Human IL-3 and GM-CSF act synergistically in stimulating hematopoiesis in primates

Biologic response modifiers: the future of cancer therapy?

The major shift today has been away from nonspecific compounds acting on immune mechanisms to using biologics which have specific, defined roles in acting on the immune response. The field of biologic response modification is progressing very rapidly. New peptides are being identified, as are receptors for these peptides, autocrines, lymphokines, cytokines, growth factors, differentiation factors, hormones, and so on-all of which will control body function, cell populations, and cell to cell interactions. This rapidly advancing area of research in cancer biology and cancer therapy may hold the key to the future of successful therapy.

The biology and clinical potential of growth factors that regulate myeloid cell production

The colony-stimulating factors are a group of growth factors important in regulating the production of myeloid cells. The past 25 years have seen the identification and characterization of many of these growth factors and, more recently, the molecular cloning of their genes. This has enabled the production of sufficient quantities to assess their biological activity in vivo and in vitro. Some of these recombinant growth factors have also been employed in clinical trials, which have indicated potential uses in the treatment of a variety of diseases. Here, Anthony Whetton considers the biology of haematopoietic growth factors, and the evidence that they may be of value in the treatment of haematopoietic, infectious and malignant disease.

Effects of interleukin-3 on hematopoietic recovery after 5-fluorouracil or cyclophosphamide treatment of cynomolgus primates

Interleukin-3 (IL-3) is a hematopoietic growth factor that supports the growth of early hematopoietic progenitors in vitro. In vivo administration of recombinant human interleukin-3 (rhIL-3) to normal primates results in a modest and delayed leukocytosis secondary to increases in neutrophils, basophils, and eosinophils. We postulated that the effects of rhIL-3 might be more pronounced in hematologically stressed primates, and therefore administered rhIL-3 to primates after intensive myelosuppressive therapy. Primates received either cyclophosphamide (CPM) at 60 mg/kg or 5-fluorouracil (5-FU) at 75 mg/kg i.v. on two consecutive days. Subsequently, rhIL-3 was administered intravenously or subcutaneously at 20 micrograms/kg per d for 14 d. Compared to controls, all rhIL-3 treated primates experienced higher absolute neutrophil count (ANC) nadirs and dramatic decreases in the period of severe neutropenia (ANC less than 500) after myelosuppressive therapy. RhIL-3 administration resulted in a significant basophilia and eosinophilia, which resolved after discontinuation of the drug. RhIL-3 did not enhance erythroid recovery. Platelet recovery was earlier in rhIL-3-treated animals. However, variations in the platelet recovery observed in control animals, precluded accurate estimation of this effect or its significance. Our results indicate that the administration of rhIL-3 following intensive myelosuppressive therapy dramatically enhances myeloid recovery and ablates the predicted period of prolonged severe neutropenia.

Stimulation of thrombopoiesis in mice by human recombinant interleukin 6

To date, testing of various cytokines for the stimulation of blood cell production has not demonstrated a consistent effect on peripheral platelet levels. In this report, we provide evidence that human recombinant IL-6 increased platelet production in mice, as measured by both peripheral platelet levels and [75Se]selenomethionine (75SeM) incorporation into newly forming platelets. Peripheral white blood cell counts also were increased, but only to a modest extent, and hematocrit values were unchanged. A dose-response relationship between the amount of IL-6 administered and platelet count, 75SeM incorporation, and white blood cell count was demonstrated. Detectable megakaryocyte and granulocyte-macrophage colony-forming cells in mice that had received IL-6 also were increased in both bone marrow and spleen. These results demonstrate the ability of a purified, recombinant protein to stimulate platelet production in vivo.

Human interleukin 3: analysis of the gene and its role in the regulation of hematopoiesis

Interleukin 3 (IL-3) is one of a family of cytokines believed to be important in regulating the growth and development of cells of both the hematopoietic and immune systems. In comparison with other hematopoietic growth factors, IL-3 preferentially supports the proliferation and differentiation of progenitors at early stages of hematopoietic development. In addition, IL-3 exerts a wide spectrum of biological activities on various target cell populations, including T cells, B cells, eosinophils, basophils and monocytes. The direct interaction between IL-3 and early multipotential progenitors has been confirmed in the primate model in which pretreatment of IL-3 primed the animals to become more responsive to late-acting hematopoietic growth factors, like granulocyte-macrophage colony-stimulating factor and erythropoietin. Furthermore, administration of IL-3 can diminish myelosuppression and accelerate hematopoietic recovery in primates treated with various chemotherapeutic drugs. These studies suggest that IL-3 alone or in combination with other hematopoietins may prove to be useful in treating myelosuppressed patients.

Synergistic activation of 2-deoxy-D-glucose uptake in rat and murine peritoneal macrophages by human macrophage colony-stimulating factor-stimulated coupling between transport and hexokinase activity and phorbol-dependent stimulation of pentose phosphate-shunt activity

1. Transport and accumulation of 2-deoxy-D-glucose (2dGlc) in rat and murine peritoneal macrophages were investigated by using C-1-3H-labelled and C-2,6-3H-labelled 2dGlc. 2. There was active accumulation of both C-1- and C-2,6-labelled 2dGlc by quiescent rat and murine macrophages via a phloretin-inhibitable transport system. 3. The rate of uptake and accumulation of 2dGlc (C-1 label) was increased by exposure to human macrophage colony-stimulating factor (mCSF-1) (1000 units/ml) in both murine and rat macrophages. This indicates that mCSF-1 enhances coupling between hexokinase activity and glucose transport at the endofacial surface of the transporter. 4. Phorbol 12-myristate 13-acetate ('phorbol') at 40 nM stimulated 2dGlc in rat macrophages entirely by increasing the C-2,6 label uptake. This indicates that phorbol stimulates 2dGlc uptake mainly by increasing the activity of the pentose phosphate pathway. 5. Simultaneous exposure to phorbol and mCSF-1 stimulates 2dGlc uptake to a greater extent than found with either phorbol or mCSF-1 alone. This result is explained by a simultaneous enhancement of pentose phosphate-pathway activity and of hexokinase activity acting at the endofacial surface of the cell membrane. The dual activation of these serial processes coupled to the loss of the reaction products of the pentose phosphate-shunt pathway from the cells in the form of reactive oxygen intermediates, protons and CO2 could explain the synergistic action of phorbol and mCSF-1 in activation of sugar transport in macrophages.

Preclinical studies on synergistic effects of IL-1, IL-3, G-CSF and GM-CSF in cynomolgus monkeys

The regulation of blood cell formation is mediated by a group of polypeptides classified as hematopoietic growth and differentiation factors. Overlapping as well as distinct functions have been described for three of these cytokines: interleukin 3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF). Furthermore, interleukin 1 (IL-1) has been shown to promote hematopoietic regeneration after cytoreductive drug treatment. Evidence has been provided by in vitro studies that combinations of these factors exert a highly synergistic action on the proliferation and differentiation of committed hematopoietic progenitor cells. Additionally, these findings have been supported by studies of in vivo blood cell formation in nonhuman primates. We report here that IL-3 acts synergistically with GM-CSF or G-CSF on myelocytic cell development only if an administration time of eight days of IL-3 is followed by GM-CSF or G-CSF. Short-time IL-3 application of two and four days only resulted in platelet production. The reverse administration schedule did not show synergistically enhanced stimulation of myelocytic cells. However, G-CSF treatment followed by IL-3 did induce a two-fold increase in platelet numbers. This would appear to confirm previously reported in vitro findings that G-CSF shortens the G0 period of human hematopoietic stem cells, which subsequently proliferate in the presence of IL-3. The effects of IL-3 on myelocytic and megakaryocytic development seems to be differently regulated. Whereas, IL-1 failed to display synergistic activity with GM-CSF or G-CSF is sequentially applied. Only simultaneous application either in combination with GM-CSF or with G-CSF demonstrated enhanced efficacy.

The role of growth factors in haemopoietic development: clinical and biological implications

Mature blood cells of all lineages are derived from a single class of cell, the haemopoietic stem cell. Stem cells are pluripotent and capable of almost limitless self-renewal. In the bone marrow they form part of a hierarchy that includes progenitor cells, which are more restricted in the lineages their progeny can adopt, and precursor cells, which are committed to differentiation. The mechanisms that regulate progression through this hierarchy are not fully understood, but evidence suggests that both bone marrow stromal cells and soluble growth factors have a role in controlling haemopoiesis. Four growth factors act on progenitor cells to promote their survival, proliferation, differentiation, and maturation: interleukin-3 (IL-3), granulocyte/macrophage-colony stimulating factor (GM-CSF), granulocyte-CSF (G-CSF), and macrophage-CSF (M-CSF). They can also activate the function of mature cells. Considerable overlap is found in the target cells for these four growth factors. We have found that growth factors acting in synergy can recruit more primitive cells than had previously been appreciated. These factors can also determine the lineage that the progeny of multipotential progenitors will adopt. Thus, colony-stimulating factors (CSFs) have the potential to regulate the development of primitive haemopoietic cells in vivo. The properties of CSFs have made them useful in treating malignant disease: G-CSF, in particular, has been used to reduce the period of neutropaenia that follows cytotoxic therapy for various malignancies. The success of these early trials gives ground for cautious optimism about the clinical use of these compounds.

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.

Synovial fluid from rheumatoid arthritis patients induces polyclonal antibody formation in vivo

Our previous studies demonstrated the presence of a T-cell replacing factor in the synovial fluid (SF) of patients with rheumatoid arthritis (RA) and that RA-SF can activate, selectively, the induction of IgG2b antibody secreting cells in lipopolysaccharide (LPS)-pretreated mouse spleen cell cultures. In the present study the effect of RA-SF was tested in vivo in mice. Injection of the polyclonal activator LPS induced the production of IgM and IgG3 secreting cells in normal mice. However, the addition of RA-SF led to a selective increase in the production of IgG2b with a peak response on day 5 and IgG1 plaque-forming cells (PFC) with a peak on day 7. Neither the IgG2b nor IgG1 responses were caused by specific immunity against heterologous proteins present in RA-SF, as injection of in vitro inactive RA-SF samples did not induce PFC. The effect on B cells of RA-SF was further evaluated by injection of RA-SF in combination with LPS to the Xid B-cell deficient CBA/N mice. RA-SF had identical effects in CBA/N as in normal mice. The biological implication of these findings is discussed. Our earlier results support the idea that B cells are endogenously activated in RA patients. We have speculated that this activation is caused by the B-cell differentiation factor which is present in SF. Therefore, we also tested whether RA-SF could influence antibody-forming cells in mice that spontaneously develop autoimmunity. We found that injection of RA-SF alone, in the absence of any other activating substance, induced a very marked increase of IgG producing cells in (NZW x NZB) F1 hybrid mice. From a relatively high background level the RA-SF could still induce an up to 100-fold increase in the numbers of PFC in spleens of such mice.

Pharmacology of the colony-stimulating factors

Leukocyte production is influenced by a family of glycoproteins called colony-stimulating factors. Two of these have been purified, cloned and produced in quantities sufficient for clinical use. Granulocyte colony-stimulating factor (G-CSF) preferentially stimulates neutrophil production and has been shown to reduce the duration of neutropenia following chemotherapy. G-CSF therapy also has beneficial effects in a variety of other neutropenic states. Granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulates neutrophil, monocyte and eosinophil production and function. GM-CSF is associated with more diverse haematological and clinical effects. George Morstyn and colleagues summarize the promising results from the early clinical trials with these new therapeutic agents.

Polypeptides controlling hematopoietic blood cell development and activation. II. Clinical results

Colony-stimulating factors (CSFs) have entered the clinical arena. Several investigators have explored, in first clinical phase I studies, different routes of administration to define the optimum biological dose, maximum tolerated dose, toxicity, and pharmacokinetics of these reagents. It has been demonstrated that recombinant human (rh) granulocyte-macrophage CSF (GM-CSF) and granulocyte CSF (G-CSF) can be safely administered over a broad dose range to increase number of circulating granulocytes in man. More recently, GM-CSF and G-CSF have been involved in phase Ib/II studies to assess the granulopoietic responses of patients with granulocytopenia due to various underlying disease states including myelodysplastic syndrome, aplastic anemia, cyclic neutropenia, Kostmann's syndrome, and the acquired immuno-deficiency syndrome. Both factors were also investigated with respect to their potential to prevent chemotherapy induced granulocytopenia or to accelerate recovery from that condition. The short-term effects of rh GM-CSF after autologous bone marrow transplantation for various solid tumors and lymphoid malignancies were assessed as well. In this article we will focus on recent results that have emerged from in vivo studies utilizing CSFs.

The pattern of myeloid suppression and recovery after the addition of methotrexate to murine long-term bone marrow culture

Treating long-term bone marrow culture with 10(-7)-10(-5) M methotrexate caused a 95% reduction in myelopoiesis as assessed by supernatant cell count and granulocyte/macrophage colony forming unit number. The suppression was irreversible with 10(-5) M methotrexate. Complete recovery of myeloid cell production occurred four and five weeks after cultures were treated with either 10(-7) M or 10(-6) M methotrexate, respectively. The suppression of myelopoiesis was completely prevented if 10(-3) M leucovorin was added to culture within 6 h of 10(-6) M methotrexate. The addition to culture of lung conditioned medium containing high concentrations of granulocyte/macrophage colony-stimulating factor shortened the time of myelopoietic suppression by one week. The addition of WEHI-3B medium containing both interleukin 3 and GM-CSF shortened the suppression by two weeks. This in vitro model provides unique opportunities to examine mechanisms involved in the myelopoietic and chemotherapy-induced suppression. A close analysis of approaches to modify the recovery process will also be possible.