathogenesis of coagulation dysfunction in acute promyelocytic leukemia

Pathogenesis and treatment of thrombohemorrhagic diathesis in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is a distinct subtype of myeloid leukemia characterized by t(15;17) chromosomal translocation, which involves the retinoic acid receptor-alpha (RAR-alpha). APL typically presents with a life-threatening hemorrhagic diathesis. Before the introduction of all-trans retinoic acid (ATRA) for the cure of APL, fatal hemorrhages due, at least in part, to the APL-associated coagulopathy, were a major cause of induction remission failure. The laboratory abnormalities of blood coagulation found in these patients indicate the occurrence of a hypercoagulable state. Major determinants of the coagulopathy of APL are endogenous factors expressed by the leukemic cells, including procoagulant factors, fibrinolytic proteins, and non-specific proteolytic enzymes. In addition, these cells have an increased capacity to adhere to the vascular endothelium, and to secrete inflammatory cytokines [i.e. interleukin-1beta (IL-1beta) and tumor necrosis factor (TNF-alpha)], which in turn stimulate the expression of prothrombotic activities by endothelial cells and leukocytes. ATRA can interfere with each of the principal hemostatic properties of the leukemic cell, thus reducing the APL cell procoagulant potential, in parallel to the induction of cellular differentiation. This effect occurs in vivo, in the bone marrow of APL patients receiving ATRA, and is associated with the improvement of the bleeding symptoms. Therapy with arsenic trioxide (ATO) also beneficially affects coagulation in APL. However, early deaths from bleeding still remain a major problem in APL and further research is required in this field. In this review, we will summarize our current knowledge of the pathogenesis of the APL-associated coagulopathy and will overview the therapeutic approaches for the management of this complication.

Distribution and shedding of the membrane phosphatidylserine during maturation and aging of erythroid cells

Maturation and aging of erythroid cells are accompanied by extensive remodeling of the membrane and a marked decrease in cell size, processes that are mediated by externalization and shedding of phosphatidylserine (PS). In the present study, we investigated the redistribution of PS in the plasma membrane of erythroid precursors during their maturation and of mature RBCs during senescence, and the involvement of changes in calcium (Ca)-flux in these processes. Maturation was studied by analyzing normal human bone marrow cells as well as cultured human normal erythroid precursors induced by erythropoietin and murine erythroleukemia cells induced by hexamethylene-bisacetamide. Senescence was studied in normal human peripheral RBCs following density fractionation. PS and Ca were determined by flow cytometry using annexin-V and Flu-3, respectively. The outer, inner and shed PS were quantified by a novel two-step binding inhibitory assay. The results indicate a bi-phasic modulation of intracellular Ca and PS externalization/shedding; both of which decreased during maturation and increased during aging. The role of intracellular Ca in PS externalization/shedding was demonstrated by modulating intracellular Ca: Ca was decreased by incubating the cells with an ion chelator (EDTA) or with decreasing concentrations of Ca, whereas treatment with the ionophore A23187 elevated intracellular Ca. The results showed that low Ca resulted in decreased outer and shed PS, whereas high Ca had the opposite effect. The results suggest that PS externalization and shedding are mediated by increased cellular Ca-flux, and that they play an important role in erythroid maturation and RBC senescence.

Physical activity and pediatric cancer survivorship

Owing to improved treatment pro-tocols in the last 25 years there have been dramatic improvements in the 5-year relative survival rate of the most prevalent childhood cancers. For instance, the 5-year relative survival rate among children for all cancer sites combined, improved from 58% to 80% in patients diagnosed in 1975-1977 and in 1996-2004 respectively. However, as survival rates have improved, there has been an increasing recognition of adverse short and longer term effects associated with treatment and cancer itself, which we describe in detail in this chapter. There is growing interest in those interventions that can counteract the adverse effects of treatment and cancer. Because such adverse effects are further aggravated by physical inactivity, a special emphasis is being placed on physical activity (PA) interventions. Results are promising: there is increasing evidence that regular PA can improve the overall health status, functional capacity, and quality of life (QOL) of children with cancer as well as of older survivors of childhood cancer.

Outcome of childhood acute promyelocytic leukemia treated using a modified AIDA protocol

Background

Combination treatment with all-trans-retinoic acid (ATRA) and anthracycline-based chemotherapy has led to major advances in the treatment of acute promyelocytic leukemia (APL).

Methods

In this study, we reviewed the outcome of pediatric APL patients treated using a modified AIDA protocol at our institution.

Results

Between May 1999 and December 2007, 23 patients were diagnosed with APL at the Department of Pediatrics, Saint Mary's Hospital, The Catholic University of Korea. Eleven patients were male (48%) (median age at diagnosis, 11 (range, 2-14) years). The treatment protocol consisted of remission induction (achieved by coadministration of ATRA and idarubicin), 3 courses of consolidation treatment, and 2 years of maintenance treatment during which ATRA was also administered. Three patients died early during remission induction due to CNS hemorrhage. The remaining 20 patients achieved complete remission (CR), with an overall CR rate of 87%. Two patients relapsed and died, and another patient died of pneumonia unrelated to APL. Four patients (17%) were diagnosed with ATRA syndrome, and all patients showed resolution of symptoms. The event-free survival (EFS) and overall survival (OS) of the cohort were 78.3±8.6% and 76.3±9.5%, respectively. Initial WBC count at diagnosis was the only significant prognostic factor for the rate of CR (P=0.039) and OS (P=0.039).

Conclusion

A modified AIDA protocol for the treatment of childhood APL leads to improved EFS and OS, with limited ATRA syndrome-associated toxicity. Active monitoring and treatment of patients with high initial WBC counts may help in reducing mortality.

D-dimer levels correlate with mortality in patients with acute pulmonary embolism: Findings from the RIETE registry

OBJECT

Few studies have addressed the prognostic implications of D-dimer in patients with pulmonary embolism. The aim of this study was to investigate the correlation between D-dimer levels and mortality in patients with pulmonary embolism.

DESIGN

Observational study.

SETTING

Hospitals participating in the Registro Informatizado de la Enfermedad Tromboembólica (RIETE).

PATIENTS

A total of 588 consecutive patients with symptomatic pulmonary embolism who were included in the RIETE between March 2001 and December 2004.

INTERVENTIONS

Quantitative D-dimer measurement was performed on admission using an automated latex agglutination test (IL Test D-dimer). All patients underwent clinical follow-up for 3 months.

MEASUREMENTS AND MAIN RESULTS

Overall mortality rate was 10.5%. The cause of death was pulmonary embolism in 18 patients (3.0%), fatal bleeding in one patient (0.2%), and other causes in 43 patients (7.3%). There were 28 (4.8%) nonfatal venous thromboembolism recurrences and 35 (6.0%) nonfatal bleeding episodes. The incidence of D-dimer 500-2499 ng/mL, D-dimer 2500-4999 ng/mL, and D-dimer >or=5000 ng/mL was 47.8%, 26.0%, and 20.4%, respectively. Compared with patients with D-dimer 500-2499 ng/mL, the relative risk (odds ratio) of overall mortality was 1.91 (95% confidence interval 0.91-4.09) and 2.94 (95% confidence interval 1.42-6.25) in patients with D-dimer 2500-4999 ng/mL and D-dimer >or= 5000 ng/mL, respectively (p = .032). Patients with D-dimer >or=5000 ng/mL showed higher risk of death from fatal pulmonary embolism (odds ratio 4.4, 95% confidence interval 0.5-33.0) than death from other causes (odds ratio 2.1, 95% confidence interval 0.7-6.0). Elevated D-dimer levels were associated with more severe disease, as assessed by clinical features.

CONCLUSIONS

In patients who present with pulmonary embolism, D-dimer concentration is an independent predictive factor associated with all-cause and pulmonary embolism-related death. D-dimer >or=5000 ng/mL occurs in about one in five patients and is associated with a 2.9-fold increased risk of overall mortality. These results suggest that D-dimer quantification could be a useful biomarker and help determine initial therapies.

Haemostatic problems in acute promyelocytic leukaemia

Despite the development of highly effective treatment strategies for acute promyelocytic leukaemia around 10% of patients die in the presentation period as a consequence of the associated bleeding diathesis. The cause of the coagulopathy is complex resulting from a combination of tissue factor (TF) and cancer procoagulant (CP) induced disseminated intravascular coagulation, exaggerated fibrinolysis due predominantly to enhanced expression of annexin II on APL blast cell membranes and blast cell production of cytokines. All-trans retinoic acid (ATRA) has revolutionised the treatment of APL. When combined with chemotherapy long term survival rates of up to 80% can be achieved. Commencement of ATRA induces APL blast cell differentiation and is associated with a rapid resolution of the bleeding tendency through a combination of effects which include up regulation of thrombomodulin and down regulation of TF and CP production and cell surface expression of annexin II.

The pathogenesis of venous thromboembolism in cancer: emerging links with tumour biology

Venous thromboembolism (VTE) is a frequent complication in individuals with cancer and is considered to be a cause of substantial mortality. Epidemiological studies identify malignancy as an independent VTE risk factor and show that cancer patients are at increased risk of both initial and recurrent VTE events. The risk due to cancer is compounded by the effects of chemotherapy and other treatments. The pathogenesis of cancer-associated VTE is complex involving multiple interactions between tumours and various components of haemostasis. The development of a systemic hypercoagulable state is considered a key pathogenetic feature and is attributed to tumour expression of tissue factor and other procoagulants, activation of vascular cells by tumour-derived cytokines and adhesive interactions between tumour cells and host cells. An increasing body of evidence indicates that the activation of haemostasis in malignant disease contributes to tumour growth and progression by stimulation of intracellular signalling pathways. The interaction of tissue factor, thrombin and other coagulation factors with protease activated receptor (PAR) proteins expressed by tumour cells and host vascular cells leads to the induction of genes related to the processes of angiogenesis, cell survival and cell adhesion and migration.

Effects of all-trans retinoic acid or chemotherapy on the molecular regulation of systemic blood coagulation and fibrinolysis in patients with acute promyelocytic leukemia

We studied the pathogenesis of the bleeding disorder in acute promyelocytic leukemia by measuring procoagulant, profibrinolytic, and proinflammatory mediators in peripheral blood and bone marrow cells from 25 previously untreated patients. Patients were induced with either all-trans retinoic acid (ATRA) or chemotherapy. Plasma levels of fibrinopeptide A (FPA), fibrin d-dimer, thrombin antithrombin (TAT) complex, prothrombin fragment 1.2 (F1.2), urokinase-type plasminogen activator (uPA), tissue-type plasminogen activator (t-PA) and plasminogen activator-inhibitor 1 (PAI-1) were measured before and after therapy, as was the cellular expression of the genes for tissue factor (TF) and interleukin-1 beta (IL-1 beta). The mean plasma levels of fibrin d-dimer, F1.2, TAT and FPA were markedly elevated prior to therapy and declined during the first 30 days of treatment with either ATRA or chemotherapy, but more rapidly and to a greater extent in patients treated with ATRA. ATRA treatment was associated with a significant decrease in TF gene expression in bone marrow cells during the first 30 days of treatment, whereas IL-1 beta gene expression, which decreased in the cells of six patients treated with either chemotherapy or ATRA, actually increased in the remaining six patients treated with either chemotherapy or ATRA. In patients with APL, treatment with either chemotherapy or ATRA rapidly ameliorates the coagulopathy, as indicated by an abrupt decline in markers of clotting activation. An increase in cytokine gene expression (e.g. IL-1 beta) may provide an explanation for the persistent hypercoagulability observed in some patients with APL, regardless of therapeutic approach. Our data confirms and extends earlier observations by others that ATRA is more effective than chemotherapy alone in rapidly reducing the procoagulant burden of APL tumor cells. However, our data also suggests that cytokine expression in some patients may be accelerated by either chemotherapy or ATRA. The implications of this observation for understanding the retinoic acid syndrome will require further studies.

Relevance of pathologic classifications and diagnosis of acute myeloid leukemia to clinical trials and clinical practice

Many new insights into the diagnosis, pathogenesis, clinical manifestation, treatment and prognosis of patients with AML reflect the heterogeneity of the disease. The initial descriptions of the various subtypes of AML, established by the FAB classification, were based on morphology and cytochemical stains. Although morphology remains the foundation for the diagnosis, additional diagnostic studies including immunophenotyping, cytogenetic evaluation, and molecular genetic studies have become critical, and in some specific cases, mandatory, complementary tools. Several specific subtypes of AML are now treated with directed or targeted therapy. Acute promyelocytic leukemia is currently the only example of a subtype of AML to which specific therapy targeted to a molecular genetic abnormality is available and this subtype now is highly curable. Future studies will address newly identified prognostic factors and gene mutations such as FLT3, Wilm's tumor (WTI), and CEBPA which will enable the further pathologic classification of patients with AML. Finally, microarray analysis will likely identify genes critically involved in the pathogenesis of specific pathologic subtypes.

Coagulopathic complications in breast cancer

Patients with cancer are highly susceptible to thromboembolic complications, which account for a significant percentage of the morbidity and mortality of the disease. Up to 15% of patients with clinically overt cancer present with venous thromboembolism during the course of their disease. Moreover, patients with cancer represent 20% of all patients in whom deep venous thrombosis and pulmonary embolism are diagnosed. This prothrombotic state in cancer can occur due to the ability of tumor cells to directly activate the blood-clotting cascade and cause thrombosis or induce procoagulant properties and inhibit anticoagulant properties of vascular endothelial cells, platelets, monocytes, and macrophages. It also is well established that this prothrombotic tendency in patients with cancer can be enhanced greatly by anticancer treatments, such as surgery and chemotherapy. This phenomenon can be seen in patients with breast cancer, particularly after surgery and chemotherapy. Increased clotting risk also is associated with the use of central venous access devices, commonly used to administer chemotherapeutic agents in patients with cancer. Thrombosis prophylaxis, therefore, should be considered for patients with breast cancer who are at risk before and during intervention. In the current review, the authors discuss the problem of thromboembolism in patients with breast cancer who are undergoing therapy, the mechanisms by which thromboembolisms occur, and the potential strategies by which these events may be prevented. Better understanding of these pathogenetic pathways may lead to the development of more targeted strategies to prevent thromboembolism in patients with cancer.

Pathogenesis and management of the bleeding diathesis in acute promyelocytic leukaemia

Life-threatening bleeding, which remains a challenging complication of acute leukaemia, is particularly characteristic of the subtype, acute promyelocytic leukaemia (APL). The clinical picture and laboratory abnormalities are most compatible with the diagnosis of disseminated intravascular coagulation (DIC). Evidence for diffuse activation of the coagulation system, hyperfibrinolysis and systemic elaboration of non-specific protease activity can usually be demonstrated and occurs most commonly during induction chemotherapy. While both host- and tumour-associated mechanisms can be implicated in the pathogenesis of the coagulopathy, leukaemic cell properties appear to be the proximate cause of activation of the haemostatic mechanisms. In this chapter we summarize the current state of knowledge of the pathogenesis of the coagulopathy of APL and the therapeutic approaches that have proved most useful for the management of this complication. Special attention is devoted to the use of all-trans-retinoic acid (ATRA), which has revolutionized the treatment of APL and markedly ameliorated the APL-related coagulopathy.

Acute promyelocytic leukaemia:a review

Acute promyelocytic leukaemia (APL) is characterised by the fusion gene transcript PML-RAR-alpha and is now the most frequently curable acute leukaemia in adults if promptly diagnosed and adequately treated. The clinical presentation is associated with a haemorrhagic diathesis and the blasts almost always have Auer rods. Poor prognostic factors include older age, elevated white blood cell count, low platelet count, and CD56 expression. The introduction of all-trans retinoic acid (ATRA), which leads to the differentiation of leukaemic blasts into mature granulocytes has been the major breakthrough in the treatment of APL. Induction treatment with concurrent ATRA and chemotherapy leads to a rapid resolution of the characteristic life-threatening coagulopathy, high complete remission rates and excellent survival rates, compared to chemotherapy alone. However, treatment with ATRA is associated with the retinoic acid syndrome (RAS), which is a major toxicity and may lead to mortality. The role of cytarabine as a part of initial induction regimen remains unclear. After achievement of complete remission (CR), there is a definitive role of maintenance therapy with ATRA with or without low-dose chemotherapy. In relapsed patients, arsenic trioxide is considered the treatment of choice. However, the best postremission treatment for patients with second CR remains unknown. With the continued improvement in the field of stem cell transplantation, it may play an important role in the few patients with relapsed/refractory disease or those in second CR.

The hypercoagulable state of malignancy: pathogenesis and current debate

A hypercoagulable or prothrombotic state of malignancy occurs due to the ability of tumor cells to activate the coagulation system. It has been estimated that hypercoagulation accounts for a significant percentage of mortality and morbidity in cancer patients. Prothrombotic factors in cancer include the ability of tumor cells to produce and secrete procoagulant/fibrinolytic substances and inflammatory cytokines, and the physical interaction between tumor cell and blood (monocytes, platelets, neutrophils) or vascular cells. Other mechanisms of thrombus promotion in malignancy include nonspecific factors such as the generation of acute phase reactants and necrosis (i.e., inflammation), abnormal protein metabolism (i.e., paraproteinemia), and hemodynamic compromise (i.e., stasis). In addition, anticancer therapy (i.e., surgery/chemotherapy/hormone therapy) may significantly increase the risk of thromboembolic events by similar mechanisms, e.g., procoagulant release, endothelial damage, or stimulation of tissue factor production by host cells. However, not all of the mechanisms for the production of a hypercoagulable state of cancer are entirely understood. In this review, we attempt to describe what is currently accepted about the pathophysiology of the hypercoagulable state of cancer. We also discuss whether or not to screen patients with idiopathic deep venous thrombosis for an underlying malignancy, and whether this would be beneficial to patients. It is hoped that a better understanding of these mechanisms will ultimately lead to the development of more targeted treatment to prevent thromboembolic complications in cancer patients. It is also hoped that antithrombotic strategies may also have a positive effect on the process of tumor growth and dissemination.

Thrombogenic role of cells undergoing apoptosis

Apoptosis is involved in many biological processes, especially during chemotherapy in cancer patients. Chemotherapy is also associated with an increased risk of thrombosis. The relationship between thrombogenicity and apoptosis was studied in various human tumour cell lines and non-tumour cell lines. Apoptosis was induced by the chemotherapeutic agent camptothecin and by Fas ligand, then quantified by staining with fluorescein isothiocyanate-conjugated annexin V and propidium iodide. A significant correlation between thrombin generation and degree of apoptosis was observed (P < 0.0005). Addition of anti-tissue factor antibody in excess or of tissue factor pathway inhibitor partially inhibited thrombin generation, suggesting that tissue factor activation was responsible for this process. A statistical correlation between tissue factor activity and degree of apoptosis was also found (P < 0.005). Both thrombin generation and tissue factor activity were blocked by the addition of annexin V, which binds and inhibits phosphatidylserine. This indicates that the exteriorization and exposure of phosphatidylserine on the cell surface membrane during apoptosis were essential for both thrombin generation and tissue factor activation.

Molecular basis for the relationship between thrombosis and cancer

Cancer patients are highly susceptible to thromboembolic complications, which some have estimated accounts for a significant percentage of the morbidity and mortality of the disease. Not all of the mechanisms for the production of the hypercoagulable state characteristic of cancer are entirely understood. Those that are known seem to interdigitate the biology of cancer with the major regulatory pathways that mediate blood coagulation, platelet-vessel wall interaction, fibrinolysis and inflammatory cytokine production. In other words, the events responsible for thrombosis in cancer appears to be a result of an over exuberant host response in an attempt to delimit tumor growth. In this brief review, therefore, we attempt to put into the context of tumor growth, angiogenesis and metastasis the current information about the pathogenesis of venous thromboembolism (VTE).

Acute progranulocytic leukemia

Acute progranulocytic leukemia (APL) is characterized by unique biologic and clinical features. Understanding of these unique features has resulted in dramatic improvements in therapy for patients with APL. Current therapy with all-trans-retinoic acid (ATRA) plus an anthracycline with or without cytosine-arabinoside has yielded complete response rates of 85% or greater and long-term disease-free survival rates of 70% or greater. Arsenic trioxide has also surfaced as an effective induction therapy for relapsed APL. Further progress in the care of patients with APL awaits better definition of optimal schedules for ATRA plus chemotherapy, the role of arsenic trioxide, the use of current molecular monitoring for minimal residual disease, optimal therapy for minimal residual disease, and improved methods to address complications of APL including early hemorrhagic deaths and ATRA toxicities.

Tissue factor expression and multidrug resistance in cancer: two aspects of a common cellular response to a hostile milieu

Tissue factor (TF) is the main physiological initiator of blood coagulation and its activation or de-encryption within plasma membranes is important for trapping, extravasation and angiogenesis in the development and spread of solid malignancies. Multidrug resistance is also an adaptive response in malignant (and normal) cells. It is often mediated by the over-expression of the P-glycoprotein (P-gP) efflux pump. Both TF and P-gP tend to be expressed together, perhaps as part of a coherent 'crisis management' response of cells to environmental change or challenge. An associated feature in such a response appears to be the reversal of normal phospholipid charge asymmetry in the plasma membrane bilayer. Responses to environmental stimuli affect function in normal and malignant tissue. Uniting the study of TF expression or de-encryption and MDR-1 phenotype would be biologically enlightening and might ultimately influence clinical cancer management and the control of thrombotic problems associated with treatment.

Decreased tissue factor and tissue-plasminogen activator antigen in relapsed acute promyelocytic leukemia

This study evaluated hemostatic data in 28 patients with newly diagnosed acute promyelocytic leukemia (APL) and 15 patients with relapsed APL. Activated partial thromboplastin time and prothrombin time were prolonged at initial onset of APL. Plasma level of fibrinogen was significantly decreased in patients with initial disease of APL, but it was not decreased significantly during the relapse of APL. Plasma fibrin and fibrinogen degradation products levels were significantly increased and platelet counts significantly decreased in both groups. Plasma levels of antiplasmin significantly decreased at initial onset but not during relapse. Plasma levels of antithrombin were within normal range in patients with initial disease but significantly decreased in those with relapse. Plasma levels of D-dimer, soluble fibrin monomer (sFM), plasmin-plasmin inhibitor complex (PPIC), and thrombin antithrombin complex (TAT) levels were significantly high in both groups. Plasma levels of PPIC, sFM, and D-dimer were significantly higher at initial onset of APL than during relapse. However, there was no significant difference in DIC score between patients with initial onset and those with relapse; plasma levels of tissue factor (TF) significantly increased in both groups, but they were significantly higher at initial onset of APL than during relapse. TF and tissue type plasminogen activator (t-PA) antigen levels in leukemic cell lysate were significantly increased in both groups, and they were significantly lower during relapse than at initial onset. Hemostatic abnormalities occurring in patients with relapsed APL might be the result of the decrease of TF and t-PA in leukemic cells. These findings suggest that DIC in APL patients with relapse might not be caused only by TF and t-PA and thus should be treated with different therapy from patients with initial onset of APL.

The role of RAR and RXR activation in retinoid-induced tissue factor suppression

Excessive expression of tissue factor (TF) is a common finding in leukaemic cells and may contribute to thrombotic complications in patients. Retinoic acid has been shown to induce differentiation and reduce TF expression in acute promyelocytic leukaemia (APL) cells in vitro, and to induce remission in APL patients. Treatment of the APL cell line NB4 with the specific retinoic acid receptor-alpha (RARalpha) agonists Ro4-6055 or TTNPB resulted in down-regulation of TF expression and in induction of differentiation. The activation of RARbeta, RARgamma or retinoid X receptor (RXR) did not suppress the constitutive TF expression in NB4 cells. Moreover, the RARalpha antagonist Ro41-5253 blocked the retinoid-induced down-regulation of TF. In contrast, in the monoblastic U-937 cell line only a partial suppression of TF antigen expression and activity was observed by treatment with the RAR agonist TTNPB or the RXR agonist SR11237 alone. However, the combination of TTNPB and SR11237 resulted in a pronounced down-regulation of TF expression and induction of differentiation in U-937 cells. We show for the first time that the activation of both subunits of the RARalpha-RXR transcriptional complex is needed for TF suppression in U-937 cells, whereas in NB4 cells RARalpha activation alone is sufficient. Thus, distinct molecular mechanisms for TF suppression seem to be operating in leukaemic cell lines of different origin.

Assessment of coagulation disorders in patients with acute leukemia before and after cytostatic treatment

Coagulation disorders are often the reason for fatal bleeding in acute promyelocytic leukemia. Their occurrence as well as pathogenesis and prognostic significance in other subtypes of acute myelogenous leukemia and acute lymphoblastic leukemia is less known. Tests were carried out in 70 patients including 49 with AML and 21 with ALL. In all patients thrombin-antithrombin complexes (TAT), D-dimer (DD) and plasmin-antiplasmin complexes (PAP), antithrombin III activity, fibrinogen/fibrin degradation products, APTT and PT were determined. The tests were performed on diagnosis and after cytostatic treatment. The level of TAT, DD and PAP was elevated in 83% of the patients on diagnosis and in 90% after treatment. The highest values were observed in AML M3 patients. Among leukemic patients with normal levels of TAT, DD and PAP at diagnosis, cytostatic treatment had a negligible effect on the level of these markers. During remission the levels of these markers returned to the normal values while in patients without remission they were either elevated or returned to normal values. No correlation between the levels of activation markers and remission rate was reported. DIC was diagnosed in 13 patients including three after chemotherapy. The DIC was acute or subacute in AML and chronic in ALL patients. In the majority of acute leukemia patients there were already changes on diagnosis indicating coagulation activation. Except for AML M3, these usually had a subclinical course. The TAT, DD and PAP tests are not reliable markers of remission in acute leukemias.

Distinct leukemia phenotypes in transgenic mice and different corepressor interactions generated by promyelocytic leukemia variant fusion genes PLZF-RARalpha and NPM-RARalpha

Acute promyelocytic leukemia (APL) is characterized by a specific chromosome translocation involving RARalpha and one of four fusion partners: PML, PLZF, NPM, and NuMA genes. To study the leukemogenic potential of the fusion genes in vivo, we generated transgenic mice with PLZF-RARalpha and NPM-RARalpha. PLZF-RARalpha transgenic animals developed chronic myeloid leukemia-like phenotypes at an early stage of life (within 3 months in five of six mice), whereas three NPM-RARalpha transgenic mice showed a spectrum of phenotypes from typical APL to chronic myeloid leukemia relatively late in life (from 12 to 15 months). In contrast to bone marrow cells from PLZF-RARalpha transgenic mice, those from NPM-RARalpha transgenic mice could be induced to differentiate by all-trans-retinoic acid (ATRA). We also studied RARE binding properties and interactions between nuclear corepressor SMRT and various fusion proteins in response to ATRA. Dissociation of SMRT from different receptors was observed at ATRA concentrations of 0.01 microM, 0.1 microM, and 1.0 microM for RARalpha-RXRalpha, NPM-RARalpha, and PML-RARalpha, respectively, but not observed for PLZF-RARalpha even in the presence of 10 microM ATRA. We also determined the expression of the tissue factor gene in transgenic mice, which was detected only in bone marrow cells of mice expressing the fusion genes. These data clearly establish the leukemogenic role of PLZF-RARalpha and NPM-RARalpha and the importance of fusion receptor/corepressor interactions in the pathogenesis as well as in determining different clinical phenotypes of APL.

Effect of all trans-retinoic acid (ATRA) on the adhesive and motility properties of acute promyelocytic leukemia cells

All trans-retinoic acid (ATRA) induces complete remission in acute-promyelocytic-leukemia (APL) patients. This study investigated the adhesive properties of APL cells for the endothelium and the extracellular matrix, their motility and the effect of ATRA on these functions. Blasts from 7 APL patients adhered to resting and IL-1-activated endothelium, to the same degree as normal PMN. Adhesion was partially mediated by ICAM-1 and, for IL-1-activated endothelium, by VCAM-1 and E-selectin. These cells showed less adhesiveness for the matrix than PMN, although they maintained the same substrate preference: they adhered to fibronectin and thrombospondin, but not to laminin and type-IV collagen. Exposure to ATRA in vitro (1 microM for 48 to 96 hr) increased the adhesiveness of APL cells; this effect was particularly evident in the case of sub-endothelial matrix and fibronectin. A similar increment in adhesiveness was observed when comparing cells from 2 patients before and after treatment with ATRA. APL cells migrated in response to fMLP and motility was increased by ATRA. In conclusion, APL cells were less adhesive to the matrix than PMN, but treatment with ATRA considerably enhanced their adhesive properties. This could be important in determining the efflux of leukemic cells from the bone marrow and their tissue infiltration during ATRA therapy.

Diagnosis of cancer-associated vascular disorders

BACKGROUND

Unexplained thromboembolism may be an early indicator of the presence of a malignant tumor before signs and symptoms of the tumor itself become obvious.

METHODS

A survey of the MEDLINE data-base was conducted concerning cancer-associated vascular disorders and their role in the diagnosis of hidden cancer. The spectrum of vascular disorders heralding occult cancer and the associated laboratory abnormalities were scrutinized.

RESULTS

Deep venous thrombosis was associated with a significantly higher frequency of malignancy during the first 6 months after diagnosis. Malignancies were found using simple clinical and diagnostic methods; additional screening was not cost-efficient. Other signs associated with deep venous thrombosis that increased the probability of an occult cancer were age older than 50 years, multiple sites of venous thrombosis, associated venous and arterial thromboembolism, thromboembolism resistant to warfarin therapy, and paraneoplastic syndrome. Among vascular syndromes, only cutaneous leukocytoclastic vasculitis presenting after the age of 50 years was consistently associated with cancer. Preliminary data with an antigen specific to tumor tissue, the cancer procoagulant, suggested its possible role as a tumor marker. The sensitivity for all samples analyzed from cancer patients was 80% and the specificity was 83%.

CONCLUSIONS

Data from the literature enabled us to outline clinical clues that might distinguish patients with cancer-associated vasculopathies from those unaffected by malignancies. Preliminary data with an antigen specific to tumor tissue, the cancer procoagulant, suggested its possible role in detecting early stage cancer. However, large-scale prospective studies are not currently available to evaluate the role of these clues and laboratory assays in the diagnosis of early stage cancer.

Tissue factor expression in human leukemic cells

Patients with acute leukemia are at increased risk for thrombotic and hemorrhagic complications, particularly those patients with acute promyelocytic leukemia (APL) undergoing induction chemotherapy. These serious complications have been attributed by some authors to the release of tissue factor (TF) procoagulant activity (PCA), particularly during cytotoxic chemotherapy. In previous studies of normal peripheral blood cells, only cells of the monocyte lineage have been found to express TF PCA. Therefore, several questions remain regarding the origin and characterization of the PCA in malignant leukemic cells, particularly those thought to be derived from granulocyte progenitor cells. We utilized a full-length cDNA probe, several monoclonal antibodies (MAbs) and a sensitive one-stage PCA assay to study the expression of TF in the human cell line, HL-60, in human peripheral blood monocytes/macrophages (Mo/Mø) and in highly purified populations of human polymorphonuclear leukocytes (PMN). In the HL-60 cells we detected low but significant levels of TF mRNA and TF antigen (TF:Ag). In unstimulated cells, coordinate increased levels of TF mRNA, TF:Ag and TF PCA expression were noted following phorbol-ester-induced macrophage differentiation of the cells, but a decreased level of TF mRNA with no change in the basal level of TF:Ag expression occurred following retinoic acid-induced granulocyte differentiation of this cell line. Long-term cultures of stimulated mature Mo/Mø demonstrated initial coordinate expression of TF mRNA, TF:Ag and TF PCA, but TF:Ag expression persisted even after 7 days (when TF PCA was undetectable). No TF PCA, TF:Ag or TF mRNA was demonstrated in highly purified populations of human PMN, regardless of culture conditions. Discordant expression of TF mRNA, TF:Ag and TF PCA in HL-60 cells suggests the possibility of novel, post-synthetic mechanisms for the regulation of TF PCA expression, which might be dependent on the phenotypic differentiation level of the cell. Such mechanisms (yet to be defined) might account for the ability of some leukemic cells, which frequently express characteristics of more than one cell line (e.g. monocytes and granulocytes), to express a TF gene product capable of activating blood coagulation.

Tretinoin. A review of its pharmacodynamic and pharmacokinetic properties and use in the management of acute promyelocytic leukaemia

Tretinoin (all-trans retinoic acid), a vitamin A derivative, induces cellular differentiation in several haematological precursor cell lines and cells from patients with acute promyelocytic leukaemia. Drug treatment with tretinoin is associated with morphological and functional maturation of leukaemic promyelocytes and a progressive reduction in the occurrence of the characteristic t(15;17) chromosomal translocation. Recent therapeutic trials indicate that tretinoin induces remission in 64 to 100% of patients with acute promyelocytic leukaemia. In newly diagnosed patients, remission induction treatment with tretinoin followed by intensive chemotherapy resulted in a significant reduction in relapse rate and prolongation of event-free and overall survival compared with chemotherapy alone in 1 comparative trial. Tretinoin alone does not totally eradicate the leukaemic clone and consolidation chemotherapy is recommended as follow-up. The use of reverse transcription polymerase chain reaction (RT-PCR) provides a sensitive and specific technique to assist in prediction and monitoring of a patient's response to treatment and to help detect the presence of residual or recurrent disease. The use of tretinoin is potentially limited by the rapid and almost universal development of drug resistance and occurrence of the often severe retinoic acid syndrome. Useful strategies have been described to manage these effects but current and future efforts must be directed at elucidating the mechanisms involved and determining the optimum therapeutic management. In summary, results to date indicate that the combination of tretinoin and intensive chemotherapy is more effective than chemotherapy alone and appears to improve the prognosis of newly diagnosed patients with acute promyelocytic leukaemia. Further information on the relative efficacy of various induction and post-remission strategies in subsets of patients will help determine optimum use of this promising agent in the management of acute promyelocytic leukaemia.

P450 inhibitors of use in medical treatment: focus on mechanisms of action

A number of cytochrome P450s are targets for compounds that are clinically used or under clinical evaluation for treatment of patients with mycotic infections, such as dermatophytosis, superficial and systemic candidiasis, cryptococcosis and aspergillosis, with skin diseases, such as psoriasis or ichthyosis, and other retinoid-sensitive malignancies, e.g., neuro-ectodermal glioma. Some of the P450 inhibitors are candidates for the treatment of hirsutism or prostate cancer, others are potent inhibitors of the P450 isomerase involved in the synthesis of thromboxane A2, a potent platelet aggregation inducer and vasoconstrictor.