Combined procoagulant activity and proteolytic activity of acute promyelocytic leukemic cells: reversal of the bleeding disorder by cell differentiation

In the human promyelocytic cell line HL60, we observed both a strong procoagulant activity (PCA) on the cell membrane and proteolytic activity in the lysate of these cells. Because these cell-line cells are susceptible to differentiation to either a more mature granulocytic or monocytic form, we were able to study the hypothesis that the combination of PCA and proteolytic activity is confined to the promyelocyte. This may explain the severe coagulopathy seen in patients with acute promyelocytic leukemia. Cell differentiation in a myeloid direction induced by retinoic acid or DMSO led to a diminished PCA, while not affecting the fibrinolytic activity. On the other hand, monocytic differentiation obtained by culturing the cells in the presence of 1; 25 dihydroxy vitamin D3 led to the complete disappearance of the proteolytic activity of the cell lysate, although the procoagulant activity was still present. Furthermore, we found that the elastase activity almost disappeared after monocytic differentiation. We also studied the PCA, proteolytic activity, and elastase activity of blast cells of patients with acute myeloid leukemia. Only in patients with acute promyelocytic leukemia did we observe both a strong PCA and fibrinolytic activity. This supports our hypothesis that the combination of these activities is unique to the promyelocyte and may explain the observed bleeding complications in patients with acute promyelocytic leukemia.     

In vitro generation of procoagulant activity by leukemic promyelocytes in response to cytotoxic drugs

Disseminated intravascular coagulation (DIC) is a frequent occurrence in acute promyelocytic leukemia (APL), especially after onset of chemotherapy. We have used a human promyelocytic leukemic established cell line (HL-60) and various other human leukemic cells to investigate the effect of cytotoxic drugs on generation of procoagulant activity (PCA). The results indicate that, unlike normal human peripheral blood monocytes and certain other cell types where PCA induction requires active mRNA and protein synthesis, in HL-60 cells, compounds such as actinomycin D, puromycin, and cytosine arabinoside and a variety of other cytotoxic agents, induced generation of a potent PCA. Although different in its mechanism of induction, this HL-60 cell PCA was similar, and may be identical, to mononuclear cell tissue factor. The PCA induction was rapid and preceded the lytic effect of the drugs. It was first detected on the outer cell surface but, following prolonged exposure to the drugs, upon lysis of the cells, it was also found in the extracellular medium. This in vitro effect mimics the development of DIC in patients with APL. The system may, therefore, serve as a model for the study of the cellular and molecular events associated with PCA generation by malignant promyelocytes and DIC occurrence in patients with APL and other malignancies.     

Enzyme alterations in leukemic cells

Recently, much attention has been focused on various enzyme alterations found in leukemic cells. Most of the data generated thus far has involved the study of terminal deoxynucleotidyl transferase, the purine pathway enzymes, and hexosaminidase and other lysosomal enzymes. Differences in both total enzyme activities and isoenzyme patterns have been found to occur among the various leukemia types and subtypes. These changes may prove to be useful aids in diagnosing, classifying, detecting subclinical recurrent or residual disease, and as therapeutic determinants in hematopoietic neoplasia, especially in the lymphoid malignancies.     

Elastase activity in leukemic cells.

Elastase, a proteolytic enzyme which digests different clotting factors, has previously been isolated from monocytes, macrophages and granulocytes. In the present work, we have isolated leukemic cells from 1 patient with acute lymphoblastic leukemia (ALL) and from 6 patients with acute nonlymphoblastic leukemia. Detectable elastase activity was found in the cells from all patients with acute nonlymphoblastic leukemia and ranged from 0.016 to 0.619 mukat/l/micrograms DNA. The highest elastase activity was found in 1 patient with promyelocytic leukemia (M3), and no activity was found in the cells from the patient with ALL. It is possible that elastase-mediated proteolysis of coagulation factors is the mechanism responsible for bleeding complications which are frequent in M3.     

急性白血病细胞促凝血活性的研究

用单个核白细胞分离技术，收集健康成人１１例、急性早幼粒细胞白血病１１例、其他急性因病１２例的白细胞或白血病细胞、融冻上清液及沉淀悬液分别测定其对激活的的部分凝血活酶时间、凝血酶原时间、凝血酶时间和血栓弹力图等的影响，并测定白细胞类凝血酶活性。结果表明：各组白细胞均显示有一定的促凝血作用，而ＡＰＬ白血病细胞的这一作用最强。     

Protein kinases in human leukemic cells

Protein kinase activities and cyclic AMP binding capacity were investigated in human peripheral blood cells from leukemic patients and normal controls. Using [γ³²P] ATP as phosphoryldonor, the phosphorylating activities were not found to be significantly different in either normal or leukemic cells when measured on both artificial basic and acidic substrates. In contrast, the GTP-dependent casein kinase activity, CK2, which is almost undetectable in normal granulocytes, was markedly increased in highly proliferating myeloblastic cells from patients with acute myelogenous leukemia (AML) or with chronic myelogenous leukemia in blastic crisis (BC-CML). Levels of endogenous phosphotyrosine were not higher in leukemic cells than in normal peripheral lymphocytes or granulocytes. Finally, cAMP binding capacity was found to be increased in several types of proliferating leukemic cells, due to a higher amount of the R1-type regulatory subunit of the cAMP-dependent protein kinases. Specific patterns of cAMP binding proteins observed in the different types of normal blood cells were rather blurred in leukemic cells. In conclusion, modifications observed in human leukemic cells seem to be more related to proliferation or blockage in normal differentiation than to their cellular origin.     

Cytochemistry of N-acetyl-beta-glucosaminidase in normal and leukemic T cells

A cytochemical study of the N-acetyl-beta-glucosaminidase (NABG) activity in normal and leukemic T cells was carried out to ascertain any relationships between cytochemical reactivity and membrane phenotype. Under normal conditions, most T4-positive cells, defined on the basis of monoclonal antibodies and immunogold, were characterized by focal reactivity. In chronic T lymphoproliferative disorders, the reaction product of T4-positive cells consisted of a single coarse granule, while T8-positive cells demonstrated many scattered granules. In all cases of acute T cell malignancies, lymphoblasts were positive with a single coarse granule or many coarse and small granules located at one pole of the cell.     

N-Acetylcysteine derivative inhibits procoagulant activity of human islet cells

Aims/hypothesis The early loss of beta cells after islet cell transplantation has been attributed in part to blood coagulation at the implant site. Tissue factor expressed by beta cells and contaminating duct cells is considered to activate this process. Here, we investigated the ability of N-acetyl-l-cysteine to suppress the in vitro procoagulant activity of duct cells and human islet cell preparations. Materials and methods The effects of Nacystelyn, a salt derivative of N-acetyl-l-cysteine, were first assessed on procoagulant activity induced in human plasma by recombinant tissue factor, human primary duct cells or human islet cell preparations. The influence of Nacystelyn on clot formation, platelet counts and d-dimers were measured in a whole blood tubing loop model. Human beta cell viability and insulin synthesis after Nacystelyn treatment were assessed to exclude cytotoxicity of Nacystelyn. Results Nacystelyn efficiently inhibited the procoagulant activity of human recombinant tissue factor, primary duct cells and human islet cell preparations at clinically relevant concentrations without cellular toxicity. Conclusions/interpretation Nacystelyn is a pharmaceutical candidate to reduce early beta cell loss related to tissue factor-dependent coagulation after islet transplantation. All the authors are partners of the JDRF Center for Beta Cell Therapy in Diabetes, Brussels, Belgium.     

CD1-reactive leukemic cells in bone marrow: presence of Langerhans cell marker on leukemic monocytic cells.

Langerhans cells originate in bone marrow and probably belong to the monocyte-macrophage lineage. CD1 is a specific marker of Langerhans cells. By immunofluorescence and immunoelectron microscopy, CD1a antigen and myeloid markers (CD11, CD13, CD14, CD15, CD33, HLA-DR) were studied in 53 cases of acute myeloid leukemias (AML) and 3 acute lymphoblastic leukemias (ALL). The 11 ANLL without monocytic component were CD1a negative. 2/5 of acute myelomonocytic leukemias (AML4) and 9/37 of acute monocytic leukemias (AML5) were positive. All 3 ALL were negative. No correlation was found between CD1a and myeloid markers. CD1a+ AML did not differ from CD1a- AML with regard to cytogenetics or response to therapy. The CD1a positive cells may originate from an abnormal proliferation of CD1a positive cells which are present in bone marrow and which may differentiate into Langerhans cell precursors.     

Flow cytometric analysis of P-glycoprotein in normal and leukemic cells

Summary Classical multidrug resistance is characterized by overexpression of a membrane protein, P-glycoprotein, which acts like a drug-extruding pump, reducing accumulation of cytotoxic drugs inside malignant cells. We have developed a simple method for detecting an intracellular epitope of P-glycoprotein in normal and leukemic cells by the monoclonal antibody JSB-1 and fluorescence-activated flow cytometry. Permeabilization of blood and bone marrow cells in unprocessed samples is achieved by a commercially available red blood cell lysing solution which excellently preserves the light scatter properties of leukocytes. The method is suitable for analyzing samples in clinical routine. Lower than 1% reactivity was seen in the lymphoid gate of normal peripheral blood and bone marrow samples as compared with over 60% of reacting cells in some leukemic samples. Twelve patients with acute de novo leukemia were studied at presentation, 13 patients at a refractory stage, and 28 in remission. There was a positive correlation between the P-glycoprotein and the CD 34 expression in acute myelogenous leukemia and an association between the P-glycoprotein expression and the blast count in both acute myelogenous and lymphatic leukemias.