Hematopoietic growth factors

Granulocyte colony-stimulating factor enhances interleukin 3-dependent proliferation of multipotential hemopoietic progenitors

In cultures of spleen cells from normal mice, recombinant human granulocyte colony-stimulating factor (G-CSF) supported the formation of multipotential blast cell colonies. Serial replating of the blast cell colonies in the presence of G-CSF, however, failed to demonstrate any direct effect of G-CSF on murine multipotential progenitors. We therefore examined the effects of G-CSF in combination with murine interleukin 3 on proliferation of murine blast cell colony-forming cells. The time course of total colony formation and multilineage colony formation by spleen cells harvested from mice 4 days after injection of 5-fluorouracil at 150 mg/kg was significantly shortened in cultures containing both factors in contrast with cultures supported by either factor alone. Serial observations of individual multipotential blast cell colonies (mapping) revealed that blast cell colonies emerged at random time intervals in the presence of interleukin 3 or G-CSF. The appearance of blast cell colonies, however, was significantly hastened in cultures containing both factors relative to cultures grown with either factor. In cultures of day-2 post-5-fluorouracil bone marrow cells, G-CSF in concentrations as low as 1 unit/ml revealed synergism with interleukin 3 in supporting the proliferation of multipotential progenitors. This synergistic activity may explain the previous in vivo studies suggesting the effects of G-CSF on apparent multipotential stem cells.

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.

Granulocyte-macrophage colony-stimulating factor enhances neutrophil function in acquired immunodeficiency syndrome patients

We conducted a clinical trial of human recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) in leukopenic patients with acquired immunodeficiency syndrome (AIDS) and analyzed neutrophil function before, during, and after in vivo administration of rGM-CSF. Prior to GM-CSF infusion, AIDS patients' neutrophil superoxide generation and neutrophil antibody-dependent cell-mediated cytotoxicity were enhanced normally by in vitro exposure to GM-CSF. Neutrophil phagocytosis and intracellular killing of Staphylococcus aureus were also normal in the majority of these patients. Two patients, however, had discrete neutrophil functional defects: one in phagocytosis and one in intracellular killing. During the period of GM-CSF infusion, these abnormalities were corrected. The number of circulating neutrophils increased in all patients treated with GM-CSF in a dose-dependent manner. Neutrophils produced in vivo in response to GM-CSF administration functioned normally and there was evidence for neutrophil priming and activation in vivo. We conclude that GM-CSF treatment of AIDS patients leads to the production of functionally active neutrophils, suggesting therapeutic potential for GM-CSF in the treatment of patients with impaired host defense.

Haemoglobin synthesis in K562 erythroleukaemia cells is affected by intimate contact with monolayers of various human cell types

The haemoglobin content of K562 erythroleukaemia cells was affected by co-culture over monolayers of various human cell types. Haemoglobin synthesis was increased after co-culture with umbilical-cord-derived endothelial cells and most monolayers of bone-marrow-derived macrophages, and inhibited after co-culture with two fibroblast lines, blood-monocyte-derived macrophages, a neuroglial cell line (U-251 MG) and most monolayers of bone-marrow-derived stromal cells. These effects were modified when a thin layer of agar was placed over the monolayers. Cell-free culture media conditioned by all but two of the seven types of monolayer studied inhibited haemoglobin synthesis by K562 cells; those conditioned by blood-monocyte-derived macrophages and two of 11 monolayers of bone-marrow-derived macrophages stimulated haemoglobin synthesis. Thus, the haemoglobin content of K562 cells appeared to be influenced both by intimate contact between K562 cells and the cells of the monolayers and by humoral factors released by the monolayers. The data support the concept that erythroid differentiation is partly dependent on intimate contact between erythroid progenitor cells and microenvironmental cells.

Detection of a human hematopoietic progenitor cell capable of forming blast cell containing colonies in vitro

A progenitor cell CFU-B1 (blast cell colony forming unit) present in human bone marrow and capable of producing blast cell containing colonies in vitro was detected using a serum containing semisolid culture system. The CFU-B1 has the capacity not only to undergo self-renewal, but also commitment to a number of hematopoietic lineages. This progenitor cell therefore has characteristics which suggest that it is identical to or closely related to the human pluripotent hematopoietic stem cell. Pretreatment of marrow cells with 5 fluorouracil facilitated detection of CFU-B1 derived colonies. The formation of CFU-B1 derived colonies was dependent upon the addition of media conditioned by the human bladder carcinoma cell line 5637. The ability of 5637 CM (conditioned media) to support blast cell colony formation was in part but not totally ablated by pretreatment of the CM with an IL-1 alpha (interleukin-1) neutralizing antibody. This data suggests that IL-1 alpha plays a role in the regulation of primitive events occurring during human hematopoiesis. IL-1 alpha might be exerting these effects by either acting directly on the CFU-B1, causing marrow accessory cells to elaborate other cytokines or by synergizing with cytokines already present in 5637 CM.

Effects of recombinant G-CSF and GM-CSF on the growth in methylcellulose and suspension of the blast cells in acute myeloblastic leukemia

The effects of two recombinant human CSFs (G-CSF and GM-CSF) on the growth of blast progenitors from 36 acute myeloblastic leukemia patients were studied in methylcellulose and suspension cultures. Blast colony formation in methylcellulose and the growth of blast progenitors in suspension were stimulated by G-CSF or GM-CSF. Their responses to CSFs were different from those of normal myeloid progenitors. First, the sensitivity of blasts to 0.01 ng/ml of G-CSF and 0.001 ng/ml of GM-CSF was significantly increased compared with normal. Second, in more than 70% of patients, the pattern of the responsiveness to the two CSFs was aberrant compared with ordered response in normal subjects. Third, in about half of the patients, combination of G-CSF and GM-CSF showed synergism for the growth of blast progenitors in both culture methods, whereas negligible or no synergism was observed in normal subjects. Finally, when stimulated by G-CSF, GM-CSF, or both, a significant relationship was noted between blast colony formation in methylcellulose and blast progenitor growth in suspension, suggesting that CSFs do not affect the balance between self-renewal and terminal divisions of blast stem cells.

Increased BPA production modulates Epo sensitivity of circulating BFU-E in sickle cell anemia

We have examined the possibility that permanent "stress" hemopoiesis in sickle cell anemia (SS) patients leads to the modification of the behavior of circulating 14 day erythroid progenitor cells (BFU-E). In these patients we find that peripheral blood BFU-E are increased in number and have high sensitivity to erythropoietin (Epo). Maximal number of BFU-E are generated from peripheral blood of SS patients at 0.3-0.75 Epo/ml of culture compared to 1.5-2.0 U Epo/ml of culture in normals. Peripheral blood adherent cells depletion leads to the shift of Epo dose response curve, so that the Epo sensitivity of BFU-E significantly decreases. This result suggests that apparent Epo hypersensitivity reflects, in fact, an increased production of a burst promoting activity (BPA) by SS peripheral blood light density adherent (PB-LDA) cells. Experiments with conditioned medium by SS PB-LDA cells confirmed this interpretation. When peripheral blood light density non-adherent (PB-LDNA) cells of SS patients or normal individuals were plated in the presence of various concentrations of SS PB-LD cells conditioned medium and constant amounts of Epo, a dose dependent increase of the number of BFU-E was observed. When the same target cells were plated in the presence of PB-LD cells conditioned medium from normal individuals, such effect does not occur. We conclude that increased BPA production may play a role in the erythropoietic regulation during constant hemopoietic stress in sickle cell anemia and might partially explain the lower than expected Epo levels in these patients.

Evidence that de novo protein synthesis participates in a time-dependent augmentation of the chemotactic peptide-induced respiratory burst in neutrophils. Effects of recombinant human colony stimulating factors and dihydrocytochalasin B

We examined the effects of the recombinant human colony stimulating factors GM-CSF and G-CSF, cycloheximide (a protein synthesis inhibitor) and dihydrocytochalasin B (a microfilament disrupting agent) upon FMLP (N-formyl-methionyl-leucylphenylalanine)-stimulated O2- production by neutrophils. We confirmed a time dependent augmentation of O2- production following preincubation of neutrophils either alone or with colony stimulating factors. Furthermore, we found that GM-CSF, but not G-CSF, increased O2- production at some concentrations of the stimulus. Preincubation of neutrophils with cycloheximide in the absence of CSF caused a marked fall in O2- -production that was first evident at 2 hours. The fall in O2- -forming capacity caused by cycloheximide was much less pronounced if dihydrocytochalasin B was also included in the preincubation buffer. These findings suggest a previously unrecognized role for de novo protein synthesis in maintaining the ability of neutrophils to manufacture O2-, and support earlier studies indicating that the cycling of FMLP receptors between the cell membrane and an intracellular compartment is important in determining the magnitude of the respiratory burst in FMLP-stimulated neutrophils.

Marrow reticulo-fibroblastoid colonies (CFU-RF derived) spontaneously release an erythroid colony (BFU-E) enhancing factor

The marrow microenvironment is composed of an extracellular matrix as well as a heterogeneous population of cells. Isolation of the various cell types and analysis of their function is necessary for a better understanding of their roles in hemopoiesis. We have recently reported a colony assay for a cellular component of the marrow microenvironment. The assay consists of a cellular component of the marrow microenvironment. The assay consists of a plasma clot-methylcellulose marrow culture. The stimulator is PHA-stimulated leukocyte conditioned medium (PHA-LCM) and hydrocortisone (5 x 10(-5)M). The fibrin strands appear to act as a substrate for the growth of Reticulo-Fibroblastoid colonies derived from the CFU-RF precursor. RF colonies can be subcultured forming adherent layers when transferred to liquid cultures. Confluent adherent layers can be maintained for long periods of time by changing medium every 3 to 5 days. Supernatants derived from unstimulated RF cultures (RF-CM) were tested for growth promotion of hemopoietic precursors. We found: (1) RF-CM by itself does not induce colony formation. (2) In the presence of erythropoietin, RF-CM enhances the growth of BFU-E. (3) Recombinant IL 4 also enhances BFU-E formation, but in our assays IL 4 induced fewer colonies than RF-CM and the colonies were smaller. (4) Because neither IL 4 nor RF-CM, by themselves, can stimulate colony formation, we compared the effect of RF-CM on assays that are known to show other IL 4 functions. RF-CM did not induce proliferation of PHA induced blast T cells, a known property of IL 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Granulocyte colony-stimulating factor (G-CSF) induces synthesis of alkaline phosphatase in neutrophilic granulocytes of chronic myelogenous leukemia patients

The monocyte, monocyte conditioned media (MoCM), giant cell tumor conditioned media (GCT) and a purified colony-stimulating factor (G-CSF) promote granulocyte-macrophage progenitors (CFU-GM) growth and differentiation along the neutrophil lineage and also induce alkaline phosphatase (NAP) synthesis in the neutrophilic cells of normal subjects and of patients with chronic phase chronic myelogenous leukemia (CML). However, it is not known if granulocyte-macrophage-CSF (GM-CSF), macrophage-CSF (CSF-1) or other cytokines can induce NAP synthesis from the neutrophilic cells of CML patients. The objective of this study were (a) to ascertain which of the three CFU-GM CSFs would induce NAP synthesis, and (b) to test if any of the other cytokines--interleukin-1 (IL-1), interleukin-2 (IL-2), alpha- and gamma-interferons (alpha-INF and r-INF), and phytohemagglutinin-stimulated T-cell conditioned media (TCM) would induce NAP synthesis. Light density cells obtained from the blood of patients with chronic phase CML were depleted of T cells and monocytes. These cells were cultured with various amounts of G-CSF, GM-CSF, CSF-1, IL-1, IL-2, alpha-INF, r-INF, MoCM, GCT and TCM in a suspension culture system over 6-7 days. Evaluation of the cultures indicated that G-CSF, MoCM and GCT, but not the other factors or cytokines, consistently induced NAP synthesis in a dose-dependent manner. Actinomycin-D and puromycin in separate cultures inhibited NAP synthesis without any significant reduction in cell counts. This indicated that NAP is not prepackaged in neutrophilic cells, and its synthesis occurs by a sequential transcription at the DNA level and translation at the ribosomal level. Our results suggest that the molecule which is responsible for promotion of CFU-GM growth and differentiation along the neutrophilic cell lineage is also responsible for derepression of NAP gene and initiation of NAP synthesis.

Hematopoietic growth factors (BPA and Epo) induce the expressions of c-myc and c-fos proto-oncogenes in normal human erythroid progenitors

We investigated serial expressions of eight proto-oncogenes during in-vitro differentiation of normal human burst-forming unit, erythroid (BFU-E), and found that c-myc and c-fos are expressed in progenies of BFU-E. The expressions of the two proto-oncogenes correlated to the replating efficiency and adversely to erythroid differentiation. The absence of hematopoietic growth factors decreased the expressions, but the addition of erythropoietin together with burst promoting activity induced a re-expression of the c-myc and c-fos after 2 h of incubation. These observations suggest that the c-myc and c-fos proto-oncogenes have a physiological role in the proliferation of erythroid progenitors and that activations of the two proto-oncogenes are early cellular events after the stimulation by hematopoietic growth factors.

Cell-surface markers on haemopoietic precursors. Reagents for the isolation and analysis of progenitor cell subpopulations

Within the last decade, major advances have been made in the analysis of cell-surface marker expression on haemopoietic progenitor cells as a result of the development of multiparameter cell sorting and monoclonal antibody techniques. Although some controversy exists with regard to the actual identification of the stem cell, markers specific for CFU-s and for particular subsets of progenitor cells have not yet been identified. An analysis of cell-surface markers on haemopoietic progenitor cells is complicated by at least three factors. First, it appears that, in mice, the clonal assays do not adequately identify the haemopoietic stem cell. Complete repopulation of all haemopoietic cell compartments in vivo over an extended period of time appears to be the only reliable method for identifying such a cell. Secondly cell-surface marker distribution on haemopoietic progenitors from normal tissues may be indicative of the cycling status of cells. Thus, expression of markers on progenitors from bone marrow or foetal liver which have been perturbed by drugs or viruses may merely reflect a change in their cycling status following drug or viral insult. Thirdly, substantial loss of cells occurs during the purification of particular cell types. For most cell separation procedures, only a minor proportion of the progenitor cells of interest are recovered and these may not be representative of the progenitor population as a whole. During differentiation to mature cells, antigenic determinants present on early progenitor cells may either be progressively lost or amplified. This differential expression of cell-surface molecules has provided a useful tool for the substantial enrichment of haemopoietic subsets, particularly CFU-E and CFU-s. To date, however, most early haemopoietic progenitor cells detected by in vitro CFC assays (day 8 CFC) cannot be completely segregated from one another. The ability to distinguish between such progenitors during the early stages of lineage commitment would provide a more detailed understanding of the relationship between lymphoid precursors, myeloid precursors and stem cells, and would lead to significant advances in developmental biology. Separation of cells at different stages of differentiation within a given lineage would provide an opportunity for studying regulatory mechanisms involved in gene expression in normal cell populations.

Recombinant human macrophage colony-stimulating factor (M-CSF) requires subliminal concentrations of granulocyte/macrophage (GM)-CSF for optimal stimulation of human macrophage colony formation in vitro

Human macrophage colony-stimulating factor (M-CSF or CSF-1), either in purified or in recombinant form, is able to generate macrophagic colonies in a murine bone marrow colony assay, but only stimulates small macrophagic colonies of 40-50 cells in a human bone marrow colony assay. We report here that recombinant human granulocytic/macrophage colony stimulating factor (rhGM-CSF) at concentrations in the range of picograms enhances the responsiveness of bone marrow progenitors to M-CSF activity, resulting in an increased number of macrophagic colonies of up to 300 cells. Polyclonal antiserum against M-CSF did not alter colony formation of bone marrow progenitors incubated with GM-CSF at optimal concentration (1-10 ng/ml) for these in vitro assays. Thus, GM-CSF at higher concentrations (nanogram range) can by itself, elicit macrophagic colonies, and at lower concentrations (picogram range) acts to enhance the responsiveness of these progenitors to M-CSF.