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PubMed1996

Improved survival of lethally irradiated recipient mice transplanted with circulating progenitor cells mobilized by IL-8 after pretreatment with stem cell factor.

We have demonstrated previously that a single bolus-injection of interleukin (IL)-8 induces instant mobilization of hematopoietic progenitor cells (HPC) in mice and primates. To further improve the mobilization of HPC, we treated mice with hematopoietic growth factors (HGF) before IL-8-administration. The mobilized HPC were transplanted into lethally irradiated recipient mice to study the effects on survival. Male donor mice (age 8-12 weeks, weight 20-25 grams) were pretreated intraperitoneally (ip) with a fixed dose of 2.5 micrograms of either granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-3, stem cell factor (SCF), or saline administered twice daily for 2 to 4 days. Then a fixed dose of 30 micrograms of IL-8 was administered ip at various time intervals before harvesting blood, bone marrow, and spleen. Cell counts and numbers of colony-forming units granulocyte/macrophage (CFU-GM) of these organs were assessed. Donor mice pretreated with HGF for 2 days and subsequently injected with IL-8 showed an increase in the numbers of circulating CFU-GM per mL blood from 168 +/- 98 to 402 +/- 201 (mean +/- SD, CFU-GM/mL blood) when GM-CSF was used, 314 +/- 133 to 2502 +/- 513 with G-CSF, and 27 +/- 15 to 524 +/- 339 with SCF compared with saline-pretreated controls (28 +/- 17 to 462 +/- 335 CFU-GM/mL blood, mean +/- SD; n = 42 and 40 per interval). Donor-mice pretreated for 4 days with IL-3 or GM-CSF showed an increase in the numbers of circulating HPC from 62 +/- 52 to 368 +/- 118 and 859 +/- 387 to 1034 +/- 421, respectively (CFU-GM/mL, mean +/- SD, n = 4 per group). Lethally irradiated (8.5 Gy) female Balb/c mice were then injected with decreasing numbers of peripheral blood mononuclear cells (PBMNC). Transplantation of 1.5 x 10(5) MNC obtained from donors pretreated with SCF for 2 days prior to IL-8 mobilization resulted in a significantly enhanced survival of 100% of the recipients, whereas recipients of PBM-NCs derived from donors treated with SCF only or IL-8 as a single injection had a survival rate at day 60 of only 50% and 60% respectively. When equal numbers of IL-8 mobilized MNCs from G-CSF, GM-CSF, or IL-3 pretreated donors were transplanted into lethally irradiated recipients, no such survival-advantage was observed. We conclude that pretreatment with SCF for 2 days improves the mobilizing effect induced by IL-8 and that transplantation of these cells enhances survival of lethally irradiated recipients.

Animals↗
PubMedDate not supplied

Immunohistological distribution of stem cell factor and kit receptor in angiosarcoma.

Angiosarcoma is a rare neoplasm, originating in the endothelium, which has a poor prognosis because of a high potential for metastasis. Although little is known about the pathogenesis of angiosarcoma, angiogenic cytokines are suggested to play an important role in tumor progression in a paracrine/autocrine fashion. Mast cells contain several mediators or cytokines influencing vascularization. To clarify the role of mast cells in angiosarcoma, mast cells were counted in primary lesions of angiosarcoma (n=7). The results showed that the number of mast cells in the lesional skin of angiosarcoma (91.2+/-14.6/mm2) was significantly increased compared to that in normal skin (30.1+/-4.6/mm2) (p < 0.001). Immunohistological localization of stem cell factor, a mast cell growth factor, demonstrated that stem cell factor-positive cells occurred in the tumors forming the vascular lumen in nodular-type angiosarcoma. In macular angiosarcoma, stem cell factor was also detected in the tumor vascular endothelial cells. Infiltrating mast cells were positive for the kit receptor in both types of angiosarcoma. These results suggest that tumor cell-derived stem cell factor may play a role in the increased number of mast cells, via the kit receptor, which may contribute to the proliferation of tumor cells, leading to the progression of angiosarcoma.

Aged↗
PubMed1994

In vitro effects of stem-cell factor or interleukin-3 on myelosuppression associated with AIDS.

OBJECTIVE: To determine whether the early-acting hematopoietic growth factors stem-cell factor (SCF) or interleukin-3 (IL-3), are able to overcome the bone-marrow suppressive effects of cytokines or drugs involved in the hematologic abnormalities that accompany HIV-1 infection. DESIGN: In vitro colony formation assays of normal human bone-marrow cells exposed to the myelosuppressive drugs, zidovudine, interferon-alpha (IFN-alpha) and ganciclovir, or the myelosuppressive cytokines, tumor necrosis factor-alpha (TNF-alpha) or transforming growth factor-beta (TGF-beta), implicated in HIV dysmyelopoiesis. RESULTS: SCF (10 ng/ml) enhanced the numbers of erythroid (BFU-E) colonies in the presence of zidovudine or ganciclovir (P < 0.05) and myeloid [colony-forming unit granulocyte macrophage (CFU-GM)] colonies in the presence of ganciclovir or IFN-alpha (P < 0.05) relative to controls. IL-3 (10 ng/ml) also improved erythroid colony numbers in the presence of zidovudine (P < 0.05) and CFU-GM in the presence of IFN-alpha (P < 0.05). Neither factor consistently altered the inhibition of TGF-beta or TNF-alpha. The 50% inhibitory concentration (IC50) of the myelosuppressive agents was altered in only one setting, using IL-3 in the presence of zidovudine. CONCLUSIONS: These data suggest that SCF or IL-3 may have a therapeutic application in overcoming hematopoietic abnormalities associated with drugs commonly used in the care of AIDS patients. However, they may have less capacity to overcome the bone-marrow inhibitory effects of the endogenous cytokines TNF-alpha and TGF-beta.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Cell-to-cell interaction of cytokine-dependent myeloblastic line constitutively expressing membrane-bound stem cell factor abrogates cytokine dependency partially through granulocyte-macrophage colony-stimulating factor production.

Stem cell factor (SCF) is a cytokine for hematopoietic progenitor cells and plays an important role in megakaryocyte proliferation. The UT-7 cell line was established from a patient with megakaryoblastic leukemia, and its growth and survival are strictly dependent on interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), erythropoietin (Epo), or IL-6. In this study, we showed that SCF also supported the growth of UT-7 in the absence of other cytokines and downregulated the cell surface c-kit receptors. Constitutive expression of SCF by introducing SCF expression vector made UT-7 grow factor-independently in liquid medium, but not in semisolid medium. This SCF-expressing factor-independent UT-7 (UT-7scf9) expressed the membrane bound form of SCF on their surface, but did not secrete detectable amounts of soluble SCF. UT-7scf9 formed aggregates as they grew in the absence of cytokines, and this aggregation was inhibited by adding soluble SCF into the medium. UT-7 cultured with SCF and UT-7scf9 cultured without cytokines expressed GM-CSF, and anti-GM-CSF neutralizing antibody partially inhibited their growth. These results suggest that SCF stimulated UT-7 proliferation partially through the autocrine-loop of GM-CSF, and UT-7scf9 expressed SCF mostly as a membrane-bound form, which transduces its growth signal through c-kit receptor as they aggregate by cell-to-cell interaction.

Base Sequence↗
PubMed1993

In vivo administration of recombinant methionyl human stem cell factor expands the number of human marrow hematopoietic stem cells.

A growing number of in vitro studies suggest that recombinant human stem cell factor (SCF) is capable of augmenting the proliferative capacity of human hematopoietic progenitor cells (HPC) and stem cells (HSC). We further evaluated this biologic effect by analyzing the response of bone marrow (BM) HPCs and HSCs to the administration of SCF in eight patients with locally advanced or metastatic breast cancer who were enrolled in an ongoing phase I study. SCF was administered for 14 days by daily subcutaneous injection at dosages of 10, 25, or 50 micrograms/kg/d. BM CD34+ HLA-DR+ and CD34+ HLA-DR- CD15- cells, previously shown by our laboratory to be enriched for various classes of differentiated and primitive HPCs, respectively, were quantitated in BM samples on day 0 (pretreatment) and day 15 (posttreatment). These CD34+ HLA-DR+ and CD34+ HLA-DR- CD15- cells were then isolated by cell-sorting and assayed for several classes of HPCs, including the high--proliferative potential colony-forming cell (HPP-CFC), the burst-forming unit--megakaryocyte (BFU-MK), and the long-term BM culture--initiating cell (LTBMC-IC). SCF administration resulted in a 3.3-fold (range, 1.4- to 18.8-fold; P = .018) increase in the absolute numbers of CD34+ cells, a 3.7-fold (range, 1.2- to 8.2-fold; P = .028) increase in the absolute numbers of CD34+ HLA-DR+ cells, and a 2.4-fold (range, 1.1- to 29.3-fold; P = .010) increase in the absolute numbers of CD34+ HLA-DR- CD15- cells. Following the infusion of SCF, a statistically significant increase in the absolute numbers of HPP-CFC (P = .018), BFU-MK (P = .046), CFU-granulocyte, erythrocyte, monocyte, megakaryocyte (CFU-GEMM: P = .043), BFU-erythrocyte (BFU-E; P = .043), CFU-granulocyte, macrophage (CFU-GM; P = .045), and CFU-megakaryocyte (CFU-MK; P = .028) per milliliter of marrow was observed. Stromal cell-free LTBMCs supplemented with SCF and interleukin-3 (IL-3), initiated with CD34+ HLA-DR- CD15- cells obtained on day 0, produced viable cells for 9.6 weeks, compared with 11.5 weeks for LTBMCs initiated with CD34+ HLA-DR- CD15- cells obtained on day 15. Cumulative cellular production by LTBMCs initiated with day 15 CD34+ HLA-DR- CD15- cells was statistically greater than that by day 0 LTBMCs (P = .031). These same cultures produced CFU-GM for 6.3 weeks (day 0) versus 9 weeks (day 15).(ABSTRACT TRUNCATED AT 400 WORDS)

Antigens, CD↗
PubMed1991

Glycosylated and unglycosylated recombinant-derived human stem cell factors are dimeric and have extensive regular secondary structure.

We have recently described the identification, isolation, and characterization of a factor, termed stem cell factor (SCF), which acts on primitive hematopoietic progenitors of the marrow. A soluble form of the factor was isolated from the conditioned medium of a rat cell line (Zsebo, K. M., Wypych, J., McNiece, I. K., Lu, H. S., Smith, K. A., Karkare, S. B., Sachdev, R. K., Yuschenkoff, V. N., Birkett, N. C., Williams, L. R., Satyagal, V. N., Tung, W., Bosselman, R. A., Mendiaz, E. A., and Langley, K. E. (1990) Cell 63, 195-201) and rat and human cDNAs have been cloned (Martin, F. H., Suggs, S. V., Langley, K. E., Lu, H. S., Ting, J., Okino, K. H., Morris, C. F., McNiece, I. K., Jacobsen, F. W., Mendiaz, E. A., Birkett, N. C., Smith, K. A., Johnson, M. J., Parker, V. P., Flores, J. C., Patel, A. C., Fisher, E. F., Erjavec, H. O., Herrera, C. J., Wypych, J., Sachdev, R. K., Pope, J. A., Leslie, I., Wen, D., Lin, C.-H., Cupples, R. L., and Zsebo, K. M. (1990) Cell 63, 203-211). The cDNAs encode amino acids C-terminal to those found in the isolated natural form, including a putative transmembrane domain. This paper describes the structural characterization of soluble forms of recombinant human SCF purified from Escherichia coli (unglycosylated) and from Chinese hamster ovary (CHO) cells (glycosylated). Fluorescence emission spectra indicate that the single Trp residue is present in a hydrophobic environment. Circular dichroism and infrared spectroscopy indicate considerable secondary structure, including both alpha-helix and beta-sheet. Molecular weight determinations by sedimentation equilibrium show that the molecules are dimeric (noncovalently associated), and gel filtration analyses are consistent with this conclusion. The CHO cell-derived SCF is about 30% carbohydrate by weight, with both N-linked and O-linked sugar. The presence or absence of the carbohydrate does not influence the results of the various structural analyses.

Circular Dichroism↗
PubMed1995

Effect of stem cell factor on myelopoiesis potential in human Dexter-type culture systems.

Hematopoiesis is influenced by the presence of the hematopoietic microenvironment, and Dexter-type liquid culture systems represent an in vitro representation of some aspects of the microenvironment that are optimal for the propagation of myeloid progenitors. Marrow stromal layers, which constitute part of these culture systems, produce growth factors, including stem cell factor (SCF), a ligand for the c-kit proto-oncogene that has been found to increase detection of myeloid, erythroid, and megakaryocytic progenitors in short-term marrow colony assays. In this work, the role of SCF in Dexter-type culture systems was examined to better define its contribution to steady-state myelopoiesis. When cultured in the continued presence of 100 ng/mL SCF, both primary and recharged cultures demonstrated significantly greater CFU-GM output, with quantitative differences noted throughout culture duration (up to 6 weeks). This increase in CFU-GM could be inhibited specifically with the addition of 1:1500 SR-1, a neutralizing anti-c-kit monoclonal antibody (MAb) that neutralizes the biological effects of SCF, and the increase was noted both with recharged light-density marrow cells and purified CD34+ progenitor cells. On the other hand, when primary or recharged marrow cultures were established in the absence of exogenous SCF, but in the continuous presence of SR-1, no inhibition of CFU-GM output was observed. When light-density marrow cells were purged of pre-existing CFU-GM by 4-hydroperoxycyclophosphamide (4-HC) and were seeded over irradiated stromal layers, exogenous SCF resulted in detection of CFU-GM from 4-HC-treated cells as early as 1 week of culture, as compared to the lack of significant emergence of CFU-GMs at 4 weeks in the control cultures. This SCF effect was also inhibited by SR-1. Purified CD34+ progenitor cells did not adhere to SCF immobilized to tissue culture plates, and the adhesion of such progenitors to murine Steel lines transfected with membrane-bound SCF was not greater than to the parent nontransfected Steel line, suggesting that the effect of SCF was not on CD34+ cell adhesion. These studies confirm the action of SCF at a pre-CFU level, and they demonstrate the ability of SCF to stimulate increased production of myeloid progenitors in long-term liquid culture systems.

Antibodies, Monoclonal↗
PubMed1995

Stem cell factor enhances the survival of murine intestinal stem cells after photon irradiation.

Recombinant rat stem cell factor (SCF) has been shown to decrease lethality in mice exposed to total-body irradiation (TBI) in the lower range of lethality through radioprotection of hematopoietic stem cells and acceleration of bone marrow repopulation. This study evaluates the effect of SCF on the survival of the intestinal mucosal stem cell after TBI. This non-hematopoietic stem cell is clinically relevant. Gastrointestinal toxicity is common during and after abdominal and pelvic radiation therapy and limits the radiation dose in these regions. As observed with bone marrow, the administration of SCF to mice prior to TBI enhanced the survival of mouse duodenal crypt stem cells. The maximum enhancement of survival was seen when 100 micrograms/kg of SCF was given intraperitoneally 8 h before irradiation. This regimen increased the survival of duodenal crypt stem cells after 12.0 Gy TBI from 22.5 +/- 0.7 per duodenal cross section for controls to 30.0 +/- 1.7 after treatment with SCF (P = 0.03). The TBI dose producing 50% mortality at 6 days (LD50/6) was increased from 14.9 Gy for control mice to 19.0 Gy for mice treated with SCF (dose modification factor = 1.28). These findings demonstrate that SCF has radioprotective effects on a non-hematopoietic stem cell population and suggest that SCF may be of clinical value in preventing radiation injury to the intestine.

Animals↗
PubMed1993

Effects of the recombinant hematopoietic growth factors interleukin-3, interleukin-6, stem cell factor, and leukemia inhibitory factor on the megakaryocytic differentiation of CD34+ cells.

Using a liquid culture system and human CD34+ marrow cells, we examined the effects of recombinant interleukin (IL)-3, IL-6, stem cell factor (SCF), and leukemia inhibitory factor (LIF) on megakaryocyte (MK) growth, endoreplication, and maturation. MK proliferation, ploidy distribution, and volume were studied by flow cytometry. IL-3 was the only cytokine that, alone, induced a marked increase in MK proliferation. At a high CD34+ cell concentration, addition of IL-6, SCF, and LIF to IL-3--containing medium increased the number of MK (approximately 20%). At a low CD34+ cell concentration, IL-3 alone was a less potent inducer of MK growth, but IL-6, SCF, and their combination had a marked effect, increasing the number of MK by a factor 1.7, 2.9, and 4.4, respectively. These differences may be related to the endogenous release of cytokines in the culture. The effects of these cytokines were subsequently tested on a more mature type of MK progenitor (CD34+ cells isolated after 6 days of incubation in liquid culture). IL-3 remained the most potent cytokine, but IL-6 or SCF alone also increased MK number in comparison to unstimulated cultures. The ploidy distribution of MKs grown with IL-3 was not markedly changed by the addition of the other cytokines, with the exception of SCF, which induced a significant increase in the mean ploidy. However, in all cultures, glycoprotein (GP)IIIa+ 2N and 4N cells were present in large but variable numbers (35% to 75%). The number of these low-ploidy MKs directly correlated with MK proliferation. Therefore, we subsequently explored the absolute number of polyploid MK produced in culture. SCF, IL-6, or their combination, in association with IL-3, increased the number of polyploid MK up to fourfold. In addition, they improved the maturation of MK grown in the presence of IL-3, leading to the synthesis of demarcation membranes and platelet shedding. A similar effect of growth factors on the maturation of day 6 CD34+ cells was observed. We conclude that IL-6 and SCF have a broad range of activities on megakaryocytopoiesis, acting both on the early and late stages. However, the proliferative properties of these cytokines largely predominate in our cultures. Therefore, in the absence of a specific MK regulator, this study further extends the need for a combination of growth factors to maximize megakaryocytopoiesis.

Adult↗
PubMed1993

Combined action of stem cell factor, leukemia inhibitory factor, and cAMP on in vitro proliferation of mouse primordial germ cells.

In the present paper we investigated the effects of stem cell factor/mastocyte growth factor (SCF/MGF), leukemia inhibitory factor/differentiating inhibitory activity (LIF/DIA) (two growth factors known to affect primordial germ cell growth in vitro) and forskolin (FRSK) (an activator of adenylate cyclase in many cell types) alone or in combination on the survival and proliferation of primordial germ cells (PGCs) obtained from 8.5, 10.5, and 11.5 days post coitum (dpc) mouse embryos and cultured without pre-formed cell feeder layers. The results showed that both at 1 and 3 days of culture the addition of 100 ng/ml SCF, 20 microM FRSK, or in some instances 20 ng/ml LIF alone caused a significant increase of PGC number as compared with controls. The highest effects were obtained when SCF and/or LIF were used together with FRSK. Moreover, we found that FRSK elevated cAMP levels in purified 11.5 dpc PGCs and that this compound, but not SCF and LIF, stimulated PGC proliferation, as assessed by 5-bromo-2'-deoxyuridin (BrdU) incorporation. These results suggest a mechanism of combined action of cAMP with SCF and/or LIF in the control of proliferation of mouse PGCs in vitro.

Animals↗
PubMed2005

Cell transplantation preserves cardiac function after infarction by infarct stabilization: augmentation by stem cell factor.

OBJECTIVE: We hypothesized that implantation of adult mesenchymal stem cells after acute myocardial infarction mobilizes bone marrow precursor cells by activating the stem cell factor pathway, and that overdriving this pathway would enhance the beneficial effects of cell transplantation. METHODS: After coronary ligation, medium, mesenchymal stem cells, or stem cell factor-overproducing mesenchymal stem cells were injected into the anterior left ventricle. Cells from beta-galactosidase transgenic mice enabled tracking of injected cells. The global and local impact of the cells was evaluated by measuring cytokine levels, endothelial progenitor cells, and myocardial angiogenesis, and by addressing cardiomyogenesis with confocal microscopy. The impact on cardiac function was evaluated by pressure-volume loops. Ventricular morphometrics were measured after in situ perfusion-fixation of the hearts at physiologic pressures. RESULTS: Implantation of mesenchymal stem cells increased myocardial stem cell factor levels 2.0-fold, endothelial progenitor cell mobilization 2.7-fold, and myocardial angiogenesis 2.3-fold (P < .05), but did not induce mitogenesis in host cardiomyocytes or give rise to beta-galactosidase-expressing cardiomyocytes. Cell-transplanted groups had improved indices of cardiac function, including preload recruitable stroke work and end-systolic elastance (P < .001). Cell transplantation resulted in 2.0-fold smaller ventricular volumes (P = .001) and 2.0-fold reduced infarct scar area (P = .056), but had no effect on the volume of spared myocardium. Stem cell factor overproduction imparted greater functional benefit without inducing detectable histologic cardiomyocyte regeneration. CONCLUSION: Mesenchymal stem cell implantation after myocardial infarction facilitates functional cardiac regeneration without myocyte regeneration through augmentation of endogenous infarct repair, which is enhanced by stem cell factor.

Animals↗
PubMed2002

Phosphorylation of forkhead transcription factors by erythropoietin and stem cell factor prevents acetylation and their interaction with coactivator p300 in erythroid progenitor cells.

The mammalian forkhead transcription factors, FOXO3a (FKHRL1), FOXO1a (FKHR) and FOXO4 (AFX) are negatively regulated by PKB/Akt kinase. In the present study we examined the engagement of forkhead family of transcription factors in erythropoietin (Epo)- and stem cell factor (SCF)-mediated signal transduction. Our data show that all three forkhead family members, FOXO3a, FOXO1a and FOXO4 are phosphorylated in human primary erythroid progenitors. Experiments performed to determine various upstream signaling pathways contributing to phosphorylation of forkhead family members show that only PI-3-kinase pathway is required for inactivation of FOXO3a. Our data also demonstrate that during Epo deprivation FOXO3a interacts with the transcriptional coactivator p300 and such interaction is disrupted by stimulation of cells with Epo. To determine the domains in FOXO3a, mediating its interaction with p300, we performed GST pull-down assays and found that the N-terminus region containing the first 52 amino acids was sufficient for binding p300. Finally, our data demonstrate that FOXO3a and FOXO1a are acetylated during growth factor deprivation and such acetylation is reversed by stimulation with Epo. Thus mammalian forkhead transcription factors are involved in Epo and SCF signaling in primary erythroid progenitors and may play a role in the induction of apoptotic and mitogenic signals.

Acetylation↗
PubMed1995

Stem cell factor modulates avidity of alpha 4 beta 1 and alpha 5 beta 1 integrins expressed on hematopoietic cell lines.

Interactions between hematopoietic cells and bone marrow (BM) stroma, composed of extracellular matrix and stromal cells, are crucial for hematopoiesis. Integrins facilitate these interactions by mediating adherence of hematopoiesis. Integrins facilitate these interactions by mediating adherence of hematopoietic cells to both the extracellular matrix and stromal cells. Marrow stromal cells secrete a variety of growth factors, including stem cell factor (SCF). Because treatment with SCF in vivo mobilizes primitive hematopoietic cells from the BM, we investigated the effect of the growth factor SCF of hematopoietic cell adhesion. These studies show that SCF modulates adhesive function in a dose- and time-dependent manner, but does not modulate expression of the integrins alpha 4 beta 1 and alpha 5 beta 1 in the SCF-responsive cell line MO7E. Treatment of MO7E cells with SCF (200 ng/mL) produced a transient increase in adherence to cytokine-activated human umbilical vein endothelial cells (HUVECs) or to vascular cell adhesion molecule 1 (VCAM-1)-transfected Chinese hamster ovary (CHO) cells with peak adhesion at 30 minutes and return to baseline by 60 to 90 minutes. This increase in adhesion was paralleled by increased binding of the beta 1 activation-dependent monoclonal antibody (MoAb) 15/7, as determined by flow cytometry. However, prolonged incubation of MO7E with SCF induced a marked decrease in integrin-mediated adherence, with maximal inhibition by 24 hours. No change in expression of integrins, as determined by flow cytometry, was observed with short- or long-term incubation with SCF. SCF-treated cells were still able to respond to phorbol esters and to the activating beta 1 MoAb 8A2 with increased adherence, but not to the level seen in control cells. This suggests that a subpopulation of expressed alpha 4 beta 1 and alpha 5 beta 1 integrins is disengaged by prolonged incubation with SCF.

Animals↗
PubMed1993

Soluble stem cell factor in human serum.

Stem cell factor (SCF) is a recently described factor active in the early stages of hematopoiesis. It can exist in membrane-bound form and in proteolytically released soluble form. The levels and nature of SCF in human serum are described. As determined by an enzyme-linked immunosorbent assay performed for 257 samples, SCF level in serum averaged 3.3 +/- 1.1 ng/mL. The serum SCF was partially purified by immunoaffinity chromatography and analyzed by glycosidase treatments in conjunction with sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting. The results show that the SCF has N-linked and O-linked carbohydrate and corresponds to the soluble form, at or about 165 amino acids in length. The findings suggest functional importance for soluble SCF in humans.

Adult↗
PubMed1991

The role of recombinant stem cell factor in early B cell development. Synergistic interaction with IL-7.

The cDNA for stem cell factor was recently isolated from Buffalo rat liver cells (BRL-3A) and recombinant rat stem cell factor produced from Escherichia coli (rrSCF164). rrSCF164 synergizes with rhIL-7 to stimulate pre-B clonal growth in agar culture of mouse bone marrow cells, and in this study we have characterized the role of rrSCF164 in B cell development. The combination of rrSCF164 plus rhIL-7 stimulated increased colony numbers compared with the sum of colonies stimulated by rrSCF164 and rhIL-7 alone. Also, increased cell proliferation per colony was stimulated by the combination of rrSCF164 plus rhIL-7 compared with rhIL-7 or rrSCF164 alone. The colonies formed with rrSCF164 plus rhIL-7 and rhIL-7 alone contained exclusively pre-B cells, which expressed B220 Ag and cytoplasmic mu-chain, but were negative for surface Ig expression. Morphological examination of the cells in the colonies showed blast-like characteristics. rrSCF164 alone and in combination with rhIL-7 stimulated generation of B220+ cells in liquid culture of B220- cells, whereas rhIL-7 alone had no stimulatory effect on B220- cells. Both stem cell factor mRNA and bioactivity were detected in a mouse bone marrow-derived stromal cell line, termed OZ-11. We propose that stem cell factor is a stromal-derived factor that synergizes with IL-7 to stimulate the proliferation and differentiation of pro-B cells to pre-B cells, which become responsive to IL-7 alone.

Animals↗
PubMed1995

Stem cell factor contributes to intestinal mucosal mast cell hyperplasia in rats infected with Nippostrongylus brasiliensis or Trichinella spiralis, but anti-stem cell factor treatment decreases parasite egg production during N brasiliensis infection.

We assessed the effects of the c-kit ligand, stem cell factor (SCF), in the jejunal mucosal mast cell hyperplasia that occurs during infection with the intestinal nematodes, Nippostrongylus brasiliensis or Trichinella spiralis in rats. Compared with vehicle-treated rats, rats treated with SCF (25 micrograms/kg/d, intravenous [i.v.] for 14 days) during N brasiliensis infection exhibited significantly higher levels of the rat mucosal mast cell (MMC)-associated protease, rat mast cell protease II (RMCP II) in the jejunum and serum on day 8 of infection, but not on days 10 or 15 of infection. By contrast, in comparison to rats treated with normal sheep IgG, rats treated with a polyclonal sheep antirat SCF antibody exhibited markedly decreased numbers of jejunal MMCs, levels of jejunal RMCP II, and serum concentrations of RMCP II during infection with either nematode, particularly at the earlier intervals of infection (< or = day 10). Taken together, these findings indicate that SCF importantly contributes to MMC hyperplasia and/or survival during N brasiliensis or T spiralis infection in rats, but that levels of endogenous SCF are adequate to sustain near maximal MMC hyperplasia during infection with these nematodes. Notably, treatment of rats with SCF somewhat increased, and treatment with anti-SCF significantly decreased, parasite egg production during N brasiliensis infection. This finding raises the interesting possibility that certain activities of intestinal MMCs may contribute to parasite fecundity during infection with this nematode.

Analysis of Variance↗
PubMed1994

Granulocyte-colony stimulating factor, granulocyte-macrophage colony stimulating factor, PIXY-321, stem cell factor, interleukin-3, and interleukin-7: receptor binding and effects on clonogenic proliferation in acute lymphoblastic leukemia.

Cytokines are frequently used after chemotherapy of leukemias and solid tumors to augment recovery of normal hematopoiesis. While the regulation of normal and leukemic myelopoiesis is well investigated, little is known about effects of cytokines on growth and differentiation of lymphoblastic leukemia. In this study, we investigated the expression of receptors for G-CSF, GM-CSF, SCF, IL-3, and IL-7 on acute lymphoblastic leukemia (ALL) blasts and the effects of these growth factors (GF) on ALL blast colony formation. The binding of fluorescence-tagged cytokines to receptors on ALL blasts was studied by flow-cytometry in 27 cases of ALL (24 precursor B-ALL, 3 T-ALL). Receptor-binding for myeloid-associated GF was observed in the majority of precursor B-ALL (G-CSF = 100%, GM-CSF = 65%, IL-3 = 83%, SCF = 74%), but not in T-ALL. Binding of labelled IL-7 was detected in both precursor B- (92%) and T-ALL (100%). The presence of receptors for SCF in ALL was confirmed by polymerase chain reaction for c-kit mRNA in 19/21 cases tested. Expression of receptors for G-CSF, GM-CSF, IL-3, and SCF was not associated with expression of myeloid antigens, or with specific cytogenetic abnormalities. The effects of these GF on clonogenic cells were tested in the ALL blast colony assay and varied between samples, but all cytokines were able to increase clonogenic growth. The GM-CSF/IL-3 fusion molecule PIXY-321 was most effective in promoting colony growth. In some cases inhibition of colony formation was found. We conclude that ALL blast cells have receptors not only for IL-7, but also for G-CSF, GM-CSF, SCF, and IL-3. ALL precursors can respond to these GF with changes in their clonogenic growth indicating the presence of functional receptors. Results may have implications for therapeutic approaches combining cytokines and chemotherapy.

Adolescent↗
PubMed1993

Paracrine and autocrine growth mechanisms of human stem cell factor (c-kit ligand) in myeloid leukemia.

A novel hematopoietic growth factor, the stem cell factor (SCF), for primitive hematopoietic progenitor cells has recently been purified and its gene has been cloned. In this study, the mitogenic activity of recombinant human SCF on myeloid leukemia cells as well as the expression of its receptor was tested. The proliferation of myeloid leukemia cell lines as well as fresh myeloid leukemic blasts from patients was investigated in a 72 h 3H-thymidine uptake assay in the presence of various concentrations of rhSCF alone or in combination with saturating concentrations of G-CSF, GM-CSF, M-CSF, IL-3, or erythropoietin (EPO). Only five out of 30 lines, but fresh leukemic blasts from 75% of the AML blast samples significantly responded to SCF. To determine the SCF binding sites on leukemic cells, 125I-radiolabelled SCF was used in Scatchard analysis and cross-linking studies. Crosslinking studies demonstrated a 150 kD SCF receptor on the surface of some myeloid leukemic cell lines and all blast preparations. The response to SCF did not correlate to the receptor numbers expressed on the cell surface or to a certain subtype of myeloid leukemia. Using PCR analysis of total RNA from the myeloid leukemia lines we found coexpression of SCF-mRNA and SCF receptor-mRNA in 29% of the myeloid leukemia lines. Soluble as well as membrane bound SCF protein was found to be expressed in myeloid leukemia cells by monoclonal antibodies generated against SCF. This suggests autocrine mechanisms in the growth of a subgroup of leukemic cells by coexpression of SCF and its receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Erythropoietin↗