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Query: UNIPROT:P10721 (c-kit)
 6,575 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have studied the effects of recombinant human interleukin-11 (rhIL-11), alone and combined with stem cell factor (SCF or c-kit ligand), IL-3, and granulocyte-macrophage colony-stimulating factor (GM-CSF) on the proliferation of highly enriched human hematopoietic CD34+ and CD34+CD33-DR- progenitor cells. CD34+ cells were purified using the avidin-biotin immunoabsorption technique and CD33+DR+ cells were subsequently removed by immuno-magnetic separation. The colony assays were performed in the presence and absence of exogenous serum. IL-11, as a single agent, induced the growth of a small number of colony-forming units-granulocyte/macrophage (CFU-GM) derived from purified CD34+ cells and failed to support the colony growth of CD34+CD33-DR- cells. The addition of erythropoietin (Epo) to IL-11 induced the growth of erythroid progenitors (BFU-E) derived from CD34+ cells but not from the same population depleted of CD33+DR+ cells. The combination of IL-11 with SCF, IL-3, or GM-CSF, in the presence of Epo, resulted in a synergistic or additive increase in the number of CFU cells (CFU-C) derived from both cell fractions. Moreover, the addition of SCF to IL-11 stimulated the development of macroscopic erythroid and multilineage colonies (CFU-GEMM) containing more than 10(4) cells. A combination of three factors (IL-11, SCF, and IL-3) resulted in the increase of the number of colonies arising from CD34+ and CD34+CD33-DR- cells (but not of their size) compared to the cultures treated with IL-11 plus SCF or IL-11 plus IL-3. The pattern of proliferative response of primitive hematopoietic progenitor cells to IL-11 in serum-free conditions was very similar to the cultures grown in serum-containing medium. It is noteworthy that IL-11 and SCF yielded colony formation that was comparable to that observed in the presence of serum. The effects of IL-11 on CD34+CD33-DR- cells were also studied in a short-term suspension culture system, which was shown to be specific for evaluating the proliferation of pluripotent hematopoietic precursors (Delta assay). In this system, IL-11 had a minimal effect on its own, whereas IL-11 plus SCF acted synergistically and their proliferative activity was improved by the addition of GM-CSF. These experiments indicate that IL-11 may be considered a "permissive" cytokine, capable of initiating the proliferation of very primitive human hematopoietic cells, which are then able to respond to late-acting CSFs.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Interleukin-11 stimulates the proliferation of human hematopoietic CD34+ and CD34+CD33-DR- cells and synergizes with stem cell factor, interleukin-3, and granulocyte-macrophage colony-stimulating factor. 769 67

Maintenance of the progenitor cells responsible for hematopoiesis has generally been accomplished using a feeder layer of stromal cells in stationary culture. Here, we compared the expansion of the total cell and progenitor cell populations using low-density mononuclear cells (LDMCs) obtained from human bone marrow in static culture (T-flasks) and in different cell culture bioreactors designed for the scale-up of mammalian cells. Static cultures were performed without the presence of a previously established stromal cell layer. Expansion of marrow in all cases was accomplished through the use of added cytokines such as IL-3, GM-CSF, and c-kit ligand. The results for the total cell expansion in static culture ranged from 4.4- to 32-fold. The cell number increase was affected by such factors as patient to patient variability, freeze-thawing, and the combination of cytokines used. Due to widespread use and the small amount of marrow needed, static cultures were used as a basis for comparison with other expansion systems. The cell culture systems used to evaluate the scale-up of marrow cultures included suspension, microcarrier, airlift, and hollow fiber bioreactors. Using identical media, cytokines, and feed schedules, LDMCs in the suspension bioreactor expanded to a value of 1.6 compared to a normalized value of 1.0 for static cultures for the two runs investigated. Expansion results for microcarrier cultures averaged 0.75 when compared to static cultures. A cell number increase in the airlift bioreactor resulted in an expansion which was 0.70 of the control static culture. Granulocyte-macrophage and erythroid progenitor assay data were also evaluated for the suspension, microcarrier, and airlift bioreactors.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Expansion and differentiation of human hematopoietic cells from static cultures through small-scale bioreactors. 776 89

IL-11 is a pleiotropic cytokine originally isolated from a bone marrow stromal cell line. It has been shown to share many activities with IL-6, namely to stimulate T cell-dependent B cell maturation, megakaryopoiesis and various stages of myeloid differentiation, but to inhibit adipogenesis. However, the activity of IL-11 on different stages of erythropoiesis in vitro clearly sets it apart form IL-6. IL-11 has little hematopoietic colony stimulatory activity of its own although it sustains terminal differentiation of the late erythroid progenitors CFU-E. In combination with IL-3, IL-11 has profound stimulatory effects on early multipotent hematopoietic progenitors (pre-CFCmulti), on multilineage colony-forming cells (CFCmulti), as well as on erythroid progenitors. The combination of IL-11 with the ligand for c-kit (KL) preferentially acts on early cells since it promotes the multiplication of pre-CFCmulti and stimulates highly proliferative erythroid progenitors that yields remarkable macroscopic erythroblast colonies in culture. The synergistic activity of IL-11 and KL, two stromal factors present in the bone marrow microenvironment, points to a pivotal role of IL-11 in early hematopoiesis. In vivo administration of recombinant human IL-11 elevates the number of circulating neutrophils and platelets and increased megakaryopoiesis in normal mice and primates.
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PMID:Interleukin 11. 795 Sep 12

The 10A1 murine leukemia virus induces tumors that lack lineage-specific markers found on myeloid, T-cell, and B-cell lineages. Either erythroid or multipotent stem cells can have this phenotype; therefore we have used fluorescence-activated cell sorter analysis with either multipotent stem cell markers or markers found on lineage-restricted precursors to differentiate between these two possibilities. The results showed that tumors induced by 10A1 expressed multipotent stem cell markers as well as some lineage-restricted precursor markers. To further study the tumor phenotype, we analyzed total RNAs from 10A1-induced tumors by Northern blotting for c-kit, erythropoietin receptor, and T-cell gamma receptor mRNAs. Most of the tumors contained these mRNAs, which are characteristic of early hematopoietic cells. These results are consistent with the hypothesis that 10A1-induced tumor cells are early multipotent hematopoietic stem cells. Southern blot analysis revealed that 14 of 14 10A1-induced tumor cell DNAs examined contained MuLV integrations into the fli-1 gene. The results strongly suggested that promoter insertion into fli-1 is required for tumor formation.
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PMID:10A1 MuLV induces a murine leukemia that expresses hematopoietic stem cell markers by a mechanism that includes fli-1 integration. 797 58

Analysis of the cellular/molecular basis of the early steps of hematopoietic proliferation and differentiation is hindered by the rarity of hematopoietic progenitors and stem cells (HP/HSC). The intensive efforts devoted to the development of purification methods for early HP and HSC, although initially largely unsuccessful, have recently provided a high level of HP/HSC yield and/or recovery. The methodology developed by our group, recently improved, provides not only virtually complete purification, but also abundant recovery of early HP/HSC such as colony forming units granulocyte/erythroid/macrophage/megakaryocyte (CFU-GEMM), burst forming units erythroid (BFU-E), CFU granulocyte/macrophage (CFU-GM)/CFU blast cells (CFU-B), and long-term culture initiating cells (LTC-IC) from adult peripheral and cord blood (CB). We have also developed a serum-free liquid suspension culture for unilineage erythroid (E), granulocytic (G) or monocytic (M) differentiation of stringently purified HP/HSC. These culture systems allow sequential collection and cellular/molecular analysis of discrete populations of hematopoietic cells at a homogenous stage of differentiation specifically along a unilineage pathway. These experimental tools have been utilized to investigate cellular/molecular mechanisms underlying early hematopoiesis. The transcription factor (TF) GATA-1 is considered to be the "master" gene of erythropoiesis. In highly purified HP/HSC undergoing E or GM differentiation, GATA-1 expression is characterized initially by proliferation-dependent activation and at later stages by sustained expression in the E pathway and suppression in the GM pathway. Hypothetically, similar on/off switches of lineage-restricted TF may underlie the binary fate decisions of early HP differentiation. The expression and modulation of hematopoietic growth factor receptors (HGFR) in early hematopoiesis have been extensively analyzed. The results suggest a model of transactivation cascade for HGFR such as interleukin 6 receptor (IL-6R), IL-3R, GM colony stimulating factor receptor (GM-CSFR), and erythropoietin receptor (EpR), whereby each HGF upmodulates the R(s) for distal-acting HGF(s). Finally, we have investigated the effect of HGF on reactivation of hemoglobin F (HbF) in clonogenic or liquid suspension serum-free culture of purified adult HP. The results suggest that c-kit ligand (KL) plays a key role in the reactivation of HbF synthesis in adult life, and IL-3/GM-CSF potentiate this effect at low KL level. The KL-induced HbF reactivation is seemingly related to an enhanced proliferation of early E progenitors in their differentiation pathway.
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PMID:Stringently purified human hematopoietic progenitors/stem cells: analysis of cellular/molecular mechanisms underlying early hematopoiesis. 824 48

All-trans retinoic acid (RA) is an important morphogen in vertebrate development, a normal constituent in human adult blood and is also involved in the control of cell growth and differentiation in acute promyelocytic leukemia. We have examined the effects of RA on normal hematopoiesis by using early hematopoietic progenitor cells (HPC) stringently purified from adult peripheral blood. In clonogenetic fetal calf serum-supplemented (FCS+) or -nonsupplemented (FCS-) culture treated with saturating levels of interleukin-3 (IL-3) granulocyte-macrophage colony-stimulating factor (GM-CSF) and erythropoietin (Ep) (combined with c-kit ligand in FCS(-)-culture conditions), RA induces a dramatic dose-dependent shift from erythroid to granulomonocytic colony formation, the latter colonies being essentially represented by granulocytic clones. This shift is apparently not caused by a recruitment phenomenon, because in FCS+ culture, the total number of colonies is not significantly modified by RA addition. In FCS- liquid-suspension culture supplemented with saturating Ep level and low-dose IL-3/GM-CSF, adult HPC undergo unilineage erythropoietic differentiation: Here again, treatment with high-dose RA induces a shift from the erythroid to granulocytic differentiation pathway. Studies on RA time-response or pulse treatment in semisolid or liquid culture show that early RA addition is most effective, thus indicating that early but not late HPC are sensitive to its action. We then analyzed the expression of the master GATA1 gene, which encodes a finger transcription factor required for normal erythroid development; addition of RA to HPC stimulated into unilineage erythropoietic differentiation in liquid culture caused a virtually complete inhibition of GATA1 mRNA induction. These results indicate that RA directly inhibits the erythroid differentiation program at the level of early adult HPC, and may lead to a shift from the erythroid to granulocytic differentiation pathway. This phenomenon is correlated with inhibition of GATA1 induction in the early stages of erythropoietic differentiation.
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PMID:Retinoic acid downmodulates erythroid differentiation and GATA1 expression in purified adult-progenitor culture. 829 27

Activation of distinct receptor tyrosine kinases (RTK), such as the products of the c-fms and c-kit proto-oncogenes, profoundly affects hematopoietic development. We have isolated a novel RTK cDNA, called met-related kinase (MRK), which is expressed on early erythroid progenitors. MRK is also expressed in many hematopoietic cell lines, and is not lineage restricted. Several regions within the catalytic domain of MRK have amino acid similarity to the c-met proto-oncogene and v-sea oncogene. Specific polyclonal anti-MRK antisera detects an 84-Kd polypeptide in COS cells transfected with an expression vector containing the MRK cDNA. Further studies of this novel RTK will provide potential insight into its role during hematopoiesis.
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PMID:Isolation of a novel receptor tyrosine kinase cDNA expressed by developing erythroid progenitors. 839 55

Recently, two different normal avian erythroid progenitors were described. They differ in the receptor tyrosine kinases they express and in their ability to undergo self-renewal in culture. A common progenitor, termed stem cell factor (SCF) progenitor, expresses the receptor for avian SCF c-Kit, and undergoes short-term self-renewal when grown in the presence of avian SCF. A second progenitor, referred to as SCF/transforming growth factor-alpha progenitor, coexpresses c-Kit and the avian epidermal growth factor receptor homologue c-ErbB. These progenitors undergo sustained self-renewal when grown in the presence of transforming growth factor-alpha plus estradiol. The phenotype of the normal SCF/transforming growth factor-alpha progenitors closely corresponded to that of erythroid cells transformed by the tyrosine kinase oncogenes v-erbB or v-sea. This suggested that these cells, but not the SCF progenitors, would be the target cells for erythroblast transformation by these oncogenes. However, we demonstrate that both progenitor cells can be transformed by the v-erbB and v-sea oncogenes and also by the ligand-activated proto-oncogene product c-ErbB. We conclude that the target cell specificity of certain tyrosine kinase oncoproteins for erythroid cells is a reflection of their ability to provide signals for self-renewal that normally emanate from the endogenous c-ErbB protein.
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PMID:Transformation of erythroid progenitors by viral and cellular tyrosine kinases. 854 28

We investigated the effect of the human ligand for flt-3 (FL) on the committed progenitor colony formation of normal bone marrow (BM) (n = 9) and BM from four aplastic anaemia (AA) and three Diamond-Blackfan anaemia (DBA) patients. Methylcellulose committed progenitor cell assays were carried out using FL alone and in combinations with granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3) and c-kit ligand (KL). FL alone had a limited, though significant, effect on the production of granulocyte-macrophage colony-forming unit (CFU-GM) colonies from normal BM and showed an additive effect with IL-3 and GM-CSF separately, but not in combination. FL did not increase the stimulation of KL and did not have an effect on the production of erythroid progenitor colonies. FL had no effect on the AA and DBA BMs studied.
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PMID:The effect of human flt-3 ligand on committed progenitor cell production from normal, aplastic anaemia and Diamond-Blackfan anaemia bone marrow. 855 52

We produced a monoclonal antibody MTK1 which recognized c-kit protein. Using MTK1, 31 leukemia cell lines and 76 leukemia blasts from pediatric patients were analyzed for expression of the c-kit receptor by flow cytometry. The c-kit receptor was detectable on four of four cell lines assigned to the megakaryo/erythromegakaryoblastic lineage and on one of seven cell lines of myeloid lineage. C-kit expression was not seen on any of 20 cell lines of erythroid and lymphoid lineages. Furthermore, c-kit was expressed on 16 of 24 nonlymphoid blasts without platelet surface antigens (67%) and on six of eight non-lymphoid blasts with platelet surface antigens (75%), but was not detectable on 44 lymphoid blasts from pediatric leukemia patients. In these cases CD34 was expressed on 26 of 32 myeloid blasts (81%) and on 27 of 44 lymphoid blasts (61%). The findings indicate a dominant expression of the c-kit receptor on established cell lines assigned to the megakaryo/erythromegakaryoblastic lineage, though a high percentage of leukemic myeloblasts also expressed the c-kit receptor on their surface.
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PMID:Cell surface c-kit receptors in human leukemia cell lines and pediatric leukemia: selective preservation of c-kit expression on megakaryoblastic cell lines during adaptation to in vitro culture. 855 13


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