fibrin and Leukemia--Promyelocytic--Acute

Early hemorrhagic death is still the main obstacle for the successful treatment of acute promyelocytic leukemia (APL). However, the mechanisms underlying hemostatic perturbations in APL have not been fully elucidated. Here, we report that CD44 on the membrane of APL blasts and NB4 cells ligated bound fibrinogen, resulting in in situ deposition of fibrin and abnormal fibrin distribution. Clots formed by leukemic cells in response to CD44 and fibrinogen interaction exhibited low permeability and resistance to fibrinolysis. Using flow cytometry and confocal microscopy, we found that CD44 was also involved in platelet and leukemic cell adhesion. CD44 bound activated platelets but not resting platelets through interaction with P-selectin. APL cell-coated fibrinogen-activated platelets directly induce enhanced procoagulant activity of platelets. In vivo studies revealed that CD44 knockdown shortened bleeding time, increased the level of fibrinogen, and elevated the number of platelets by approximately twofold in an APL mouse model. Moreover, CD44 expression on leukemic cells in an APL mouse model was not only associated with bleeding complications but was also related to the wound-healing process and the survival time of APL mice. Collectively, our results suggest that CD44 may be a potential intervention target for preventing bleeding complications in APL.

Topics: Animals; Estrone; Fibrin; Fibrinogen; Hemorrhage; Leukemia, Promyelocytic, Acute; Mice

The role of vascular endothelium in acute promyelocytic leukaemia (APL) remains unknown. We aimed to investigate the mechanisms by which APL cells interact with endothelial cells (ECs) and to further explore how the endothelium affects bleeding as well as therapeutic interventions.. APL cells and an original APL cell line, NB4 cells, were used for experiments. The effects of leukaemic cells on ECs were analyzed in vitro and in vivo. Moreover, the endothelial barrier function and procoagulant activity were detected. An APL mouse model was established for in vivo studies.. APL cells interacted with ECs via ICAM-1 and VCAM-1 receptors to disrupt endothelial integrity. This binding activated MLCK signaling, resulting in the trans-endothelial passage of protein and red blood cells (RBCs). Combined treatment with asiatic acid or anti-adhesion receptor antibody inhibited the response of ECs to APL cells, thereby preventing APL-associated haemorrhage in vitro and in vivo. Activated ECs exhibited a procoagulant phenotype after phosphatidylserine exposure. Plasma from APL patients formed a thin fibrin network between procoagulant ECs, and this intercellular fibrin decreased the passage of albumin and RBCs. Ex vivo addition of fibrinogen further enhanced this barrier function in a dose-dependent manner.. Endothelial damage induced by leukaemic cell adherence promotes haemorrhaging in APL. Stabilization of ECs, decreasing adhesion receptor expression, and increasing fibrinogen transfusion levels may be a new therapeutic avenue to alleviate this fatal bleeding complication.. National Science Foundation of China (81670128, 81873433).

Topics: Adult; Aged; Animals; Biomarkers; Capillary Permeability; Cell Adhesion; Cell Communication; Cell Line; Disease Models, Animal; Disease Susceptibility; Endothelial Cells; Endothelium, Vascular; Female; Fibrin; Fluorescent Antibody Technique; Hemorrhage; Humans; Intracellular Space; Leukemia, Promyelocytic, Acute; Male; Mice; Middle Aged; Models, Biological

Despite routine treatment of unselected acute promyelocytic leukemia (APL) with all-

Topics: Blood Coagulation; Cells, Cultured; Chromatin; Endothelial Cells; Fibrin; Fibrinolysis; Granulocyte Precursor Cells; Humans; Leukemia, Promyelocytic, Acute; Tretinoin; Tumor Cells, Cultured

The annexin A2 (A2) heterotetramer, consisting of two copies of A2 and two copies of S100A10/p11, promotes fibrinolytic activity on the surface of vascular endothelial cells by assembling plasminogen and tissue plasminogen activator (tPA) and accelerating the generation of plasmin. In humans, overexpression of A2 by acute promyelocytic leukemia cells is associated with excessive fibrinolysis and hemorrhage, whereas anti-A2 autoantibodies appear to accentuate the risk of thrombosis in patients with anti-phospholipid syndrome. Complete deficiency of A2 in mice leads to a lack of tPA cofactor activity, accumulation of intravascular fibrin, and failure to clear arterial thrombi. Within the endothelial cell, p11 is required for Src kinase-mediated tyrosine phosphorylation of A2, which signals translocation of both proteins to the cell surface. Here we show that p11 is expressed at very low levels in the absence of A2 both in vitro and in vivo. We demonstrate further that unpartnered p11 becomes polyubiquitinated and degraded via a proteasome-dependent mechanism. A2 stabilizes intracellular p11 through direct binding, thus masking an autonomous p11 polyubiquitination signal that triggers proteasomal degradation. This interaction requires both the p11-binding N-terminal domain of A2 and the C-terminal domain of p11. This mechanism prevents accumulation of free p11 in the endothelial cell and suggests that regulation of tPA-dependent cell surface fibrinolytic activity is precisely tuned to the intracellular level of p11.

Topics: Animals; Annexin A2; Antiphospholipid Syndrome; Autoantibodies; Cell Line, Tumor; Endothelial Cells; Fibrin; Fibrinolysin; Fibrinolysis; Hemorrhage; Humans; Leukemia, Promyelocytic, Acute; Mice; Mice, Knockout; Oncogene Protein pp60(v-src); Proteasome Endopeptidase Complex; Protein Binding; Protein Transport; S100 Proteins; Thrombosis; Tissue Plasminogen Activator; Ubiquitin; Ubiquitination

The bleeding syndrome of acute promyelocytic leukemia (APL) is complex and consists of disseminated intravascular coagulation (DIC) and hyperfibrinolysis. Elastase, derived from malignant promyelocytes, is believed to mediate the fibrinogeno- and fibrinolysis by aspecific proteolysis. In this study we measured the role of elastase in fifteen patients with APL by using an assay for elastase degraded fibrin(ogen) and the results were compared with those obtained in patients with sepsis induced DIC. High levels of elastase were observed in sepsis and APL. The levels of fibrinogen and fibrin degradation products were significantly higher in APL patients compared to patients with sepsis induced DIC. Nevertheless, the level of elastase degraded fibrin(ogen) was higher in the sepsis group (635.3 ng/ml, compared to 144.3 ng/ml in APL; p <0.0001). So, the enormous increase in fibrin and fibrinogen degradation products in APL cannot be explained by elastase activity. This study suggests a minor role for elastase mediated proteolysis in the hemorrhagic diathesis in APL patients.

Topics: Adult; Aged; Aged, 80 and over; Antibodies, Monoclonal; Blood Coagulation Tests; Disease Susceptibility; Disseminated Intravascular Coagulation; Female; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Fibrinolysis; Hemorrhage; Humans; Leukemia, Promyelocytic, Acute; Male; Middle Aged; Neoplasm Proteins; Pancreatic Elastase; Sepsis

The bleeding diathesis in patients with acute promyelocytic leukemia (APL) is generally attributed to disseminated intravascular coagulation (DIC), initiated by the release of procoagulant activity from leukemic cells. Primary fibrinogenolysis, mediated by the release of leukocyte proteases, may also contribute to this disorder. We analyzed coagulation parameters in 15 non-septic APL patients. Before treatment, there was evidence of thrombin activation with DIC: increased levels of circulating thrombin-antithrombin III complexes, prothrombin fragments 1 + 2 and D-Dimer complexes. This DIC syndrome was probably limited, since no prothrombin time decrease, no significant factor V consumption, and normal levels of coagulation inhibitors (antithrombin III and protein C) were observed in APL patients when compared to normal controls. In this context, marked hypofibrinogenemia suggested primary fibrinogenolysis as the predominant etiology. Despite normal or high tissue plasminogen activator (tPA) and plasminogen activator inhibitor (PAI-1) antigen levels, the plasma PAI-1 activity and the formation of tPA/PAI-1 complexes were lower in APL patients than in normal controls, suggesting a proteolytic degradation of PAI-1, not able to complex tPA. Two other fibrinolytic inhibitor molecules (alpha-2 plasmin inhibitor antigen and histidine-rich glycoprotein antigen) were also significantly reduced, as well as the two subunits of fibrin stability factor XIII, although only subunit A is known to be susceptible to thrombin action. Evidence of degraded forms of von Willebrand factor in the plasma suggested an extended proteolytic activity. Four patients treated with all-trans-retinoic acid (ATRA) as a single differentiating agent were studied serially. A dissociation between these two syndromes--DIC and fibrinogenolysis/proteolysis--was observed. The rapid correction of the lysis markers contrasted with a more prolonged persistence of the procoagulant activity. We observed persistently high elastase/alpha 1-proteinase inhibitor complex levels during ATRA therapy, despite progressive correction of all lysis markers. Thus, the release of elastase from promyelocytic leukemic cells is probably not the only determinant of the fibrinogenolytic/proteolytic syndrome. In summary, the present findings provide new arguments for the association of DIC and proteolysis syndromes in APL-associated coagulation disorders. Further prospective studies are needed in order to confirm the pers

Topics: Adolescent; Cell Differentiation; Child; Disseminated Intravascular Coagulation; Female; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Humans; Leukemia, Promyelocytic, Acute; Male; Middle Aged; Prospective Studies; Thrombin; Time Factors; Tretinoin

The glycoprotein P-selectin is a cell adhesion molecule of stimulated platelets and endothelial cells, which mediates the interaction of these cells with neutrophils and monocytes. It is a membrane component of cell storage granules, and is a member of the selectin family which includes E-selectin and L-selectin. P-selectin recognizes both lineage-specific carbohydrate ligands on monocytes and neutrophils, including the Lewis x antigen, sialic acid, and a protein component. In inflammation and thrombosis, P-selectin may mediate the interaction of leukocytes with platelets bound in the region of tissue injury and with stimulated endothelium. To evaluate the role of P-selectin in platelet-leukocyte adhesion in vivo, the accumulation of leukocytes within an experimental thrombus was explored in an arteriovenous shunt model in baboons. A Dacron graft implanted within an arteriovenous shunt is thrombogenic, accumulating platelets and fibrin within its lumen. These bound platelets express P-selectin. Here we show that antibody inhibition of leukocyte binding to P-selectin expressed on platelets immobilized on the graft blocks leukocyte accumulation and inhibits the deposition of fibrin within the thrombus. These results indicate that P-selectin is an important adhesion molecule on platelets, mediating platelet-leukocyte binding in vivo, that the presence of leukocytes in thrombi is mediated by P-selectin, and that these leukocytes promote fibrin deposition.

Topics: Animals; Antibodies, Monoclonal; Arteriovenous Shunt, Surgical; Blood Platelets; Cell Adhesion Molecules; Fibrin; Humans; Kinetics; Leukemia, Promyelocytic, Acute; Leukocytes; Mice; Mice, Inbred BALB C; Microscopy, Electron, Scanning; P-Selectin; Papio; Platelet Adhesiveness; Platelet Membrane Glycoproteins; Polyethylene Terephthalates; Tumor Cells, Cultured

The coagulation abnormalities in 20 cases of acute promyelocytic leukemia (APL) treated at a single institution were reviewed. A remarkably uniform picture of defibrination and increased FDPs with well-preserved levels of other coagulation factors including AT-III was seen. Our data, together with those available in the literature, do not support DIC as the underlying mechanism of bleeding but seem rather to point to increased proteolysis as the cause.

Topics: Adult; Blood Coagulation Disorders; Female; Fibrin; Fibrinolysis; Hemorrhage; Humans; Leukemia, Promyelocytic, Acute; Male; Retrospective Studies

A promyelocytic leukemia cell line, PL-21, was found to produce an inhibitor of plasminogen activators (PAI). The PAI reacted to anti-PAI-2 but not anti-PAI-1 anti-serum and had an apparent molecular weight of 43 kDa on unreduced SDS-PAGE. The PAI inhibited not only urokinase-type plasminogen activator (u-PA) but single- and two-chain tissue-type plasminogen activators (t-PAs) on plasminogen-containing fibrin plate. It formed SDS-stable complexes with both t-PA and u-PA but not with prourokinase as demonstrated by both fibrin zymography and immunoblotting using anti-PA and anti-PAI-2 antisera after SDS-PAGE. These complexes were still present even after reduction with dithiothreitol. The PAI appears to bind to the carboxy-terminal chain of both PAs, because the part of the band corresponding to the carboxy-terminal chain of PAs moved to an upper position as a result of complex formation when two-chain form of PAs were incubated with the PAI and analyzed by SDS-PAGE followed by immunoblotting.

Topics: Amino Acid Sequence; Electrophoresis, Polyacrylamide Gel; Fibrin; Humans; Immunoblotting; Leukemia, Promyelocytic, Acute; Molecular Sequence Data; Plasminogen Activators; Plasminogen Inactivators; Protein Binding; Tumor Cells, Cultured