Promyelocytic Line HL-60 Research Articles

Indirect immunofluorescence on human B lymphoma cell line Raji and promyelocytic line HL60 for detection of DNA-associated autoantibodies to cell membrane in systemic lupus erythematosus

Objective To compare the significance of DNA-associated autoantibodies to cell membrane(cmDNA)in systemic lupus erythematosus(SLE)detected with indirect immunofluorescence on human B lymphoma cell line Raji and pmmyelocytic line HL60.Methods Indirect immunofluorescence assay both on cell line Raji and HL60 was used to measure anti-cmDNA antibodies in sera of 306 SLE patients.192 patients with other rheumatic diseases and 50 healthy controls.Results Indirect immunofluorescence assay on cell line Raji was used to measure anti-cmDNA antibodies.72.5% SLE and 10.4% other rheumatic diseases were positive for anti-cmDNA,but negative in 50 blood donors(P 0.05).The methods of culture,freeze and resuscitation on the two cells were similar.but cell line Raji was easier to resuscitate than cell line HL60.Observing with fluorescence microscope.we find that cmDNA was expressed on the both cells and the staining was stronger on cellline Raji than HL60.Conclusion Anti-cmDNA antibody has high positivity which is one of the most valuable marker in the diagnosis of SLE.We recommend to measure anti-cmDNA antibodies with indirect immunofluorescence assay on cell line Raji rather than HL60. Key words: Lupus erythematosus,systemic; Autoantibodies; Anti-cmDNA antibodies; Cell line Raji; Cell line HL60

Hemodynamic effects of peptide fragments of differentiation factor HLDF

Hemodynamic activity of peptides from differentiation factor HLDF (promyelocytic HL-60 line) was studied on WKY and SHR-SP rats. Intravenous infusion of the test peptides was accompanied by changes in blood pressure and heart rate, which depended on the structure of peptides and functional activity of the organism and differed in normotensive and hypertensive animals.

Induction of Apoptosis in HL-60 Human Promyelocytic Leukemia Cells by Adenosine A3Receptor Agonists

The effects of adenosine (ADO) analogs on cells of the human promyelocytic HL-60 line were examined. ADO A3receptor agonists, N6-(3-iodobenzyl)adenosine-5′-N-methylcarboxamide (IB-MECA, 30–60 μM) and 2-chloro-N6-(3-iodobenzyl)adenosine-5′-N-methyluronamide (CI-IB-MECA, 10–30 μM) induced apoptotic cell death. In contrast, neither an A1/A2antagonist (XAC) nor other selective ADO receptor agonists (CPA, NECA and CGS21680) induced apoptosis at concentrations of ≤30 μM. Both IB-MECA and CI-IB-MECA significantly induced Ca2+release from intracellular Ca2+pools followed by Ca2+influx, suggesting the presence of phospholipase C-coupled ADO A3receptors on HL-60 cells. This was further supported by the presence of mRNA of ADO A3 receptor in the cells. These results suggest that activation of ADO A3receptors is responsible for the ADO-induced apoptosis in HL-60 cells and could be of potential therapeutic value in the treatment of leukemia.

Expression of Bruton's agammaglobulinemia tyrosine kinase gene, BTK, is selectively down-regulated in T lymphocytes and plasma cells.

The gene mutated in the human disease, X-linked agammaglobulinemia (XLA), is related to the Src gene family of cytoplasmic protein-tyrosine kinases and is designated Btk (Bruton's agammaglobulinemia tyrosine kinase; formerly Atk/Bpk; the human gene is denoted BTK, using capital letters according to the kinase nomenclature). We have recently reported that this gene is expressed in B lymphocytes and that the specific mRNA was undetectable in T cells using Northern blotting. Further analyses of different sources of B and T lymphocytes confirmed this pattern. However, BTK transcripts were undetectable in four plasmacytoma lines. Moreover, as virtually normal amounts of BTK transcripts were found in PBMC from two patients carrying a point mutation in BTK, despite low B cell numbers, we anticipated that the gene would also be expressed in cells of other lineages. The erythroleukemia cell line K-562, the promyelocytic line HL-60 and the histiocytic lymphoma line U-937 were found to have BTK mRNA levels comparable to B cells. BTK mRNA was also detected in monocytes from healthy donors as well as in the human immature basophilic cell line KU812, in the human mast cell leukemia cell line HMC-1 and in the CD34 expressing myeloblast KG-1. A similar expression pattern was obtained when BTK protein was analyzed by immunoprecipitation and Western blotting. Using a polymerase chain reaction-based analysis, a small amount (less than 1% of the level in B cells) of BTK mRNA was identified in T lymphocytes. Our findings are compatible with a general expression of the BTK gene in hematopoietic cells, except in T lymphocytes and plasma cells, in which the transcript level is selectively down-regulated.

Different patterns of apoptosis of HL‐60 cells induced by cycloheximide and camptothecin

Cells of the human promyelocytic HL-60 line, when treated with a variety of antitumor agents in the presence of the protein synthesis inhibitor cycloheximide (CHX), or with CHX alone, rapidly undergo apoptosis ("active cell death"). It is presumed, therefore, that such cells are "primed" to apoptosis in that no new protein synthesis is required for induction of their death. We have studied apoptosis of HL-60 cells triggered by the DNA topoisomerase I inhibitor camptothecin (CAM) in the absence and presence of CHX and apoptosis induced by CHX alone. Two different flow cytometric methods were used, each allowing us to relate the apoptosis-associated DNA degradation to the cell cycle position. Apoptosis induced by CAM was limited to S phase cells, e.g., at a CAM concentration of 0.15 microM, nearly 90% of the S phase cells underwent apoptosis after 4 h. In contrast, apoptosis triggered by CHX was indiscriminate, affecting all phases of the cycle: approximately 40% of the cells from each phase the cycle underwent apoptosis at 5 microM CHX concentration. When CAM and CHX were added together, the pattern of apoptosis resembled that of cycloheximide alone, namely, cells in all phases of the cycle in similar proportion were affected. Thus, CHX, while itself inducing apoptosis of a fraction of cells, protected the S phase cells against apoptosis triggered by CAM. Because CHX (5 microM) did not significantly affect the rate of cell progression through S phase, the observed protective effect was most likely directly related to inhibition of protein synthesis, rather than to its possible indirect effect on DNA replication. Furthermore, whereas apoptosis (DNA degradation) triggered by CAM was prevented by the serine protease inhibitor N-tosyl-L-lysylchloromethyl ketone (TLCK), this process was actually potentiated by this inhibitor when induced by CHX. The present data indicate differences in mechanism of apoptosis triggered by CAM (and perhaps other antitumor drugs) as compared with CHX. Apoptosis caused by CHX may be unique in that it may not involve new protein synthesis. These data are compatible with the assumption that the loss of a hypothetical, rapidly turning over suppressor of apoptosis may be the trigger of apoptosis of HL-60 cells treated with CHX, whereas de novo protein synthesis is required when apoptosis is triggered by other agents.

Differential expression of the histone H1 zero gene in U937 and HL-60 leukemia cell lines.

The expression of the human H1 zero histone gene and of a main type H1 gene was analyzed in two human leukemia cell lines. The main type, replication dependent H1 gene expression reflected the state of proliferation of both cell lines. No H1 zero mRNA was detected in the promyelocytic HL-60 line, whereas the monocytic U937 cells showed low steady-state levels of 1H zero mRNA. Stimulation of HL-60 with several known inducers of differentiation failed to induce any accumulation of H1 zero mRNA. Treatment of U937 with phorbol ester or butyrate, on the other hand, led to an increase of the H1 zero mRNA concentration.

1,25-Dihydroxyvitamin D3 induces monocytic differentiation of the PLB-985 leukemic line and promotes c-fgr mRNA expression.

1,25-dihydroxyvitamin D3 [1,25(OH)2D] is known to stimulate maturation of the human promyelocytic line HL-60 and murine bone marrow precursor cells along a monocyte/macrophage pathway. In this study, the steroid's effects on the PLB-985 leukemic line were examined. We found that 1,25(OH)2D induces monocytic differentiation of PLB-985 as manifested by morphological appearance, histochemical staining, and changes in cell surface antigen expression. Additionally, there was acquisition of functional monocyte characteristics including phagocytic activity and superoxide anion production via the respiratory burst pathway. Steady state levels of mRNA derived from the leukocyte-specific proto-oncogene c-fgr were also increased by the steroid. Thus, 1,25(OH2)D effectively differentiates PLB-985 cells along a monocytic pathway, providing a useful model of macrophage differentiation.

Genuine CD7 expression in acute leukemia and lymphoblastic lymphoma

CD7 has been used as a valuable marker for normal and malignant T cells and also for a proportion of acute nonlymphocytic leukemia (ANLL) cells. Difference in reactivity was noticed among CD7 antibodies, however, when tested against ANLL cells and myeloid/monocytoid cell lines; Tp40 antibody produced in our laboratories was not reactive with the HL-60 promyelocytic line, whereas 4A antibody was reactive, even though both detected a quite similar or an identical epitope on CD7 molecule. Preincubation of HL-60 cells with human immunoglobulin preparation clearly negated the reactivity by 4A, suggesting that 4A antibody is not reactive to CD7 itself, but it probably binds with immunoglobulin G Fc receptors expressed on HL-60 cells. Five cases of ANLL which were positive with 4A antibody were selected and tested with Tp40 antibody, and only two were found to be positive. Expression of CD7 mRNA in these two cases (but not in other cases) was also demonstrated by Northern blotting with a cDNA probe for CD7 recently cloned in our laboratories, indicating that CD7 is expressed on a certain fraction of ANLL, although the positive cases may be smaller than the reports so far appeared. A Northern blot study was also conducted with two acute lymphocytic leukemia cases and one lymphoblastic lymphoma case with CD7 +, CD2 −/+, CD5 −/+ phenotype and germline T cell receptor β genes. CD7 mRNA is expressed in all three cases and CD3 mRNA is also observed in two cases, suggesting that these tumor cells are of T precursor origin.

Redox Buffering Ability of Lymphoid Cells Evaluated by the Oxidation of 2′,7′-Dichlorofluorescin

The redox buffering activity of several lymphoid cells against endogenous and exogenous H2O2 has been evaluated using 2',7'-dichlorofluorescin diacetate (DCFH2-DA). The mechanism of 2',7'-dichlorofluorescin (DCFH2) oxidation has also been investigated. It was found that while the oxidation by external H2O2 is completely inhibited by azide or cyanide, the oxidation by endogenous species is still present, even under anaerobic conditions. The data herein reported indicate that autoxidation and peroxidation of DCFH2 are distinct reactions. Hence only by addition of increasing concentrations of exogenous hydrogen peroxide, the fluorescence of DCF can be used to evaluate the cellular ability of scavenging H2O2. By this method we have found that the erythroleukaemia cell line K562 and promyelocytic line HL-60 show a faster rate of DCFH2 oxidation than peripheral blood leukocytes (PBL), mature T-cells (MOLT-3 and MOLT-4) and B-cells (DAUDI). Using this method the balance between antioxidant enzymes activity and the redox state of the cell can be easily assessed by fluorescence both in single cells and in cell populations.

Use of monoclonal antibody against human neutrophil elastase in normal and leukaemic myeloid cells.

A monoclonal antibody, NP57, was produced and used against the neutrophil granule protein elastase, which selectively stain neutrophils in cryostat and paraffin wax sections. The antibody stains neutrophils and a subpopulation of monocytes in blood smears and neutrophil precursors in bone marrow smears, and gives positive reactions with the cell lines HL60 and U-937. It labelled the blast cells in 68% of cases of acute myeloid leukaemia (M1-M5) but was unreactive with all cases of lymphoid leukaemias. Most of the elastase negative myeloid leukaemias were labelled by monoclonal anti-myeloperoxidase (antibody MPO-7) as were cells from the promyelocytic line HL60. No cases of myeloid leukaemia showed the opposite pattern--that is elastase positive, myeloperoxidase negative, suggesting that the production of myeloperoxidase precedes the onset of elastase synthesis during myeloid maturation. The anti-elastase antibody NP57 is a useful addition to the range of monoclonal antibodies available for the differential diagnosis of acute leukaemia by alkaline phosphatase-antialkaline phosphatase (APAAP) labelling of cell smears; it may also be of value for the histopathological diagnosis of tumour deposits in myeloid leukaemia and for the detection of neutrophils in paraffin sections.

Receptors for B cell stimulatory factor 2. Quantitation, specificity, distribution, and regulation of their expression.

B cell stimulatory factor 2 receptors (BSF-2-R) were studied using radioiodinated recombinant BSF-2 with a specific activity of 6.16 X 10(13) cpm/g. Kinetic studies showed that binding of 125I-BSF-2 to CESS cells reached maximum level within 150 min at 0 degrees C. There was a single class of receptors with high affinity (Kd 3.4 X 10(-10) M) on CESS, and the number of receptors was 2,700 per cell. Binding of 125I-BSF-2 to CESS was competitively inhibited by unlabeled BSF-2 but not by IL-1, IL-2, IFN-beta, IFN-gamma, and G-CSF, indicating the presence of the receptors specific for BSF-2. EBV-transformed B lymphoblastoid cell lines (CESS, SKW6-CL4, LCL13, and LCL14) expressed BSF-2-R, whereas Burkitt's lines did not. EBV or EBNA2 did not induce the expression of the receptors on Burkitt's cells. The plasma cell lines (ARH-77 and U266) expressed BSF-2-R, fitting the function of BSF-2 as plasma cell growth factor. Several other cell lines, the histiocytic line U937, the promyelocytic line HL60, the astrocytoma line U373 and the glioblastoma line SK-MG-4, in which BSF-2 was inducible with IL-1 or TPA, displayed BSF-2-R with Kd in the range of 1.3-6.4 X 10(-10) M, suggesting the autocrine mechanism in BSF-2 function. The four T cell lines (CEM, HSB, Jurkat, and OM 1) did not express a detectable number of receptors, but normal resting T cells expressed 100-1,000 receptors per cell. BSF-2-R were not present on normal resting B cells but expressed on activated B cells with a Kd of 3.6-5.0 X 10(-10) M, fitting the function of BSF-2, which acts on B cells at the final maturation stage to induce immunoglobulin production.

Differences in the plasma membrane glycoproteins of cultured myeloblastoid and promyelocytic human leukemia (HL60) cells

Since the mechanisms that control synthesis of surface and internal granule membranes are closely-related within the Golgi apparatus, we have compared the plasma membrane proteins and glycolipids of cells of the human promyelocytic line HL-60 with those of its agranular myeloblastoid variant (HL60-D), and of other human myeloid lines (KG-1a, KG-1 and ML-2). Proteolytic degradation by granule enzymes altered the protein profiles unless multiple inhibitors were included in the cell suspension before lysis and during subsequent handling of the extracts. Polyacrylamide gel electrophoretic profiles of the proteins accessible to lactoperoxidase-catalyzed 125I-labeling or to periodate [ 3H]-borohydride labeling, as well as those of the glycoproteins bound to and eluted from immobilized concanavalin A, showed distinct patterns. The apparent molecular weights of the two major sialylated glycoproteins were larger in cell lines with a greater content of azurophilic granules. Also, the blastic line incorporated less fucose into glycolipid and contained less complex gangliosides and neutral glycolipids than did the parent. These data demonstrate that, within the limits of this culture model, cells capable of cytoplasmic granule production express a different constellation of surface components.

Myeloperoxidase: its structure and expression during myeloid differentiation

Myeloperoxidase (MPO) is a major protein present in myeloid cells and is used by these cells to help kill microbes. The human promyelocytic HL-60 line can be induced to differentiate to granulocytes or macrophagelike cells. Poly (A) containing RNA was isolated from HL-60 granulocytes, HL-60 macrophages, HL-60 blasts, and normal human granulocytes. The mRNA was translated in a reticulocyte lysate system in the presence of 35S-methionine. The MPO was precipitated from the lysate with rabbit IgG antiserum to human MPO. The resulting precipitate from HL-60 blasts gave a major band of radioactivity of approximately 77,000 daltons and another band at approximately 46,000 daltons on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The MPO identity of the labeled bands was confirmed by cold competition. The relative mRNA activity expressed as a percentage of radioactivity incorporated into MPO (77,000-dalton band) as compared with total trichloracetic acid (TCA) precipitable radioactivity was 0.2%. Negligible mRNA activity for MPO was present in HL-60 granulocytes, HL-60 macrophages, and normal human granulocytes. Pulse- chase experiments showed that MPO was an approximate 75,000-dalton major band and 77,000-dalton minor band of radioactivity after HL-60 blasts were labeled for 1/2 hour with 35S-methionine and the cell lysate immunoprecipitated and subjected to SDS-PAGE. The chase experiments (one to 24 hours) showed that the 77,000- and 75,000-dalton bands of radioactivity were replaced with two major bands (55,000 and 15,000 daltons) and one minor band (approximately 39,000 daltons) of radioactivity. Six-hour 35S-methionine labeling experiments showed that the relative rate of MPO synthesis compared with total TCA precipitable radioactivity was 0.5% in HL-60 blasts and almost negligible in HL-60 macrophages and granulocytes, normal human granulocytes, and B- lymphocytes. The KG-1 myeloblasts and KG-1a early myeloblasts synthesized a small amount of the 75,000-dalton MPO protein. Although HL-60 cells no longer synthesized MPO after differentiation, HL-60 granulocytes and HL-60 macrophages continued to contain MPO as measured by enzyme activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Myeloperoxidase: Its Structure and Expression During Myeloid Differentiation

Myeloperoxidase (MPO) is a major protein present in myeloid cells and is used by these cells to help kill microbes. The human promyelocytic HL-60 line can be induced to differentiate to granulocytes or macrophagelike cells. Poly (A) containing RNA was isolated from HL-60 granulocytes, HL-60 macrophages, HL-60 blasts, and normal human granulocytes. The mRNA was translated in a reticulocyte lysate system in the presence of 35S-methionine. The MPO was precipitated from the lysate with rabbit IgG antiserum to human MPO. The resulting precipitate from HL-60 blasts gave a major band of radioactivity of approximately 77,000 daltons and another band at approximately 46,000 daltons on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The MPO identity of the labeled bands was confirmed by cold competition. The relative mRNA activity expressed as a percentage of radioactivity incorporated into MPO (77,000-dalton band) as compared with total trichloracetic acid (TCA) precipitable radioactivity was 0.2%. Negligible mRNA activity for MPO was present in HL-60 granulocytes, HL-60 macrophages, and normal human granulocytes. Pulse-chase experiments showed that MPO was an approximate 75,000-dalton major band and 77,000-dalton minor band of radioactivity after HL-60 blasts were labeled for 1/2 hour with 35S-methionine and the cell lysate immunoprecipitated and subjected to SDS-PAGE. The chase experiments (one to 24 hours) showed that the 77,000- and 75,000-dalton bands of radioactivity were replaced with two major bands (55,000 and 15,000 daltons) and one minor band (approximately 39,000 daltons) of radioactivity. Six-hour 35S-methionine labeling experiments showed that the relative rate of MPO synthesis compared with total TCA precipitable radioactivity was 0.5% in HL-60 blasts and almost negligible in HL-60 macrophages and granulocytes, normal human granulocytes, and B-lymphocytes. The KG-1 myeloblasts and KG-1a early myeloblasts synthesized a small amount of the 75,000-dalton MPO protein. Although HL-60 cells no longer synthesized MPO after differentiation, HL-60 granulocytes and HL-60 macrophages continued to contain MPO as measured by enzyme activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Distribution of androgen and estrogen receptors among lymphoid and haemopoietic cell lines

Estrogen receptors (ER) and androgen receptors (AR) were determined in a series of 23 leukemia or lymphoma cell lines including 8 T-cell lines, 12 B-cell lines, and 3 non lymphoid cell lines. The phenotypic characterization of these cells by currently available immunological markers provides an estimate of their stage of differentiation. The result indicate that none of the investigated cell lines bear simultaneously ER and AR. Four were found to bear ER: U266, RPM1 8226, HL60, IARC/310/LT2, and four to express AR: RAJI, IARC/301/LTI, U937, REH6. The presence of cytosolic receptors was always associated with that of nuclear receptors. The expression of either ER or AR is restricted to discrete maturation stages of different haemopoietic cell lineages. Thus AR were found among the most immature lines of the T, B or monocytic lineage but they could be detected neither in the promyelocytic line HL60, nor in the pluripotential K562. The present results are in keeping with the demonstration of AR in some leukaemic blasts or in non Hodgkin's lymphomas. In contrast with AR, ER are present in two myeloma cell lines, in the promyelocytic cell line, HL60 and in a T-cell line bearing the phenotype of mature suppressor/cytotoxic T cells.

Myeloperoxidase is synthesized as larger phosphorylated precursor.

Synthesis and processing of myeloperoxidase were examined in metabolically labeled cells of the human promyelocyte line HL-60 and in an in vitro rabbit reticulocyte lysate system directed with HL-60 mRNA. Radioactivity labeled products were isolated by immunoprecipitation and analyzed by gel electrophoresis and fluorography. In vivo, myeloperoxidase was labeled initially as a 85-K glycosylated polypeptide (75 K after treatment with endo-beta-N-acetylglucosaminidase H). This polypeptide was soon processed to an 81-K intermediate and to smaller mature fragments of 60 K and 13 K within approximately 1 day. A minor portion of the precursor was converted to fragments of 40 K and 43 K. The pattern of labeled polypeptides of mature myeloperoxidase was similar to that of the enzyme purified from human leucocytes. The modifications of the polypeptide and of the oligosaccharide side chains in myeloperoxidase resembled those known to occur during the processing of lysosomal enzymes. In the absence or presence of dog pancreas membranes, myeloperoxidase was synthesized in vitro as a 76-K polypeptide or a 87-K glycosylated polypeptide, respectively. In HL-60 cells [32P]phosphate was incorporated into endo-beta-N-acetylglucosaminidase H-sensitive oligosaccharides. The presence of phosphorylated oligosaccharides was inferred from the fact that endocytosis of leucocyte myeloperoxidase in fibroblasts was sensitive to mannose 6-phosphate. It is suggested that myeloperoxidase is synthesized in the rough endoplasmic reticulum as a precursor of larger molecular mass and that the oligosaccharide side chains in the precursor are modified to contain mannose 6-phosphate residues which may be involved in the segregation and transport of the precursor.

Three different mutations in codon 61 of the human N-ras gene detected by synthetic oligonucleotide hybridization.

The activation of ras genes in naturally occurring tumors has, thus far, been found to be due to mutations in codon 12 or 61 resulting in single amino acid substitutions. We have used highly labeled synthetic oligonucleotides to detect mutations in these codons and to determine the exact position of the mutation. Using this approach we have found three different mutations in codon 61 of the N-ras gene of various human tumor cell lines. In the fibrosarcoma line HT1080 the first nucleotide of the codon is mutated; in the promyelocytic line HL60 the second and in the rhabdomyosarcoma line RD301 the third nucleotide. For RD301 this implies that the normal glutamine residue at position 61 is replaced by histidine. In addition to the mutated N-ras gene the three cell lines have a normal N-ras gene which is indicative of the dominant character of the mutations.

Synthesis of cathepsin B by cells derived from the HL60 promyelocytic leukaemia cell line.

Cells of the human promyelocytic HL60 line were induced to differentiate into granulocyte-like cells with dimethylsulphoxide (DMSO) or macrophage-like cells with 12-0-tetradecanoylphorbol-13-acetate (TPA). The synthesis of Cathepsin B by these cells was studied by immunoperoxidase staining and assay of cell lysates using the fluorimetric substrate benzoyloxycarbonyl-phenylanalyl-arginine-4-methyl-7-coumarylamide. Only 2-5% of the uninduced HL60 cells and DMSO-induced cells were immunohistochemically positive for Cathepsin B, compared with over 80% of the TPA-induced cells. Cathepsin B activity was lowest in the lysates of uninduced HL60s. DMSO-induced cells contained 1.5-2-fold the enzyme activity of HL60s and TPA-induced cell lysates demonstrated 5-14-fold the activity of uninduced HL60s. Induction of Cathepsin B synthesis was therefore associated with differentiation of the promyelocytes into cells of the monocyte/macrophage type, but not granulocyte-like cells. Cathepsin B was located immunohistochemically in human palatine tonsils. The enzyme was only demonstrated within macrophages in these tissues. Cathepsin B may therefore be a useful immunohistochemical marker for malignant and nonmalignant cells of the monocyte/macrophage lineage.

Mechanisms for induction of differentiation in the human promyelocytic cell line HL-60.

Acute myeloid leukemia (AML) is characterized by a block in cell differentiation. Leukemic cell lines which grow continuously in vitro can be used to explore regulation of differentiation in leukemia. The promyelocytic HL-60 line [3] is induced to mature into granulocytes by incubation with agents such as dimethylsulfoxide (DMSO) [4] and retinoic acid (RA) [2]. The mechanisms by which these and other agents induce differentiation are unknown. Knowledge of them could improve understanding of the defects in terminal differentiation characteristic of AML. We have concentrated on mechanisms of action of RA, DIF (see below), and cAMP-inducing agents [1] because these act at low concentrations and most of them are regarded as physiological. Nitroblue tetrazolium (NBT) reduction has been used as the parameter of induced differentiation as it is a reliable measure of functional maturation in HL-60.KeywordsAcute Myeloid LeukemiaRetinoic AcidLeukemic Cell LineHuman Promyelocytic Leukemic Cell LineHuman Myeloid Leukemic Cell LineThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Human Blood Monocytes and Platelets Share a Cell Surface Component

Abstract We describe a surface determinant shared by human monocytes and cells of the megakaryocytic axis that has been identified using a mouse monoclonal antibody. This monocyte-platelet antigen (MPA) is expressed on all (greater than 99%) of peripheral blood monocytes, platelets, and megakaryocytes. It is also expressed weakly on the monocytic cell line U937 and the promyelocytic line HL60 and is present on cells from 3 of 4 AML patients examined. It is absent from polymorphonuclear leukocytes, T and B lymphocytes, erythrocytes, and a panel of hematopoietic cell lines. MPA is stripped from monocyte membranes with pronase and is reexpressed overnight. The determinant is carried on a noncovalently linked biomolecular complex with molecular weights of 93,000 and 135,000.