FLT3LG and IFITM3P6 consolidate T cell activity in the bone marrow microenvironment and are prognostic factors in acute myelocytic leukemia

Acute myelocytic leukemia (AML) is a malignancy of the stem cell precursors of the myeloid lineage. CD4+ and CD8+ T cells play pivotal roles in influencing AML progression but are functionally suppressed in the bone marrow microenvironment. We aimed to find hub genes related to T cell exhaustion and suppression, thereby providing evidence for immunotherapy. In this study, gene transcriptome expression data from TCGA and TARGET databases were utilized to find key genes. Firstly, CIBERSORT immune cell infiltration algorithm and WGCNA method were used to identify CD4+ and CD8+ T cells-related genes. Univariate and multivariate cox regression analyses were then introduced to construct the overall survival prognosis model and included hub genes. The ESTIMATE and ssGSEA scoring methods were used to analyze the correlation between the hub genes and immune activity. Single-cell transcriptome analysis was applied to detect the immune cells expressing hub genes, hence, to detect exact mechanisms. Consequently, FLT3LG and IFITM3P6 were determined to be positively correlated with patients’ overall survival and microenvironment immune activity. Further study suggested FLT3-FLT3LG and IFITM3P6-miR-6748-3p-CBX7 signaling axes were involved in CD4+ and CD8+ T cells activation. This may be one of the mechanisms of T cells suppression in AML.

[Physiopathology and possible clinical use of hematopoietic stem cells. Recent advances]

Studies carried out during these last years have lead to a considerable improvement in the understanding of the biology of hematopoietic stem cells. The development of hematopoietic stem cell transplantation had a considerable impact on the therapy of leukemias. The improvement in transplantation protocols allowed the development of allogenic transplantations in which the graft versus tumor contributes to the anti-tumor effects. In parallel many growth factors acting on hematopoietic cells have been isolated and used in clinic to stimulate hematopoietic recovery and stem cell mobilization. Finally, malignant stem cells have been isolated and characterized in acute and chronic leukemias: these cells are responsible for the development and maintenance of the leukemic process and must be eradicated to obtain an effective treatment of leukemias.

Haemopoietic growth factors: structure and receptor interactions

The proteins which regulate the production of blood cells appear to have overlapping functions. There are several forms of the haemopoietic growth factors (HGFs). Although a few have been purified, the functions of the different growth factors have not yet been clarified. The amino acid sequence of murine granulocyte-macrophage colonystimulating factor (GM-CSF) has been determined from a cDNA clone and several molecular forms of the molecule have been purified. Although there is no extensive homology with other haemopoietic growth factors, the mRNA for GM-CSF suggests two possible functions for this molecule. Radioiodination of GM-CSF to high specific activity has permitted the detection of two classes of specific GM-CSF receptors on myeloid cells. Although the different haemopoietic growth factors do not compete directly for binding to their specific receptors, GM-CSF and interleukin 3 (IL-3) can modulate the availability of other HGF receptors.

The role of haemopoietic cell growth factor (interleukin 3) in the development of haemopoietic cells

Haemopoietic cell development in vivo occurs in restricted sites in association with stromal cells. Haemopoiesis in vitro can be induced in the absence of stromal cells, provided the haemopoietic cells are supplied with appropriate growth stimulatory molecules. Evidence indicates that the same, or functionally similar, growth factors are normally supplied in vivo by the surrounding stromal cells and that the control of haemopoietic cell proliferation and development is regulated locally and is mediated by cell-cell interactions. We have been studying the effects of a growth factor which induces self-renewal and differentiation of multipotential stem cells as well as proliferation and development of lineage-restricted progenitor cells and activation of mature cells. Because of the wide range of activities embraced by this molecule we have termed it haemopoietic cell growth factor (HCGF). It is also known as interleukin 3 and multi-CSF. HCGF allows the survival, proliferation and development of cells and can be used to generate continuously growing, non-leukaemic, factor-dependent cell lines, in vitro (FDC-P). In the absence of HCGF. FDC-P cells die within hours. We have shown that HCGF may exert its primary effects (in terms of cell survival) on ATP generation, via its influence on glucose transport. Studies are also described which indicate that a primary event in differentiation induced by HCGF involves ADP-ribosylation of membrane-associated proteins. The significance of these findings for normal haemopoiesis and in leukaemogenesis is discussed.

Haemopoietic growth factor regulation of protein kinases and genes associated with cell proliferation

Haemopoietic growth factors stimulate a number of common biochemical and molecular events despite the high specificity of individual ligand-receptor interactions. Analysis of three distinct colony-stimulating factors (CSFs), interleukin 3 (IL-3), granulocyte-CSF and granulocyte macrophage-CSF, and the lymphocytotropic growth factor IL-2 revealed remarkably similar distal subcellular biochemical signals, although the mode of initial membrane signal transduction may differ significantly. Both early progenitor cell growth factors, such as IL-3, and late-acting factors, such as CSF-1, stimulate tyrosine and serine/threonine substrate phosphorylations. One substrate (p68) is phosphorylated in response to many CSFs and to IL-2, suggesting that it plays a highly conserved role in the signal transduction processes of many different receptor(s). The proliferative CSFs and IL-2 also stimulate the expression of many of the same genes, including protooncogenes, the ornithine decarboxylase gene, and members of the phylogenetically ancient family of stress response genes. Thus although initial membrane events may differ among the proliferative stimulants, the biochemical and molecular convergence of signalling pathways on highly conserved cellular substrates and on the programme of gene expression is seen.

Haemopoietic growth factors: their relevance in osteoclast formation and function

The major recent advance in our knowledge of the haemopoietic system has been the purification and characterization of a family of haemopoietic growth factors, and their availability in recombinant form. In the bone marrow the sequences of differentiation and proliferation leading to the production of mature cells that these factors regulate may be determined by the relative availability of the factors in microenvironmental domains. The observation that growth factor-producing cells and haemopoietic progenitor cells are not evenly distributed in the bone marrow leads us to expect that the overall effect of growth factors (and other regulatory molecules) on the production and function of macrophages and osteoclasts may differ when in vivo or in vitro assays are used as end-points and, in the latter case, when whole marrow or purified cell populations are tested. The availability of an in vitro assay in which osteoclast-like cells are generated will allow these concepts to be tested.

Erythropoiesis stimulating agents

May not be safe in people with cancer

Familial hemophagocytic lymphohistiocytosis with the MUNC13-4 mutation: a case report

A 44-day-old male infant with familial hemophagocytic lymphohistiocytosis (FHL) associated with the MUNC13-4 mutation is reported. He presented with fever and poor feeding, lymphocytosis with thrombocytopenia and CSF pleocytosis without virological explanation. On the basis of progressive hyperferritinemia (1323 ng/ml), anemia (hemoglobin: 5.2 g/dl), hypertriglyceridemia (547 mg/dl) and increased LDH (1063 IU/l) with hemophagocytosis in the bone marrow, hemophagocytic lymphohistiocytosis was diagnosed. He showed a good response to corticosteroid therapy and the disease was stable for more than 5 months. Thereafter, he suffered from central nervous system complications, and successfully underwent unrelated cord blood stem cell transplantation. A remission was observed for more than 2 years, with mild mental retardation. Genetic analysis revealed that he had a compound heterozygous mutation of MUNC13-4; namely a novel 2163G>A mutation resulting in W721X, and 754-1G>C resulting in a premature stop codon in this gene. Western blot analysis showed the complete loss of the MUNC13-4 protein, whereas other molecules associated with the SNARE systems were detected at normal levels. Conclusion. FHL may have a broad clinical spectrum, and further analysis on its phenotype-genotype association is required to establish an appropriate treatment strategy, including immunochemotherapy and stem cell transplantation in the future.

Erythropoietin: the story of hypoxia and a finely regulated hematopoietic hormone

The dramatic increase in knowledge during the last half century about the hormone erythropoietin is reviewed. The description of these events has been separated into two parts. The first part describes how the rapid changes in response to tissue oxygenation in the kidneys changes the rate of erythropoietin production. The second part describes how changes in erythropoietin concentrations act on erythroid progenitor cells, resulting in prompt changes in rates of erythrocyte production. Together these two aspects of erythropoietin biology provide an explanation for the tight physiological regulation of the numbers of circulating erythrocytes and, in a more general manner, provide a model for the control of the numbers of other specific blood cells by their respective hematopoietic growth factors.

Thrombopoietin, flt3-ligand and c-kit-ligand modulate HOX gene expression in expanding cord blood CD133 cells

Haemopoietic stem/progenitor cell (HSPC) development is regulated by extrinsic and intrinsic stimuli. Extrinsic modulators include growth factors and cell adhesion molecules, whereas intrinsic regulation is achieved with many transcription factor families, of which the HOX gene products are known to be important in haemopoiesis. Umbilical cord blood CD133+ HSPC proliferation potential was tested in liquid culture with 'TPOFLK' (thrombopoietin, flt-3 ligand and c-kit ligand, promoting HSPC survival and self-renewal), in comparison to 'K36EG' (c-kit-ligand, interleukins-3 and -6, erythropoietin and granulocyte colony-stimulating factor, inducing haemopoietic differentiation). TPOFLK induced a higher CD133+ HSPC proliferation (up to 60-fold more, at week 8) and maintained a higher frequency of the primitive colony-forming cells than K36EG. Quantitative polymerase chain reaction analysis revealed opposite expression patterns for specific HOX genes in expanding cord blood CD133+ HSPC. After 8 weeks in liquid culture, TPOFLK increased the expression of HOX B3, B4 and A9 (associated with uncommitted HSPC) and reduced the expression of HOX B8 and A10 (expressed in committed myeloid cells) when compared to K36EG. These results suggest that TPOFLK induces CD133+ HSPC proliferation, self-renewal and maintenance, up-regulation of HOX B3, B4 and A9 and down-regulation of HOX B8 and A10 gene expression.

Ex vivo expansion of neutrophil precursor cells from fresh and cryopreserved cord blood cells

BACKGROUND

Neutropenia following cord blood (CB) transplantation may be abrogated by infusion of granulopoietic progenitor cells. The purpose of this study was to determine whether myeloid progenitors can be obtained by ex vivo expansion of cryopreserved cord blood aliquots, and whether these progenitors present the morphologic, biologic and functional properties of myeloid progenitors at various stages of differentiation.

METHODS

The cells, plated for 7 days in serum-free medium with SCF, IL-3, G-CSF, Flt3-ligand and thrombopoietin in various combinations were assessed for the expression of CD34, CD38 and CD13. Maturation of cells into the myeloid lineage was evaluated by the expression of CD15, CD11b and CD16 and by the presence of primary (myeloperoxidase) and secondary granules (lactoferrin). The capacity of cells to phagocyte latex beads was evaluated to assess their functionality.

RESULTS

We have shown that a). CD34+ cells isolated from thawed samples were able to produce expansions similar to fresh samples. b). The best combination for the expansion of neutrophil precursor cells was S3FG; c). in these conditions, all stages of myeloid progenitors were represented, but few mature cells were observed. d). However, when the cells were plated on a BM stroma to try to reproduce conditions occurring during transplant, they acquired rapidly the characteristics of mature segmented cells. e). The ex vivo generated granulocytes were able to phagocyte latex beads.

DISCUSSION

In conclusion, it seems reasonable to systematically aliquot CB samples before cryopreservation. Some aliquots can then be thawed, enriched in CD34+ cells and ex vivo differentiated into myeloid lineage, while the other aliquots are conserved to be infused without manipulation.

[Pitfalls of hematopoietic growth factors on MR images]

We report the effects of hematopoietic growth factors on MR signal intensity of bone marrow in 2 children undergoing chemotherapy for musculoskeletal malignancies. The two patients with initially fatty marrow had signal intensity changes: diffuse decreased signal of the distal femoral metaphysis and patchy areas in the diaphysis of both tibia and fibula, simulating metastases. These changes coincided with dramatic increase in neutrophil counts. Technetium 99 skeletal scintigraphy was normal. After a three year follow-up the patients are in good health.

Expression of LSLCL, a new C-type lectin, is closely restricted, in bone marrow, to immature neutrophils

In vitro, LSLCL is expressed by numerous myeloid, promyelocytic, and T or B lymphoblastoid cell lines. In vivo, LSLCL is strongly expressed in bone marrow and only faintly in lymphoid organs. We show here that, in bone marrow, LSLCL is detected: (i) concentrated in the cytoplasm of immature neutrophils but not in myeloblasts nor in mature neutrophils, (ii) in extracellular bone marrow fluid. Besides, numerous cDNAs, similar to LSLCL (identity of 93-99%), are found in 'expressed sequence tags' databases from various origins, mostly fetal and undifferentiated tumour tissues. Since LSLCL and various closely related cDNAs are expressed at definite stages of cellular maturation processes, we hypothesize that this class of proteins could play an important role in the control of cellular differentiation.

Serum-free ex vivo expansion of CD34(+) hematopoietic progenitor cells

In an effort to obtain defined culture conditions for ex vivo expansion of hematopoietic stem and progenitor cells which avoid the supplementation of serum, we cultured human CD34(+) hematopoietic progenitor cells in a chemically defined, serum-free medium in the presence of hematopoietic growth factors (HGFs), stem cell factor (SCF), interleukin (IL)-1beta, IL-3, IL-6, and erythropoietin (EPO). A medium, SFM-1, was prepared according to a protocol previously optimized for semisolid progenitor cell assays containing Iscove's Modified Dulbecco's Medium (IMDM) plus cholesterol, bovine serum albumin, transferrin, nucleotides and nucleosides, insulin, and beta-mercaptoethanol. In static cultures seeded with CD34(+)-enriched progenitor cells isolated from human peripheral blood, a mean 76.6-fold expansion of total nucleated cells and a mean 4.6-fold expansion of colony-forming cells (CFC) was recorded after 14 days. Morphological analysis of the expanded cells revealed formation of myeloid, erythroid, and megakaryocytic cells. Flow cytometric analysis indicated that CD34(+) antigen expressing cells were maintained to a limited degree only, and cell populations expressing surface markers for myeloid (CD33, CD14, and CD15) and megakaryocytic (CD41a) lineages predominated. Within SFM-1, bovine serum albumin (BSA), cholesterin, and transferrin represented the most critical components needed for efficient total cell and CFC expansion. Addition of autologous patient plasma (APP) or fetal calf serum (FCS) to SFM-1 resulted in inferior cell amplification and CFC formation compared to controls in SFM-1, indicating that the components used in SFM-1 could replace exogenous serum. Four commercially available serum-free media resulted in either comparable or lower total cell and CFC yields as SFM-1. The transplantation potential of CD34(+) cells after culture in SFM-1 was assayed using limiting dilution analysis on preformed irradiated bone marrow stroma and revealed maintenance of long-term bone marrow culture initiating cell (LTCIC) levels during the culture period. These data indicate that HGF-supported multilineage ex vivo expansion of human CD34(+) hematopoietic progenitor cells is feasible using an IMDM-based culture medium which contains a restricted number of additives, resulting in analogous or improved yields of both primitive and differentiated cells compared to previously established protocols. We suggest that this culture protocol is of advantage when working with pharmaceutical-grade preparations under serum-free conditions.

Mpl: from an acute myeloproliferative virus to the isolation of the long sought thrombopoietin

Mpl, the receptor for thrombopoietin (TPO), was isolated as a cellular sequence transduced by a new acute myeloproliferative virus. Human and murine c-mpl were subsequently cloned and Mpl was identified as a member of the growth factor receptor superfamily. For a time, Mpl remained an orphan receptor. Engineering of cell lines expressing c-mpl provided a sensitive tool for detecting the ligand of Mpl, and led to the molecular cloning of TPO, the long sought proliferation and differentiation factor for the megakaryocytic lineage. Afterwards, signal transduction by Mpl was studied, and the functional elements of the cytoplasmic domain responsible for cell proliferation and differentiation were identified. When studied in various human hematologic malignancies, Mpl expression was shown to be increased in 50% of the patients with acute myeloblastic leukemia (AML). In vitro treatment of AML cells by TPO led to proliferation, suggesting that TPO could contribute, at least in part, to abnormal growth of AML cells. A tremendous number of studies have followed the isolation of TPO, and have shown that TPO is the primary regulator of physiological platelet production. However, roles for Mpl and TPO in other lineages, especially in erythroid and immature hematopoietic progenitors, have also emerged from these studies.

Ex vivo expansion of hematopoietic progenitor cells for clinical use

The development of efficient stem and progenitor cell selection methods in combination with the development of hematopoietic growth factors facilitated the development of ex vivo expansion techniques. Currently, this novel domain of cellular therapy aims to generate stem and progenitor cells, as well as more differentiated post-progenitor cells and antigen-presenting dendritic cells. The feasibility of generating and transplanting hematopoietic progenitor cells ex vivo (using various cytokine combinations) has been successfully shown preclinically as well as clinically. Furthermore, cytokines (eg, Flt-3-ligand; thrombopoietin) have been identified that play important roles with regard to amplification of undifferentiated early hematopoietic cells. The use of lineage-specific cytokines such as granulocyte colony-stimulating factor and thrombopoietin facilitated the generation of large numbers of myeloid and megakaryocytic post-progenitor cells. The clinical usefulness of such ex vivo generated cells, however, has not yet been convincingly shown. Last, ex vivo expansion techniques can be used to generate large numbers of antigen-presenting dendritic cells from CD34+ peripheral blood progenitor cells that might be ideally used for immunotherapeutic approaches.

Molecular cloning of a new secreted sulfated mucin-like protein with a C-type lectin domain that is expressed in lymphoblastic cells

We have previously demonstrated hyposialylation of the two major CD45 and leukosialin (CD43) molecules at the surface of latently human immunodeficiency virus type 1-infected CEM T cells (CEMLAI/NP), (Lefebvre, J. C., Giordanengo, V., Doglio, A., Cagnon, L., Breittmayer, J. P., Peyron, J. F., and Lesimple, J. (1994) Virology 199, 265-274; Lefebvre, J. C., Giordanengo, V., Limouse, M., Doglio, A., Cucchiarini, M., Monpoux, F., Mariani, R., and Peyron, J. F. (1994) J. Exp. Med. 180, 1609-1617). Searching to clarify mechanism(s) of hyposialylation, we observed two sulfated secreted glycoproteins (molecular mass approximately 47 and approximately 40 kDa) (P47 and P40), which were differentially sulfated and/or differentially secreted in the culture supernatants of CEMLAI/NP cells when compared with parental CEM cells. A hybridoma clone (7H1) resulting from the fusion between CEMLAI/NP and human embryonic fibroblasts MRC5 cells produced very large amounts of P47 that was purified using Jacalin lectin (specific for O-glycans) and microsequenced. Cloning of P47 was achieved using a CEMLAI/NP cDNA library screened with a degenerate oligonucleotide probe based on its NH2-terminal amino acid sequence. A single open reading frame encoding a protein of 323 amino acids was deduced from the longest isolated recombinant (1.4 kilobase). P47 is a secreted sulfated protein. It carries an NH2-terminal RGD (Arg-Gly-Asp) triplet, a striking alpha-helical leucine zipper composed of six heptads, and a C-terminal C-type lectin domain. The NH2-terminal portion is rich in glutamic acids with a predicted pI of 3.9. In addition, a hinge region with numerous condensed potential sites for O-glycan side chains, which are also the most likely sulfation sites, is located between the RGD and leucine zipper domains. Transcripts were detected in lymphoid tissues (notably bone marrow) and abundantly in T and B lymphoblastoid but very faintly in monocytoid cell lines.

Standardization of the CFU-GM assay using hematopoietic growth factors

The colony-forming unit-granulocyte-macrophage (CFU-GM) assay is used commonly to assess adequacy of progenitor number in bone marrow transplantation. The assay is poorly standardized, resulting in variability of results between and within laboratories. We assessed three variables that contribute to the lack of standardization. The colony-stimulating activity of human placental-conditioned medium (HPCM) was compared with combinations of recombinant hematopoietic growth factors (HGF) in 5 normal bone marrow donors. A protocol for batch testing of fetal calf serum (FCS) is described. In addition, a rigid training program has been introduced to minimize interstaff and intrastaff variability in the counting of colonies. We show that a five-factor combination of interleukin-3 (IL-3), IL-6, granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage CSF (GM-CSF), and stem cell factor (SCF) produces a mean increase of 85% in colony number. Some combinations of three HGF produce similar growth to HPCM, and all four HGF combinations are equivalent or superior to HPCM. Batch testing of FCS shows variability between batches. We show significant interstaff and intrastaff variability between a new and experienced staff member that improves following a period of training. In summary, the use of recombinant HGF in association with a rigorous program of batch testing of FCS and staff training results in a CFU-GM assay that can be standardized between laboratories.

The contribution of animal models to the development of treatments for hematologic recovery following myeloablative therapy: a review

This review describes the role that animal models have played in the development of clinical procedures for growth factor and hematopoietic cell therapies following high-dose cancer chemotherapy, radiotherapy or both. Data are discussed describing animal models that add to the understanding of human hematopoiesis, including myeloid and lymphoid lineage localization and in vivo maturation. Finally, current animal models of cytokine and cell therapies are presented in the context of their contributions to early clinical trials and future therapies. These studies underscore the past and current contributions animal investigations have made to improving clinical therapies.

Growth factors and their impact on transfusion medicine

Hematopoietic growth factors, glycoproteins that stimulate self-renewal, differentiation, and proliferation of responsive hematopoietic cells, promise to revolutionize transfusion medicine. Recombinant DNA technology has made several of these cytokines available at pharmacologic doses, and new candidate agents for clinical application appear regularly. Growth factors prescribed for patients have already reduced the requirement for red blood cell and granulocyte transfusions in selected clinical circumstances. A lineage-specific thrombopoietin will likely limit the need for platelet transfusions. Hematopoietic cytokine injections have also been used to increase the number of red blood cells, granulocytes and circulating primitive progenitor cells in blood donors. Cytokine-stimulated peripheral blood progenitor cell infusions have complemented and, in some instances, replaced bone marrow for adjunctive cancer chemotherapy and for bone marrow transplantation. Finally, synergistic combinations of cytokines can effect ex vivo expansion of lymphocytes and of progenitor cells to provide novel blood components. Hematopoietic growth factors are still expensive and their long-term effects remain to be determined. However, as the biologic activities of cytokines and the physiology of hematopoietic progenitor cells become better understood, the clinical application of novel cellular components may redefine the concept of blood transfusion.

Hematopoietic cell proliferation and differentiation

The use of colony-stimulating factors to stimulate hematopoietic cell proliferation and differentiation in vivo is under still increasing investigation, particularly in the field of stem cell transplantation. This review discusses recently published results and tries to extrapolate lines of future development from the achievements reached to date.

Cyclophosphamide dose escalation in combination with vincristine and actinomycin-D (VAC) in gross residual sarcoma. A pilot study without hematopoietic growth factor support evaluating toxicity and response

PURPOSE

The Intergroup Rhabdomyosarcoma Study (IRS) initiated an escalating-dose cyclophosphamide (Cyc) pilot without hematopoietic growth factor (HGF) support in combination with vincristine (Vcr) and actinomycin-D (Amd), known as VAC, to establish a Cyc dose with myelotoxicity comparable to an ifosfamide (Ifos), Vcr, and Amd combination regimen (VAI). A Cyc dose equivalent to Ifos was to be determined when comparable myelotoxicity was achieved.

PATIENTS AND METHODS

Patients with either rhabdomyosarcoma or undifferentiated soft-tissue sarcoma and gross residual (clinical group III) disease were eligible for the VAC pilot. Feasibility and toxicity were evaluated in the VAC pilot at each Cyc level before escalating the dose. Starting at CYC 1.2 g/m2 dose escalation was planned at increments of 20-25% in cohorts of 8-10 patients until myelotoxicity at a severe or worse grade was seen in > 90% of the patients.

RESULTS

One hundred nineteen eligible patients were evaluated for toxicity and response at four Cyc levels: 1.2, 1.5, 1.8, and 2.2 g/m2. Eight of 87 (9%) evaluable at 2.2 g/m2 had a toxic death. Six of these were attributable to myelotoxicity. Patients age 1-3 years were most vulnerable. The overall complete response (CR) rate of 68% was poorly predicted by the weeks 8 and 20 CR rates of 20 and 40%, respectively. During the first year and overall, myelotoxicity at 2.2 g/m2'1 with VAC was comparable to Ifos 1.8 g/m2'5. Cyc was relatively more myelotoxic than Ifos in the second year of the VAC pilot. Based on actual amount of drug given, a standardized Ifos dose of 9.0 g/m2 was equivalent to 2.1 g/m2 of Cyc, giving an Ifos/Cyc ratio of 4.3.

CONCLUSION

Myelotoxicity using 2.2 g Cyc/m2 in a single intravenous infusion was dose limiting in this VAC pilot without HGF. In the first year and overall, myelotoxicity is comparable to that with VAI using Ifos at 9.0 g/m2. An ongoing IRS-IV randomized trial of VAC and VAI should provide a comparison of the efficacy of Ifos and Cyc in children and adolescents with embryonal or alveolar rhabdomyosarcoma and undifferentiated soft-tissue sarcomas.

Myelodysplastic syndrome

Myelodysplastic syndrome continues to present a formidable clinical challenge. Despite considerable effort, no therapy apart from allogeneic bone marrow transplantation has been shown to prolong survival. Lack of effective therapy for myelodysplastic syndrome is of further concern given recent reports on the high incidence of myelodysplastic syndrome in patients undergoing intensive chemotherapy and radiation therapy for other malignancies. However, significant strides have been made in the past year toward understanding the molecular pathogenesis of some forms of myelodysplastic syndrome, as well as developing new approaches for therapy of myelodysplastic syndrome. This review highlights recent advances in the molecular genetics of myelodysplastic syndrome, including clonality analysis and identification of genes that are causally implicated in the pathogenesis of myelodysplastic syndrome; results from recent clinical trials for therapy of myelodysplastic syndrome using growth factors, chemotherapy or both; and recent literature on therapy-related myelodysplastic syndrome in intensively treated patients.

Hematopoietic stem cell compartment: acute and late effects of radiation therapy and chemotherapy

The bone marrow is an important dose-limiting cell renewal tissue for chemotherapy, wide-field irradiation, and autologous bone marrow transplantation. Over the past 5-10 years a great deal has been discovered about the hematopoietic stem cell compartment. Although the toxicity associated with prolonged myelosuppression continues to limit the wider use of chemotherapy and irradiation, ways are being discovered to circumvent this toxicity such as with the increasing use of cytokines. This review describes what is known of how chemotherapy and irradiation damage stem cells and the microenvironment, how cytokines protect hematopoietic cells from radiation damage and speed marrow recovery after chemotherapy or marrow transplantation, and how various types of blood marrow cells contribute to engraftment and long-term hematopoiesis after high doses of cytotoxic agents and/or total body irradiation.

An effective strategy for decontamination, ex vivo expansion, and storage of human fetal liver hematopoietic stem cells

The transplantation of human fetal tissue has the potential to cure a variety of life-threatening diseases. The strategy for procurement, quality control, and functional assessment of human fetal liver HSC may prove useful for the transplantation of other fetal tissues. In addition to technical limitations, there are ethical and legal issues which need to be resolved before widespread use of fetal tissue. Further development of regulatory standards for the acquisition and distribution of fetal tissues will foster the application of this novel technology.

Differentiation of human mast cells from bone-marrow and cord-blood progenitor cells by factors produced by a mouse stromal cell line

Human bone-marrow or cord-blood progenitors (i.e., CD34+ cells) are easily purified by immunological methods and can be cultured on normal human-bone-marrow stromal cells for limited periods of time. Under these culture conditions, the number of progenitors declines in a few weeks and these cells disappear completely in less than 8 weeks. This fact suggests that this culture system is deprived of growth factor(s) able to support the self-renewal of stem cells. We have developed the culture of immunomagnetically purified human-bone-marrow- or cord-blood-derived CD34+ cells on a supportive mouse lipoblastic stromal cell line, MS-5. The long-term survival of clonogenic cells was analyzed in these cultures and compared with the results obtained by culture on human-bone-marrow stromal cells. The results demonstrated that only coculture of CD34+ cells on MS-5 layers allows the survival of clonogenic progenitors for at least 12 weeks. Cytospin smears were regularly performed and cell morphology was examined after classical staining methods (i.e., M.G.G. and toluidine blue staining). Histologic analysis demonstrated the growth of mast-cell-like metachromatic cells after the second week of incubation on MS-5 layer. The highest percentage of these cells was observed after 8 weeks, and averaged about 30 percent for cord-blood cells and 70 percent for bone-marrow cells. To further confirm the nature of the metachromatic cells obtained under this culture condition, immunohistochemical staining of tryptase was performed on the same samples. The results demonstrated similar percentages of tryptase+ cells and of metachromatic elements. Measurement of cellular histamine demonstrated that culture of CD34+ cells on MS-5 monolayers induced the formation and increase of this mediator. To determine whether the contact between MS-5 layers and CD34+ cells was an absolute requirement for the development of mast cells, CD34+ cells were cultured in the presence of MS-5 conditioned medium. This condition allowed the development of similar percentage of mast cells when compared with the coculture experiments, indicating that a soluble factor was involved in mast cell differentiation. Whatever the soluble factor(s) responsible for this mast cell growth activity, our culture system allows us to obtain significant amounts of highly enriched normal human mast cell populations useful for further studies on the reactivity of this cell subset.

Expression of the Kit and KitA receptor isoforms in human acute myelogenous leukemia

Genetic and biologic evidence suggests that the Kit receptor tyrosine kinase is important in early events in hematopoietic stem cell differentiation. Two naturally occurring isoforms of the Kit receptor, termed Kit and KitA, were originally described in mouse cells and, subsequently, in human cells. These isoforms differ by the presence (KitA) or absence (Kit) of four amino acids (Gly-Asn-Asn-Lys) that lie immediately outside the transmembrane domain. RNase protection was used to measure the levels of Kit and KitA mRNA in normal bone marrow and the blast cells from individuals with acute myelogenous leukemia (AML). Although both isoforms were present in all the AML samples tested, there was considerable heterogeneity in the relative levels of the two transcripts, with Kit to KitA RNA ratios varying from as low as 1.3 to as high as 12. In contrast, the ratio of Kit to KitA transcripts in normal bone marrow was tightly clustered between 4.4 and 5.5. Because alterations in the relative levels of expression of Kit and KitA may affect the ability of a cell to respond to the Kit ligand, Steel factor, we examined the Kit/KitA RNA ratio in AML patients that differed with respect to a number of diagnostic, prognostic, and biologic parameters. The relative levels of Kit to KitA RNA was independent of French-American-British subtype, response to therapy, and primary and secondary plating efficiencies in vitro. Thus, these data suggest that the relative levels of the two isoforms of the Kit receptor in AML are not associated with any obvious biologic or clinical parameters and, therefore, may reflect naturally occurring changes in splicing mechanisms as stem cells differentiate.

Polymerase chain reaction detection of a novel human KIT (mast/stem cell growth factor receptor) gene polymorphism by single-strand conformation polymorphism analysis or by SmaI or BstNI cleavage

We describe a common single-base polymorphism of the KIT gene that alters both SmaI and BstNI restriction sites, but is most easily detected as a single-strand conformation polymorphism (SSCP) using the polymerase chain reaction (PCR).

Hematopoietic growth factors in pediatrics

The human recombinant hematopoietic growth factors have attracted widespread interest because of their potential efficacy in a number of clinical settings. Recombinant human erythropoietin is now an established therapy to treat and prevent the anemia associated with chronic renal failure in children and adults. This agent also shows extraordinary promise to stimulate erythrocyte production and reduce transfusion requirements in premature infants. Granulocyte and granulocyte-macrophage colony-stimulating factors stimulate the production and function of myeloid cells and have provided major clinical benefit to children with congenital disorders of neutrophil production. The myeloid growth factors also show great promise in reducing the duration and severity of neutropenias associated with cytotoxic cancer treatment and in improving granulocyte production in patients with human immunodeficiency virus infections.

Ex vivo differentiation therapy as a method of leukemic cell purging in murine bone marrow expansion cultures

We investigated the use of differentiation therapy as a method of purging bone marrow (BM) of leukemic cells in ex vivo murine BM expansion cultures (delta-cultures). In clonal cultures and in suspension cultures a combination of the differentiation-inducing agents granulocyte colony-stimulating factor (G-CSF), interleukin (IL)-6, and all-trans-retinoic acid (ATRA) was found to be most effective in inducing the differentiation of the murine myelomonocytic leukemic cell line WEHI 3B D+ LacZ clone 2.8 (clone 2.8). Furthermore, we investigated the activity of a mutant form of IL-6, mutein, and found it to have a greater specific activity in cell proliferation assays and in a clone 2.8 differentiation assay than the native form of IL-6. Coculture of clone 2.8 and BM in IL-1 and kit-ligand-stimulated delta-cultures showed that the added stimuli, G-CSF, mutein, and ATRA, decreased the expansion of leukemic cells. Mice transplanted with G-CSF, mutein, and ATRA-purged BM had an increased survival time relative to nonpurged controls. The addition of G-CSF, mutein, and ATRA to delta-cultures did not result in any impairment of hematopoietic stem cells when measured 5 wk after transplantation.

Isolation of rat bone marrow mast lineage cells using Thy 1.1 and rat stem cell factor

Recent reports have shown that various marrow-derived cell populations respond vigorously to recombinant rat stem cell factor (rrSCF164), one form of the kit-ligand. In the present study, we isolated cell populations from rat bone marrow using the Thy 1.1 antigen (an antigen that in the rat is differentially expressed on primitive hemopoietic progenitor cells) and fluorescently conjugated rrSCF164 (rrSCF164-PE). We show that rrSCF164 only stimulates cells that are enriched in the brightest Thy 1.1 populations (Thy 1.1bright). Numerous cell lines were generated by serial passage in rrSCF164 containing medium, and the prototypic cell lines have been designated SRT002 and SRT003. Each cell line retains the Thy 1.1bright phenotype and does not respond to interleukins (IL) 1-8, IL-10, granulocyte (G) colony-stimulating factor (CSF), granulocyte macrophage (GM) CSF, M-CSF, or crude preparations of mitogen-stimulated T-cell supernatants. The Thy 1.1bright population of rat marrow was subdivided into a subset that binds rrSCF164-PE (Thy 1.1bright, rrSCF164+). The majority of these cells possess certain characteristics in common with marrow-derived mast cells and the Thy 1.1bright, rrSCF164 responsive cell lines, having similar granule morphology, being metachromatic, and reacting positively with alcian blue. Moreover, rats treated with rrSCF164 displayed significant increases in Thy 1.1bright, rrSCF164+ cells in the bone marrow. These studies show that the combination of Thy 1.1 and rrSCF164 makes possible the isolation of a unique subset of rat bone marrow cells that differentially express the Thy 1.1 antigen and the cell surface receptor c-kit, the majority of which are morphologically similar to marrow-derived mast cells.

[Function,molecular structure and gene expression of macrophage colony-stimulating factor]

Human urinary macrophage colony-stimulating factor (hM-CSF) is a glycoprotein with a molecular weight of 85 kDa which consists of two homologous subunits with a molecular weight of 43 kDa. It stimulates monocyte production through the stimulation of progenitor cells to differentiate to mature monocytes as well as neutrophil production through the stimulation of mature monocytes to produce granulocyte-macrophage and granulocyte CSF. It also enhances platelet production through the production of megakaryocyte potentiator (Meg-POT). Recently, proteoglycan type M-CSF has been found by our group. This type of M-CSF has a molecular weight of greater than 200 kDa and consists of a 43 kDa subunit and a 150-200 kDa subunit, the latter of which contains chondroitin sulfate glycosaminoglycan. This proteoglycan type M-CSF binds to extra-cellular matrix at the part of glycosaminoglycan. In addition to hematopoiesis-stimulating activity, M-CSF has a promoting activity on monocyte tumor-killing, osteoclast production and differentiation of cytotrophoblasts to syncytiotrophoblasts which secrete gonadotropin. M-CSF receptor (M-CSF-R) was found as a product of proto-oncogene, c-fms which consists of 972 amino acids. Mutations at Tyr 969 and Ser 301 of M-CSF-R has been found in patients with myelodysplastic syndrome and monocytic leukemia.

The action of bryostatin on normal human hematopoietic progenitors is mediated by accessory cell release of growth factors

Since enrichment of human bone-marrow hematopoietic progenitors is becoming more feasible and since purified growth factors are now available, we sought to study the action of growth factors on CD34-positive enriched cultures of human bone-marrow cells. We tested the effect of recombinant human (rh) granulocyte-macrophage colony-stimulating factor (GM-CSF), rh interleukin-3 (IL-3), or a unique biologic response modifier, bryostatin 1, on the growth of purified CD34 cells obtained by limiting dilution in single-cell cultures. We have shown previously that bryostatin 1 stimulates both myeloid and erythroid progenitors of human origin in vitro. In this study both IL-3 and GM-CSF supported colony formation from 500, 100, or single-cell cultures at equivalent plating efficiences, suggesting a direct action of these factors on hematopoietic cell growth. Conversely, bryostatin 1 did not support the growth of CD34 cells in single-cell cultures, and the cloning efficiency increased with increasing the number of cells in the culture. To test whether the indirect action of bryostatin 1 might be mediated through the production of growth factors by accessory cells, studies were performed using antibodies directed against human IL-3 and GM-CSF in culture with bryostatin 1 and normal human bone-marrow cells. Results are consistent with the hypothesis that bryostatin 1 could have a stimulatory effect on the accessory cell populations to produce either IL-3 or GM-CSF. Further support for this notion was obtained by demonstrating that T cells, which are cells known to be able to produce IL-3 and GM-CSF, are stimulated by bryostatin 1 to express messenger RNA (mRNA) for specific growth factors, including GM-CSF. These results provide further support that bryostatin 1 may be a useful clinical agent to stimulate hematopoiesis in vivo.

Hemopoietin-1 activity of interleukin-1 (IL-1) on acute myeloid leukemia colony-forming cells (AML-CFU) in vitro: IL-1 induces production of tumor necrosis factor-alpha which synergizes with IL-3 or granulocyte-macrophage colony-stimulating factor

Interleukin-1 (IL-1) has hemopoietin-1 (H-1) activity, i.e., it synergizes with macrophage-colony stimulating factor (M-CSF), granulocyte-macrophage-CSF (GM-CSF) and interleukin-3 (IL-3) in stimulating in vitro colony formation of hematopoietic progenitor cells. In this study the synergistic activity of IL-1 was investigated on IL-3 and GM-CSF induced growth of acute myeloid leukemia colony forming cells (AML-CFU) in vitro. Among 12 cases of human AML, IL-1 significantly elevated IL-3 stimulated colony numbers in eight instances and enhanced GM-CSF induced colony growth in five cases. As IL-1 is an inducer of cytokine production and since tumor necrosis factor (TNF) elevates IL-3 or GM-CSF induced proliferation of AML-CFU, we examined whether IL-1 enhanced AML-CFU growth via the induction of TNF production. Neutralizing anti-TNF-alpha antibodies significantly decreased IL-1/IL-3 or IL-1/GM-CSF stimulated colony numbers in six of seven cases studied, whereas anti-TNF-beta had no effect, indicating that endogenously produced TNF-alpha costimulated the growth of AML-CFU. Furthermore, AML blast cells stimulated by IL-1 released increased amounts of TNF-alpha (between 25 and 533 pg/ml; median 255 pg/ml) into the culture medium (TNF-alpha specific radioimmunoassay) as compared with noninduced AML cells (less than 1 to 149 pg TNF-alpha/ml; median 31 pg/ml). Thus, the effect of IL-1 on AML-CFU proliferation is not the result of direct activation of AML progenitors, but IL-1 stimulates the release of TNF-alpha by AML cells and endogenous TNF subsequently synergizes with IL-3 or GM-CSF.

A simple and rapid method to determine hematopoietic growth factor activity

A rapid and simple colorimetric microassay method for the determination of hematopoietic growth factor activities was established. The assay was used to detect CSF-1, GM-CSF, and IL-3 activities. The assay was based on the metabolism of the tetrazolium dye 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide to formazan by metabolically active cells. Results obtained with the colorimetric microassay are comparable with those obtained with the soft agarose assay. Advantages of the colorimetric microassay include the conservation of reagents, the shorter incubation time for the experiment, the shorter assay time, and the ability to evaluate large numbers of samples.