Hematopoietic growth factors: overview and clinical applications, Part I

Biological and mechanical quality of red blood cells cultured from human umbilical cord blood stem cells

Human umbilical cord blood (CB) has moved from the status of biological waste to that of a valuable source of haematopoietic stem (HS) cells. There are potentially three major clinical applications for HS cells and ex vivo-expanded HS cells: reconstitution of haematopoiesis in patients undergoing chemotherapy; gene therapy (e.g. in thalassaemia, sickle cell anaemia); and large-scale production of mature blood cells. Erythropoiesis is accomplished by highly complex interactions of haematopoietic progenitor cells, stromal cells and cytokines in the bone marrow. Among them, erythropoietin is the principal regulator. Ex vivo cell culture experiments to obtain mature red blood cells were the focus of this study. Attempts to elucidate appropriate medium components and amounts of haematopoietic growth factors were successful: enucleated and haemoglobin-filled erythroid cells were obtained from primitive HS cells. Dimethylsulphoxide (DMSO) was found to be of particular importance as an efficient differentiation inducer. The differentiation process was followed microscopically and by fluorescence-activated cell sorting (FACS). Using the micropipette aspiration technique, the elastic properties of erythroid cells were evaluated as erythropoiesis progressed. Discocyte-like cells, comprising reticulocytes and finally differentiated red blood cells, showed an about ten-fold higher membrane shear modulus compared with control cells.

Pathologic thrombopoiesis of rheumatoid arthritis

Rheumatoid arthritis (RA) is frequently complicated by thrombocytosis correlated with disease activity. The exact pathogenetic mechanism(s) that cause increased platelet counts in RA are still unknown. Recent investigations indicate that proinflammatory pleiotropic cytokines of RA also have megakaryocytopoietic/thrombopoietic properties. Moreover, several lineage-dominant hematopoietic cytokines can also act as acute phase responders and contribute to the inflammation. This review focuses on the current literature and our experience regarding the dual relationships of the pathologic thrombopoiesis of RA. Growth factors contributing to it, namely interleukin (IL)-6, IL-11, stem cell factor, leukemia inhibitory factor, granulocyte colony stimulating factor, thrombopoietin (TPO), and the regulation of megakaryocytopoiesis during the inflammatory cascade are reviewed. Some data indicate that thrombopoietin could contribute to the reactive thrombocytosis of RA. In the non-lineage-specific gp130 cytokine family, IL-6 appears to predominate for the induction of megakaryopoiesis. However, other cytokines and growth factors may also contribute to the pathologic megakaryocytopoiesis of RA. Those pleiotropic mediators seem to act in concert to regulate this enigmatic process. Clarification of the pathobiologic basis of thrombopoiesis in RA may improve understanding of the disease pathogenesis and management of the inflammatory thrombocytosis.

Modulation of in vitro chemosensitivity in acute myelogenous leukemia cell line by GM-CSF: opposing effects observed with different cytotoxic drugs and time exposure

In some studies the GM-CSF (granulocyte-macrophage colony-stimulating factor) increased the in vitro sensitivity of acute myeloid leukemia (AML) cells to cytosine arabinoside (Ara-C), however, in clinical trials no favorable effects were shown. We used a GM-CSF responsive AML cell line (AML 193) to test the effects of growth stimulation on in vitro efficacy of Ara-C and methotrexate (MTX). In 6 days continuous exposure, dose dependent Ara-C cytotoxicity was counteracted by GM-CSF. Conversely, MTX cytotoxicity was increased significantly. However, in a short term treatment (24 h, high doses) the GM-CSF increased both MTX and Ara-C cytotoxicity. These effects might depend on different drug regimens and cell features.

Potent inhibition of cell density-dependent apoptosis and enhancement of survival by dimethyl sulfoxide in human myeloblastic HL-60 cells

Human myeloblastic cell line HL-60 cells undergo apoptosis during in vitro culture in a cell density-dependent manner, and this cell density-dependent apoptosis was observed when the concentration of cultured cells exceeded 8-10 x 10(5) cells/ml. Dimethyl sulfoxide (DMSO), a differentiation inducer of HL-60 cells, did not amplify, but rather potently inhibited, this apoptosis. In a low density culture condition, DMSO attenuated proliferation of HL-60 cells in spite of its inhibition of apoptosis. In contrast, DMSO did support cell survival under high cell density conditions, and DMSO-treated HL-60 cells reached an extremely high concentration of 2-3 x 10(6) cells/ml, a condition which could never be possible in a usual culture environment. Thus, DMSO exerted dual effects on cell proliferation, i.e., growth inhibition and apoptosis inhibition, and the sum of these effects resulted in an apparently distinct phenomenon according to the culture conditions including cell density.

Influence of circadian rhythm on 41.8 degrees C whole body hyperthermia induction of haematopoietic growth factors

It has previously been reported by the authors that the induction of a series of cytokines by 41.8 degrees C Whole Body Hyperthermia (WBH), i.e., interleukin (IL)-1 beta, IL-6, IL-8, IL-10, tumour necrosis factor alpha, and granulocyte colony stimulating factor (G-CSF). As cytokine levels are known to fluctuate as a function of time, i.e. circadian rhythm, the influence of circadian time structure on specific haemotopoetic growth factors is studied, i.e. granulocyte macrophage colony stimulating factor (GM-CSF), G-CSF and IL-3. Samples derived from four cancer patients undergoing extracorporeal WBH resulted in the following observations: G-CSF is induced by WBH, but unaffected by circadian rhythm, IL-3 fluctuates with circadian rhythm, but is unaffected by WBH. Specifically, a biphasic temporal pattern of IL-3 (i.e. with a peak at 2:00 and 5:00 a.m. and a nadir concentration at 5:00 p.m.) was found by analysis of variance. GM-CSF was below the lower detection limit pre and post WBH. The data show the importance of measuring cytokines as a function of time to circumvent conflicting results in the inter-relationship of 'true' cytokine induction and circadian rhythm. The implications of the differential induction of G-CSF, GM-CSF, and IL-3 for myeloprotection after WBH are discussed.

Effect of age on marrow macrophage number and function

Employing flow cytometry and a monoclonal antibody against the murine macrophage antigen, Mac-1, we found a significant increase in the number of marrow macrophages in aged mice. This was reflected as significant increase with age in the number of alpha-naphthyl acetate esterase positive cells, as well as in colony forming unit-macrophage (CFU-M) progenitor cells. Macrophages from the marrow of old mice generated significantly less tumor necrosis factor alpha (TNF alpha) than did macrophages from young mice, either spontaneously or when activated by granulocyte-macrophage colony stimulating factor (GM-CSF). Furthermore, conditioned medium (CM) derived from either marrow or peritoneal macrophages of old mice caused less suppression of burst forming unit-erythroid (BFU-E) colony growth than did CM obtained from young mice. Aging, therefore, is associated with an increase in the number of marrow macrophages that have an impaired ability to generate or release cytokines. The increase in macrophage number may reflect a compensation for their reduced function. Altered macrophage number and function may contribute to the age-related decline in hematopoietic reserve capacity.

Hematopoietic stem cell cytokine response

The process of hematopoiesis can be modelled on the concept of a pluripotential stem cell able to differentiate and proliferate in multiple lineages. This process proceeds under the permissive or directive influence of "early" and "late" acting hematopoietic cytokines probably acting in synergistic combinations within the context of the marrow stromal microenvironment. Further characterization of the biochemical events that transduce cytokine signalling into cellular events and the ultimate description of the earliest progenitor cell populations and the cytokines which influence them will provide key insights into embryogenesis and tissue maintenance as well as suggest new therapeutic approaches for hematologic and malignant diseases.

G-CSF in the biology and treatment of acute myeloid leukemias

Granulocyte colony-stimulating factor (G-CSF) is an hemopoietic growth factor produced by fibroblasts, monocytes and endothelial cells. The role of G-CSF in the biology of acute myeloid leukemia (AML) has been investigated by several authors, who have demonstrated receptor mediated enhanced proliferation of AML blasts in vitro, in the presence of G-CSF. This effect is further increased by addition of other cytokines such as GM-CSF, IL3, IL4, Stem cell factor (SCF), while Tumor Necrosis Factor (TNF) and Transforming Growth Factor beta 1 (TGF beta 1) seem to exert an inhibitory activity. An autocrine production of G-CSF by AML cells, a paracrine production by accessory cells and a protective effect displayed by G-CSF against programmed cell death could partially contribute to explain the pathogenesis of AML. In vivo, G-CSF has been used after chemotherapy in AML, in order to improve hemopoietic recovery in patients at high risk of infection. Current studies are focusing on better definition of the role of G-CSF, as such or combined with other biological modifiers, in dose intensification and autologous bone marrow or peripheral blood stem cell transplantation.

Clinical implications of cytokine and soluble receptor measurements in patients with newly-diagnosed aggressive non-Hodgkin's lymphoma

Serum levels of 13 different cytokines and receptors were measured serially in 78 patients with aggressive non-Hodgkin's lymphoma (NHL) treated by 4 cycles of an intensive multi-agent chemotherapy regimen. Recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) was administered subcutaneously in 36 of these patients from day + 5 to day + 18 after each chemotherapy. Statistically significantly higher pretreatment levels of interleukin-2 (IL-2), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10), the soluble IL-2 receptor (sIL-2r), the soluble transferrin receptor (sTf-r), and neopterin, were observed in NHL patients as compared to controls (p < 0.001 for all molecules). sIL-2r and sTf-r levels correlated with tumor burden (p < 0.001 and p = 0.003, respectively) whereas IL-6 was higher in patients presenting B symptoms (p < 0.001). Cytokine levels progressively declined to normal ranges in responding patients, while they remained elevated in non-responders. Relapsed patients also presented increased concentrations of several molecules. During the administration of GM-CSF, we observed the drastic increase of sIL-2r, while lower elevations were recorded for a number of cytokines, including IL-8, tumor necrosis factor-alpha, interleukin-1 beta, IL-6, and IL-2. However, upon completion of the induction treatment, cytokine/receptor levels were comparable among individuals with the same type of response, whether or not they had received GM-CSF. No single parameter was found to be of prognostic significance, but the combination of elevated IL-10 and of sIL-2r greater than 3000 U/ml selected a subgroup of 7 patients who failed induction treatment (p = 0.002). These results demonstrate that cytokine and soluble receptor measurements can provide valuable informations for a better management of NHL, in terms both of markers to monitor disease activity and of prognostic indicators.

Mast cell growth factor (C-kit ligand) in combination with granulocyte-macrophage colony-stimulating factor and interleukin-3: in vivo hemopoietic effects in irradiated mice compared to in vitro effects

In the presence of hemopoietic cytokines such as granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3), mast cell growth factor (MGF; also known as steel factor, stem cell factor, and c-kit ligand) has proven to be a potent hemopoietic regulator in vitro. In these studies, we examined the in vivo effects of MGF in combination with GM-CSF or GM-CSF plus IL-3. Effects were based on the ability of these cytokines to stimulate recovery from radiation-induced hemopoietic aplasia. Female B6D2F1 mice were exposed to a sublethal 7.75-Gy dose of 60Co radiation followed by subcutaneous administration of either saline, recombinant murine (rm) MGF (100 micrograms/kg/day), rmGM-CSF (100 micrograms/kg/day), rmIL-3 (100 micrograms/kg/day), or combinations of these cytokines on days 1-17 postirradiation. Recoveries of bone marrow and splenic spleen colony-forming units (CFU-s), granulocyte macrophage colony-forming cells (GM-CFC), and peripheral white blood cells (WBC), red blood cells (RBC) and platelets (PLT) were determined on days 14 and 17 during the postirradiation recovery period. MGF administered in combination with GM-CSF or in combination with GM-CSF plus IL-3 either produced no greater response than GM-CSF alone or down-regulated the GM-CSF-induced recovery. These results sharply contrasted results of in vitro studies evaluating the effects of these cytokines on induction of GM-CFC colony formation from bone marrow cells obtained from normal or irradiated B6D2F1 mice, in which MGF synergized with GM-CSF or GM-CSF plus IL-3 to increase both GM-CFC colony numbers and colony size. These studies demonstrate a dichotomy between MGF-induced effects in vivo and in vitro and emphasize that caution should be taken in attempting to predict cytokine interactions in vivo in hemopoietically injured animals based on in vitro cytokine effects.

The colony stimulating factors

Hematopoiesis is a dynamic process, which generate in the range of 10(9) cells/kg each day of erythroid and myeloid cells respectively. In vitro assays that were developed 20 years ago, have been used to define factors that can stimulate growth and differentiation of bone marrow (BM) derived progenitor cells. These growth factors for hematopoiesis were termed Colony Stimulating Factors (CSFs) since the assay system was to induce colonies. With the application of molecular biologic approaches, the genes encoding for these CSFs have been localized and cloned. Production of CSFs and other soluble signal substances (cytokines) as pure proteins have led to important insights into how hematopoiesis is regulated by a complex network made up by interactions between cells and cytokines. The availability of CSFs in clinically useful amounts has also led to clinical trials with new strategies for treating hematopoietic dysfunctions, congenital or acquired. Because others have recently reviewed clinical applications or basic science studies on the colony stimulating factors, we will summarize the two with focus on common features between the different CSFs.

Treatment of neutropenia in Felty's syndrome with granulocyte-macrophage colony-stimulating factor--hematological response accompanied by pulmonary complications with lethal outcome

We report on a 67-year-old man with Felty's syndrome (FS) complicated by recurrent pneumonia and an infected wound, which was not healing in spite of maximal antibiotic and local therapy. Encouraged by previous experience, we treated him with granulocyte-macrophage colony-stimulating factor (GM-CSF). His total leukocyte count rose, but the patient's pneumonia deteriorated. In addition, a previously known chronic obstructive lung disease (COLD) was exacerbated acutely. These complications finally led to his death. Postmortem examination revealed widespread pneumonia with invasive aspergillosis and a peripheral adenocarcinoma in his left lung.

Postirradiation treatment with granulocyte colony-stimulating factor and preirradiation WR-2721 administration synergize to enhance hemopoietic reconstitution and increase survival

These studies tested whether WR-2721 could be used to protect hemopoietic stem cells, which after irradiation could be stimulated by granulocyte colony-stimulating factor (G-CSF) to proliferate and reconstitute the hemopoietic system. Female C3H/HeN mice were administered WR-2721 (4 mg/mouse, i.p.) 30 min before 60Co irradiation and G-CSF (2.5 micrograms/mouse/day, s.c.) from days 1-16 after irradiation. In survival studies, saline, G-CSF, WR-2721, and WR-2721 + G-CSF treatments resulted in LD50/30 values of 7.85 Gy, 8.30 Gy, 11.30 Gy, and 12.85 Gy, respectively. At these LD50/30 values, the dose reduction factor (DRF) of 1.64 obtained in combination-treated mice was more than additive between the DRF's of G-CSF-treated mice (1.06) and WR-2721-treated mice (1.44). Bone marrow and splenic multipotent hemopoietic stem cell (CFU-s) and granulocyte-macrophage progenitor cell (GM-CFC) recoveries were also accelerated most in mice treated with WR-2721 + G-CSF. In addition, mice treated with WR-2721 + G-CSF exhibited the most accelerated peripheral blood white cell, platelet, and red cell recoveries. These studies (a) demonstrate that therapeutically administered G-CSF accelerates hemopoietic reconstitution from WR-2721-protected stem and progenitor cells, increasing the survival-enhancing effects of WR-2721 and (b) suggest that classic radioprotectants and recombinant hemopoietic growth factors can be used in combination to reduce risks associated with myelosuppression induced by radiation or radiomimetic drugs.

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.

Secretion of insulinlike growth factor I and insulinlike growth factor-binding proteins by murine bone marrow stromal cells

Insulin-like growth factor I (IGF-I) stimulates hematopoiesis. We examined whether bone marrow stromal cells synthesize IGF-I. Secretion of IGF-I immunoreactivity by cells from TC-1 murine bone marrow stromal cells was time-dependent and inhibited by cycloheximide. Gel filtration chromatography under denaturing conditions of TC-1 conditioned medium demonstrated two major peaks of apparent IGF-I immunoreactivity with molecular weights of approximately 7.5-8.0 kD, the size of native IGF-I, and greater than 25 kD. Expression of IGF-I mRNA was identified by both RNase protection assay and reverse transcription/polymerase chain reaction. To determine whether the greater than 25-kD species identified by RIA possessed IGF-binding activity, a potential cause of artifactual IGF-I immunoreactivity, charcoal adsorption assay of these gel filtration fractions was performed. The peak of IGF-binding activity coeluted with apparent IGF-I immunoreactivity suggesting that TC-1 cells secrete IGF-binding protein(s). Unfractionated conditioned medium exhibited linear dose-dependent increase in specific binding of [125I]-IGF-I with a pattern of displacement (IGF-I and IGF-II much greater than insulin) characteristic of IGF-binding proteins. Western ligand analysis of conditioned medium showed three IGF-I binding species of approximately 31, 38, and 40 kD. These data indicate that TC-1 bone marrow stromal cells synthesize and secrete IGF-I and IGF-binding proteins and constitute a useful model system to study their regulation and role in hematopoiesis.