High Fibrinopeptide A (FPA) Levels in Acute Non-Lymphocytic Leukemia Are Reduced by Heparin Administration

Activation markers of coagulation

Advances in our understanding of the biochemistry of the haemostatic mechanism have led to the development of sensitive methods for measuring peptides, enzyme-inhibitor complexes, and enzymes that are liberated with the activation of the coagulation system in vivo. Studies employing these markers have provided important mechanistic information regarding haemostatic mechanism function both under normal conditions and in response to pathogenic stimuli. While assays for particular components can denote the presence of a 'biochemical' hypercoagulable state prior to the appearance of overt thrombotic phenomena, most of these markers thus far have not been shown to be useful in managing individual patients. Properly designed prospective studies will be required to determine whether these assay techniques will aid in the identification of patients predisposed to thrombotic events or the monitoring of antithrombotic therapy.

Activation markers of coagulation

Advances in our understanding of the biochemistry of the haemostatic mechanism have led to the development of sensitive methods for measuring peptides, enzyme-inhibitor complexes or enzymes that are liberated with the activation of the coagulation system in vivo. Studies employing these markers indicate that a biochemical imbalance between procoagulant and anticoagulant mechanisms can be detected in the blood of humans prior to the appearance of thrombotic phenomena. Properly designed prospective studies will be required to determine whether these assay techniques will enable us to identify individuals who are entering a clinically relevant hypercoagulable state, and intervene with appropriate therapy prior to the onset of overt thrombotic disease.

Supranormal antithrombin III levels induced by concentrate administration are ineffective in quenching thrombin generation in acute promyelocytic leukemia

Coagulation abnormalities occurring in patients with acute promyelocytic leukemia (APL) are partially corrected by heparin administration. This study was undertaken to verify if "supra-normal" levels of antithrombin III (AT-III) are similarly able to quench intravascular thrombin generation triggered by APL cells. Eight patients with APL were randomly assigned to receive either 50 U/kg (Group A) or 100 U/kg (Group B) of an AT-III concentrate, starting on the first day of chemotherapy and continuing for 7 days thereafter. Fibrinopeptide A (FPA), prothrombin fragment F1+2 and thrombin-AT III complexes, measured before and 15 minutes after each AT-III infusion, decreased significantly after each infusion, but the effect was minimal and short-lived, despite the achievement of post-infusion levels of AT-III activity well above 150% (Group A) or 200% (Group B). Small amounts of heparin were consistently detected in AT-III concentrates and post-infusion plasma samples. The short-lived quenching of thrombin generation after AT-III concentrate could be partially explained by the infusion of heparin, rather than by supranormal AT-III levels.

Hemostasis in malignancy

Hemostatic abnormalities are present in a majority of patients with metastatic cancer. These abnormalities can be categorized as 1) increased platelet aggregation and activation, 2) abnormal activation of coagulation cascade, 3) release of plasminogen activator, and 4) decreased hepatic synthesis of anticoagulant proteins like Protein C and antithrombin III. The abnormal activation of coagulation cascade is mediated through release of Tissue Factor, Factor X activators, and other miscellaneous procoagulants from the plasma membrane vesicles of tumor cells. Macrophages of a tumor-bearing host also produce increased amounts of Tissue Factor. Production of Factor X activators and macrophage Tissue Factor is decreased by warfarin. The ability of the tumor cells to produce platelet-aggregating activity and plasminogen activator parallels their metastatic potential in animal and experimental systems. These studies also show that antiplatelet agents and antibodies against plasminogen activator can suppress the metastatic process. One or more laboratory abnormalities of hemostasis can be shown in up to 95% of patients with metastatic cancer. These abnormalities, however, are unable to predict subsequent development of thromboembolic or hemorrhagic complications. Clinical complications occur in 9-15% of the patients in the form of thrombotic or hemorrhagic disorders. The therapy of tumor-related coagulopathy should be guided by its clinical expression. Subclinical DIC should not be treated. Coumadin is generally ineffective for therapy of thrombosis in cancer patients. There is no consensus regarding the use of heparin in acute promyelocytic leukemia (APL). The defibrination in APL may be from disseminated intravascular coagulation as well as systemic fibrinolysis, as shown by decreased alpha 2 antiplasmin levels. In such cases, epsilon aminocaproic acid plus heparin therapy may be of benefit.

What's new in the causes of hemorrhage in acute myelogenous leukemia?

Hemorrhages in AML are still a major problem, although not the most important and different factors are involved in its genesis. The causes that predispose an AML patient to bleed will be reviewed, the hypotheses concerning the coagulation disorder specially found in the FAB M3 type will be discussed and the increasingly recognized role of plasminogen activators and enzymes released from blasts will be emphasized.

Relationship of thrombin generation to peripheral blast cell count in patients with acute myeloblastic leukemia (AML)

Disseminated intravascular coagulation (DIC) commonly occurs in patients with acute promyelocytic leukemia (APL, FAB-M3) but may also be seen in other subtypes of AML. DIC in patients with AML has been attributed to procoagulants released from granular fractions of leukemic blast cells. The present study was designed (i) to evaluate thrombin activity in patients with AML by measuring plasma levels of fibrinopeptide A (FPA) prior to chemotherapy, and (ii) to examine whether a relationship between FPA levels and the number of peripheral blast cells exists. Plasma levels of FPA were determined using a commercially available RIA kit. To remove fibrinogen and the majority of elastase-induced fibrinopeptides (A alpha 1-21) known to crossreact with the FPA (A alpha 1-16) antiserum used in this assay, plasma samples were treated with bentonite prior to further processing. The study was conducted on 5 patients with APL and on 22 patients with other subtypes of AML. Peripheral blast cell counts at initial diagnosis ranged from 2100 to 56,000/microliters in patients with APL and from 1900 to 151,000/microliters in patients with other AML subtypes. The mean (+/- 1 SEM) pretreatment plasma level of FPA was significantly higher (p = 0.021) in the 5 patients with APL (38.2 +/- 8.3 ng/ml) than in patients with other AML subtypes (8.1 +/- 0.7 ng/ml). No relationship was found between peripheral blast cell counts and the corresponding FPA levels in the total group of 27 patients. However, when considering the 5 patients with APL separately, a significant correlation was observed between peripheral blast cell number and FPA plasma levels (r = 0.88, p = 0.050). This study confirms that thrombin generation is considerably greater in patients with acute promyelocytic leukemia than in other subtypes of AML. We conclude that type and number of circulating blast cells and their related capacity to express procoagulant activities appear to be major determinants of excessive fibrinogen degradation in AML.

Fibrinopeptide A changes during remission induction treatment with L-asparaginase in acute lymphoblastic leukemia: evidence for activation of blood coagulation

L-Asparaginase, a widely used antileukemic agent, inhibits liver protein synthesis leading to hypofibrinogenemia and hypoprothrombinemia together with a severe reduction of antithrombin III and protein C. An increased risk of thrombosis has been reported in leukemic patients treated with this agent. We measured fibrinopeptide A (FPA) changes in 14 patients with acute lymphoblastic leukemia during induction remission treatment with a protocol including L-Asparaginase (10,000 U/m2/daily intravenous for 14 days). At diagnosis, 9/14 patients had FPA level above upper limit of normal range (mean = 4.1 ng/ml). After two days of therapy, FPA rose to 5.2 ng/ml and thereafter showed a slight increase throughout. Antithrombin III, protein C and fibrinogen dropped to its nadir on day 6 and 9. However, the ratio FPA/fibrinogen on a molar basis showed a three-fold increase during this days, demonstrating that the thrombin-dependent consumption of fibrinogen was also increased. In conclusion, our data show that activation of blood coagulation occurs in concomitance with the hemostatic derangement caused by L-Asparaginase. Replacement therapy with the recently available antithrombin III concentrates may be worthy of a clinical trial to test its effectiveness in preventing the thrombotic phenomena reported in these patients.

Tissue factor gene expression in acute myeloblastic leukemia

We have studied tissue factor gene expression in the leukocytes of 22 patients with acute myeloblastic leukemia (AML). Total RNA from peripheral blood or bone marrow cells depleted of monocytes was analyzed by Northern blot analysis using a 32P-labeled tissue factor cDNA probe. Cells from 10 cases expressed tissue factor mRNA and positive cases were distributed among the myeloblastic, myelomonocytic, and monocytic subtypes of AML. Tissue factor transcripts were not detected in cells derived from normal bone marrow. The expression of this gene product on the surface of leukemic cells could contribute to the excessive thrombin generation that has been observed in some individuals with this disorder.

Clinical significance of fibrinopeptide A in acute lymphocytic and non-lymphocytic leukaemia

Fibrinopeptide A (FPA) was systematically investigated in 74 patients with acute leukaemia at different stages of the disease (50 with non-lymphocytic leukaemia, ANLL; 24 with lymphocytic leukaemia, ALL). At diagnosis, 75% of the cases had high FPA levels (86% in ANLL and 54% in ALL) with significantly higher levels in ANLL than in ALL (13.4 vs 4.4 ng/ml; p less than 0.001). Patients with DIC (20 cases in ANLL and 1 case in ALL) had significantly higher levels (p less than 0.001). FPA levels were neither correlated with fibrinogen or FDP levels nor with blast cell count. During chemotherapy, median FPA did not show significant changes whereas, at the end of therapy, a return toward normality was generally observed both in ALL and ANLL apart from the group of patients with acute promyelocytic leukaemia. Among the 24 patients who entered post-remission follow-up (13 ANLL and 11 ALL), 10 cases out of the 11 relapsing (6/6 with ANLL and 4/5 with ALL) had increased FPA 1 to 2 months before the ascertainment of the relapse. However, 16% and 9% of the samples obtained on different occasions, respectively from ANLL and ALL cases in maintained first remission, showed FPA above the normal limit. This study demonstrates that subclinical activation of blood coagulation, as indicated by high FPA level, is common both in lymphocytic and non-lymphocytic leukemia and suggests that this phenomenon is related to disease activity.

Depressed fibrinolysis in patients with acute leukaemia

The fibrinolytic system was studied in 46 patients with acute leukaemia at diagnosis. Untreated patients (with the sole exception of the M3 subgroup) showed an inhibition of fibrinolytic activity, measured by the euglobulin lysis time and area. This inhibition was accompanied by reduced t-PA antigen and t-PA inhibitor activity. No correlation was found between the above-mentioned fibrinolytic parameters and the biochemical haematological values considered, nor with clinical and/or laboratory features of DIC, fever, liver failure. The decrease in immunological plasminogen and functional alpha 2-antiplasmin, showed a significant correlation with the presence of clinical and/or laboratory signs of DIC, as diagnosed on the basis of concomitant increase in fibrin monomers, plasmatic fibrinopeptide A and serum FDP.