Effects of recombinant human G-CSF, GM-CSF, IL-3, and IL-1 alpha on the growth of purified human peripheral blood progenitors.

The effects of recombinant products of granulocyte colony-stimulating factors (G-CSF), granulocyte/macrophage CSF (GM-CSF), human interleukin-3 (IL-3), and interleukin-1 (IL-1) were studied using purified target cell populations from patients undergoing peripheral blood stem cell transplantation after myeloablative therapy. Cells were subjected to combined purification procedures including negative selection with a panel of monoclonal antibodies (CD2, 3, 5, 10, and 20). The purified cells were enriched for HLA-DR+ (51% to 71%) and My-10+ (CD34; 37% to 54%) and had a plating efficiency of up to 20%. In the liquid-suspension limiting dilution clonal assay (LDA), purified progenitors responded directly to IL-3 by proliferation with single-hit kinetics. The ability of GM-CSF to support progenitor growth was inferior to that of IL-3, and the cells were virtually unresponsive when cultured with G-CSF, supporting the notion that these blood-derived progenitors belong to a primitive population of hematopoietic progenitor cells. The results obtained in simultaneous methycellulose cultures (MC) showed the same trend and provided additional information on the ability of GM-CSF and IL-3 to support erythroid progenitor growth. The combination of IL-3 plus G-CSF, but not IL-3 plus GM-CSF, resulted in a synergistic increase in colony number. IL-1 alpha increased both the size and number of colonies when added to IL-3 or G-CSF. Study of this enriched progenitor cell population in MC and LDA represents an excellent model for the investigation of myeloid and erythroid differentiation and for evaluating the influence of various cytokines on human hematopoiesis.     

Effects of recombinant interleukin 4 on the growth and differentiation of blast progenitors stimulated with G-CSF, GM-CSF and IL-3 from acute myeloblastic leukaemia patients

The effects of human recombinant interleukin 4 (rIL-4) on the growth of leukaemic blast progenitors were investigated. Cells obtained from 20 acute myeloblastic leukaemia (AML) patients were evaluated using the blast colony assay in methylcellulose and suspension cultures. While rIL-4 by itself did not show any colony stimulatory activity in the blast colony assay, it suppressed the blast colony formation in methylcellulose stimulated with G-CSF, GM-CSF or IL-3 in 14 patients. In another six patients, rIL-4 enhanced blast colony growth in four patients or did not show any significant effect with any CSF in two patients. In suspension cultures of 12 cases studied, the effects of rIL-4 on the clonogenic cell recoveries were essentially similar to the results of the blast colony assay in each case. In three patients, rIL-4 augmented the differentiation of the leukaemic cells to monocyte lineage. Further, the clinical outcome was significantly different between the patients whose blast progenitors were stimulated by rIL-4 and the patients whose blast progenitors were suppressed by rIL-4 (P less than 0.05); three out of four patients in the former group failed in achieving complete remission (CR), while 12 out of 14 patients in the latter group achieved CR. The results show that the effects of IL-4 on leukaemic blast progenitors were diverse and the responsiveness to IL-4 may be correlated with the prognoses of the patients.     

Expression of a constitutively active erythropoietin receptor in primary hematopoietic progenitors abrogates erythropoietin dependence and enhances erythroid colony-forming unit, erythroid burst-forming unit, and granulocyte/macrophage progenitor growth.

We tested the ability of a constitutively activated erythropoietin receptor [EpoR(R129C)] to alter the growth requirements of primary hematopoietic precursors that terminally differentiate in culture. Two recombinant retroviruses expressing EpoR(R129C), spleen focus-forming virus (SFFVc-EpoR) and myeloproliferative sarcoma virus (MPSVcEpoR), were used to infect fetal liver cells that served as a source of hematopoietic progenitors. Methylcellulose cultures were incubated in the absence of any added growth factors or in combination with selected growth factors. EpoR(R129C) completely abrogated the Epo requirement of erythroid colony-forming units to form erythrocytes after 2-5 days in culture and did not interfere with the differentiation program of these cells. In the absence of added growth factors EpoR(R129C) did not enhance erythroid burst-forming unit development. In contrast to experiments in heterologous cell lines, EpoR(R129C) did not render progenitor cells independent of interleukin 3 or granulocyte/macrophage colony-stimulating factor (GM-CSF). However, when progenitors were cultured with added steel factor, but not with interleukin 3 or GM-CSF, EpoR(R129C) augmented the growth and differentiation of erythroid bursts, mixed erythroid/myeloid, and granulocyte/macrophage (GM) colonies. Furthermore, both viruses were capable of expressing EpoR(R129C) in erythroid, mixed erythroid/myeloid, and GM colonies. Thus an aberrantly expressed and constitutively activated EpoR can stimulate proliferation of some GM progenitors. The ability of EpoR(R129C) to abrogate the Epo requirement of primary hematopoietic cells, but not the requirement for other cytokines, is consistent with the induction of erythroblastosis in vivo.     

Recombinant gibbon interleukin-3 acts synergistically with recombinant human G-CSF and GM-CSF in vitro

Recombinant gibbon interleukin-3 (IL-3) is a multilineage hematopoietic colony-stimulating factor (CSF) that recently was cloned and found to be highly homologous with human IL-3. Gibbon IL-3, as well as human granulocyte-CSF (G-CSF) and human granulocyte-macrophage CSF (GM-CSF), stimulated normal human bone marrow cells to form myeloid colonies in soft agar in a sigmoidal dose-response manner. When IL-3 was added to increasing concentrations of G-CSF or GM-CSF, synergistic colony formation occurred as compared with the effects of each CSF alone. Synergism was also noted when G-CSF was added with GM-CSF and when all the CSFs were added simultaneously. The combination of IL-3 and GM-CSF was less stimulatory than all the other CSF combinations. At day 11 of culture, IL-3 induced granulocyte-macrophage (38%), eosinophil (30%), granulocyte (18%), and macrophage (14%) colony formation. In summary, gibbon IL-3 is a growth factor that can synergize with other CSFs to enhance proliferation of myeloid-committed progenitors, suggesting that combinations of CSFs may have clinical utility in patients with neutropenia of various etiologies.     

In vitro effects of high titers of recombinant human erythropoietin on the bone marrow erythroid progenitors in patients with aplastic anemia

To investigate the role of erythropoietin in aplastic anemia, the effects of high titers of recombinant human erythropoietin (rh-Ep) on CFU-E and BFU-E in patients with aplastic anemia were studied in vitro. Colony assays were performed by methylcellulose culture methods added with 1 to 500 units of rh-Ep. In normal bone marrow, the maximum CFU-E colony formation was observed at 2 to 5 units of rh-Ep, and BFU-E at 2 to 10 units. Colonies did not increase by addition of higher titer of rh-Ep to the cultures. In aplastic anemia, the numbers of CFU-E and BFU-E were low at 2 units of rh-Ep in culture system. In most patients with aplastic anemia studied, erythroid colonies were increased in accordance with the increase of rh-Ep added to cultures. These results suggest that the administration of high titers of rh-Ep in vivo may be useful for the improvement of anemia in aplastic anemia.     

Demonstration of burst-promoting activity of recombinant human GM-CSF on circulating erythroid progenitors using an assay involving the delayed addition of erythropoietin

We demonstrate through the use of an in vitro assay involving the delayed addition of erythropoietin that human recombinant GM-CSF, cloned from a mature T cell line, Mo, clearly has burst-promoting activity (BPA) on peripheral blood erythroid progenitors at picomolar concentrations. Delay for up to 72 hours of the addition of erythropoietin to semi-solid methylcellulose cultures of concentrated peripheral blood progenitors minimizes or eliminates BPA-independent erythroid colony formation with little loss of BPA-dependent erythroid colony formation. This assay will prove useful in accurately detecting sources of BPA.     

Comparative analysis of the influences of IL-1, IL-3 and GM-CSF on the commitment of granulocyte-macrophage progenitors in vitro

Summary Our experiments were directed towards the detection of the influence of interleukin-1 (IL-1); interleukin-3 (IL-3), and granulocyte-macrophage colonystimulating factor (GM-CSF) on the generation of granulocyte-macrophage progenitor cells. We also set out to examine whether this process is connected with changes within the early precursor cell compartment. Bone marrow suspension cultures (12 days) supplemented with these cytokines were tested for the presence of GM colony-forming cells (GM-CFC) in a colony-forming unit assay. The percentage of CD 34⁺ and HLA-DR⁺ as well as the number of blasts and promyelocytes were estimated cytofluorometrically and morphologically. The proliferative effect of GM-CSF was associated with a net increase of GM-CFC and HLA-DR⁺ myeloid cells and a decrease in the percentage of CD 34⁺ early precursor cells. IL-3 acted similarly and also caused an absolute decrease of CD 34⁺ cells in the cultures. IL-1 did not stimulate the generation of blasts or GM-CFC but elevated the number of CD 34^– as well as HLA-DR-expressing cells in the cultures. These results imply that GM-CSF supported the maintenance of hematopoiesis in vitro. The transition from early precursor cells to committed myeloid progenitor cells (GM-CFC) and more mature precursor cells (G-CFC, M-CFC) may be supported by GM-CSF without affecting the self-renewing capacity of CD 34⁺ early precursors. In contrast, the blast-generating and proliferation-inducing action of IL-3 is associated with a drop in the total number of CD 34⁺ stem cells. An efficient renewal of this population obviously depends on the presence of IL-1.     

Recombinant human stem cell factor synergises with GM-CSF, G-CSF, IL-3 and epo to stimulate human progenitor cells of the myeloid and erythroid lineages.

The cDNA for human stem cell factor (hSCF) has been cloned and expressed in mammalian and bacterial hosts and recombinant protein purified. We have examined the stimulatory effect of recombinant human SCF (rhSCF) on human bone marrow cells alone and in combination with recombinant human colony stimulating factors (CSFs) and erythropoietin (rhEpo). RhSCF alone resulted in no significant colony formation, however, in the presence of rhGM-CSF, rhG-CSF or rhIL-3, rhSCF stimulated a synergistic increase in colony numbers. In addition, increased colony size was stimulated by all combinations. The morphology of cells in the colonies obtained with the CSFs plus rhSCF was identical to the morphology obtained with rhGM-CSF, rhG-CSF or rhIL-3 alone. RhEpo also synergised with rhSCF to stimulate the formation of large compact hemoglobinized colonies which stained positive for spectrin and transferrin receptor and had a morphological appearance consistent with normoblasts. RhSCF stimulation of low density non-adherent, antibody depleted, CD34+ cells suggests that rhSCF directly stimulates progenitor cells capable of myeloid and erythroid differentiation.     

Effects of recombinant G-CSF and GM-CSF on in vitro differentiation of the blast cells of RAEB and RAEB-T

To evaluate the effects of recombinant G-CSF and GM-CSF on RAEB and RAEB-T cells, blast cells from 6 patients were incubated in liquid culture systems with these CSFs for 7 days, and their numerical, morphological and functional changes were assessed. Both CSFs stimulated cell growth, but decreased the proportion of blast cells in 5 of the 6 cases. Karyotypic abnormalities persisted during cultivation in some cases. The CSFs also stimulated the expression of part of the esterase activities, and a positive interaction of both CSFs was seen in part. Although CSFs had no significant effects on the ability of cells to reduce NBT or to phagocytize latex particles, the results indicated that they induce partial differentiation of blast cells. It appears that such pathological cells still retain the capacity to respond to growth factors.     

Bipotential murine hemopoietic cell line (NFS-60) that is responsive to IL-3, GM-CSF, G-CSF, and erythropoietin

NFS-60 cells were previously obtained from leukemia cells that were infected with the Cas-Br-M murine leukemia virus in vivo. We examined the proliferation and differentiation capacity of NFS-60 cells in the presence of native and recombinant (r) interleukin 3 (IL-3), recombinant granulocyte colony-stimulating factor (rG-CSF), recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF), and r-erythropoietin (Ep) using methylcellulose culture methods. This cell line was able to form colonies in response to each hemopoietic factor, but colony formation was rarely seen in their absence. Some populations of NFS-60 cells could differentiate into neutrophils and macrophages in the presence of IL-3 and GM-CSF. Moreover, in the presence of Ep, this cell line formed well-hemoglobinized colonies as well as nonerythroid colonies. In the presence of G-CSF, NFS-60 cells remained in the promyelocytic state. Electron microscopic studies confirmed these morphologies. A single-cell transfer experiment demonstrated that neutrophils, macrophages, and erythroblasts were derived from a single cell. It is concluded that the NFS-60 cell line is a factor-dependent, bipotential hemopoietic cell line.     

Responsiveness of bone marrow erythroid progenitors (CFU-E and BFU-E) to recombinant human erythropoietin (rh-Ep) in vitro in multiple myeloma

The responsiveness of bone marrow erythroid progenitors (CFU-E and BFU-E) to recombinant human erythropoietin (rh-Ep) was investigated in vitro in 21 patients with multiple myeloma to assess the clinical usefulness of rh-Ep in this disease. CFU-E and BFU-E assays were performed by methylcellulose culture methods. The myeloma patients were divided into two groups according to the percentage of plasma cells in the bone marrow (over 50% and under 50%). Among the patients with few plasma cells, some revealed normal CFU-E and BFU-E growth at 2 units of rh-Ep, and no further increase was observed even with an increasing dose of rh-Ep. Among the other patients, more than half demonstrated a good response to rh-Ep. Among the patients with a high percentage of plasma cells, some revealed no response to rh-Ep, but there were patients with a high percentage of plasma cells in the bone marrow who had a good response to rh-Ep. High doses of rh-Ep may be clinically effective in some patients with multiple myeloma independently of the level of plasma cells in the bone marrow.     

Action of interleukin-3, G-CSF, and GM-CSF on highly enriched human hematopoietic progenitor cells: synergistic interaction of GM-CSF plus G-CSF

Purified preparations of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte CSF (G-CSF), and interleukin 3 (IL-3 or multi-CSF) alone and in combination, have been compared for their stimulatory effects on human granulocyte-macrophage colony forming cells (GM-CFC). In cultures of unseparated normal human bone marrow, the combinations of G-CSF plus IL-3 and GM-CSF plus IL-3 stimulated additive numbers of GM colonies, while GM-CSF plus G-CSF stimulated greater than additive numbers of GM colonies, compared with the sum of the colony formation obtained with each factor alone. Cultures of unseparated bone marrow, harvested from patients four to six days after administration of 5-fluorouracil (5-FU), resulted in additive GM colony formation with GM-CSF plus G-CSF, GM-CSF plus IL-3, and G-CSF plus IL-3. In order to address the possibility of secondary factor involvement in the synergistic interaction of GM-CSF and G-CSF, CD33+/CD34+ colony forming cells were separated from normal and post FU marrow by two color fluorescence activated cell sorting. In cultures of CD33+/CD34+ cells the combination of GM-CSF plus G-CSF stimulated a synergistic increase in GM colonies while GM-CSF plus IL-3 stimulated additive numbers of colonies. These results suggest that GM-CSF, G-CSF, and IL-3 stimulate distinct populations of GM-CFC. Furthermore GM-CSF and G-CSF interact synergistically and this action is a direct effect on progenitor cells not stimulated by GM-CSF or G-CSF alone.     

Human IL-3/GM-CSF knock-in mice support human alveolar macrophage development and human immune responses in the lung

Mice with a functional human immune system have the potential to allow in vivo studies of human infectious diseases and to enable vaccine testing. To this end, mice need to fully support the development of human immune cells, allow infection with human pathogens, and be capable of mounting effective human immune responses. A major limitation of humanized mice is the poor development and function of human myeloid cells and the absence of human immune responses at mucosal surfaces, such as the lung. To overcome this, we generated human IL-3/GM-CSF knock-in (hIL-3/GM-CSF KI) mice. These mice faithfully expressed human GM-CSF and IL-3 and developed pulmonary alveolar proteinosis because of elimination of mouse GM-CSF. We demonstrate that hIL-3/GM-CSF KI mice engrafted with human CD34(+) hematopoietic cells had improved human myeloid cell reconstitution in the lung. In particular, hIL-3/GM-CSF KI mice supported the development of human alveolar macrophages that partially rescued the pulmonary alveolar proteinosis syndrome. Moreover, human alveolar macrophages mounted correlates of a human innate immune response against influenza virus. The hIL-3/GM-CSF KI mice represent a unique mouse model that permits the study of human mucosal immune responses to lung pathogens.     

Comparative effects of G-CSF, GM-CSF and IL-3 on cytosine arabinoside- and daunorubicin-mediated cytotoxicity of acute myeloid leukemia cells and normal myeloid progenitors.

We carried out an in vitro study on the combined effects of three CSF (G-CSF, GM-CSF and IL-3) plus the cycle-specific chemotherapeutic drugs [cytosine arabinoside (Ara-C) and daunorubicin (DNR)] on the proliferation and cytotoxicity of blasts and clonogenic cells (CFU-AML) in the AML-193 cell line, in AML patients and in normal bone marrow CFU-GM. The number of surviving blasts and/or DNA synthesis in blasts treated with CSF plus Ara-C or DNR was greater than those treated without CSF in the AML-193 cell line, and in some AML patients. On the other hand, the Ara-C- and DNR-mediated cytotoxicity of CFU-AML was not abrogated by CSF in any instance, but rather, it was significantly enhanced by all the CSF in the majority of instances. Although the enhancement was clearer when Ara-C was used, compared with DNR, there were no significant differences among the enhancing effects of the CSF. Under the same culture conditions as those for CFU-AML, all of the CSF significantly enhanced the Ara-C-mediated cytotoxicity of day 7 normal CFU-GM, although to a lesser extent than in CFU-AML. However, none of the CSF significantly affected the Ara-C-mediated cytotoxicity of day 14 normal CFU-GM or the DNR-mediated cytotoxicity of day 7 or day 14 normal CFU-GM. These results suggest that in the selection of a strategy entailing combined use of cycle-specific drugs plus CSF to increase the antileukemic effectiveness of chemotherapy in AML, G-CSF is preferable to GM-CSF or IL-3, since it has fewer potential clinical side effects, and that, furthermore, DNR may be as useful as Ara-C.     

In vitro proliferation and differentiation of erythroid progenitors from patients with myelodysplastic syndromes: evidence for Fas-dependent apoptosis

Erythropoiesis results from the proliferation and differentiation of pluripotent stem cells into immature erythroid progenitors (ie, erythroid burst-forming units (BFU-Es), whose growth, survival, and terminal differentiation depends on erythropoietin (Epo). Ineffective erythropoiesis is a common feature of myelodysplastic syndromes (MDS). We used a 2-step liquid-culture procedure to study erythropoiesis in MDS. CD34(+) cells from the marrow of patients with MDS were cultured for 10 days in serum-containing medium with Epo, stem cell factor, insulin-like growth factor 1, and steroid hormones until they reached the proerythroblast stage. The cells were then placed in medium containing Epo and insulin for terminal erythroid differentiation. Numbers of both MDS and normal control cells increased 10(3) fold by day 15. However, in semisolid culture, cells from patients with refractory anemia (RA) with ringed sideroblasts and RA or RA with excess of blasts produced significantly fewer BFU-Es than cells from controls. Fluorescence in situ hybridization analysis of interphase nuclei from patients with chromosomal defects indicated that abnormal clones were expanded in vitro. Epo-signaling pathways (STAT5, Akt, and ERK 1/2) were normally activated in MDS erythroid progenitors. In contrast, apoptosis was significantly increased in MDS cells once they differentiated, whereas it remained low in normal cells. Fas was overexpressed on freshly isolated MDS CD34(+) cells and on MDS erythroid cells throughout the culture. Apoptosis coincided with overproduction of Fas ligand during the differentiation stage and was inhibited by Fas-Fc chimeric protein. Thus, MDS CD34(+)-derived erythroid progenitors proliferated normally in our 2-step liquid culture with Epo but underwent abnormal Fas-dependent apoptosis during differentiation that could be responsible for the impaired erythropoiesis.     

A comparison of treatment of canine cyclic hematopoiesis with recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF), G-CSF interleukin-3, and canine G-CSF.

Cyclic hematopoiesis in gray collie dogs is a stem cell disease in which abnormal regulation of cell production in the bone marrow causes cyclic fluctuations of blood cell counts. In vitro studies demonstrated that recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and granulocyte colony stimulating factor (G-CSF) all stimulated increases in colony formation by canine bone marrow progenitor cells. Based on these results, gray collie dogs were then treated with recombinant human (rh) GM-CSF, IL-3, or G-CSF subcutaneously to test the hypothesis that pharmacologic doses of one of these hematopoietic growth factors could alter cyclic production of cells. When recombinant canine G-CSF became available, it was tested over a range of doses. In vivo rhIL-3 had no effect on the recurrent neutropenia but was associated with eosinophilia, rhGM-CSF caused neutrophilia and eosinophilia but cycling of hematopoiesis persisted. However, rhG-CSF caused neutrophilia, prevented the recurrent neutropenia and, in the two animals not developing antibodies to rhG-CSF, obliterated periodic fluctuation of monocyte, eosinophil, reticulocyte, and platelet counts. Recombinant canine G-CSF increased the nadir neutrophil counts and amplitude of fluctuations at low doses (1 micrograms/kg/d) and eliminated all cycling of cell counts at high doses (5 and 10 micrograms/kg/d). These data suggest significant differences in the actions of these growth factors and imply a critical role for G-CSF in the homeostatic regulation of hematopoiesis.     

Differential effects of IL-3, GM-CSF and G-CSF in an adult with congenital neutropenia.

Using a methylcellulose culture system, we studied the effects of recombinant human interleukin-3 (IL-3), recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF), and recombinant human granulocyte colony-stimulating factor (G-CSF) on the growth of myeloid progenitor cells (CFU-C) from an adult patient with congenital neutropenia. The moderate clinical course and the maturation arrest at blast-promyelocyte stage in the marrow differentiated this patient from those described as having Kostmann-type congenital neutropenia. CFU-C growth in bone marrow cells from the patient responded to IL-3 normally in a dose-dependent manner. GM-CSF stimulated only macrophage colony formation in a dose-dependent manner comparable to that in normal subjects. Neither GM-CSF nor G-CSF stimulated any significant granulocyte colony formation. This evidence suggests that the hematopoietic progenitor cells in this patient had the potential for developing CFU-C with IL-3, and that the neutropenia in this patient could be a result of an intrinsic defect in myelopoiesis along a granulocytic pathway responsive to GM-CSF or G-CSF.     

The influence of purified recombinant human heavy-subunit and light- subunit ferritins on colony formation in vitro by granulocyte- macrophage and erythroid progenitor cells

Purified recombinant human heavy subunit (rHF, acidic) and recombinant human light subunit (rLF, basic) ferritins were assessed for their effects in vitro on colony formation by normal human granulocyte- macrophage (CFU-GM) and erythroid (BFU-E) progenitor cells. The purity of the samples was confirmed by electrophoresis in both nondenaturing and denaturing conditions and silver staining. Concentrations of 10(-8) to 10(-10) mol/L rHF caused an approximately 40% significant decrease in colony formation. Some significant activity was detected at 10(-11) mol/L, and activity was lost at 10(-12) mol/L. In contrast, rLF had no significant activity at 10(-8) to 10(-16) mol/L. rHF was significantly active against mouse bone marrow CFU-GM to concentrations as low as 10(- 8) to 10(-9) mol/L. The inhibitory activity of rHF was inactivated with three different monoclonal antibodies recognizing the heavy subunit of ferritin, but not with two monoclonal antibodies recognizing the light subunit of ferritin. The inhibitory activity of rHF was similar in the absence or presence of serum, monocytes, and T lymphocytes. We and others have shown an association of a glycosylated natural acidic isoferritin (AIF) with inhibitory activity, but since the rHF was expressed in Escherichia coli and did not bind to concanavalin A, glycosylation of AIF is not an absolute prerequisite for this activity. These results demonstrate that rHF has suppressive activity in vitro and substantiate our original observations using purified natural acidic isoferritins.     

In vivo hematopoietic effects of recombinant interleukin-1 alpha in mice: stimulation of granulocytic, monocytic, megakaryocytic, and early erythroid progenitors, suppression of late-stage erythropoiesis, and reversal of erythroid suppression with erythropoietin

Interleukin-1 alpha (IL-1 alpha) is a macrophage-derived, multifunctional cytokine that broadly potentiates myelopoiesis and induces the synthesis of hematopoietic colony-stimulating factors (CSF) in vitro and in vivo. To evaluate the possibility for use of IL-1 alpha in ameliorating in vivo bone marrow suppression induced by drugs or radiation, we examined the in vivo effects of the cytokine on erythropoietic and other hematopoietic progenitor cells. Normal mice were treated with a single intraperitoneal (IP) injection of recombinant human IL-1 alpha at varying doses and were assayed at various times post-treatment. By six hours postinjection, a significant suppression of mature erythroid progenitors (CFU-E) was observed in animals treated with IL-1 alpha (0.5 micrograms/mouse), with maximum suppression of CFU-E and peripheral blood reticulocyte counts occurring at 24 hours. Decreases in peripheral blood hematocrit did not occur after a single IL-1 alpha injection but were observed after multiple injections of the cytokine. The suppressive effects of IL-1 alpha on late-stage erythropoiesis were abrogated by simultaneous administration of erythropoietin (EPO). At 48 hours post-treatment, a marked stimulation was observed in the numbers of spleen and marrow immature erythroid (BFU-E), macrophage (CFU-M), granulocyte (CFU-G), granulocyte- macrophage (CFU-GM), and megakaryocyte (CFU-meg) progenitor cells. These results demonstrate the potential use of IL-1 alpha as a generalized stimulator of hematopoiesis and show that the cytokine- induced suppression of late-stage erythropoiesis can be prevented by EPO.     

In vitro response of blasts to IL-3, GM-CSF,and G-CSF is different for individual AML patients: factors that stimulate leukemic clonogenic cells also enhance Ara-C cytotoxicity

Summary In vivo, growth factors are currently investigated for their capacity to trigger leukemic stem cells into cycle and thus overcome kinetic drug resistance. In this study, the susceptibility of leukemic clonogenic cells to individual growth factors was related to cytosine-arabinoside (Ara-C) sensitivity. The effects of interleukin-3 (IL-3), granulocyte-macrophage colonystimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF), and combinations of these recombinant hematopoietic factors were tested on blast cells of nine acute myeloid leukemia (AML) patients. Growth factor responses were assessed in semi-solid clonogenic assay and in a 10-day liquid culture followed by clonogenic assay. Heterogeneity in growth factor response was observed in both test systems, resulting in a variable pattern for individual leukemias. In the majority of cases (six of nine) the response patterns in the semi-solid and liquid cultures were divergent. To test the Ara-C sensitivity, leukemic blasts were exposed in liquid to various concentrations of Ara-C in the absence and presence of preselected growth factors. After 10 days, the number of surviving leukemic colony-forming cells (CFU-L) was assessed. Exposure to Ara-C in the presence of optimal stimulatory factor(s) resulted in a 3- to 1000-fold increase of the Ara-C toxicity in seven patients. The Ara-C concentrations resulting in 50% inhibition of clonogenicity (ID₅₀) were 0.48–123 x 10^–8 M Ara-C in the absence of stimulatory growth factors, versus only 0.12–0.40 × 10^–8 M Ara-C in the presence of these factors. In two patients, addition of one or more factors neither increased the number of CFU-L in liquid nor enhanced the Ara-C toxicity. Even in the absence of growth factors the ID₅₀ values in these cases were as low as 0.20 and 0.28 × 10^–8 M Ara-C and in the same range as the ID₅₀ values observed with maximum growth factor stimulation in the other seven patients. These results indicate that Ara-C cytotoxicity can be enhanced by individually selected, clonogenic cell growth-promoting hematopoietic factors.