Effect of granulocyte colony stimulating factor on neutropenia induced by cytotoxic chemotherapy

Role of interleukin-1 in 4-hydroperoxycyclophosphamide toxicity to bone marrow progenitor cells: a review

We have demonstrated that in vitro preincubation with IL-1 or TNFa for 20 hours can protect human hematopoietic progenitors from lethal doses of 4-HC. On the other hand, preincubation with IL-6 or IL-3, in a similar fashion, did not provide any protection but in fact demonstrated a slight increase in 4-HC toxicity in the same experiments. The observation that IL-1 was still protective even when a purified cell population depleted of accessory cells was used is suggestive of a direct effect of IL-1. Our data also suggest that early progenitor cells including the replatable B;-CFC are the main target of that protection. We believe that using this in vitro assay system will enable us to investigate the possible mechanisms responsible for the protection of these primitive progenitors. From a clinical perspective, future studies should attempt to clarify whether protection by IL-1 is selective for normal hematopoietic cells versus malignant cells and whether these protected primitive progenitors represent the pluripotent stem cells responsible for engraftment of transplanted bone marrow by using an animal model system.

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.

The kinetics of human granulopoiesis following treatment with granulocyte colony-stimulating factor in vivo

Cell proliferation in the bone marrow and blood of two patients with metastatic breast cancer who were treated with granulocyte colony-stimulating factor was studied by using [3H]thymidine labeling and autoradiography. Additionally, the fate of neutrophils labeled with 99mTc-hexamethylpropyleneamineoxime was observed following granulocyte colony-stimulating factor infusion. Proliferation increased in all stages of granulopoiesis, but a significant amount of the increased production stemmed from a greater input to the myeloblast compartment. Changes in the myelogram combined with the increased labeling indicated a faster throughput of cells, which resulted in labeled cells appearing in the circulation within 1 day compared to the normal 4 or 5 days. The 99mTc studies demonstrated no sequestration of circulating neutrophils by spleen, lungs, or liver. The half-life of the circulating neutrophils was not significantly changed, and calculations from the flow of labeled cells to the peripheral blood indicated an increase of 3.2 extra amplification divisions during neutrophil development. The dramatic neutrophil response to granulocyte colony-stimulating factor can therefore be accommodated by a relatively modest increase in granulopoietic activity.

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.

Long-term exposure to retrovirally expressed granulocyte-colony-stimulating factor induces a nonneoplastic granulocytic and progenitor cell hyperplasia without tissue damage in mice

Murine marrow cells infected with a retroviral vector (MPZen) bearing a granulocyte-colony-stimulating factor (G-CSF) cDNA insert were transplanted into lethally irradiated recipients to study the effects of autocrine production of G-CSF in normal hemopoietic cells. Most animals remained healthy with no evidence of tissue damage throughout the observation period (4-30 wk) despite high circulating G-CSF levels (range 2,000-26,000,000 U/ml). A dramatic neutrophilic granulocytosis was observed in all hemopoietic tissues with neutrophilic infiltration occurring in the lung and liver. Spleen, peritoneal, and peripheral blood cellularity increased approximately three-, two-, and eightfold, respectively, but total bone marrow cell counts remained unchanged. Progenitor cell numbers granulocyte-macrophage colony-forming cell (GM-CFC), granulocyte colony-forming cell (G-CFC), burst-forming unit-erythroid (BFU-E), colony-forming unit-erythroid (CFU-E) and mixed colony-forming cells (Mix-CFC) were elevated between 10-100-fold in the spleen, peritoneal cavity, and peripheral blood, but were unaffected or slightly depressed in the marrow. No tumors developed in syngeneic recipients transplanted with bone marrow or spleen cells from such mice, confirming the nonneoplastic nature of the hyperplasia induced by chronic G-CSF stimulation. These experiments also indicated the stable integration of MPZen vectors in infected cells, as evident from the continuous expression of the inserted gene for at least 6 mo, and from the ability of infected stem cells from the primary recipients to express the gene in lethally irradiated secondary recipients.

Bone marrow purging with mafosfamide--a critical survey

Autologous bone marrow transplantation (ABMT) is increasingly used to consolidate remissions, primarily in hematological disease. Various purging strategies have been developed to minimize the risk of reimplantation of tumor cells with the bone marrow autotransplant. Pharmacological purging with the oxazaphosphorine derivative mafosfamide has been studied extensively, and recent clinical data suggest that purging with mafosfamide may translate into superior remission duration if compared to nonpurged ABMT in acute leukemia. Chemical and experimental data relevant to mafosfamide-purging and clinical results are reviewed, with special emphasis on safety aspects.

Granulocyte colony-stimulating factor and neutrophil recovery after high-dose chemotherapy and autologous bone marrow transplantation

Granulocyte colony-stimulating factor (G-CSF) was administered by continuous subcutaneous infusion to 15 patients with non-myeloid malignancies treated by high-dose chemotherapy and autologous bone marrow infusion. G-CSF was given at variable dosage based on neutrophil count. Sustained serum levels of G-CSF were achieved. Neutrophil recovery was accelerated in G-CSF treated patients compared with 18 historical controls and exceeded 0.5 x 10(9)/l at a mean of 11 days after marrow infusion compared with 20 days for controls, a significant difference. This reduction led to significantly fewer days of parenteral antibiotic therapy, 11 versus 18 days in controls, and less isolation in reverse-barrier nursing, 10 versus 18 days.

High-dose chemotherapy with busulphan and cyclophosphamide and bone-marrow transplantation for drug-sensitive malignancies in adults: a preliminary report

The technique of high-dose chemotherapy and bone-marrow transplantation takes advantage of any potential dose-response effect in the treatment of cancer and the ability of infused marrow to circumvent severe myelotoxicity. We report our initial experience of 20 high-dose chemotherapy procedures with busulphan and cyclophosphamide as the treatment regimen. Autologous (14 patients), human leukocyte antigen-matched, sibling-allogeneic (five patients) and identical-twin (one patient) transplantations were performed in patients with leukaemias (12 patients), lymphomas (seven patients) or a germ-cell tumour (one patient). One in-hospital and one late death occurred as a result of the toxicity of high-dose chemotherapy. All evaluable patients demonstrated bone-marrow engraftment and became independent of blood transfusions. Five of six patients who were treated in partial remission or relapse obtained a complete remission. Seven patients have relapsed. Eleven patients currently are alive and disease-free and nine patients have returned to their full-time occupations. High-dose chemotherapy can be undertaken with an over-all morbidity that is similar to that which is experienced during the induction chemotherapy of acute leukaemia.

Granulocyte-macrophage colony-stimulating factor to harvest circulating haemopoietic stem cells for autotransplantation

Granulocyte-macrophage colony-stimulating factor (GM-CSF), given to accelerate recovery from cytopenia induced by high-dose (7 g/m2) cyclophosphamide, reproducibly brought about a dramatic increase (up to 1000-fold) in the number of peripheral blood granulocyte-macrophage colony-forming units (CFU-GM). These circulating progenitors were harvested by leucapheresis and reinfused, together with autologous bone marrow cells, in seven patients with cancer after total body irradiation and melphalan. Complete haemopoietic recovery occurred in all seven transplanted patients in a very short time: mean (SD) 9.1 (0.9) days (range 8-11) to achieve more than 0.5 x 10(9)/l neutrophils, 9.9 (1.7) days (range 8-13) to over 1 x 10(9)/l neutrophils, 10.7 (2.6) days (range 9-16) to over 0.5 x 10(11)/l platelets, and 13.6 (4.2) days (range 13-21) to over 1.0 x 10(11)/l platelets. A reduction in the severity of mucositis was also observed. The rapid haematological recovery made possible by this approach promises to increase the therapeutic index of high-dose chemoradiotherapy regimens and to widen their role as treatment for chemoradiosensitive tumours.

Interleukin-1 and hematopoiesis

Interleukin-1 alpha and interleukin-1 beta are 17.5 kDa peptides which exert a wide variety of biological activities. Both forms of interleukin bind to a common 60-70 kDa receptor expressed by most somatic cells. One major effect of interleukin-1 is to induce the expression of other genes, including genes for other interleukins (IL-6), colony stimulating factors (GM-CSF and G-CSF) and growth factors (PDGFA) and adhesion proteins (ELAM-1, ICAM-1). In vitro, cells of the hematopoietic stroma including thymic epithelium, endothelial cells, fibroblasts, T-lymphocytes, and macrophages, are all capable of responding to interleukin-1 by expressing most of these IL-1 inducible genes. Accordingly, because interleukin-1 has no direct effect on hematopoietic progenitor cells, its major effect on hematopoiesis is to regulate the expression of hematopoietic growth factor genes by other cells. The mechanism by which interleukin-1 induces gene expression is to first induce mRNA accumulation which accounts for an increase in translation of the mRNA. The accumulation of RNA, interestingly, does not result from increased transcription of these genes but by the stabilization of the mRNA. Ordinarily, the hematopoietic growth factor gene transcripts have a very short half-life but in an interleukin-1 induced cell, the half-life of these transcripts is markedly prolonged (greater than 24 h). This particular effect of IL-1 on transcript stability likely accounts for virtually all of the hematopoietic activities of interleukin-1 including: (1) induction of growth factors; (2) synergy with other factors; (3) priming; and (4) auto-induction. Three clinical models of hematopoiesis are presented which suggest that the interleukin-1 CSF network is operative in vivo. The ability of interleukin-1 to induce the expression of hematopoietic growth factor genes as well as genes whose products regulate cellular function and traffic suggest that interleukin-1 is an essential molecular master switch for a number of cellular responses occurring in organisms facing the vicissitudes of their environment.

Effect in vivo of recombinant GM-CSF on neutropenia and survival in mice treated by high-dose melphalan

High doses of melphalan cause severe neutropenia and may irreversibly damage hematopoietic stem cells. Treatment of mice with recombinant murine GM-CSF (GM-CSF) for 5 days immediately after 400 micrograms of melphalan did not prevent the severe neutropenia. However, GM-CSF accelerated the neutrophil recovery and reduced the mortality rate during the neutropenic period compared to melphalan-only treated mice. CFU-GM levels measured 6 d after melphalan treatment without GM-CSF were markedly reduced in the bone marrow while being elevated in the spleen. In comparison, GM-CSF further reduced the total CFU-GM population in melphalan-treated mice including the levels in the bone marrow and in the spleen. On d 14 after melphalan, the spleen regained its active CFU-GM production. By d 90, the number of circulating neutrophils, the number of bone marrow CFU-GM and splenic CFU-GM were the same in GM-CSF-treated and -untreated mice. The results suggest that GM-CSF could be used to shorten the neutropenic period and reduce mortality caused by a high dose of melphalan. Though this effect could be at the expense of a temporary reduction in CFU-GM population, GM-CSF did not induce more long-term damage to myelopoiesis than that already caused by melphalan alone.

Effects of recombinant human granulocyte colony-stimulating factor on neutropenia in patients with congenital agranulocytosis

Congenital agranulocytosis is a disorder characterized by severe neutropenia and a profound deficiency of identifiable neutrophil progenitors in bone marrow. In an attempt to stimulate neutrophil production and thereby reduce the morbidity and mortality associated with this disease, we administered recombinant human granulocyte colony-stimulating factor (rhG-CSF) in doses of 3 to 60 micrograms per kilogram of body weight per day to five patients with congenital agranulocytosis. In all five patients, an increase in the number of neutrophils was noted eight to nine days after the initiation of the effective dosage (the dose at which the neutrophil count reached 1000 cells per microliter or more and the bone marrow showed granulocyte maturation beyond the myelocyte stage). The absolute neutrophil counts rose from less than 100 to between 1300 and 9500 cells per microliter. Marrow aspirates obtained after 14 days at the effective dosage showed maturation to the mature neutrophil stage. The side effects that were observed were medullary pain, splenomegaly, and an elevation of levels of leukocyte alkaline phosphatase. All five patients have had sustained neutrophil counts of 1000 cells per microliter or more for 9 to 13 months while receiving subcutaneous maintenance therapy. Preexisting chronic infections have resolved clinically, and the number of new infectious episodes and the requirement for intravenous antibiotics have decreased. We conclude that treatment with rhG-CSF can lead to a large increase in the numbers of functional neutrophils in patients with congenital agranulocytosis.

Effects of the in vivo administration of recombinant human granulocyte colony-stimulating factor following cytotoxic chemotherapy on granulocytic precursors in patients with malignant lymphoma

We examined the effects of the in vivo administration of recombinant granulocyte colony-stimulating factor (rhG-CSF) on granulocytic precursors in the bone marrow of 4 patients with malignant lymphoma who received chemotherapy. Patients were treated with rhG-CSF at doses of 100-800 micrograms/m2/day intravenously for 14 days only in the first course of chemotherapy (G-CSF course) followed by the second course of chemotherapy without rhG-CSF which was used as a control course. In the G-CSF course, white blood cell counts (WBCs) demonstrated a biphasic response consisting of a first peak observed within a few days after the initiation of rhG-CSF administration, and a second peak observed on the last day of rhG-CSF injection or the day after. In the second peak, the incidence of granulocyte-macrophage colony-forming units (CFU-GM) in mononucleated bone marrow cells did not change significantly after treatment with rhG-CSF as compared with a control. However, since the number of nucleated cells in the bone marrow increased, the absolute number of CFU-GM in the bone marrow increased. The number of mature and immature granulocytes in the bone marrow increased. These findings suggest that G-CSF stimulates the proliferation and differentiation of granulocytic precursors in the bone marrow in granulocytopenic patients who received cytotoxic drugs and causes mature granulocytes to be released from the bone marrow.

Treatment of cyclic neutropenia with granulocyte colony-stimulating factor

Six patients with cyclic neutropenia were treated with recombinant human granulocyte colony-stimulating factor (G-CSF) for 3 to 15 months. All had a history of recurrent aphthous stomatitis, pharyngitis, lymphadenopathy, fever, and numerous infections during periods of neutropenia. Serial blood-cell counts, findings on bone marrow examination, and signs and symptoms were evaluated before and during the daily administration of G-CSF (3 to 10 micrograms per kilogram of body weight per day), either intravenously or subcutaneously. The kinetics of labeled autologous blood neutrophils and the migration of neutrophils to skin chambers were also measured. Recombinant human G-CSF increased the mean (+/- SEM) neutrophil counts from 717 +/- 171 per microliter to 9814 +/- 2198 per microliter (P = 0.009). In five of the six patients, the cycling of blood-cell counts continued, but the length of the period decreased from 21 to 14 days. The number of days of severe neutropenia was reduced (P = 0.002). Neutrophil turnover increased almost four-fold (P = 0.005), whereas neutrophil migration to a skin chamber was normal. G-CSF therapy reduced the frequency of oropharyngeal inflammation, fever, and infections in these patients. During the first 40 months of treatment, no typical mouth ulcers or bacterial infections occurred; recurrent gingivitis improved. We conclude that G-CSF is effective for the treatment of cyclic neutropenia in humans.

The molecular control of cell division, differentiation commitment and maturation in haemopoietic cells

Several glycoproteins that control blood-cell production and function have been purified and sequenced. The four colony-stimulating factors interact in a complex way to regulate the differentiation and maturation of the granulocyte and macrophage lineages and have potential applications for the clinical manipulation of blood-cell production.

Gene structure and function of granulocyte colony-stimulating factor

In the last few years, the molecular and genetic nature of the granulocyte colony-stimulating factor, which controls proliferation and differentiation of neutrophils, has been characterized. Recent clinical application of G-CSF proves that this hormone is effective in the treatment of patients suffering from neutropenia.

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.

Clinical use of haematopoietic growth factors

Over the past decade experimental haematologists have identified and eventually characterised a number of polypeptide growth factors capable of stimulating the proliferation and differentiation of haemopoietic progenitor cells in vitro. The molecular cloning of these growth factors has now allowed their use in vivo, and some of them have shown promise in recent clinical trials. Most of the work has been done on erythropoietin and myeloid growth factors, which are discussed in this review. Erythropoietin has been used successfully as replacement therapy in the anaemia of end-stage renal failure, but may also prove clinically useful in other chronic anaemias and, in combination with other growth factors, as a stimulant of bone marrow regeneration following bone marrow transplant. Myeloid growth factors, and, in particular, granulocyte colony-stimulating factor, have been shown to accelerate neutrophil recover in cancer patients following chemotherapy, with a reduction in the number of severe infections and mucositis.

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.

Lung cancer in Australia

Lung cancer is the leading cause of death of cancer in Australian men and the third leading cause in Australian women. Efforts are being made to reduce the incidence of this disease by smoking-cessation programmes and improved industrial hygiene, and these measures need to be encouraged strongly by all sectors of the community. On a population basis, insufficient evidence is available to justify screening procedures for the early detection of lung cancer in "at-risk" groups. Cure is possible by surgical resection in early cases. Improvements in therapeutic results with traditional cancer treatments largely have reached a plateau, but a number of newer therapies, and combinations of standard therapies, currently are being evaluated. Of particular interest is concurrent radiotherapy and chemotherapy in localized non-small-cell lung cancer; laser "debulking" in conjunction with radiotherapy in non-small-cell lung cancer, and biological response-modifying agents in non-small-cell and small-cell lung cancer. It is important that data be collected adequately to define epidemiological changes and to evaluate treatment results (including repeat bronchoscopy, to assess local control of tumour), and that the quality of life is recorded and reported in the evaluation process. Finally, phase-III studies in lung-cancer treatments require adequate numbers of subjects to enable meaningful conclusions to be achieve objectives within a reasonable study period.

Treatment of myelodysplastic syndromes with recombinant human granulocyte colony-stimulating factor: a preliminary report

PURPOSE

The expansion of an abnormal hemopoietic stem cell line is responsible for the myelodysplastic syndromes, which are characterized by pancytopenias, often resulting in lethal infections. Cloned granulocyte colony-stimulating factor (G-CSF) was recently shown to enhance the growth and differentiation of normal granulocyte progenitor cells in vitro. The aim of our study was to examine the effects of recombinant human G-CSF in patients with myelodysplastic syndromes.

PATIENTS AND METHODS

Four patients with myelodysplastic syndromes and one patient with smoldering acute myelogenous leukemia following the occurrence of a myelodysplastic syndrome received recombinant human G-CSF by intravenous infusion for six days. Patients received different dosage levels (50 to 1,600 micrograms/m2).

RESULTS

A response was seen in all patients, with an increase in both immature myeloid cells in the bone marrow and mature granulocytes in the peripheral blood. The dose levels that could stimulate granulocytopoiesis differed among patients.

CONCLUSION

These results suggest that, at least in some cases of myelodysplastic syndromes, granulocytopenia can be improved by G-CSF, although it still remains to be determined whether the increase in the number of granulocytes is due to the differentiation and maturation of the myelodysplastic clone or restoration of a residual normal clone.

Disulfide and secondary structures of recombinant human granulocyte colony stimulating factor

Molecular characteristics and secondary structures of recombinant methionyl human granulocyte colony stimulating factor produced by genetically engineered Escherichia coli are described. Limited radiolabeling of the protein with tritiated iodoacetate and determination of the labeled residue revealed that this recombinant protein contains only one free cysteine at position 17 which is not essential for activity. The free cysteine is inaccessible to modification unless the molecule is unfolded under denaturing conditions. The molecule forms two disulfide bridges which were assigned as Cys(36)-Cys(42) and Cys(64)-Cys(74) based on the results of isolation and characterization of disulfide-containing peptides obtained from a subtilisin digest of the intact protein. CD analyses and secondary structure prediction suggest that the molecule is abundant in alpha-helical structures.

Clinical trials with haemopoietic growth factors

Five glycoprotein growth factors capable of stimulating the proliferation and differentiation of haemopoietic progenitor cells in vitro have been identified and sequenced over the past ten years. Recombinant DNA technology has recently enabled the production of sufficient amounts of these agents for preclinical testing. Erythropoietin (EPO), granulocyte-macrophage colony-stimulating factor (GM-CSF), and granulocyte colony-stimulating factor (G-CSF) have already entered clinical studies in humans. Interleukin-3 (IL-3) and macrophage colony-stimulating factor (M-CSF) should soon be available for use in humans. EPO corrects the anaemia of end stage renal failure, improving the quality of life for such patients and preventing the need for red cell transfusions. At high dose it increases platelet production in vitro and in vivo and may be of value in humans to prevent the thrombocytopaenia associated with chemotherapy. G-CSF and GM-CSF have been used in several clinical studies. Administration of both growth factors results in a leucocytosis, G-CSF predominantly increasing neutrophil production and GM-CSF increasing production of neutrophils, eosinophils and monocytes. The optimal administration of these agents is via continuous intravenous infusion or daily subcutaneous injections at doses of 3-10 micrograms/kg/24 h. GM-CSF has shown promising results in patients with AIDS and the myelodysplastic syndrome and both G-CSF and GM-CSF have reduced the duration of neutropaenia and incidence of infection associated with chemotherapy. These agents may allow an escalation of the dose-intensity of chemotherapy in the future and thereby, hopefully, increase the response rate and survival for patients with a variety of neoplasms. Several other potential roles for these haemopoietic growth factors are discussed.

Human hemopoietic growth factors

Hematopoiesis is regulated by a complex network of soluble stimulators and inhibitors, as well as by cellular interactions in the bone marrow microenvironment. Progress in molecular biology and protein biochemistry has provided a number of hemopoietic growth factors that are now available in large quantities for in vitro and in vivo studies. Several of them seem to hold great promise for patients suffering from insufficient hematopoiesis of various causes. This review focuses on new developments in the understanding of hemopoietic growth factors activity, and on recent clinical data.

Use of recombinant granulocyte-macrophage colony stimulating factor in the Brazil radiation accident

8 patients with bone marrow failure after a caesium-137 radiation accident were treated with recombinant human granulocyte-macrophage colony stimulating factor (rHuGM-CSF). The 7 who were evaluable had prompt increases in granulocytes and bone marrow cellularity. 2 patients died of radiation toxicity and haemorrhage and 2 of bacterial sepsis acquired before the start of rHuGM-CSF treatment. 4 patients survive, including 2 who were treated early and never became infected. This therapeutic approach to radiation-induced granulocytopenia may therefore be useful after radiation and nuclear accidents.

In vitro and in vivo analysis of the effects of recombinant human granulocyte colony-stimulating factor in patients

Twelve patients with small cell lung cancer were treated with recombinant human granulocyte colony-stimulating factor, rhG-CSF, given by continuous infusion at doses ranging from 1 to 40 micrograms kg-1 day-1. Patients received the rhG-CSF before the start of intensive chemotherapy and after alternate cycles of chemotherapy. Several in vitro assays were performed using peripheral blood neutrophils and marrow progenitor cells collected from patients prior to and after infusion of the growth factor. Peripheral blood neutrophils were tested for mobility and phagocytic activity. In addition, in vitro clonogenic assays of marrow haemopoietic progenitor cells and analysis of bone marrow trephines and aspirates were carried out. We found that rhG-CSF in vivo has at least two main effects: (a) an early fall in peripheral neutrophils, within the first hour, followed by a rapid influx of mature neutrophils into the circulatory pool; (b) stimulation of proliferation and differentiation of neutrophil precursors in the bone marrow. Neutrophils released into the circulation were normal in tests of their mobility and phagocytic activity.

Conformational homologies among cytokines: interleukins and colony stimulating factors

Some 30 cytokine amino acid sequences (mainly interleukins, colony stimulating factors and tumor necrosis factors) have been examined for evidence of secondary structure as well as longer-range interactions of a type likely to lead to stable alpha-helical bundles. Most, though not all, of the cytokines examined have a high predicted alpha-helical content (40-60%) and quasi-repeating heptads containing i/i + 3 apolar periodicities. This major subset of the cytokines is predicted to be characterized by molecules in which 4-alpha-helical bundles with an average length of 25A are the most marked conformational features. Based on these conclusions, we suggest structures for huG-CSF, huGM-CSF and muIL-5 in which defined loop segments at the ends of helical bundles are the most likely sites for binding and recognition by specific cell receptors. As such, they provide a means for testing or refining the three working models we have defined, using currently available methods of site-directed substitution and deletion mutagenesis, as well as synthetic peptides corresponding to the proposed loop sequences and the use of monoclonal antibodies of defined epitopic specificity. The structure arrived at for huGM-CSF is consistent with the limited data currently available concerning the residues which are important for binding and activity.

Cellular processing of murine colony-stimulating factor (Multi-CSF, GM-CSF, G-CSF) receptors by normal hemopoietic cells and cell lines

The binding, internalization and degradation rates of three different murine colony-stimulating factors (Multi-CSF or interleukin-3, GM-CSF and G-CSF) and their receptor turnover rates were determined for normal bone marrow cells and a number of different cell lines at 37 degrees C. The kinetic parameters were extracted from a curve-fitting analysis of the approach to steady-state of surface-bound and internalized CSFs by methods described by Myers et al. (1987). The primary binding kinetic constants (association and dissociation) for each CSF on different cell types were similar, suggesting a single type of receptor for each CSF. In all cases, CSF binding induced a faster rate of internalization of occupied receptors than unoccupied receptors and resulted in significant accumulation of CSF inside the cell under steady-state conditions. The steady-state constant, determining the relationship between CSF concentration and receptor occupancy, indicated that, in all cases, more receptors were occupied at a given CSF concentration under steady-state conditions than would be under equilibrium conditions. Nevertheless, the data predicted that maximal biological effects of the CSFs were exerted at concentrations that did not result in full receptor occupancy. Comparison of the kinetic constants derived for the same CSF interacting with different types of cells or different CSFs interacting with the same cell type indicated that CSF and receptor processing resulted from a dynamic interplay of receptor-determined and cell-determined events. This resulted in a flexibility of the kinetic parameters that matched the variety of biological responses elicited by CSFs in different cell types.