Biomedical subjects

H E Broxmeyer

Publications and source records attributed to H E Broxmeyer.

At least 235 records · Page 13Linked to original sources

PubMed1991

Identification of cell surface receptors for murine macrophage inflammatory protein-1 alpha.

We have produced recombinant proteins for a cytokine, L2G25BP (macrophage inflammatory protein-1 alpha) (MIP-1 alpha). By using the recombinant protein (rMIP-1 alpha), receptors for MIP-1 alpha were identified on Con A-stimulated and unstimulated CTLL-R8, a T cell line, and LPS-stimulated RAW 264.7, a macrophage cell line. The 125I-rMIP-1 alpha binds to the receptor in a specific and saturable manner. Scatchard analysis indicated a single class of high affinity receptor, with a Kd of approximately 1.5 x 10(-9) M and approximately 1200 binding sites/Con A-stimulated CTLL-R8 cell and a Kd of 0.9 x 10(-9) M and approximately 380 binding sites/RAW 264.7 cell. 125I-rMIP-1 alpha binding was inhibited by unlabeled rMIP-1 alpha in a dose-dependent manner, but not by IL-1 alpha or IL-2. rMIP-1 alpha inhibited the proliferation of unstimulated CTLL-R8 cells. Rabbit anti-rMIP-1 alpha antibodies blocked the growth-inhibitory effect of the rMIP-1 alpha on CTLL-R8 cells.

Animals↗

PubMed1991

Mast cell growth factor (c-kit ligand) supports the growth of human multipotential progenitor cells with a high replating potential.

The replating capability of human multipotential (colony-forming unit-granulocyte-erythrocyte-macrophage-megakaryocyte [CFU-GEMM]) and erythroid (burst-forming unit-erythroid [BFU-E]) progenitors was assessed in vitro as a potential measure of self-renewal using purified, recombinant (r) human (hu) or murine (mu) mast cell growth factor (MGF), a ligand for the c-kit proto-oncogene receptor. Primary cultures of human umbilical cord blood or adult human bone marrow cells were initiated in methylcellulose with erythropoietin (Epo) alone or in combination with rhu interleukin-3 (IL-3) or MGF. Individual day 14 to 18 CFU-GEMM or BFU-E colonies were removed from primary cultures and reseeded into secondary methylcellulose cultures containing a combination of Epo, MGF, and rhu granulocyte-macrophage colony-stimulating factor (GM-CSF). The data showed a high replating efficiency of cord blood and bone marrow CFU-GEMM in response to Epo + MGF in terms of the percentage of colonies that could be replated and the number of secondary colonies formed per replated primary colony. The average number of hematopoietic colonies and clusters apparent from replated cultures of cord blood or bone marrow CFU-GEMM stimulated by Epo + MGF was greater than with Epo + rhuIL-3 or Epo alone. Replated cord blood CFU-GEMM gave rise to CFU-GEMM, BFU-E, and GM colony-forming units (CFU-GM) in secondary cultures. Replated bone marrow CFU-GEMM gave rise mainly to CFU-GM in secondary cultures. A more limited capacity for replating of cord blood and bone marrow BFU-E was observed. These studies show that CFU-GEMM responding to MGF have an enhanced replating potential, which may be promoted by MGF. These studies also support the concept that MGF acts on more primitive progenitors than IL-3.

Bone Marrow Cells↗

PubMed1991

Macrophage inflammatory protein (MIP)-1 beta abrogates the capacity of MIP-1 alpha to suppress myeloid progenitor cell growth.

The effects of recombinant murine macrophage inflammatory protein (MIP)-1 beta and MIP-2 on the suppressive activity of MIP-1 alpha were tested using colony formation by human and murine bone marrow burst-forming unit-erythroid (BFU-E), colony-forming unit-granulocyte erythroid macrophage, megakaryocyte (CFU-GEMM), and colony-forming unit-granulocyte macrophage (CFU-GM) progenitor cells. MIP-1 beta, but not MIP-2, when added with MIP-1 alpha to cells, blocked the suppressive effects of MIP-1 alpha on both human and murine BFU-E, CFU-GEMM, and CFU-GM colony formation. Similar results were observed regardless of the early acting cytokines used: human rGM-CSF plus human rIL-3, and two recently described potent cytokines, a genetically engineered human rGM-CSF/IL-3 fusion protein and MGF, a c-kit ligand. The more potent the stimuli, the greater the suppressive activity noted. Pulse treatment of hu bone marrow cells with MIP-1 alpha at 4 degrees C for 1 h was as effective in inhibiting colony formation as continuous exposure of cells to MIP-1 alpha, and the pulsing effect with MIP-1 alpha could not be overcome by subsequent exposure of cells to MIP-1 beta. Also, pulse exposure of cells to MIP-1 beta blocked the activity of subsequently added MIP-1 alpha. For specificity, the action of a nonrelated myelosuppressive factor H-ferritin, was compared. MIP-1 alpha and H-ferritin were shown to act on similar target populations of early BFU-E, CFU-GEMM, and CFU-GM. MIP-1 beta did not block the suppressive activity of H-ferritin. Also, hemin and an inactive recombinant human H-ferritin mutein counteracted the suppressive effects of the wildtype H-ferritin molecule, but did not block the suppressive effects of MIP-1 alpha. These results show that MIP-1 beta's ability to block the action of MIP-1 alpha is specific. In addition, the results suggest that MIP-1 alpha and MIP-beta can, through rapid action, modulate early myeloid progenitor cell proliferation.

Bone Marrow↗

PubMed1991

CD45 cell surface antigens are linked to stimulation of early human myeloid progenitor cells by interleukin 3 (IL-3), granulocyte/macrophage colony-stimulating factor (GM-CSF), a GM-CSF/IL-3 fusion protein, and mast cell growth factor (a c-kit ligand).

CD45 antigens are protein tyrosine phosphatases. A possible link was evaluated between expression of CD45 antigens on human myeloid progenitor cells (MPC) (colony-forming unit-granulocyte/macrophage [CFU-GM], burst-forming unit-erythroid [BFU-E], and colony-forming unit-granulocyte/erythroid/macrophage/megakaryocyte [CFU-GEMM]) and regulation of MPC by colony-stimulating factors (CSF) (interleukin 3 [IL-3], GM-CSF, G-CSF, M-CSF, and erythropoietin [Epo]), a GM-CSF/IL-3 fusion protein, and mast cell growth factor (MGF; a c-kit ligand). Treatment of cells with antisense oligodeoxynucleotides (oligos) to exons 1 and 2, but not 4, 5, or 6, of the CD45 gene, or with monoclonal anti-CD45, significantly decreased CFU-GM colony formation stimulated with GM-CSF, IL-3, fusion protein, and GM-CSF + MGF, but not with G-CSF or M-CSF. It also decreased GM-CSF, IL-3, fusion protein, and MGF-enhanced Epo-dependent BFU-E and CFU-GEMM colony formation, but had little or no effect on BFU-E or CFU-GEMM colony formation stimulated by Epo alone. Similar results were obtained with unseparated or purified (greater than or equal to one of two cells being a MPC) bone marrow cells. Sorted populations of CD343+ HLA-DR+ marrow cells composed of 90% MPC were used to demonstrate capping of CD45 after crosslinking protocols. Also, a decreased percent of CD45+ cells and CD45 antigen density was noted after treatment of column-separated CD34+ cells with antisense oligos to exon 1 of the CD45 gene. These results demonstrate that CD45 cell surface antigens are linked to stimulation of early human MPC by IL-3, GM-CSF, a GM-CSF/IL-3 fusion protein, and MGF.

Animals↗

PubMed1991

Differential transcriptional and posttranscriptional regulation of gene expression of the colony-stimulating factors by interleukin-1 and fetal bovine serum in murine fibroblasts.

Colony-stimulating factors (CSF) are important factors in the proliferation and differentiation of hematopoietic progenitor cells (HPC), and in the survival and activation of mature blood cells. Interleukin-1 (IL-1) combined with fetal bovine serum (FBS) strongly induces the expression of macrophage-CSF (M-CSF), granulocyte-CSF (G-CSF), and granulocyte-macrophage-CSF (GM-CSF) in fibroblasts. Here, we report on the regulation of CSF gene expression in murine fibroblasts following IL-1 and FBS stimulation. We demonstrate that 10T1/2 murine fibroblasts induced by FBS or IL-1 accumulate M-CSF messenger RNA (mRNA). G-CSF mRNA expression was induced by IL-1, and not by FBS. For GM-CSF expression, induction with both FBS and IL-1 was required. Blocking studies with actinomycin-D showed that active transcription is essential for accumulation of all three CSF mRNAs. After blocking protein synthesis with cycloheximide, IL-1- or FBS-induced M-CSF expression and IL-1 plus FBS-induced GM-CSF expression still occurred and was increased. IL-1-induced G-CSF expression was completely prevented in these cells by pretreatment with cycloheximide, illustrating that, for this effect, intermediate protein synthesis was required. The half-lives of M-CSF transcripts were not substantially altered by addition of IL-1, FBS, or FBS plus IL-1. Using nuclear run-on assays, we demonstrated that the transcription rate of M-CSF was increased up to 20-fold by the addition of FBS, IL-1, or FBS plus IL-1. After blocking protein synthesis with cycloheximide, IL-1-or FBS-induced increase in M-CSF transcription rate was also observed. GM-CSF transcription increased up to fourfold after induction with FBS or IL-1. G-CSF transcription rate was not altered by FBS or IL-1. Our results indicate that M-CSF expression induced by FBS or IL-1 in these fibroblasts is primarily regulated at the transcriptional level. GM-CSF expression appears to be regulated both transcriptionally and posttranscriptionally, and G-CSF expression is regulated mainly at the posttranscriptional level.

Animals↗

PubMed1991

Enhanced hematopoietic activity of a human granulocyte/macrophage colony-stimulating factor-interleukin 3 fusion protein.

Granulocyte/macrophage colony-stimulating factor-interleukin 3 (GM-CSF-IL-3) fusion proteins were generated by construction of a plasmid in which the coding regions of human GM-CSF and IL-3 cDNAs were connected by a synthetic linker sequence followed by subsequent expression in yeast. Both GM-CSF-IL-3 and IL-3-GM-CSF fusion proteins were purified to homogeneity and shown to bind to cell-surface receptors through either their GM-CSF or IL-3 domains. The fusion proteins exhibited enhanced receptor affinity, proliferative activity, and hematopoietic colony-stimulating activity compared with either IL-3 and/or GM-CSF alone. This suggests that GM-CSF-IL-3 fusion proteins may hold future promise as therapeutic agents.

Base Sequence↗

PubMed1991

Cloning and characterization of the murine promoter for the colony-stimulating factor-1-encoding gene.

Colony-stimulating factor-1 (CSF-1 or M-CSF) is required for the growth and differentiation of macrophage progenitors, and for the survival of mature macrophages. Expression of the CSF-1 gene in monocytes and fibroblasts is controlled at both the transcriptional and post-transcriptional levels. To study the molecular mechanisms which mediate changes in CSF-1 expression, the 5' promoter region of the mouse CSF-1 gene was cloned. A high degree of structural and sequence similarity between the mouse and human CSF-1 genes was observed. A transcription start point was located 182 bp upstream from the start codon. Several sequences homologous to known cis-acting elements were identified in the 5'-flanking region. The CSF-1 promoter region was able to direct expression of a linked reporter gene in C3H10T1/2 mouse embryo fibroblasts. Deletion in the CSF-1 promoter region between bp -774 and -629 resulted in a significant decrease in promoter activity. The identification of a functional promoter for CSF-1 will serve as a valuable tool for studying the regulation of CSF-1 expression.

Animals↗

PubMed1991

Effect of murine mast cell growth factor (c-kit proto-oncogene ligand) on colony formation by human marrow hematopoietic progenitor cells.

Purified natural (n) and recombinant (r) murine (mu) mast cell growth factor (MGF, a c-kit ligand) were evaluated alone and in combination with r human (hu) erythropoietin (Epo), rhu granulocyte-macrophage colony-stimulating factor (rhuGM-CSF), rhuG-CSF, and/or rhuM-CSF for effects in vitro on colony formation by multipotential (colony-forming unit-granulocyte, erythroid, monocyte, megakaryocyte [CFU-GEMM]), erythroid (burst-forming unit erythroid [BFU-E]) and granulocyte-macrophage (CFU-GM) progenitor cells from normal human bone marrow. MGF was a potent enhancing cytokine for Epo-dependent CFU-GEMM and BFU-E colony formation, stimulating more colonies and of a larger size than either rhu interleukin-3 (rhuIL-3) or rhuGM-CSF. MGF, especially at lower concentrations, also acted with rhuIL-3 or rhuGM-CSF to enhance Epo-dependent CFU-GEMM and BFU-E colony formation. MGF had little stimulating activity for CFU-GM colonies by itself, but in combination with suboptimal to optimal amounts of rhuGM-CSF enhanced the numbers and the size of CFU-GM colonies in an additive to greater than additive manner. While we did not detect an effect of MGF on CFU-G colony numbers stimulated by maximal concentrations of rhuG-CSF, MGF did enhance the size of CFU-G-derived colonies. MGF did not enhance the activity of rhuM-CSF. In a comparative assay, maximal concentrations of rmu and rhuMGF were equally effective in the enhancement of human bone marrow colony formation, but rhuMGF, in contrast to rmuMGF, did not at the concentrations tested enhance colony formation by mouse bone marrow cells. MGF effects on BFU-E, CFU-GM, and CFU-GEMM may be direct acting ones as MGF-enhanced colony formation by these cells in highly enriched progenitor cell populations of CD34 HLA-DR+ and CD34 HLA-DR+CD33- sorted cells in which greater than or equal to 1 of 2 cells was a BFU-E plus CFU-GM plus CFU-GEMM. MGF appears to be an early acting cytokine that preferentially stimulates the growth of immature hematopoietic progenitor cells.

Antigens, CD34↗

PubMed1991

Mutated recombinant human heavy-chain ferritins and myelosuppression in vitro and in vivo: a link between ferritin ferroxidase activity and biological function.

Human heavy-chain (H-) ferritin muteins obtained by oligonucleotide site-directed mutagenesis, together with wild-type recombinant human H- and light-chain (L-) ferritins, were evaluated for in vitro effects on the suppression of human bone marrow myeloid progenitor cells and for in vivo effects on marrow and splenic myelopoiesis in C3H/HeJ mice. The 10 H-ferritin muteins exhibited alterations of various regions of the molecule, including ones exposed on the outer surface, on the inner cavity, and on the hydrophilic and hydrophobic channels and of the four-alpha-helix bundle forming the subunit structure. They were stable and were electrophoretically analogous to wild-type H-ferritin. The muteins showed in vitro and in vivo myelosuppressive activity analogous to wild type, except for mutein 222, which was totally inactive and which lacked ferroxidase activity. Recombinant human L-ferritin, devoid of ferroxidase activity, was also inactive as a suppressor. The results demonstrate that H-ferritin myelosuppressive and ferroxidase activities are linked. One possibility is that ferroxidase activity may interfere with the cellular uptake of transferrin iron that is needed for cell proliferation, an interpretation consistent with the presently described ability of hemin to overcome H-ferritin suppressive effects.

Animals↗

PubMed1991

Regulation of human bone marrow lactoferrin and myeloperoxidase gene expression by tumor necrosis factor-alpha.

Lactoferrin (LF) and myeloperoxidase (MPO) are glycoproteins synthesized in early myeloid cells (promyelocytes, myelocytes) and stored in granules of polymorphonuclear neutrophilic granulocytes. Both proteins are involved in the host inflammatory response, and LF has been found to have myelosuppressive activity in vivo and in vitro. Little is known, however, about the regulation of their production. We investigated the stability of LF and MPO mRNA and the effects of purified recombinant human TNF-alpha on LF and MPO levels in normal human bone marrow. Low density human bone marrow cells were cultured in the presence or absence of actinomycin D (10 micrograms/ml) or TNF-alpha (200 U/ml). LF and MPO RNA levels were analyzed by Northern blots using, respectively, a 650-bp insert from the plasmid pHL41, and a 2.3-kb insert from the plasmid pMPO2 as probes. It was found that: 1) LF mRNA is a fairly stable molecule, with a half-life of between 8 and 9 h, whereas MPO is less stable, with a half-life of between 4 and 5 h; 2) TNF-alpha decreases both LF and MPO mRNA levels, an effect seen by 24 h with MPO mRNA and 48 h with LF mRNA; 3) nuclear run-on assays revealed that TNF decreases transcription of the LF gene by 70% and the MPO gene by 50%; and 4) the suppressive effect of TNF-alpha on LF and MPO mRNA levels is not due to cell killing or selective differentiation and is reversible.

Bone Marrow↗

PubMed1991

Lactoferrin-lipopolysaccharide interactions. Effect on lactoferrin binding to monocyte/macrophage-differentiated HL-60 cells.

Lactoferrin (LF) has been implicated in a number of functions including the negative regulation of myelopoiesis in vitro and in vivo, an effect mediated by suppression of cytokine release from monocytes/macrophages. This suppression is abrogated by bacterial LPS. In the present study, HL-60 cells were induced to differentiate to monocytes/macrophages by 12-O-tetradecanoyl phorbol-13-acetate, and LF-binding assays were performed. After differentiation, HL-60 cells showed a twofold increase of LF-binding sites with no difference in the specificity or affinity of LF between pre- and post-differentiated cells. CD11a, CD11b, and CD11c Ag, which have been associated with specific binding sites for LPS on monocytes/macrophages, were also increased three- to fourfold after differentiation. With the use of this system, the effect of LPS on LF binding was studied. At 37 degrees C, LPS enhanced LF binding on HL-60 cells, especially after differentiation. Conversely, at 4 degrees C, LPS inhibited LF binding. There was little effect of temperature on LF binding in the absence of LPS. In the presence of polymyxin B sulfate, the enhanced LF binding by LPS was abrogated. Also, pretreatment with mAbCD11 and/or mAb5D3, which are associated with or directed against candidate LPS receptors, reduced LF binding. Cross-linking studies using an iodinated, photoactivatable LPS derivative ([125I]ASD-LPS) demonstrated directly the specific binding of LPS to LF. These data indicate a dichotomous nature of LF binding on monocyte/macrophage-differentiated HL-60 cells--one being mediated by specific LF receptors whereas the other is apparently mainly via LPS receptors after formation of an LF-LPS complex. These interactions, for which a model is proposed, help to explain the mechanism behind LPS abrogation of the myelopoietic suppressive effects of LF, and a situation that probably occurs during bacterial infection.

Affinity Labels↗

PubMed1991

Anti-tumor effects of recombinant human macrophage colony-stimulating factor, alone or in combination with local irradiation, in mice inoculated with Lewis lung carcinoma cells.

Recombinant human (rhu) macrophage colony-stimulating factor (M-CSF) was evaluated for efficacy, either alone or in combination with local X-irradiation (LR), in mice inoculated subcutaneously (s.c.) with Lewis lung carcinoma (LLC) cells. The size of the primary tumor and numbers of lung metastases, 21 days after tumor inoculation and 15 days after the start of treatment, were reduced by 87% in tumor-bearing mice treated with 20 micrograms/dose M-CSF s.c. twice a day for 5 days. LR (800 cGy) to the tumor once a week for 2 weeks had a moderate anti-tumor effect and enhanced the anti-tumor effect of M-CSF. Hematological parameters, including nucleated cellularity in peripheral blood, femoral marrow, spleen and peritoneal exudate, as well as marrow and splenic granulocyte-macrophage progenitor cells, and numbers of splenic Thy 1.2+ cell and peritoneal mast cells, were perturbed in LLC-bearing mice, and were influenced by treatment with M-CSF and LR. Treatment with M-CSF plus LR, but not with either agent alone, was associated with a significant, although slight, enhancement in survival time for LLC-bearing mice. Inability to obtain a better survival-enhancing effect appeared to be related to the limited treatment, since the anti-tumor effects of M-CSF were more notable early on in disease progression and were related to the dose of M-CSF used. The effects of M-CSF were most probably indirect ones on the host immune system. M-CSF, in combination with LR, may be of benefit in the treatment of human tumors that have metastatic potential.

Animals↗

PubMed1991

In vivo effects of recombinant human interleukin 6, alone or in combination with local irradiation, on tumor growth in Lewis lung carcinoma-bearing mice.

Lewis lung carcinoma (LLC)-bearing mice were used as a mouse model to evaluate effects of recombinant human (rh) interleukin (IL) 6 and local X-irradiation (LR) on the growth of primary tumors and lung metastases. Mice were inoculated s.c. with LLC tumor cells and then treated with rhIL-6 (100 ng/dose) s.c. twice a day (b.i.d.) for 5 days, beginning 6 days after tumor inoculation. LR (800 cGy) was administered to the site of the primary tumor 6 days after tumor inoculation and again 1 wk later. Mice were then observed for survival or sacrificed at day 21 after tumor inoculation to determine size of primary tumor, numbers and size of lung metastases, and other hematological parameters including numbers of granulocyte-macrophage progenitor cells (CFU-gm). The size of the primary tumor and numbers of lung metastases were reduced by rhIL-6. LR enhanced the antitumor effect of rhIL-6 significantly, while LR alone had only a slight antitumor effect. Tumor-associated increases in peripheral blood, femoral marrow, splenic-nucleated cellularity, and marrow and splenic CFU-gm were reduced in mice treated with rhIL-6 plus LR. Prolonged survival time was observed only in tumor-bearing mice treated with rhIL-6 in combination with LR. The antitumor effects in vivo of rhIL-6 appear to be mediated indirectly as rhIL-6 had no effect on proliferation of LLC cells in vitro as assessed by colony and 3H-thymidine incorporation assays. These studies suggest that rhIL-6 may have therapeutic value in the treatment of certain malignancies, especially if used in combination with LR.

Animals↗

PubMed1991

Hybrid cytokines as hematopoietic growth factors.

A large body of in vitro and in vivo data suggests that combinations of cytokines provide the most effective mechanism for stimulating multilineage acceleration of hematopoiesis. Creation of a granulocyte-macrophage colony-stimulating factor (GM-CSF)/interleukin 3 (IL-3) fusion protein has yielded a single therapeutic which has enhanced biological activity in comparison to the individual cytokines from which it is composed. In vivo studies with this fusion protein (PIXY321) suggest that it may provide a means to accelerate both neutrophil and platelet recovery in clinical settings in which hematopoiesis is suppressed. The biology of PIXY321 and the potential for other fusion proteins is discussed.

Drug Combinations↗

PubMed1991

DNA amplification for DQ typing as an adjunct to serological prenatal HLA typing for the identification of potential donors for umbilical cord blood transplantation.

It has recently been demonstrated that umbilical cord blood from genotypically human leukocyte antigen (HLA)-matched donors can provide sufficient numbers of progenitor cells for hematopoietic reconstitution. This technique has been successfully applied in the treatment of two children affected with Fanconi anemia (FA). Fetal cells from the potential sibling donors were first tested to determine that the fetus was not affected with FA. Unaffected fetal cells were then tested for HLA type. Cord blood from compatible donors can be harvested at birth and used immediately or frozen for subsequent use in hematopoietic reconstitution. We now show that fetal cell DNA amplification and hybridization for DQ typing can be an important adjunct procedure to verify serologically determined HLA class II types and/or to establish class II haplotype identity with the affected sibling.

Blood Transfusion↗

PubMed1991

Whole body hyperthermia: a potent radioprotector in vivo.

Interleukin-1 has been reported to be an effective radioprotective agent in mice subjected to lethal doses of irradiation. Production of Interleukin-1 can be increased by whole body hyperthermia. Therefore, whole body hyperthermia was assessed for its efficacy in protecting the lethal effects of ionizing radiation in DBA/2 mice. One hour of 40 degrees C +/- 0.2 whole body hyperthermia given 20 hr before 900 cGy total body irradiation protected 100% of DBA/2 mice from an LD 100/16 radiation dose (dose of irradiation that killed 100% of the mice in 16 days). Lethal doses of total body irradiation produced profound monocytopenia, decreased cellularity of thymus, spleen, and bone marrow, and suppressed Interleukin-1 production. Interleukin-1 production was determined using the thymocyte proliferation assay. Whole body hyperthermia accelerated recovery of blood leukocytes by up to 5 days post-total body irradiation in DBA/2 mice. Thymocytes, spleen, and bone marrow cells were activated by whole body hyperthermia, as assessed by the cell's response to Concanavalin A. This was accompanied by accelerated Interleukin-1 generation. Our results provide the first evidence that whole body hyperthermia acts as a potent radioprotector in vivo, effects that may be mediated by Interleukin-1.

Animals↗

PubMed1991

Role of transforming growth factor-beta 1 in regulation of hematopoiesis.

The data presented above suggest that one possible clinical use of TGF-beta would be to protect the bone marrow from the effects of myelosuppressive chemotherapeutic drugs by preventing entry or removing primitive stem cells from the cell cycle. It may also have the additional benefit of reducing the drug-induced neutrophil nadir by stimulating granulopoiesis. The availability of large quantities of recombinant TGF-beta will allow study of the pharmacokinetics with different routes of administration, dosage effects, and details of the pleiotropic effects on other cell systems. Experiments are in progress to determine whether TGF-beta will allow the delivery of higher amounts or more frequent doses of chemotherapeutic drugs and thus allow increased antitumor efficacy in tumor-bearing animals.

Animals↗

PubMed1991

Interleukin-6 ablates the accessory cell-mediated suppressive effects of lactoferrin on human hematopoietic progenitor cell proliferation in vitro.

LF, an iron-binding glycoprotein, has myelosuppressive effects in vitro and in vivo. The present study evaluated the mode of LF action in vitro and the effects of various recombinant CSFs and ILs on this action. Normal human low-density BMC, at 2 x 10(6)/ml, were exposed to purified and endotoxin-depleted iron-saturated LF for 2 h, washed three times, and plated for CFU-GM and BFU-E in the presence of rhuCSFs (e.g., GM-CSF, Epo, IL-3) and in the absence and presence of rhuIL-6, rhuIL-1 alpha, or rhuIL-1 beta. LF caused a 40-65% plateau curve of inhibition for CFU-GM and BFU-E that was not apparent when adherent mononuclear cells (monocytes) were removed from the target population of cells. This myelosuppression was ablated by rhuIL-6, but not by rhuIL-1 alpha or rhuIL-beta. These results suggests a role for IL-6 in the accessory cell-mediated suppressive effect of LF on CFU-GM and BFU-E and open up the possibility that IL-6 may have stimulatory/enhancing or cofactor activities necessary for optimal proliferation of hematopoietic progenitor cells.

Animals↗