Human recombinant granulocyte-macrophage colony-stimulating factor: a multilineage hematopoietin

Granulocyte Macrophage Colony-Stimulating Factor (GM-CSF) Reduces Pancytopenia After Rescue Therapy in a Patient with Hodgkin's Lymphoma

After several relapses, a stage IV lymphocyte depletion Hodgkin Lymphoma patient, with a bone marrow progenitor compartment depleted by several courses of chemotherapy, received further combination chemotherapy which caused severe and long-lasting pancytopenia. Because of an objective degree of tumor regression, a second identical course was administered, followed by Granulocyte Macrophage Colony-Stimulating Factor (GM-CSF) in an attempt to accelerate bone marrow recovery. This led to a significantly shorter period of neutropenia and thrombocytopenia with no additional red blood cell and platelet transfusion requirements. Furthermore, the neutropenic phase was not accompanied by septic complications. It is suggested that patients with solid tumors, even with a severely compromised bone marrow after several chemotherapy courses, may benefit from GM-CSF administration after rescue chemotherapy.

Effect of recombinant human granulocyte-macrophage colony stimulating factor on progenitor cells in patients with advanced malignancies

Haemopoietic progenitor cell levels were determined in the blood and marrow of 37 patients with advanced malignancies undergoing a phase I/II clinical trial of 0.3-30 micrograms/kg/d recombinant human granulocyte-macrophage colony stimulating factor (rGM-CSF). After injection of rGM-CSF, the absolute number of circulating progenitor cells fell initially but after 4 d of infusion a dose-dependent increase was observed in progenitor cells of all lineages with a slight bias favouring granulocyte-macrophage progenitors. A mean 8.4-fold increase in GM-CFC and a 3.3-fold increase in BFU-E were observed at a dose level of 20 micrograms/kg/d of rGM-CSF. Patients with malignant lymphoma showed a greater response than other patients at the same dose level and the CFU-E rise correlated with the haematocrit. This study suggests that GM-CSF may be of value in elevating circulating progenitor cells for subsequent autografting.

Molecular mechanisms underlying erythropoiesis: cycling activity of adult BFU-e relates to their requirement for c-myb function and potential for HbF synthesis

Highly purified erythroid burst-forming units (BFU-e) from human embryonic liver, adult marrow and blood were manipulated in vitro by cytokine addition in order to explore their requirements for c-myb function and potential for fetal hemoglobin (HbF) synthesis, particularly as related to their cycling activity. c-myb is expressed at a minimal level and functionally required to a limited extent in quiescent adult BFU-e. However, c-myb is actively transcribed and stringently required for differentiation of actively cycling progenitors (embryonic BFU-e, embryonic and adult erythroid colony-forming units). The cycling activity of highly purified adult BFU-e, gradually enhanced by interleukin 3 (IL-3) addition, is strictly and directly related to both their functional requirements for c-myb and the level of myb mRNA expression in the progenitor population. It may be concluded that the transcriptional activity and the functional role of c-myb in early erythropoiesis are dependent upon the cycling activity of the erythroid progenitors. The reactivation of HbF synthesis in normal adult bursts, observed in the standard fetal calf serum-rich (FCS+) clonogenic system, is suppressed in cultures with a drastically limited growth of accessory cells (i.e., in FCS- or FCS+ Mo- conditions). In these cultures, addition of granulocyte/macrophage colony-stimulating factor (GM-CSF) or IL-3 induces a dose-related rise of gamma-chain synthesis, at least in part via a direct action at the BFU-e level. Preliminary studies involving priming of adult BFU-e with IL-3 in liquid phase suggest that the HbF potential is relatively low in quiescent BFU-e, but distinctly higher in actively cycling ones. It is postulated that the in vivo reactivation of HbF synthesis in bone marrow regeneration may be mediated via increased IL-3 and GM-CSF activity, leading to enhanced cycling and differentiation of BFU-e.

Sequential study on spontaneous colony formation by bone marrow cells during butylnitrosourea-induced leukemogenesis in the rat

The spontaneous colony (SC)-forming activity of bone marrow cells of rats during butylnitrosourea (BNU) treatment was studied sequentially in an attempt to analyze stages of leukemogenesis. Aspirated bone marrow cells from female Sprague-Dawley (SD) rats that had been given continuous access to drinking water containing 400 ppm BNU were examined at intervals of 3-5 weeks for colony formation of granulomonocytic cells with or without supplemental colony-stimulating factor (CSF). Granulocytic leukemia was first observed at week 12, and the cumulative incidence reached 80% by week 30. SCs were obtained in 56% of rats in the early stage (3 weeks) and in up to 59% of rats in the late stages (20-25 weeks). However, in the middle stages colony formation was rare, even with the addition of CSF. When adherent cells were removed from the bone marrow cells, the SC-forming activity in the early stage was almost entirely lost, whereas much of that in the late stage remained. It is possible that in the former case, overproduction of endogenous CSF by adherent cells under the influence of BNU treatment could be involved. In contrast, late stage SC formation may be associated with the generation of altered cells, including leukemic or preleukemic elements, which have increased capacity for autonomous growth. The loss of SC-forming activity in the middle stage appeared to be attributable to an extreme reduction in endogenous CSF due to marked devastation of the bone marrow. Technical improvement in adjusting more precisely the level of CSF in the culture medium is required to enable further analysis of leukemogenesis, focused on the colony-forming activity of target cells.

Synthesis and expression of the gene encoding human interleukin-3

To perform structure-function studies of human interleukin-3 (hIL-3) we have synthesized a cDNA encompassing the complete coding region of 484 bp. The strategy we employed involved construction of the cDNA in four sections. Each fragment contained six to ten oligodeoxyribonucleotides. Unique restriction sites were engineered to flank the natural sequence for cloning. Naturally occurring restriction sites were placed internally to these, to allow ligation of the four fragments. The gene was cloned into a modified pJL4 vector and expressed in COS cells. Biological assays of supernatants collected from these cells, for both mature cell function and proliferative activity, showed that synthetic hIL-3 had the same activity as that previously determined for recombinant hIL-3.

Hematopoietic growth factors. Biology and clinical applications

The hematopoietic growth factors are potent regulators of blood-cell proliferation and development. The first phase of clinical trials suggests that they may augment hematopoiesis in a number of different conditions of primary and secondary bone marrow dysfunction. Future clinical use is likely to include combinations of these growth factors, in order to stimulate early marrow progenitors and obtain multilineage effects. An improved understanding of the biologic and clinical effects of hematopoietic growth factors promises future clinical applications for conditions of impaired function and reduced numbers of blood cells.

Effect of UV irradiation on epidermal cell cytokine production

Within the last decade it has been found that the keratinocyte is not only a mechanical barrier to the outside but is also a fully immunocompetent cell that can release immunomodulating cytokines such as interleukin (IL) 1, IL 3, IL 6 and colony-stimulating factors (CSF). The constitutive production of these mediators by keratinocytes both in vivo and in vitro is very low; however, it can be dramatically enhanced by various stimuli such as tumour promotors or endotoxin. In addition, UV light is one of the most potent inducers of cytokine release. Accordingly, UV exposure results in increased production of IL 1, IL 3, IL 6, tumour necrosis factor and granulocyte/macrophage-CSF by epidermal cells. The secretion of these cytokines causes local immunologic and inflammatory reactions following UV irradiation. These factors, however, may also enter the circulation and thus may be responsible for systemic effects. In addition, UV light causes keratinocytes to release immunosuppressive factors which block contact hypersensitivity reaction and IL 1 activity. The production of such immunoinhibitors may play an essential pathogenic role during systemic UV-induced immunosuppression. This review will focus on the biological effects of epidermal-cell-derived cytokines, whose release is induced by UV light, and their role in immunologic and inflammatory reactions following UV exposure will be discussed.

Isolation of human megakaryocytes by immunomagnetic beads

A simple method was developed to purify human megakaryocytes to homogeneity from normal bone marrow aspirates. An initial separation of marrow between 1.020 and 1.050 g/ml. Percoll density cut was used to enrich megakaryocytes. After washing, the cells were suspended with immunomagnetic beads which were coated with sheep anti-mouse IgG antibody and treated with anti-human glycoprotein (GP) IIb/IIIa monoclonal antibody, or the cells were treated with human platelet GP IIb/IIIa monoclonal antibody and suspended with the immunomagnetic beads which were coated with sheep anti-mouse IgG antibody. Megakaryocytes were selectively separated using a magnet. All of the isolated cells were morphologically recognizable megakaryocytes. 1.5-3.1 x 10(4) megakaryocytes were obtained from 1.7-4.5 x 10(8) bone marrow nuleated cells. These cells were all positive in immunoenzymatic staining for GP IIb/IIIa. Megakaryocytes obtained by this method responded to recombinant human GM-CSF (rhGM-CSF) showing an increased 3H-thymidine (3H-dT) incorporation. These data show that this method is useful for obtaining pure megakaryocyte populations which can be submitted to comprehensive biological studies.

In vivo biologic activities of recombinant human granulocyte-macrophage colony-stimulating factor

We evaluated the biologic effects of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) in 25 patients with malignancy and/or bone marrow failure of diverse etiologies. The continuous infusion of GM-CSF (15 to 500 micrograms/m2/day) elicited marked leukocytosis (2- to 70-fold increase), consisting primarily of neutrophils, eosinophils, and monocytes. Six patients with cytopenias experienced a multilineage response characterized by significant increases in platelet counts and improvement in erythropoiesis. Response in blood counts was accompanied by significant increases in bone marrow cellularity, myeloid:erythroid cell ratios, and frequency of cycling progenitors, indicating an effect at the stem cell level. By premature chromosome condensation analysis, neutrophils from patients with myeloid diseases were found to be derived from normal as well as abnormal clones. Side effects were generally mild and commonly included constitutional symptoms and bone pain. These results indicate that GM-CSF is a significant stimulus for hematopoiesis in vivo and might play an important role in several clinical arenas.

The effects of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) on human osteoblast-like cells

The activity of human osteoblast-like cells cultured in vitro is regulated by a number of factors, which include systemic hormones as well as agents that can be produced locally within bone. Several cytokines and growth factors have been demonstrated to be produced by osteoblasts themselves, and this includes granulocyte-macrophage colony-stimulating factor (GM-CSF). In this report we show that recombinant human GM-CSF (rhGM-CSF) modulates the activities of osteoblast-like cells derived from human trabecular bone in vitro. rhGM-CSF stimulated the proliferation of the cultured human osteoblast-like cells, but antagonised the induction by 1,25(OH)2D3 of osteocalcin synthesis and alkaline phosphatase activity, two characteristic products of osteoblasts. rhGM-CSF however, had no appreciable effect on the production of prostaglandin E2, or on the plasminogen activator activity associated with human osteoblast-like cells. These results are the first report of which we are aware of an apparently direct action of GM-CSF on cells of the osteoblast phenotype. These studies indicate that GM-CSF represents another haematological factor that can potentially exert regulatory actions on human osteoblast-like cells. GM-CSF may therefore be a potential paracrine/autocrine regulator of osteoblast activity.

Effects of five recombinant hematopoietic growth factors on enriched human erythroid progenitors in serum-replaced cultures

Erythroid progenitors from normal human marrow were purified by a two-step immune panning method permitting both the enrichment of erythroid progenitors (plating efficiency up to 10%) and the separation of CFU-E from BFU-E. The purified erythroid progenitors were grown in serum-replaced conditions; in some experiments at an average of one cell per well. Human recombinant granulocyte-macrophage colony stimulating factor (GM-CSF), interleukin 3 (IL3), erythroid potentiating activity (EPA), and human erythropoietin (Epo) either recombinant or homogenous native were tested for their effect on CFU-E growth. Epo was an absolute requirement for CFU-E growth and was sufficient to obtain colony formation at the unicellular level whereas GM-CSF and IL3 did not further increase the plating efficiency. EPA potentiated the effect of Epo on this progenitor only in experiments performed at unicellular level. Human recombinant GM-CSF, IL3, Interleukin 1 alpha (IL1 alpha), and Epo were subsequently tested for their ability to promote BFU-E growth. GM-CSF and IL3 supported the growth of erythroid bursts in the presence of Epo, even at the unicellular level. However, IL3 promoted a higher number of bursts than GM-CSF under all conditions tested. These two growth factors have no or very small additive effects when tested in combination. IL1 alpha added to Epo alone had no effect on the growth of BFU-E whereas it potentiated the combined action of IL3 and GM-CSF on the primitive BFU-E. In conclusion, this study confirms at the unicellular level and under serum-free conditions that erythroid progenitors are regulated by multipotential growth factors in early phases of erythropoiesis and become sensitive only to Epo in later phases of differentiation.

Granulocyte macrophage colony stimulating factor induced changes in cellular adhesion molecule expression and adhesion to endothelium: in-vitro and in-vivo studies in man

The administration of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) causes a transient leucopenia. Radionuclide labelling studies showed this to be due to margination of neutrophils and monocytes predominantly in the pulmonary vasculature. No evidence of complement activation was found. A rapid in-vivo rise in neutrophil cellular adhesion molecule (CAM) expression was observed paralleling the development of the neutropenia. Neutrophils exposed to rhGM-CSF in-vitro showed similar rapid increases in CAM expression. The adherence of chromium-labelled neutrophils to endothelial cell cultures was modestly but highly significantly increased by rhGM-CSF, an effect that was reduced by the binding of a monoclonal antibody to the beta chain of neutrophil CAM. The margination of phagocytic cells induced by rhGM-CSF administration is therefore likely to be due at least in part to increased expression of adhesion promoting glycoproteins. The demargination, however, occurred at a time when neutrophil CAM expression was still high, suggesting that dissociation of the neutrophil-endothelial cell interaction depends on factors other than downregulation of CAM expression. In-vivo modulation of phagocyte CAMS and adhesive properties by GM-CSF may be of importance in the normal inflammatory response.

Polypeptides controlling hematopoietic cell development and activation. I. In vitro results

Recombinant DNA technology has been central in answering some of the most relevant questions in the research of regulation of the functional status of hematopoietic progenitor cells and their progeny. This leading article will focus on recent results that have emerged from studies utilizing recombinant molecules that control hematopoietic blood cell development and activation. The following features will be detailed: The molecular and biological characteristics and biochemistry of hematopoietic growth factors, synergizing factors and releasing factors, their role in the regulation of hematopoiesis and activation of normal and leukemic cells, their cellular sources, and regulation of production.

Transcriptional and posttranscriptional modulation of myeloid colony-stimulating factor expression by tumor necrosis factor and other agents

Granulocyte (G) and granulocyte-macrophage (GM) colony-stimulating factors (CSF) are necessary for proliferation and differentiation of myeloid hematopoietic cells. Fibroblasts stimulated by tumor necrosis factor alpha (TNF alpha) and several other agents are a rich source of these CSF. The GM-CSF synthesized by these cells had the same molecular weight and glycosylation pattern as that produced by activated T lymphocytes, as shown by [35S]methionine labeling studies. Northern (RNA) blot analysis showed that the fibroblasts had trace levels of G- and GM-CSF mRNA. Both G- and GM-CSF mRNA concentrations coordinately increased after exposure of the cells to TNF alpha (greater than or equal to 5 ng/ml), 12-O-tetradecanoylphorbol 13-acetate (TPA) (greater than or equal to 5 x 10(-10) M), or cycloheximide (20 micrograms/ml). Both TNF alpha and TPA increased levels of G- and GM-CSF mRNA in the absence of new protein synthesis. Transcriptional run-on studies demonstrated that fibroblasts constitutively transcribed GM-CSF, and transcription was enhanced 3.0-fold by TNF alpha and 2.5-fold by TPA and was unchanged by cycloheximide. The stability of G- and GM-CSF transcripts was determined after exposure of the cells to actinomycin D; the half-lives of G- and GM-CSF mRNA in unstimulated cells were less than 0.25 h and were increased 2- to 16-fold in cells cultured with TNF, TPA, or cycloheximide. In summary, both transcriptional and posttranscriptional signals acted coordinately to modulate the levels of G- and GM-CSF mRNAs in fibroblasts.

Kinetics of human hemopoietic cells after in vivo administration of granulocyte-macrophage colony-stimulating factor

The kinetic changes induced by granulocyte-macrophage colony-stimulating factor (GM-CSF) on hemopoietic cells were assessed in physiological conditions by administering GM-CSF (8 micrograms/kg per d) for 3 d to nine patients with solid tumors and normal bone marrow (BM), before chemotherapy. GM-CSF increased the number of circulating granulocytes and monocytes; platelets, erythrocytes, lymphocyte number, and subsets were unmodified. GM-CSF increased the percentage of BM S phase BFU-E (from 32 +/- 7 to 79 +/- 16%), day 14 colony-forming unit granulocyte-macrophage (CFU-GM) (from 43 +/- 20 to 82 +/- 11%) and day 7 CFU-GM (from 41 +/- 14 to 56 +/- 20%). The percentage of BM myeloblasts, promyelocytes, and myelocytes in S phase increased from 26 +/- 14 to 41 +/- 6%, and that of erythroblasts increased from 25 +/- 12 to 30 +/- 12%. This suggests that GM-CSF activates both erythroid and granulomonopoietic progenitors but that, among the morphologically recognizable BM precursors, only the granulomonopoietic lineage is a direct target of the molecule. GM-CSF increased the birth rate of cycling cells from 1.3 to 3.4 cells %/h and decreased the duration of the S phase from 14.3 to 9.1 h and the cell cycle time from 86 to 26 h. After treatment discontinuation, the number of circulating granulocytes and monocytes rapidly fell. The proportion of S phase BM cells dropped to values lower than pretreatment levels, suggesting a period of relative refractoriness to cell cycle-active antineoplastic agents.

Effects of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) on single CD34-positive hemopoietic progenitors from human bone marrow

To determine the extent accessory cells mediate the effects of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) on human hemopoietic progenitors in vitro, we added this hemopoietin to liquid cultures of single CD34-positive marrow cells. These were selected on a fluorescence-activated cell sorter using the HPCA-1 (My10) antibody. Myeloid, erythroid and a few mixed clones developed in 13% of wells in the apparent absence of accessory cells at the beginning of culture. Although accessory cells were generated quickly from the myeloid progenitors and could have mediated the action of rhGM-CSF, this was not the case in the majority of the erythroid clones in which no other cell types were recorded. We conclude that rhGM-CSF can act directly on a subset of erythroid progenitors and probably induces a substantial number of myeloid clones directly.

Effect of recombinant human interleukin 3, granulocyte-macrophage colony-stimulating factor and granulocyte colony-stimulating factor on human BFU-e in serum-free cultures

The effects of recombinant human hemopoietic growth factors on early and late human erythroid progenitors (BFU-e and CFU-e) were investigated in serum-free cultures. Recombinant human erythropoietin (rhEpo) induced the formation of not only human CFU-e-derived colonies but also human BFU-e-derived bursts. Recombinant human interleukin 3 (rhIL-3) alone did not induce the formation of human BFU-e-derived bursts and human CFU-e-derived colonies. In the presence of rhEpo, rhIL-3 dose dependently increased the number of bursts stimulated by rhEpo, although rhIL-3 did not have the augmentative effect on human CFU-e growth. On the other hand, rhIL-3 did not stimulate the formation of murine BFU-e-derived bursts, and murine IL-3 did not stimulate the formation of human BFU-e-derived bursts. The results indicated that the burst-promoting activity of IL-3 was species-specific between human and murine cells. Recombinant human GM-CSF (rhGM-CSF) or recombinant human G-CSF (rhG-CSF) failed to induce human burst formation and did not augment the effect of rhEpo on human burst formation. The results of the present study suggest that in vitro, IL-3 can stimulate BFU-e in collaboration with Epo, but GM-CSF and G-CSF do not stimulate BFU-e growth in the presence or absence of Epo.

c-myc protein kinetics during growth and differentiation of CD34 (MY10)-positive blast cells from normal human marrow

We have used flow cytometry to quantitate nuclear c-myc protein, at each phase of the cell cycle, during in-vitro differentiation of CD34-positive stem cells isolated from normal human bone marrow by the monoclonal antibody, MY10. Mean c-myc protein levels in CD34-positive cells, consisting of greater than 70% blasts, are lower than a marrow fraction containing myeloid cells of intermediate maturation, but have an invariant proportional relationship, with regard to nuclear mass, over the cell cycle. The majority of these primitive cells are non-cycling, as revealed by DNA content. Under our assay conditions, nuclear c-myc protein distribution over the cell cycle did not change as these progenitors entered a proliferative phase in culture. In cultures containing factors supporting myeloid maturation, mean G0/G1 p62c-myc levels initially decline, then rise above starting values as promyelocytes and myelocytes differentiate from CD34-positive cells, and as proliferation begins. With further myeloid maturation, and while cell numbers are increasing, c-myc protein continues to increase. C-myc protein kinetics differ in cultures in which macrophages, rather than myeloid cells, predominate. These data indicate that a complex relationship exists between c-myc gene expression and proliferation, maturation and lineage in haemopoietic cells, and lend support to the notion that early down regulation may be causally associated with the differentiation process.

Human interleukin 3: effects on normal and leukemic cells

The effects of recombinant human interleukin 3 (IL3) on normal bone marrow cells and human leukemic cells were studied. In clonal assays, IL3 supported the growth of all colony types including megakaryocytes. Erythroid colonies were formed in the presence of IL3 and erythropoietin, but not in the absence of erythropoietin. Replating experiments using blast cell colonies derived from a cell population enriched for progenitor cells by fluorescence-activated cell sorting with the monoclonal antibody 3C5, showed that IL3 supported the continued replating of colonies. The clonal proliferation of human bone marrow cells in response to IL3 was inhibited by tumor necrosis factor and by lymphotoxin, but not by interferon-gamma. In suspension cultures, IL3 supported the proliferation of mast cells. Human IL3 had no effect on the growth responses, morphology, cytochemistry, or clonogenicity of the human leukemic cell lines HL60, U-937, KG1a, and HEL. Transcripts for IL3 mRNA were not detectable in these cells, nor in the K562 cell line, implying that autocrine secretion of IL3 was not the mechanism by which these leukemias were maintained. Although cells derived from the bone marrow or peripheral blood of twenty patients with myeloproliferative disorders, myelodysplastic syndromes or acute myeloid leukemia frequently showed proliferative responses to IL3, mRNA transcripts for IL3 were not detected in these cells.

Stimulation of myelopoiesis in patients with aplastic anemia by recombinant human granulocyte-macrophage colony-stimulating factor

Aplastic anemia is a syndrome in which pancytopenia occurs in the presence of hypocellularity of the bone marrow. To assess the biologic activities of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) in aplastic anemia, we gave GM-CSF (60 to 500 micrograms per square meter of body-surface area) to 10 patients with moderate or severe disease, by continuous intravenous infusion daily for two weeks, and repeated the treatment after a two-week rest period. The treatment increased the white-cell count (1.6- to 10-fold) in all patients, primarily because of an increase in the numbers of neutrophils (1.5 to 20-fold), eosinophils (12- to greater than 70-fold), and monocytes (2- to 32-fold). Rates of hydrogen peroxide production in purified granulocyte fractions increased during GM-CSF treatment. Increases in bone marrow cellularity, myeloid precursor cells, and myeloid:erythroid cell ratios accompanied the white-cell response. Despite the in vivo response of the white-cells, the concentration of colony-forming cells remained the same. Measurable concentrations of interleukin-2 (2 to 15 units per milliliter) were found in the serum of 8 patients, and high levels of erythropoietin (81 to 1200 IU per liter) were found in 10 patients. The predominant side effects were constitutional symptoms. These results indicate that recombinant human GM-CSF is effective in stimulating myelopoiesis in patients with severe aplastic anemia and may benefit some patients in whom the disorder is refractory to standard forms of therapy.

Cytokine activation of antibacterial activity in human pulmonary macrophages: comparison of recombinant interferon-gamma and granulocyte-macrophage colony-stimulating factor

We examined the ability of two recombinant human cytokines, granulocyte-macrophage colony-stimulating factor (rHu-GM-CSF) and interferon-gamma (rHu-IFN-gamma) to activate antibacterial mechanisms in human pulmonary macrophages (PM) and peripheral blood monocytes (PBM). Growth of Legionella pneumophila (LP) was assessed in PM or PBM which had been exposed to either rHu-IFN-gamma (500-1000 u/ml) or rHu-GM-CSF (1 to 10,000 u/ml). In both PM and PBM exposed to 500 u/ml rHu-IFN-gamma, growth of LP was reduced compared to cells exposed to media alone. By comparison, exposure of these cell types to rHu-GM-CSF had no detectable effect on bacterial replication. In order to investigate potential mechanisms accounting for this observation, the effect of these cytokines on the hydrogen peroxide (H2O2)-releasing capacity of cells was studied. Exposure of PM and PBM to rHu-IFN-gamma (500 to 1000 u/ml) resulted in increased production of H2O2 triggered by phorbol myristate acetate; when subjected to the same experimental conditions, rHu-GM-CSF-exposed cells exhibited no increase in H2O2 production. To further clarify the role of rHu-IFN-gamma-induced augmentation of oxidative metabolism on cellular inhibition of bacterial growth, an amount of catalase capable of completely neutralizing extracellular H2O2 was added to cells before and during infection. This did not abrogate the antibacterial activity of rHu-IFN-gamma. These studies demonstrate that rHu-IFN-gamma but not rHu-GM-CSF is capable of augmenting the capacity of PM and PBM to restrict LP growth. These data suggest that the antibacterial activity of rHu-IFN-gamma in this system may involve oxidative as well as nonoxidative mechanisms.

Biological activities of human granulocyte-macrophage colony-stimulating factor

Granulocyte-macrophage colony-stimulating factor (GM-CSF) has emerged as an important regulation for hematopoietic cell development and function. Within the myeloid lineages, GM-CSF serves as a growth and developmental factor for intermediate-stage progenitors between early, interleukin 3-responsive and late granulocyte colony-stimulating factor-responsive precursors. GM-CSF also serves as an activator of circulating effector cells. The ability of GM-CSF to induce monocyte expression of tumor necrosis factor, interleukin 1 and other factors, further ties this hormone into a network of cytokines that interact to regulate many hematologic and immunologic responses. The availability of large quantities of recombinant GM-CSF now provides the opportunity and challenge not only for unraveling the mechanisms regulating hematopoiesis, but also for developing new therapies for enhancement of host defense against infection that were not previously possible.

Tumor-promoting phorbol esters stimulate the proliferation of interleukin-3 dependent cells

To determine whether activation of protein kinase C is involved in the proliferation of interleukin-3 (IL-3) -dependent cells, we examined the effect of tumor-promoting phorbol esters on the in vitro proliferation of the IL-3-dependent cell lines FD and DA-1. The viability of FD and DA-1 cells cultured for 24 hours in 100 nM phorbol myristate acetate (PMA) and 10% FCS was similar to that of cells cultured in 25% WEHI-3 conditioned medium as a source of IL-3, and 10% FCS. FD cells failed to proliferate in concentrations of FCS of up to 50%, while DA-1 cell proliferation was not markedly influenced by FCS. By contrast, PMA promoted the proliferation of FD and DA-1 cells in the absence of FCS and enhanced their proliferation in the presence of 10% FCS, 60- and 20-fold, respectively. Stimulation of proliferation was achieved with as little as 10 nM PMA and was maximal at 100 nM PMA. Low concentrations (0.05-0.1%) of WEHI-3 CM promoted the proliferative response of FD and DA-1 cells to PMA, but at concentrations of WEHI-3 CM greater than 0.8%, no further increment in proliferation was obtained with PMA. As little as 1/2 hour of exposure to phorbol esters was sufficient to cause translocation of protein kinase C from the cytosol to the membranes of DA-1 cells, and 1 hour of exposure to phorbol esters was sufficient to stimulate DNA synthesis. A protein kinase C inhibitor, H-7, at a concentration of 10 microM inhibited phorbol ester-induced stimulation of DA-1 cell proliferation. When DA-1 cells were exposed to the calcium ionophore A23187 in addition to both a phorbol ester and IL-3, their proliferation was enhanced over that stimulated by only the phorbol ester and IL-3. The data indicate that stimulation of proliferation of IL-3-dependent cells involves the activation of protein kinase C.

Human recombinant granulocyte-macrophage colony stimulating factor and interleukin 3 have overlapping but distinct hematopoietic activities

The hematopoietic stimulatory activities of human recombinant IL-3 and granulocyte-macrophage colony stimulating factor (GM-CSF) were directly compared using highly enriched human bone marrow progenitor target cells. IL-3 supported a larger number of erythroid and megakaryocytic progenitor cells than did GM-CSF, while GM-CSF supported more myeloid progenitors. IL-3 directly stimulated the division and migration of primitive erythroid burst forming units, while GM-CSF merely sustained their net survival in culture without promoting division and expansion. IL-3 promoted the formation of larger numbers of multipotential granulocyte-erythroid-macrophage-megakaryocyte colony forming unit--derived colonies than did GM-CSF. These data indicate that human IL-3 and GM-CSF have overlapping but distinct hematopoietic activities, and suggest a potential role for the clinical application of combined IL-3/GM-CSF therapy.

Effect of recombinant human granulocyte-macrophage colony-stimulating factor on chemotherapy-induced myelosuppression

An increase in the dose of chemotherapy enhances the response of many experimental and clinical cancers, but the extent of dose escalation is often limited by myelosuppression. In preliminary trials, recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) has augmented leukocyte numbers and function, but the optimal dose is not established. We treated 16 adults who had inoperable or metastatic sarcomas with escalating doses of rhGM-CSF before and immediately after a first cycle of chemotherapy (cycle 1) to assess hematologic response and toxicity. A second cycle of chemotherapy (cycle 2) was given without rhGM-CSF. RhGM-CSF was tolerated well at doses of 4 to 32 micrograms per kilogram of body weight per day. At 64 micrograms per kilogram per day, edema and thrombi around a central venous catheter developed in two of four patients. Leukocyte and granulocyte counts increased significantly during the rhGM-CSF infusion. Neutropenia after cycle 1 was significantly less severe and shorter in duration than after cycle 2 (P less than 0.01). Mean total leukocyte and platelet nadirs were 1.0 and 101 x 10(9) per liter for cycle 1 and 0.45 and 44 x 10(9) per liter for cycle 2 (P less than 0.01), and the median intervals from day 1 of chemotherapy to neutrophil recovery (greater than 0.500 x 10(9) per liter) were 15 and 19 days, respectively (P less than 0.01). The duration of neutropenia was 3.5 days with cycle 1 and 7.4 days with cycle 2 (P less than 0.01). We conclude that rhGM-CSF is tolerated well at doses up to 32 micrograms per kilogram per day and is biologically active in leukopenic patients. It merits further evaluation for the prevention of morbidity from chemotherapy.

Transcriptional and posttranscriptional modulation of myeloid colony-stimulating factor expression by tumor necrosis factor and other agents

Granulocyte (G) and granulocyte-macrophage (GM) colony-stimulating factors (CSF) are necessary for proliferation and differentiation of myeloid hematopoietic cells. Fibroblasts stimulated by tumor necrosis factor alpha (TNF alpha) and several other agents are a rich source of these CSF. The GM-CSF synthesized by these cells had the same molecular weight and glycosylation pattern as that produced by activated T lymphocytes, as shown by [35S]methionine labeling studies. Northern (RNA) blot analysis showed that the fibroblasts had trace levels of G- and GM-CSF mRNA. Both G- and GM-CSF mRNA concentrations coordinately increased after exposure of the cells to TNF alpha (greater than or equal to 5 ng/ml), 12-O-tetradecanoylphorbol 13-acetate (TPA) (greater than or equal to 5 x 10(-10) M), or cycloheximide (20 micrograms/ml). Both TNF alpha and TPA increased levels of G- and GM-CSF mRNA in the absence of new protein synthesis. Transcriptional run-on studies demonstrated that fibroblasts constitutively transcribed GM-CSF, and transcription was enhanced 3.0-fold by TNF alpha and 2.5-fold by TPA and was unchanged by cycloheximide. The stability of G- and GM-CSF transcripts was determined after exposure of the cells to actinomycin D; the half-lives of G- and GM-CSF mRNA in unstimulated cells were less than 0.25 h and were increased 2- to 16-fold in cells cultured with TNF, TPA, or cycloheximide. In summary, both transcriptional and posttranscriptional signals acted coordinately to modulate the levels of G- and GM-CSF mRNAs in fibroblasts.

Characterization of the human granulocyte-macrophage colony-stimulating factor promoter region by genetic analysis: correlation with DNase I footprinting

T-cell activation induces expression of the hematopoietic growth factor granulocyte-macrophage colony-stimulating factor (GM-CSF). To define the molecular events involved in the induction of GM-CSF gene expression more clearly, we prepared and analyzed deletion mutants of GM-CSF promoter recombinant constructs. The results localized inducible expression to a 90-base-pair region (-53 to +37) which is active in uninfected and human T-cell leukemia virus-infected T-cell lines but not in resting or mitogen-stimulated B cells. DNase I footprinting experiments revealed protection of sequences contained within this region, including a repeated nucleotide sequence, CATT(A/T), which could serve as a core recognition sequence for a cellular transcription factor. Upstream of these GM-CSF promoter sequences is a 15-base-pair region (-193 to -179) which has negative regulatory activity in human T-cell leukemia virus-infected T cells. These studies revealed a complex pattern of regulation of GM-CSF expression in T cells; positive and negative regulatory sequences may play critical roles in controlling the expression of this potent granulopoietin in the bone marrow microenvironment and in localized inflammatory responses.

The suppressive effects of recombinant human tumor necrosis factor-alpha on normal and malignant myelopoiesis: synergism with interferon-gamma

The modulation of growth of normal and leukemic myeloid progenitor cells in soft agar cultures by recombinant human tumor necrosis factor-alpha (TNF alpha) and recombinant human interferon-gamma (IFN gamma) was investigated. TNF alpha inhibited colony formation of all colony types representing different maturational stages of normal progenitor cells committed to the myeloid lineage with different orders of sensitivity. Blast-type colonies derived from patients with acute myelogenous leukemia were more sensitive to TNF alpha inhibition than progenitor cells purified from normal bone marrow or bone marrow from patients with stable-phase chronic myelogenous leukemia. The response of most colony types to IFN gamma was poor. However, when IFN gamma was administered together with TNF alpha, synergistically enhanced antiproliferative effects were detected in all colony types tested. The antiproliferative action of IFN gamma on myelopoiesis was enhanced in culture by the presence of autologous monocytes, presumedly by inducing endogenous production of TNF alpha. However, TNF alpha seemed to act directly on the progenitor cells themselves to suppress their clonal growth, rather than involving accessory marrow elements such as monocytes and/or T lymphocytes.

Erythropoietin stimulates a rise in intracellular free calcium concentration in single early human erythroid precursors

Erythropoietin and granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulate the differentiation and proliferation of erythroid cells. To determine the cellular mechanism of action of these growth factors, we measured changes in intracellular free calcium concentration [( Cac]) in single human erythroid precursors in response to recombinant erythropoietin and GM-CSF. [Cac] in immature erythroblasts derived from cultured human cord blood erythroid progenitors was measured with fluorescence microscopy digital video imaging. When stimulated with erythropoietin, [Cac] in the majority of erythroblasts increased within 3 min, peaked at 5 min, and returned toward baseline at 10 min. The percentage of cells that responded to erythropoietin stimulation increased in a dose-dependent manner. Additional stimulation with GM-CSF in cells previously exposed to erythropoietin resulted in a second [Cac] increase. Immature erythroblasts treated with GM-CSF followed by erythropoietin responded similarly to each factor with a rise in [Cac]. The source of transient calcium is intracellular since erythroblasts were incubated in medium devoid of extracellular calcium. Our observations suggest that changes in [Cac] may be an intracellular signal that mediates the proliferative/differentiating effect of hematopoietic growth factors.

Hemopoietic colony growth-promoting activities in the plasma of bone marrow transplant recipients

Plasma samples were obtained from 34 bone marrow transplant (BMT) recipients before and after administration of the preparative regimen and tested for their ability to promote and/or support growth of hemopoietic colonies. The ability of plasma samples to promote colony formation on their own was tested on normal nonadherent target cells without addition of exogenous growth factors. The growth-supporting activity was examined in the presence of medium conditioned by phytohemagglutinin-stimulated leukocytes (PHA-LCM) and/or erythropoietin (EPO). A series of kinetic changes was routinely observed. Pretransplant samples rarely gave rise to colonies without addition of exogenous growth factors. Plasma samples obtained after completion of the preparative regimen demonstrated increments of growth-promoting activities for megakaryocyte and granulocyte-macrophage progenitors (CFU-Meg and CFU-GM), respectively, that peaked between 7 and 21 d after transplantation. By day 30, activity levels of some patients had returned to pretransplant values, whereas in other patients, activities remained elevated. Persisting activity levels were associated with delayed engraftment. In contrast, activities for progenitors committed to erythropoiesis (BFU-E) and pluripotent precursors (CFU-GEMM) were only rarely observed. The activities were independent of febrile episodes. Their growth-promoting influence on CFU-GM could be neutralized completely by anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) antibodies. These data suggest that at least some of the observed activities in post-BMT plasma are related to GM-CSF. The growth-supporting activities of pretransplant plasma samples are lower than normal plasma when tested on CFU-Meg and CFU-GM. The growth-supporting activities improved transiently within the first month after BMT. A decline during the second and third month was followed by a gradual return to activity levels that were comparable to normal plasma. The effects of these plasma samples on BFU-E and CFU-GEMM were assessed with PHA-LCM and EPO. Similar to CFU-Meg- and CFU-GM-supporting capabilities, they improved transiently after BMT with a return of normal support function after 5-6 mo. The observed endogenous production of growth-promoting and growth-supporting activities for hemopoietic progenitors may serve as a background to design clinical trials for the timely administration of recombinant hemopoietic growth factors to BMT recipients.

Recombinant granulocyte-macrophage colony-stimulating factor improves hematopoietic recovery after 5-fluorouracil

Antitumor chemotherapy is often limited by hematopoietic toxicity. In an attempt to determine if it is possible to attenuate the myelosuppressive effects of chemotherapy, we administered recombinant murine granulocyte-macrophage colony-stimulating factor (rmGM-CSF), a multilineage hematopoietic growth factor, to mice receiving 5-fluorouracil (5-FU). Mice receiving injection of 5-FU followed 24 hr later by a single 1-microgram injection of rmGM-CSF had significantly increased femoral bone marrow granulocyte-macrophage colony-forming cells (GM-CFC) 48 hr after 5-FU injection compared to animals receiving 5-FU alone. Animals receiving rmGM-CSF twice daily beginning 24 hr after 5-FU had significantly elevated white blood cell counts and increased granulocyte and monocyte counts at Day 7 following 5-FU injection, compared to those of 5-FU animals. The total reserve of GM-CFC was also expanded initially in the femoral marrow and later in the spleen of animals receiving rmGM-CSF following 5-FU. A means of accelerating bone marrow recovery and restoration circulating granulocytes and monocytes could allow more frequent doses of chemotherapy to be administered or shorten the time period that patients are leukopenic.

1,25-Dihydroxyvitamin D3 modulates the expression of a lymphokine (granulocyte-macrophage colony-stimulating factor) posttranscriptionally

We recently showed that 1,25(OH)2D3 sensitively inhibited the expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) in normal human mitogen-activated peripheral blood lymphocytes and in the human T lymphotropic virus I immortalized T cell line known as S-LB1 at the levels of both mRNA and protein. Using S-LB1 cells as a model system the present paper identifies at least in part the mechanisms by which 1,25(OH)2D3 regulates the expression of GM-CSF. Time-course studies demonstrated that by 6 and 48 h of exposure of S-LB1 cells to 1,25(OH)2D3 (10(-8) M) the GM-CSF mRNA levels were reduced by 50 and 90%, respectively. Studies using cycloheximide as a protein synthesis inhibitor showed that the inhibitory action of 1,25(OH)2D3 on GM-CSF expression was dependent on new protein synthesis. In vitro nuclear run-on assays demonstrated that 1,25(OH)2D3 (10(-8) M) did not change the rate of transcription of the GM-CSF gene. The t1/2 of GM-CSF mRNA, however, was profoundly reduced by 1,25(OH)2D3 when transcription was blocked by actinomycin D compared with the half-life of GM-CSF in the presence of actinomycin D alone (t1/2, less than 0.5 and 4 h, respectively). Taken together, these results demonstrate that 1,25(OH)2D3 regulates expression of the lymphokine GM-CSF posttranscriptionally by influencing the stability of GM-CSF mRNA.

Proliferation and differentiation of highly enriched mouse hematopoietic stem cells and progenitor cells in response to defined growth factors

Three distinct hematopoietic populations derived from normal bone marrow were analyzed for their response to defined growth factors. The Thy-1loT- B- G- M-population, composing 0.2% of bone marrow, is 370-fold enriched for pluripotent hematopoietic stem cells. The two other populations, the Thy-1- T- B- G- M- and the predominantly mature Thy-1+ T+ B+ G+ M+ cells, lack stem cells. Thy-1loT- B- G- M- cells respond with a frequency of one in seven cells to IL-3 in an in vitro CFU-C assay, and give rise to many mixed colonies as expected from an early multipotent or pluripotent progenitor. The Thy-1- T- B- G- M- population also contains progenitor cells which responded to IL-3. However, colonies derived from Thy-1- T- B- G- M- cells are almost exclusively restricted to the macrophage/granulocyte lineages. This indicates that IL-3 can stimulate at least two distinct clonogenic early progenitor cells in normal bone marrow: multipotent Thy-1loT- B- G- M- cells and restricted Thy-1- T- B- G- M- cells. Thy-1loT- B- G- M-cells could not be stimulated by macrophage colony-stimulating factor (M-CSF), granulocyte CSF (G-CSF) or IL-5 (Eosinophil-CSF). The hematopoietic precursors that react to these factors are enriched in the Thy-1- T- G- B- M- population. Thus, multipotent and restricted progenitors can be separated on the basis of the expression of the cell surface antigen Thy-1.

Characterization of the human granulocyte-macrophage colony-stimulating factor promoter region by genetic analysis: correlation with DNase I footprinting

T-cell activation induces expression of the hematopoietic growth factor granulocyte-macrophage colony-stimulating factor (GM-CSF). To define the molecular events involved in the induction of GM-CSF gene expression more clearly, we prepared and analyzed deletion mutants of GM-CSF promoter recombinant constructs. The results localized inducible expression to a 90-base-pair region (-53 to +37) which is active in uninfected and human T-cell leukemia virus-infected T-cell lines but not in resting or mitogen-stimulated B cells. DNase I footprinting experiments revealed protection of sequences contained within this region, including a repeated nucleotide sequence, CATT(A/T), which could serve as a core recognition sequence for a cellular transcription factor. Upstream of these GM-CSF promoter sequences is a 15-base-pair region (-193 to -179) which has negative regulatory activity in human T-cell leukemia virus-infected T cells. These studies revealed a complex pattern of regulation of GM-CSF expression in T cells; positive and negative regulatory sequences may play critical roles in controlling the expression of this potent granulopoietin in the bone marrow microenvironment and in localized inflammatory responses.

Postnatal changes in plasma burst-promoting activity (BPA) levels in preterm infants

Two-stage cell culture assays were used to determine burst-promoting activity (BPA) levels in the plasma of untransfused premature infants during the early anaemic period. The plasma BPA levels decreased during the early phase of the postnatal fall in haemoglobin and the mean plasma BPA levels at 2 and 4 weeks of age were significantly lower (24 +/- 9% and 20 +/- 14%) than those of normal adults (53 +/- 17%). After 8 weeks of age, plasma BPA levels increased markedly in correlation with the recovery of erythropoiesis. Inhibitors of erythroid colony growth were not significantly elevated in the plasma of premature infants. These results suggest that BPA may act as a regulator of erythropoiesis in preterm infants along with erythropoietin.

Effect of recombinant human granulocyte-macrophage colony-stimulating factor on hematopoietic reconstitution after high-dose chemotherapy and autologous bone marrow transplantation

Recombinant human granulocyte-macrophage colony-stimulating factor (rHuGM-CSF) has been reported to increase the leukocyte count in subhuman primates subjected to total-body irradiation and in patients with the acquired immunodeficiency syndrome. We administered this substance to 19 patients with breast cancer or melanoma treated with high-dose combination chemotherapy and autologous bone marrow support. Groups of three or four patients were treated with 2.0, 4.0, 8.0, 16.0, or 32.0 micrograms per kilogram of body weight per day of glycosylated rHuGM-CSF by continuous intravenous infusion for 14 days, beginning three hours after bone marrow infusion. Total leukocyte and granulocyte recovery was accelerated in these patients as compared with 24 historical controls matched for age, diagnosis, and treatment. Leukocyte counts (mean +/- SD) obtained 14 days after transplantation were 1511 +/- 1003 per microliter in patients given 2 to 8 micrograms per kilogram per day, 2575 +/- 2304 in those given 16 micrograms, and 3120 +/- 1744 in those given 32 micrograms, as compared with 863 +/- 645 per microliter in the controls. No consistent effect on platelet counts was noted. Toxic effects were generally mild and not clearly dose-related in patients given 2 to 16 micrograms per kilogram per day. Edema, weight gain, or myalgias occurred in all patients given 32 micrograms per kilogram; marked weight gain, generalized edema, pleural effusions, and hypotension developed in two patients, one of whom also had acute renal failure. Our results indicate that rHuGM-CSF can accelerate myeloid recovery after high-dose chemotherapy and autologous bone marrow transplantation, over a range of doses that can be tolerated. In this setting the ability to increase the dose is limited by the development of myalgias and fluid retention.

Haematopoietic progenitor cells in an infant who developed pancytopenia following an extensive burn

We observed a 24-month-old infant who developed anaemia, thrombocytopenia and neutropenia while recuperating from an extensive burn. In order to determine the mechanism(s) responsible for the pancytopenia, we quantified marrow-derived haematopoietic progenitor cells, assessed the relative proliferative rate of haematopoietic progenitor cells, and sought the presence of progenitor cell inhibitors. The concentration and relative proliferative rate of pluripotent progenitors (CFU-GEMM) were elevated. No inhibitors of progenitor cells were observed; in fact, the patient's serum contained very high levels of stimulatory activity for CFU-GEMM as well as for granulocyte-macrophage progenitors (CFU-GM). However, the marrow concentration of erythroid progenitors (BFU-E and CFU-E) was diminished. We conclude that the anaemia in this patient was the result of either hypoproduction of differentiated erythroid progenitors or intramyeloid destruction of early erythroid cells. In contrast, the neutropenia was likely to be due to accelerated neutrophil consumption at a rate that exceeded the capacity for increasing neutrophil production.