Molecular cloning of cDNA encoding a murine haematopoietic growth regulator, granulocyte-macrophage colony stimulating factor

Three-dimensional structure of recombinant human granulocyte-macrophage colony-stimulating factor

The crystal structure of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) has been determined at 2.8 A resolution using multiple isomorphous replacement techniques. There are two molecules in the crystallographic asymmetric unit, which are related by an approximate non-crystallographic 2-fold axis. The overall structure is highly compact and globular with a predominantly hydrophobic core. The main structural feature of rhGM-CSF is a four alpha-helix bundle, which represents approximately 42% of the structure. The helices are arranged in a left-handed antiparallel bundle with two overhand connections. Within the connections is a two-stranded antiparallel beta-sheet. The tertiary structure of rhGM-CSF has a topology similar to that of porcine growth factor and interferon-beta. Most of the proposed critical regions for receptor binding are located on a continuous surface at one end of the molecule that includes the C terminus.

Epidermal growth factor stimulates macrophage colony-stimulating factor (M-CSF) mRNA expression and M-CSF release in cultured murine stromal cells

Macrophage colony-stimulating factor (M-CSF) released by stromal cells of the bone marrow microenvironment plays a crucial role in the growth and proliferation of mononuclear cells. Several peptide mitogens including interleukin-1, tumour necrosis factor, platelet-derived growth factor and fibroblast growth factor stimulate the release of M-CSF and may be important in mediating the haematopoietic response to inflammation. Epidermal growth factor (EGF), released from platelets during aggregation, is mitogenic for a variety of cell types and may cause the release of certain cytokines. In this study we used the TC-1 murine stromal cells which constitutively secrete M-CSF as a model to study the regulation of M-CSF in response to EGF. EGF markedly stimulated the steady state expression of M-CSF mRNA with a peak effect observed at 3 h. This was associated with the release of M-CSF protein as determined by radioimmunoassay. EGF also stimulated DNA synthesis in a concentration dependent manner. Although TC-1 cells express GM-CSF mRNA, this was not induced by EGF. These findings suggest that EGF is a key regulatory molecule for M-CSF and may indirectly effect haematopoiesis via the release of M-CSF from stromal cells.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF): receptor biology, signal transduction, and neutrophil activation

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) are two of the growing number of recognized cytokines involved in the regulation of hematopoiesis. The purification of these factors and the subsequent cloning of the cDNAs which encode these proteins have led to their widespread clinical use in the setting of therapy or disease-induced myelosuppression. Although originally purified on the basis of their colony-stimulating properties, GM-CSF and G-CSF may also play important roles in the regulation of effector cell function. The mechanisms underlying progenitor cell proliferation and effector cell stimulation remain poorly understood. However, the characterization of the GM-CSF and G-CSF receptors and recent work in signal transduction are helping to elucidate these mechanisms. This paper will review the biology of the GM-CSF and G-CSF receptors, the mechanisms of post-receptor signal transduction, and the resultant effects on neutrophil function. In addition, the current and potential clinical uses of these factors will be examined in light of their ability to activate and perhaps enhance the function of neutrophils.

Evaluation of human N-linked glycosylation sites in murine granulocyte-macrophage colony-stimulating factor

Nonglycosylated murine and human granulocyte-macrophage colony-stimulating factor have a molecular mass of approximately 14.5 kDa predicted from the primary amino acid sequence. The expression of both proteins in COS cells leads to a heterogeneous population of molecules that differ in the degree of glycosylation. Both human and murine molecules contain two N-linked glycosylation sites that are situated in nonhomologous locations along the linear sequence. Despite this difference both proteins show a similar size distribution among the glycosylation variants. These studies analyze the effects of introducing in the murine protein novel N-linked glycosylation sites corresponding to those sites found in the human molecule. A panel of molecules composed of various combinations of human N-linked glycosylation sites in either the presence or the absence of murine N-linked glycosylation was compared. Substitution of a proper human N-linked glycosylation consensus sequence at Asn 24 did not result in N-linked glycosylation, nor was there any considerable effect on bioactivity. Replacement of the N-linked glycosylation consensus sequence at Asn 34 results in glycosylation similar to that found in the human molecule and causes a significant decrease in bioactivity. These data suggest that the position of N-linked glycosylation is critical for maximal bioactivity in a particular species and that the changes in position of these sites in different species probably occurred during evolution in response to changes in their receptors.

Molecular cloning of calmodulin mRNA species which are preferentially expressed in neurons in the rat brain

A cDNA clone designated NGB, which was isolated from a rat brain expression library, detected two mRNA species of 1.8 and 4.0 kb which are highly enriched in brain tissue. cDNAs NGB1 and NGB2 corresponding to these two mRNAs have been isolated and characterized. Sequence data showed that both mRNA species contain the same open reading frames but differ in their 3' untranslated regions. The open reading frame encodes a calmodulin protein of 148 amino acids. Both mRNA species are derived from the rat CaMI gene by utilization of different polyadenylation addition sites. Analysis of the 3' untranslated sequence which is unique to the larger mRNA species revealed a putative AU-rich 'destabilizer' sequence which is thought to be involved in mechanisms of selective mRNA breakdown. In situ hybridization studies revealed that the two calmodulin mRNAs are expressed strongly in neuronal cells in the adult rat brain. Levels of the two mRNA species increased during early postnatal development.

Recombinant human hematopoietic growth factors in the treatment of cytopenias

The hemolymphopoietic growth factors, including the colony-stimulating factors (CSF) and interleukins (IL), are described and categorized on the basis of their biological features in laboratory systems. Although these agents are varied and exceptions exist, in general they lack lineage specificity although they may express lineage-predominant activity. They act at multiple levels of hemolymphopoietic cell differentiation, demonstrate additive or synergistic effects when combined in vitro, require surface receptors on target cells to directly express their activity, and may be produced by a variety of cells. This framework of behavioral generalizations, completed by the specifics of each factor's activity, despite the artifactual and simplified nature of in vivo systems, forms the basis for concepts of in vitro activity and for clinical applications. Hemolymphopoietic growth factors studied in the clinic have demonstrated impressive and important activity, validating much of the in vitro data. Granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) have clearly reduced neutropenia and infection rates when administered following conventional chemotherapy and high-dose chemotherapy followed by autologous bone marrow transplantation. To a varying degree, similar results with G-CSF and/or GM-CSF have been described in other diseases including acute myelogenous leukemia (AML) treated following induction chemotherapy, myelodysplastic syndrome, hairy cell leukemia, aplastic anemia, and chronic neutropenias. In preliminary studies IL-3 has been shown to have similar qualitative activities. However, these agents have not demonstrated a reproducible salutary impact on platelet or red cell lineages. Adverse effects on platelet counts and/or platelet recovery have been noted. Additionally, hemolymphopoietic growth factor receptors have been identified on malignant cells, suggesting that these factors could stimulate neoplastic growth. Studies with GM-CSF and IL-3 have demonstrated blast proliferation in some cases of AML and myelodysplasia, underscoring the capacity of these agents to stimulate the growth of myeloid leukemia. No clinically evident impact of these factors upon the growth of solid tumors has been identified but this issue has not been adequately studied. The toxicity of these agents has been surprisingly limited and appears to be related to their biologic activities. Hemolymphopoietic growth factors as single agents have broad clinical applications in cytopenias. Several methods for enhancing the clinical activity of these agents are under study, including the use of combinations of growth factors synergistic in vitro.

Novel fold and putative receptor binding site of granulocyte-macrophage colony-stimulating factor

Granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulates the development of and the cytotoxic activity of white blood cells. Recombinant human GM-CSF has proven useful in the treatment of blood disorders. The structure of GM-CSF, which was determined at 2.4 angstrom resolution by x-ray crystallography, has a novel fold combining a two-stranded antiparallel beta sheet with an open bundle of four alpha helices. Residues implicated in receptor recognition, which are distant in the primary sequence, are on adjacent alpha helices in the folded protein. A working model for the receptor binding site is presented.

Staphylococcal lipoteichoic acid exerts growth factor-like activity towards human and murine cells

Lipoteichoic acid (LTA) was extracted from Staphylococcus saprophyticus strain S1 and tested for the capacity to induce hematopoietic and lymphatic cell proliferation. As compared to nontreated cells, the number of human bone marrow cells significantly increased in the presence of low LTA concentrations. Optimal growth was observed on the fifth day of in vitro incubation. After exposure to LTA, the lymphocyte proliferation rate also increased in a dose and time dependent manner. On the other hand, human epithelial cells and fibroblasts did not show enhanced growth activities in the presence of LTA.

Interleukin-1 administration to C3H/HeJ mice after but not prior to infection increases resistance to Salmonella typhimurium

Interleukin-1 (IL-1) treatment of C3H/HeN and C3H/HeJ mice prior to infection with Salmonella typhimurium increased the survival fraction only in C3H/HeN mice. IL-1 administration after infection resulted in a significant increase in mean survival time in C3H/HeJ but not C3H/HeN mice. Bacterial growth in IL-1-treated C3H/HeJ mice was less than that in control mice.

Cloning and expression of a cDNA encoding ovine granulocyte-macrophage colony-stimulating factor

A cDNA encoding ovine granulocyte-macrophage colony-stimulating factor (GM-CSF) has been cloned using the polymerase chain reaction. The nucleotide sequence is approx. 93% identical to the published bovine GM-CSF-encoding sequence, 84% to the human sequence and 73% to the murine sequence. The deduced amino acid sequence of the ovine GM-CSF protein was found to be 80% identical to both the human and bovine proteins and 57% to the murine protein. Transient expression of recombinant ovine GM-CSF in COS-1 cells was obtained and its biological activity investigated in a bone-marrow colony-forming assay. Ovine GM-CSF was found to promote the formation of granulocyte-macrophage colonies as well as eosinophil, neutrophil and monocyte/macrophage colonies, an activity characteristic of GM-CSF in other species. Recombinant human GM-CSF was found to have no proliferative effect on ovine bone-marrow cells.

GM-CSF augments the immunosuppressive capacity of neonatal spleen cells in vitro

Addition of exogenous granulocyte-macrophage colony stimulating factor (GM-CSF) to cultures of adult murine spleen cells with sheep red blood cells (SRBC) results in an augmented plaque forming cell (PFC) response. The influence of GM-CSF on the ability of neonatal spleen cells to suppress the anti-SRBC plaque forming response of adult spleen cells was tested by adding GM-CSF to cultures of neonatal and adult spleen cells. The suppressive capacity of the neonatal spleen cells was augmented by exogenous GM-CSF. The augmented suppression of the neonatal spleen cells was dependent on a G-10 adherent population since the addition of GM-CSF to cultures containing G-10 passed neonatal spleen cells resulted in an augmented PFC response and not suppression. Neonatal splenic glass adherent cells were also capable of suppressing the response. Neonatal spleen cells or purified neonatal glass adherent spleen cells cultured in the presence of GM-CSF had markedly increased levels of PGE2 in the culture supernatant. Neonatal spleen cells cultured with GM-CSF had increased numbers of morphologically identifiable macrophages after 48 hr of culture. Both irradiation and G-10 passage of the neonatal spleen diminished the numbers of macrophages formed in response to GM-CSF, and both of these manipulations resulted in reversal of suppression in response to GM-CSF. Thus, the augmented suppressive capacity of neonatal spleen cells in response to GM-CSF is probably mediated by its ability to drive monocyte to macrophage differentiation as well as increase the suppressive capacity of the existing neonatal splenic macrophages by increasing their production of PGE2.

Linkage mapping of the human CSF2 and IL3 genes

Interleukin 3 (encoded by the IL3 gene) and granulocyte-macrophage colony-stimulating factor (encoded by the CSF2 gene) are small secreted polypeptides that bind to specific cell surface receptors and regulate the growth, gene expression, and differentiation of many of the hematopoietic cell lineages, particularly nonlymphoid cells. The IL3 and CSF2 genes have been cloned and mapped to human chromosome bands 5q23-31. Only 10 kilobases of DNA separates the two genes, suggesting that they have a common origin and/or regulation. We have cloned 70 kilobases of genomic DNA that includes the IL3 and CSF2 genes, as well as flanking sequences, and report a physical map of this region. Several unique-sequence DNA segments have been identified in this region, and one of these fragments detects two restriction fragment length polymorphisms in DNA from unrelated Caucasians. Segregation of these DNA polymorphisms was followed in the Centre Etudé du Polymorphisme Humaine (CEPH) panel of 40 large three-generation pedigrees, and linkage was detected with 17 genetic markers previously typed in these families. Multipoint linkage analysis permits the placement of the region containing the IL3 and CSF2 structural genes on the recombination-genetic linkage map of chromosome 5q and thereby allows the role of these genes in leukemogenesis to be more critically examined.

Colony-stimulating factor 1 expression is down-regulated during the adipocyte differentiation of H-1/A marrow stromal cells and induced by cachectin/tumor necrosis factor

We isolated clonal sublines of the established mouse marrow stromal cell line, H-1. These clonal sublines underwent differentiation into adipocytes in various degrees. One subline, H-1/A, underwent adipocyte differentiation after confluence, while another subline, H-1/D, did not differentiate. In H-1/A cells, the 4.5- and 2.5-kb major mRNA species of colony-stimulating factor 1 (CSF-1) were expressed before differentiation and were down-regulated at a posttranscriptional level during the differentiation of H-1/A cells. The down-regulation of the CSF-1 gene was not a result of arrested cellular growth, because no down-regulation was detected in the nondifferentiating sister line, H-1/D. This down-regulation appeared to be an early event in differentiation. Cachectin/tumor necrosis factor transiently induced the expression of CSF-1 and inhibited the differentiation of H-1/A cells into adipocytes. This induced expression of CSF-1 was due to an increased rate of transcription.

Monoclonal antibodies against a preadipose cell line (MC3T3-G2/PA6) which can support hemopoiesis

Monoclonal antibodies against a mouse preadipose cell line (MC3T3-G2/PA6:PA6), which can support hemopoiesis by direct cell-to-cell interaction, were produced and characterized. The antibodies react with PA6 but not PA6-M (a mutant cell line) which has the capacity neither to contact with hemopoietic stem cells (HSCs) nor to support hemopoiesis. Endosteal cells in the bone marrow show positive staining to these antibodies. They inhibit pseudoemperipolesis of PA6 to HSCs, resulting in a significant decrease in hemopoietic cell number. These findings suggest that the monoclonal antibodies bind to the stromal cell receptors for HSCs and block the binding of HSCs to stromal cells leading to suppression of hemopoiesis.

A correlation between GM-CSF gene expression and metastases in murine tumors

Using 14 transplantable murine tumors, we investigated a possible correlation between their ability to produce the cytokine GM-CSF and the spontaneous metastatic potential when mice were subcutaneously inoculated. The following results were obtained: (1) seven tumors, which produced severe pulmonary metastases and metastatic swelling of lymph nodes, exhibited the ability to produce GM-CSF activity in culture. The cell population analysis revealed that the cells producing GM-CSF were tumor cells themselves, but that contaminating macrophages/granulocytes and T lymphocytes did not produce GM-CSF. The mRNA for GM-CSF was also found in all of these highly metastatic tumors tested. In mice inoculated with a highly metastatic tumor, the GM-CSF mRNA was also found in lungs; (2) in 3 other tumors, which produced histological but not macroscopical pulmonary metastases, no GM-CSF activity could be detected in the culture fluids. GM-CSF mRNA was, however, detected in the tumor cells in the presence of an mRNA-stabilizing agent, cycloheximide, suggesting the possibility that the tumor cells of this type were transcribing GM-CSF gene, and secreting it in undetectable levels; (3) in culture of the 4 remaining poorly or non-metastatic tumors, neither CSF activity nor GM-CSF mRNA could be detected even in the presence of cycloheximide. GM-CSF mRNA was also not found in lungs of tumor-bearing mice. Our results indicate that there may be a correlation between GM-CSF gene expression in tumor cells and spontaneous metastases.

Cloning and sequencing of the cDNA for ovine granulocyte-macrophage colony-stimulating factor (GM-CSF)

Colony-stimulating factors (CSFs) are not only regulators of haemopoiesis but can also enhance the function of mature myeloid cells, and are therefore potential immune adjuvants. By use of the polymerase chain reaction (PCR) with primers based on the bovine granulocyte-macrophage CSF (GM-CSF) sequence, we have amplified the cDNA for ovine GM-CSF, produced from crude mRNA extracted from alveolar macrophages. The PCR product was cloned into pUC119, and electroporated into Escherichia coli. The complete nucleotide sequence of two clones, and the partial sequence of eight others, was determined. At the nucleotide and amino acid levels, the ovine and bovine GM-CSF sequences are 91% and 81% homologous, respectively.

Chronic neutropenia. A new canine model induced by human granulocyte colony-stimulating factor

Normal dogs were treated with recombinant human granulocyte colony-stimulating factor (rhG-CSF) at 10 micrograms/kg/day for 30 d, which caused an initial neutrophilia, followed by a prolonged period of chronic neutropenia. A control dog treated with recombinant canine G-CSF (rcG-CSF) showed persistent neutrophilia over 3 mo. Serum from dogs during neutropenia contained an antibody to rhG-CSF, which neutralized the stimulatory effects of both rhG-CSF and rcG-CSF on dog marrow neutrophilic progenitor cell growth and on NFS-60 cell proliferation. 4 mo after discontinuation of rhG-CSF, the dogs' neutrophil counts returned to the normal range. Rechallenge with the rhG-CSF re-induced severe neutropenia in 1 wk. Neutropenia was transferred by plasma infusion from a neutropenic dog to a previously normal dog. These data suggest that human rhG-CSF immunizes normal dogs and thereby induces neutralization of endogenous canine G-CSF and neutropenia. This model system should allow more precise definition of the in vivo role of G-CSF.

Colony-stimulating factor 1 expression is down-regulated during the adipocyte differentiation of H-1/A marrow stromal cells and induced by cachectin/tumor necrosis factor

We isolated clonal sublines of the established mouse marrow stromal cell line, H-1. These clonal sublines underwent differentiation into adipocytes in various degrees. One subline, H-1/A, underwent adipocyte differentiation after confluence, while another subline, H-1/D, did not differentiate. In H-1/A cells, the 4.5- and 2.5-kb major mRNA species of colony-stimulating factor 1 (CSF-1) were expressed before differentiation and were down-regulated at a posttranscriptional level during the differentiation of H-1/A cells. The down-regulation of the CSF-1 gene was not a result of arrested cellular growth, because no down-regulation was detected in the nondifferentiating sister line, H-1/D. This down-regulation appeared to be an early event in differentiation. Cachectin/tumor necrosis factor transiently induced the expression of CSF-1 and inhibited the differentiation of H-1/A cells into adipocytes. This induced expression of CSF-1 was due to an increased rate of transcription.

In vivo effect of a large amount of allogeneic granulocytes on reconstitution of hemopoietic cells of irradiated mice

The in vivo effects of allogeneic granulocytes on the reconstitution of splenic and bone marrow CFUs and CFUc numbers were investigated using irradiated mice. When allogeneic granulocytes were intraperitoneally injected into irradiated BDF1 mice (260 rads), the reconstitution of CFUs in both spleen and bone marrow as well as the hematocrit were enhanced, while the reconstitution of splenic or bone marrow CFUc numbers was transiently suppressed and then enhanced. The magnitude of enhancement was dose-dependent. These results suggest that granulocytes injected into irradiated mice might act as enhancing effectors on the in vivo reconstitution of hemopoietic cells.

Hematopoietic colony-stimulating factors

In summary, hematopoietic growth factors have been discovered, biochemically characterized, cloned, produced by recombinant DNA technology, and put into clinical use in a period of 25 years. We are approaching a greater understanding of the cellular anatomy and molecular mechanisms that regulate production of the CSFs, the ways in which the CSFs interact with their cell surface receptors and trigger their biological effects, the nature of these receptors themselves and their mechanisms of signal transduction, and the effects of the CSFs in vitro and in vivo on hematopoietic progenitor cells and mature leukocytes. However, many questions remain. What is the mechanism that couples growth-factor binding to the triggering of cellular proliferation? How do multi-CSF and GM-CSF cross-compete at the level of the cell-surface receptor, and yet show no primary amino acid sequence homology? What are the mechanisms that regulate the tissue expression profile of multi-CSF compared to the genetically similar growth factor GM-CSF? And, what are the optimal dosages, schedules of administration, and combinations of CSFs optimal for each of several conditions of marrow failure? These are but a few of the questions that continue to occupy much current research interest.

Methylcholanthrene-induced murine fibrosarcoma cell line BMT-11 secretes granulocyte colony-stimulating factor

Murine fibrosarcoma cell line BMT-11 was induced with 3-methylcholanthrene and maintained in culture. Transplantation of BMT-11 into syngeneic C57BL/6 mice produced leukocytosis consisting of marked increments of neutrophils and monocytes associated with massive splenomegaly. In order to elucidate the mechanisms of this leukemoid reaction, we studied the changes occurring in hematopoietic progenitor cells in BMT-11-transplanted mice. The numbers of granulocyte-macrophage colony-forming units (CFU-GM), erythroid colony-forming units (CFU-E), erythroid burst-forming units (BFU-E), and mixed colony-forming units (CFU-Mix) in the spleen showed dramatic 216-fold, 18-fold, 64-fold, and 80-fold increases, respectively, relative to the value in the control mice 5 weeks after the BMT-11 implantation. In contrast, the levels of progenitor cells in the bone marrow remained within normal limits. The nature of the colony-stimulating factor (CSF) secreted from BMT-11 tumor cells was also studied. BMT-11-conditioned medium (BMT-11-CM), BMT-11 tumor extract, and sera from the mice bearing transplanted BMT-11 tumor contained CSF that stimulated mainly granulocyte and macrophage lineages. Furthermore, the expression of the granulocyte colony-stimulating factor (G-CSF) gene in BMT-11 cells were detected by Northern blot analysis.

Trophic effect of granulocyte-macrophage colony-stimulating factor on central cholinergic neurons in vitro

Granulocyte-macrophage colony-stimulating factor (GM-CSF) elevated choline acetyltransferase (ChAT) activities of mouse septal neurons as well as of cholinergic hybridoma line cells SN6.10.2.2 in vitro. It augmented ChAT activities and neurite extension of interleukin 3-activated cholinergic neurons. Thus, GM-CSF should be added as a trophic factor for central cholinergic neurons.

The expression of granulocyte/macrophage colony-stimulating factor in activated mouse lymphocytes declines with age

The expression of granulocyte/macrophage colony-stimulating factor (GM-CSF) was studied in spleen lymphocytes isolated from male C57BL/6J mice of 6, 20, and 29 months of age. GM-CSF expression (biological activity and mRNA level) was maximum after culturing the lymphocytes for 45 hr with concanavalin A and phorbol myristate acetate. The induction of both GM-CSF activity and mRNA levels was observed to decline over 60% between 6 and 29 months of age. The age-related decline in the level of GM-CSF paralleled the age-related decline in the mRNA levels of interleukin-2 and interleukin-3.

The influence of S17 stromal cells and interleukin 7 on B cell development

A clonal assay was used to study different stimuli involved in the progression of fetal liver B cell precursors to mature B lymphocytes. In this report we replaced fetal liver heterogenous feeder cells by a recombinant growth factor, interleukin 7 (IL 7), and a clonal stromal cell line, S17. Under those conditions we could clone 1 in 10 B220+ B cell precursors from fetal liver and the cells could differentiate to a mitogen-responsive, immunoglobulin-secreting stage. We found that IL 7 stimulates proliferation of B220+ precursors but is not sufficient to support maturation of those precursors to a stage of mitogen responsiveness. We show further that the cell line S17 does not produce IL 7 at functionally detectable level but provides support for B cell maturation. We conclude that this cell line supplies an exogenous stimulus required by B cell precursors to become mature lymphocytes. We describe therefore two stages in pre-B cell development: (a) IL 7-dependent proliferation and (b) S17-dependent maturation to mitogen reactivity. Further studies demonstrate that S17 has a profound effect on B cells by increasing the clonal efficiency of lipopolysaccharide-responsive cells to nearly 1:1 B cell in the spleen of adult C57BL/6 mice.

Hematopoietic growth factors: overview and clinical applications, Part II

The growth and differentiation of blood cells is regulated by a group of at least 12 glycoproteins, collectively known as hematopoietic growth factors. Advances in protein biochemistry and molecular genetics have provided the tools for the bulk production of these hormones for clinical application. Clinical trials of macrophage colony-stimulating factor, granulocyte macrophage colony-stimulating factor, granulocyte colony-stimulating factor, and interleukin-3 have all demonstrated significant effects on the peripheral blood counts of the recipients. The clinical usefulness of at least two of these agents in ameliorating post-chemotherapy myelosuppression, in the treatment of other cytopenias, and in enhancing engraftment after bone marrow transplantation has already been demonstrated. Potential applications to the therapy and diagnosis of other clinical disorders is under study. The history of the elucidation of these growth factors, our current understanding of their properties, interactions, and clinical effects, and the potential prospects for their future use in the manipulation of human blood cell production are the subject of this review.

In vivo administration of cytokine in allogeneic bone marrow chimeras

When we analyzed the in vivo efficacy of cytokine administration in murine allogeneic bone marrow chimeras, mitogen-induced responses to ConA, PHA, LPS, or PWM were increased by the in vivo administration of human recombinant granulocyte colony-stimulating factor (rG-CSF), human recombinant interleukin 2 (rIL-2), or WEHI-3B conditioned medium (CM). Furthermore, we found increased alloreactive mixed lymphocyte reactions (MLRs) against donor and/or host type alloantigens in spleen cells from (BALB/c----C3H/He) chimeras, although cytotoxic activity against BALB/c or C3H/He target cells was not detected in spleen cells from these chimeras. Since no significant increase of T cells or Ia positive cells was observed, some functional activation, rather than changes in the cell count, appeared to relate to increase immunoreactivity. An increased IL-2 production in spleen cells from chimeras injected with cytokine was observed shortly after the cessation of cytokine administration. Thereafter, an IL-2 production in these chimeras decreased around 45 days after bone marrow transplantation and then recovered nearly to the control level. An increased IL-2 responsiveness was also observed in spleen cells from these chimeras. These findings suggest that the in vivo administration of rG-CSF as well as rIL-2 or WEHI-3B CM (IL-3) can modulate the immunoreactivity in chimeras via the network of immune systems.

The effects of recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 on the secretory capacity of human blood eosinophils

The effects of recombinant human GM-CSF and interleukin-3 (IL-3) on human blood eosinophil survival, activation, and secretion were studied. Purified normal density eosinophils from patients with the idiopathic hypereosinophilic syndrome (HES) survived in culture for 7 days (50% viable) in the presence of 50 nM GM-CSF or 50 nM IL-3. Neutrophils did not survive after 4 days. No eosinophils survived in the absence of GM-CSF or IL-3. In two out of five patients studied, the cultured eosinophils became elongated with numerous processes. In all five patients the cells became adherent, but there were no morphological signs of degranulation. Both GM-CSF and IL-3 activated eosinophils, transforming the storage form of eosinophil cationic protein (ECP) into the secreted form. The proportion of activated cells increased from less than 20% to over 50% after 4 days in culture. However, GM-CSF and IL-3 did not induce secretion on their own. On the other hand, when GM-CSF/IL-3-activated eosinophils were exposed to known secretory stimuli, there was a six-fold increase in the amount of ECP released when the cells were stimulated with sepharose coated with C3b, and a two-fold increase when they were stimulated with sepharose-activated whole autologous serum. Eosinophils from patients taking steroids were unable to secrete their granule contents, even though they became activated by GM-CSF and IL-3. A novel finding was that sepharose-activated whole serum was an extremely potent secretory signal for ECP, releasing up to 50% of the total ECP content. These studies showed that GM-CSF and IL-3 prime eosinophil effector function by initiating granule solubilization which is the first step in the secretory event, without affecting the subsequent extracellular release of granule proteins.

Polarized transport of the polymeric immunoglobulin receptor in transfected rabbit mammary epithelial cells

A cDNA for the rabbit low Mr polymeric immunoglobulin (poly-Ig) receptor was expressed in an immortalized rabbit mammary cell line. The intracellular routing of the receptor and its cell surface expression was analyzed in stably transfected cells grown on permeable supports. Initially the cells formed a monolayer with no transmural electrical resistance. All monolayer cells expressed the poly-Ig receptor and cytokeratin 7 filaments characteristic of luminal mammary cells but absent in myoepithelial cells. Within 7 d in culture, the cells underwent cytodifferentiation and formed a bilayer with a transepithelial electrical resistance of approximately 500 omega x cm2. Upper layer cells formed tight junctions with adjacent cells and gap junctions with basal cells. Expression of the poly-Ig receptor and cytokeratin 7 was restricted to the cells from the upper layer. The kinetics of receptor biosynthesis and processing was similar to that reported for rabbit mammary gland and rat liver. The receptor was cleaved at the apical cell surface and release of secretory component into the apical medium occurred with a half-time of approximately 2 h. Selective cell surface trypsinization combined with pulse-chase experiments served to determine at which cell surface domain newly synthesized receptor appeared first. The receptor was digested with a half-time of approximately 60 min with trypsin present in the basolateral medium and 90 min with apical trypsin. These data are consistent with selective targeting of newly synthesized receptor to the basolateral surface. The results indicate that transcytosis of the receptor from basolateral to apical membrane in the presence or the absence of its ligand requires approximately 30 min. Cleavage of the receptor by endogenous protease is not concomitant with its appearance at the apical surface, but requires additional time, thus explaining the presence of intact receptor on the apical membrane.

Localization of the murine leukemia inhibitory factor gene near the centromere on chromosome 11

Leukemia inhibitory factor (LIF) is a glycoprotein with divergent activities: It induces the differentiation of certain myeloid leukemic cells, inhibits the differentiation of embryonic stem cells, and promotes bone remodelling in vivo and in vitro. The murine LIF gene has been assigned to the proximal region of chromosome 11 at sub-bands A1-A2, by analysis of a panel of mouse x Chinese hamster somatic cell hybrids and by in situ hybridization. Interestingly, the proximal portion of chromosome 11 has been shown, by virtue of its parental origin effects, to contain gene(s) involved in fetal growth. It is also interesting that there is a preponderance of chromosome 11 abnormalities in embryonal carcinoma cells. The localization of the murine LIF gene confirms the homology of a portion of murine chromosome 11 with human chromosome 22q, the site of the human LIF gene.

Effects of bestatin on myelopoietic stem cells in normal and cyclophosphamide-treated mice

The effect of bestatin on hematopoietic parameters and bone marrow progenitor activity (colony-forming unit - granulocyte/macrophage: CFU-GM) was examined in normal and myelosuppressed C57BL/6 mice. CFU-GM frequency and absolute number were determined with a limiting dilution analysis of bone marrow cells in soft agar using recombinant murine colony-stimulating factor - granulocyte/macrophage. We report that bestatin increased splenic, bone marrow, and peripheral blood cellularity and the number of CFU-GM over a dose range from 2.5 mg/kg through 100 mg/kg following i.p., i.v., or oral administration. The greatest myeloid stimulation was observed following multiple injections of bestatin. Bestatin also increased the recovery from cyclophosphamide-induced myelodepression as measured by these parameters. The hematopoietic properties of bestatin following oral administration is of potential importance for clinical application.

Increased H-2Dd expression following infection by a molecularly cloned ecotropic MuLV

The biological consequences of radiation leukemia virus (RadLV) infection include the stimulation of H-2Dd antigen expression in resistant mouse strains and thymoma induction in susceptible strains. In an effort to understand the genetic basis of these phenomena, the integrated ecotropic RadLV genome has been examined in a number of primary RadLV-induced tumors, as well as thymomas adapted to in vitro passage; considerable heterogeneity was observed. Examination of these polymorphic viral sequences should help define the viral gene(s) involved in the biological effects of RadLV infection; toward this end, integrated RadLV genomes were molecularly cloned and examined. The genomes and their flanking sequence were characterized by restriction enzyme analysis. Three unique viral genomes were obtained which represent four integration sites. The three RadLV genomes are shown to carry polymorphisms of the original tumor. Following DNA transfection, one of the three genomes replicated in and reinfected both mouse thymocytes and fibroblasts, but not mink fibroblasts in vitro. Virus encoded by the other two DNA genomes could not be recovered following transfection into any of the three cell types. One of these two apparently defective retroviruses encodes a truncated p15E molecule, while the other has elongated long terminal repeats (LTRs). The non-defective ecotropic isolate was collected from in vitro tissue culture supernatants, concentrated, and used to infect mice. Thymocytes of infected, resistant mice were shown to express elevated levels of H-2Dd antigen as early as 12 days post infection, a hallmark of RadLV infection.

Flow cytometric analysis of recombinant murine GM-CSF (rmuGM-CSF) induced changes in the distribution of specific cell populations in vivo

The changes in the distribution of granulocytes, monocytes, and lymphocytes in various tissue compartments following subcutaneous (SC) administration of recombinant murine GM-CSF (rmuGM-CSF) in vivo was determined by flow cytometry in time course studies. Balb/c mice were given single, daily SC injections of 1 or 4 micrograms of rmuGM-CSF for 10 days. Flow cytometric analysis was performed on bone marrow (BMC), peritoneal exudate (PEC), and peripheral blood (PBC) cell preparations from mice treated for 1, 3, and 10 days. Dual fluorescence was employed to gate on leukocytes (T200+) and analyze for Ig+, Thy 1.2+, MAC+, and 8C5+ (granulocytes) cells. The analyses indicated that SC-rmuGM-CSF increased the percentage of 8C5+ cells in PBC after 1 day of treatment. However, significant changes in the cell composition of PEC and BMC were not observed until day 10 of treatment and included increases in 8C5+ cells and the myeloid cell population, respectively. Side scatter analysis (cell density) of PBC and PEC indicated that the percentage of the granulocytic cell population increased significantly in rmuGM-CSF treated mice. The changes observed in PEC and BMC appeared to be dose-related whereas those observed in PBC were not. These data clearly demonstrate the utility of flow cytometric analyses for detecting selective effects of cytokines on cell populations that are involved in host defense mechanisms.

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.

Expression cloning of a receptor for human granulocyte-macrophage colony-stimulating factor

Two cDNA clones encoding a receptor for human granulocyte-macrophage colony-stimulating factor (hGM-CSF-R) were isolated by expression screening of a library made from human placental mRNA. Pools of recombinant plasmid DNA were electroporated into COS cells which were then screened for their capacity to bind radioiodinated hGM-CSF using a sensitive microscopic autoradiographic approach. The cloned GM-CSF-R precursor is a 400 amino acid polypeptide (Mr 45,000) with a single transmembrane domain, a glycosylated extracellular domain and a short (54 amino acids) intracytoplasmic tail. It does not contain a tyrosine kinase domain nor show homology with members of the immunoglobulin super gene family, but does show some significant sequence homologies with receptors for several other haemopoietic growth factors, including those for interleukin-6, erythropoietin and interleukin-2 (beta-chain) and also to the prolactin receptor. When transfected into COS cells the cloned cDNA directed the expression of a GM-CSF-R showing a single class of affinity (KD = 2(-8) nM) and specificity for human GM-CSF but not interleukin-3. Messenger RNA coding for this receptor was detected in a variety of haemopoietic cells known to display hGM-CSF binding, and cross-linking experiments revealed a similar size for the glycosylated receptors in transfected COS and haemopoietic cells.

Granulocyte-macrophage colony-stimulating factor binding sites and oxidative metabolism in human granulocytes

We investigated the interaction between GM-CSF and its receptor on human granulocytes and on several human tumor cell lines. Specific high-affinity binding for GM-CSF was characterized by Scatchard plot analysis. The specific radioactivity of the 125I-labeled derivative of rH. GM-CSF was determined by self-displacement analysis and calculated to be 30 microCi/micrograms. The maximum concentration of binding sites (B max) in granulocytes was 40 fmol/mg protein (2,200 molecules GM-CSF bound/cell) and the dissociation constant (KD) was 0.42 nM. No binding sites for GM-CSF were found in two lung cancer cell lines, SCLC-16HV and NCI-N417 or in the urinary bladder carcinoma cell line 5637, whereas the promyelocytic leukemia cell line HL60 was positive for GM-CSF binding. Time course experiments showed maximum binding of GM-CSF in granulocytes after an incubation period of 60 min and a decrease in binding after an incubation period of 2 h. In parallel, we found a maximum biological signal when granulocytes were preincubated for 90 min with GM-CSF, and a decrease after an incubation time of 120 min. Preincubation of the cells with rH. GM-CSF induced an enhancement of the production of activated oxygen species by the cells in response to PMA.

T-cell nuclei contain a protein that binds upstream of the murine granulocyte-macrophage colony-stimulating factor gene

Stimulation of a murine T-cell line (O18A) by Con A has been shown to cause a large increase in the cytoplasmic granulocyte-macrophage colony-stimulating factor (GM-CSF) mRNA level. Using run-on transcription experiments in isolated nuclei, we have shown that some of this response is from enhanced transcription of the GM-CSF gene. Changes in the transcription rate of this gene can be seen as early as 30 min after adding the Con A. With a DNA fragment mobility-shift assay on nuclear extracts from these cells we detected a protein that binds upstream of the murine GM-CSF gene. Partial purification and concentration of this protein by DEAE-Sephacel and phosphocellulose chromatography enabled us to examine its interaction with DNA in more detail. Competition and methylation interference experiments have shown that the protein binds to the sequence 3'-TCCATCAAGGGG-5' (positions -90 to -82). This sequence is contained within a region found to be involved in regulating inducible GM-CSF transcription in a human T-cell line [Miyatake, S., Seiki, M., Yoshida, M. & Arai, K. (1988) Mol. Cell. Biol. 8, 5581-5587].