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B Löwenberg

Publications and source records attributed to B Löwenberg.

At least 19 recordsLinked to original sources
PubMed1992

Involvement of tumor necrosis factor (TNF) receptors p55 and p75 in TNF responses of acute myeloid leukemia blasts in vitro.

Tumor necrosis factor (TNF)-alpha and TNF-beta have multiple effects on human acute myeloid leukemia (AML) cells in vitro, including (1) synergistic stimulation of proliferation with interleukin-3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF) and upregulation of interleukin-3 (IL-3) and GM-CSF receptors; (2) inhibition of granulocyte-CSF (G-CSF)-induced growth and rapid downmodulation of G-CSF receptors; and (3) induction of autocrine growth. Recently, two distinct TNF receptors (TNF-Rs), TNF-R(p55) and TNF-R(p75), have been identified. In this study, we show that both receptor types may be expressed by AML blasts. It has been investigated whether the different effects of TNF on AML blasts can be explained by differential activation of the distinct TNF-R structures. For this purpose, we used the monoclonal antibodies HTR-1 and HTR-9, specifically recognizing TNF-R(p55), and UTR-1, specific for TNF-R(p75). TNF-(alpha and -beta) mediated synergistic activation with IL-3/GM-CSF, upregulation of IL-3/GM-CSF receptors, inhibition of G-CSF-induced growth, and rapid downmodulation of G-CSF receptors exclusively result from activation of TNF-R(p55). In certain cases in which TNF-alpha, rather than TNF-beta, induces AML growth through an autocrine mechanism, both TNF-R(p55) and (p75) are involved. These data indicate that the variety of TNF responses observed in AML can only be partially explained by differential activation of the TNF-R(p55) and (p75) structures, and that TNF-R(p55) on AML blasts can transduce both positive (synergism with IL-3/GM-CSF) and negative regulatory signals (inhibition of G-CSF-induced proliferation) following TNF activation.

Acute Disease↗
PubMed1992

Kit ligand improves in vitro erythropoiesis in myelodysplastic syndrome.

Erythropoiesis in response to erythropoietin (Epo) in myelodysplastic syndrome (MDS) in vitro and in vivo is severely impaired. We investigated the stimulative effect of c-kit ligand (KL) on the erythroid colony-forming abilities of bone marrow cells from 17 patients with MDS. The effects of normal donor-derived marrow were examined in comparison. Suppression of erythroid colony formation in MDS in response to Epo could not be restored by the addition of interleukin-3 (IL-3) to culture. In cultures dishes supplemented with KL, erythroid colony formation was dramatically enhanced, regarding both colony number and size. Colony-forming abilities by MDS progenitors were improved following costimulation with KL, particularly in refractory anemia (RA) and refractory anemia with ring sideroblasts (RARS); however, little enhancement was apparent following KL stimulation of marrow from patients with refractory anemia with excess of blasts (RAEB), refractory anemia with excess of blasts in transformation (RAEB-t), and chronic myelomonocytic leukemia (CMML). These results suggest that KL responsiveness of patients with low-risk MDS may still be intact, and that with progression to high-risk MDS, erythroid progenitors lose proliferative reactivity to both KL and Epo stimulation. KL may have a therapeutic role in restoring erythropoiesis in a subset of patients with MDS.

Adolescent↗
PubMed1992

Modulation of multidrug-resistant multiple myeloma by cyclosporin. The Leukaemia Group of the EORTC and the HOVON.

Resistance to chemotherapy in refractory multiple myeloma is frequently associated with expression of multidrug resistance (MDR). In resistant cells, intracellular accumulation of doxorubicin and vincristine does not occur because the MDR-1 gene product, a membrane glycoprotein (PgP), is an energy-dependent efflux pump. Cyclosporin is one of several non-cytotoxic drugs that can block the function of PgP. In a prospective study, we assessed the possibility that cyclosporin could be used clinically to modulate MDR. We studied 21 patients with multiple myeloma; disease had progressed during primary chemotherapy in 6 and was resistant to VAD (vincristine, doxorubicin, dexamethasone) in 15. The patients received cyclosporin by continuous infusion during VAD treatment; there were three cyclosporin dosage groups (5, 7.5, 10 mg/kg daily). Serum cyclosporin concentrations adequate for MDR modulation were reached in all patients receiving 7.5 or 10 mg/kg daily. 47% (7) of the VAD-refractory patients and 48% (10) of the whole group responded to VAD. Before treatment, MDR-1 expression was present in 12 patients. After VAD plus cyclosporin, no MDR-1-positive plasma cells were present in 6 of 8 patients tested. The response rate in MDR-1-positive patients was 58% compared with 33% in all our patients. Toxic effects were mild and reversible and did not include nephrotoxic or serious cardiovascular side-effects. 12 months after the start of treatment, survival was 85%, and disease-free survival at a median of 9 months after the response was 65%. Thus, in multiple myeloma clinical resistance to VAD can be circumvented by cyclosporin, which enables the cytotoxic drugs to eliminate resistant myeloma cells.

Adult↗
PubMed1992

Introduction of the human interleukin-6 (IL-6) receptor in murine IL-3-dependent hematopoietic cells restores responsiveness to IL-6.

To create experimental systems that facilitate studies aimed at the responsiveness of hematopoietic progenitors to interleukin (IL)-6 in combination with IL-3, we introduced the human IL-6 receptor (hIL-6R) into the IL-3-dependent cell line 32D. For this purpose, a retroviral vector containing the hIL-6R cDNA was constructed. 32D parental cells did not respond to IL-6, neither alone nor in combination with increasing concentrations of IL-3, and did not express detectable numbers of IL-6R as determined by 125I-IL-6 binding. 32D/hIL-6R cells expressed high-affinity IL-6 binding and responded synergistically to IL-6 in combination with suboptimal amounts of IL-3 in DNA synthesis assays. In addition, IL-6 promoted the short-term survival of IL-3-responsive clonogenic 32D/hIL-6R cells. On the other hand, although introduction of hIL-6R resulted in the formation of high-affinity IL-6 receptor structures in the IL-2-dependent thymocyte cell line CTLL, CTLL/hIL-6R cells did not respond to IL-6 in synergy with IL-2. We conclude that 32D cells possess the intracellular machinery permissive for IL-6 signal transduction. Murine IL-3-dependent cell lines with ectopic IL-6 receptors can serve as models for dissecting the molecular basis of IL-6 responses in primitive hematopoietic cells.

Animals↗
PubMed1992

Haemopoietic growth factors in acute myeloblastic and lymphoblastic leukaemia.

Acute leukaemia blast cells fail to mature into terminally differentiated cells and accumulate in the haemopoietic tissues. In analogy with normal haemopoiesis, the leukaemic mass is largely non-dividing and descends from a small pool of leukaemic progenitor cells with high proliferative activity. In vitro culture methods have become powerful instruments to analyse human leukaemia progenitor cells. These techniques have in recent years been considerably improved as the result of the availability of the recombinant HGFs. Here we have summarized the current insights in the growth properties of acute leukaemia progenitor cells, derived from the application of fully defined in vitro assays. We have discussed the proliferation and maturation abilities in relation to cytogenetic abnormalities, status of growth factor receptors and the property of autocrine growth stimulation and evaluated the significance of these findings for the understanding of the pathogenesis of acute myeloblastic leukaemia and acute lymphoblastic leukaemia.

Animals↗
PubMed1992

Analysis of the TNF receptors on human leukaemia cells by affinity cross-linking.

Tumour necrosis factor (TNF) affects the growth of human leukaemic cells by different modes of action depending on the type of leukaemia involved. We have analysed the structure of TNF receptors on cells from different types of leukaemia, including acute lymphoblastic leukaemia (ALL), acute myeloblastic leukaemia (AML), chronic lymphocytic leukaemia (CLL), and chronic myelocytic leukaemia (CML) either in chronic phase (CML-CP) or blastic crisis (CML-BC). The affinity crosslinking technique showed the existence of TNF receptors on cells from all the leukaemic cases studied with similar receptor structures. The TNF receptor showed a molecular weight of 76 kD when examined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. In conclusion, we provide evidence for existence of TNF receptors on several types of human leukaemia cells with an apparent molecular weight of 76 kD. Apparently, the discrepancy of TNF actions on the leukaemic growth are not related to the structure of TNF receptors.

Electrophoresis, Polyacrylamide Gel↗
PubMed1992

Tumor necrosis factor alpha is associated with disease activity and the degree of anemia in patients with rheumatoid arthritis.

To elucidate the role of tumor necrosis factor alpha (TNF) in determining anemia of chronic disease (ACD) in rheumatoid arthritis (RA), 24 patients were studied for disease parameters, TNF serum levels and bone marrow for erythroid colony growth and compared with six controls. Serum TNF alpha was highest in ACD and correlated well with RA disease parameters. Both TNF and other RA disease parameters correlated inversely with degree of anemia. BFUe counts were lower in ACD, correlated positively with Hb and negatively with erythrocyte sedimentation rate (ESR). TNF reduced whereas anti-TNF upregulated in vitro erythroid colony counts. TNF production occurred in similar amounts in bone marrow cultures in the three groups. From these preliminary findings we conclude that ACD in RA correlates with by RA disease activity and that TNF may serve not only as an RA disease marker but also could be one of the factors mediating impaired erythropoiesis in ACD in active RA.

Anemia↗
PubMed1991

Tumor necrosis factor regulates the expression of granulocyte-macrophage colony-stimulating factor and interleukin-3 receptors on human acute myeloid leukemia cells.

Tumor necrosis factor (TNF) acts as a potent enhancer of granulocyte-macrophage colony-stimulating factor (GM-CSF)- and interleukin-3 (IL-3)-induced human acute myeloid leukemia (AML) growth in vitro. We have analyzed the effects of TNF alpha on the expression of GM-CSF and IL-3 receptors on AML cells. Incubation of blasts from seven patients with AML in serum-free medium with TNF (10(3) U/mL) and subsequent binding studies using 125I-GM-CSF and 125I-IL-3 show that TNF increases the specific binding of GM-CSF (30% to 280%) and IL-3 (40% to 600%) in all cases. From Scatchard plot analysis it appears that TNF upregulates (1) low-affinity GM-CSF binding sites, (2) common high-affinity IL-3/GM-CSF binding sites, and (3) unique (non-GM-CSF binding) IL-3 binding sites. The effect of TNF is dose dependent and is half maximal at a concentration of 100 U/mL, and becomes evident at 18 hours of incubation with TNF at 37 degrees C, but not at 0 degree C. The GM-CSF dose-response curve of AML-colony-forming units plateaus at a higher level in the presence of TNF, which indicates that additional numbers of cells become responsive to GM-CSF. Incubation of AML blasts with the phorbol ester 12-0-tetradecanoylphorbol-13-acetate or formyl-Met-Leu-Phe (protein kinase C activators) does not influence GM-CSF receptor expression, suggesting that receptor upregulation by TNF is not mediated through activation of protein kinase C. On the other hand, the protein synthesis inhibitor cycloheximide abrogates receptor upregulation induced by TNF. In contrast to these findings in AML, TNF does not upregulate GM-CSF receptor numbers on blood granulocytes or monocytes. We conclude that TNF exerts positive effects on growth factor receptor expression of hematopoietic cells.

Cycloheximide↗
PubMed1991

Induction of granulocytic maturation in acute myeloid leukemia by G-CSF and retinoic acid.

AML cells were cultured free of serum with G-CSF in combination with all-trans-retinoic acid (RA), prostaglandin E2 or 8-bromocyclic AMP to see whether the maturation blockade of these cells could be overcome. The combination G-CSF + RA was most effective in inducing morphologic maturation, i.e. in 7/10 cases. Morphological alterations in response to G-CSF + RA indicated progression of the cells along the granulocytic pathway towards metamyelocytes and granulocytes. However, morphologically mature AML cells remained negative for myeloperoxidase and Sudan black stainings, indicators of granulocytic maturation. Chloracetate esterase positivity and CD15 membrane antigens became expressed on cultured AML cells, i.e. on unstimulated and G-CSF/RA exposed blasts. Ingestion of latex beads and reduction of nitroblue tetrazolium salt occurred in cultured AML cells regardless of the presence of inducers. In almost all cases clonogenic cells persisted after exposure to G-CSF + RA suggesting that subpopulations of immature cells escaped the action of these inducers. Thus although G-CSF + RA were capable of inducing maturation of AML cells along the granulocytic lineage, maturation was incomplete and the effect was evident in a subfraction of the cells only.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1991

Primary human acute myeloblastic leukaemia: an analysis of in vitro granulocytic maturation following stimulation with retinoic acid and G-CSF.

Acute myeloid leukaemia (AML) is characterized by the inability of myeloid cells to reach terminal maturation. We examined to what degree granulocytic maturation could be achieved by stimulating AML blast cells in an in vitro serum-free system with a combination of granulocyte-colony stimulating factor (G-CSF) and all-trans-retinoic acid (RA). Specimens from 41 AML patients were cultured for 7 d and then examined for cytochemistry (myeloperoxidase, Sudan Black, naphthyl-ASD-chloracetate esterase, periodic acid Schiff) an nitroblue tetrazolium reduction. The expression of CD11a, CD11b, CD11c, CD15, CD18, CD10, CD24 and B13-3 membrane antigens was also evaluated. Morphological and cytochemical studies were also performed after AML colony culture and culture of normal bone marrow cells (NBM). The comparative analysis of the panel of parameters was indicative of granulocytic maturation although to different degrees. The cells from 25/41 cases showed morphologic maturation (May-Grünwald-Giemsa). A positive correlation was evident between morphological maturation and CD11b expression (11/22 patients) as well as that of CD11c and CD15 (6 patients). Napthyl ASD chloroacetate esterase and PAS stainings also correlated with morphology (in 10/22 and 10/24 patients respectively). Nevertheless, the pattern of granulocytic maturation was remarkably variable among the 41 cases examined. The cells from only a few patients acquired the full spectrum of granulocytic markers. The comparison with normal bone marrow blasts indicates that serum-free culture conditions can, per se, limit granulocytic maturation, but it also confirms the intrinsic inability of AML cells to attain complete maturation in response to two potent granulocytic inducers.

Adult↗
PubMed1991

Tumor necrosis factor downregulates granulocyte-colony-stimulating factor receptor expression on human acute myeloid leukemia cells and granulocytes.

Tumor necrosis factor (TNF) inhibits granulocyte-colony-stimulating factor (G-CSF)-induced human acute myeloid leukemia (AML) growth in vitro. Incubation of blasts from three patients with AML in serum-free medium with TNF (10(3) U/ml), and subsequent binding studies using 125I-G-CSF reveal that TNF downregulates the numbers of G-CSF receptors by approximately 70%. G-CSF receptor numbers on purified blood granulocytes are also downmodulated by TNF. Downregulation of G-CSF receptor expression becomes evident within 10 min after incubation of the cells with TNF at 37 degrees C and is not associated with an apparent change of the dissociation constant (Kd). The TNF effect does not occur at 0 degrees C and cannot be induced by IL-2, IL-6, or GM-CSF. TNF probably exerts its effect through activation of protein kinase C (PKC) as the TNF effect on G-CSF receptor levels can be mimicked by 12-O-tetradecanoylphorbol-13- acetate. The PKC inhibitor Staurosporine (Sigma Chemical Co., St. Louis, MO) as well as protease inhibitors can completely prevent G-CSF receptor downmodulation. Thus, it appears TNF may act as a regulator of G-CSF receptor expression in myeloid cells and shut off G-CSF dependent hematopoiesis. The regulatory ability of TNF may explain the antagonism between TNF and G-CSF stimulation.

Acute Disease↗
PubMed1991

Positive and negative effects of tumor necrosis factor on colony growth from highly purified normal marrow progenitors.

The effects of recombinant human tumor necrosis factor alpha (TNF alpha) on colony growth were studied using highly enriched progenitor cells from normal human bone marrow. Supplementation of TNF to culture resulted in a dose-dependent suppression of granulocyte colony-stimulating factor (G-CSF) induced granulocytic colony formation and also erythropoietin (Epo) induced erythroid burst formation. However, the number of erythroid bursts, stimulated by interleukin-3 (IL-3) plus Epo, increased when TNF was added at comparable concentrations. Further, TNF enhanced eosinophilic colony growth induced by IL-3 or granulocytic-macrophage colony-stimulating factor (GM-CSF). In GM-CSF cultures TNF (100-1000 U/ml) also induced granulocytic and macrophage colonies. The addition of neutralizing antibodies against G-CSF, GM-CSF, or interleukin-6 (IL-6) to culture did not abrogate the observed effects of TNF, so that stimulation of myeloid colony growth was unlikely to result from the secondary induction of G-CSF or GM-CSF. TNF therefore exerts favourable effects on hematopoietic progenitors responsive to the more primitive colony-stimulating factors (IL-3, GM-CSF) and potent negative effects on precursors reactive to the single lineage G-CSF and Epo. These contrasting effects of TNF suggest that TNF, when available to marrow progenitors at similar tissue concentrations, may drive hematopoiesis within the progenitor cell compartment into selected directions.

Adult↗
PubMed1991

Acute myeloid leukemias with chromosomal abnormalities involving the 21q22 region identified by their in vitro responsiveness to interleukin-5.

Among 52 patients diagnosed as acute myeloid leukemia (AML), nine cases were found in which interleukin-5 (IL-5) induced a proliferative response in the leukemic cells, as measured by the stimulation of DNA synthesis or colony formation in vitro. All cases (n = 7) with the cytogenetic abnormality t(8;21)(q22;q22) belonged to this group of IL-5 responders. Of the additional two cases, one had an apparently normal karyotype, but the other expressed a dicentric chromosome 21, an abnormality also involving the breakpoint region 21q22. The leukemic cells of the IL-5 responsive patients could also be stimulated to proliferate by IL-3, GM-CSF and G-CSF, and in some cases by IL-6 or M-CSF. Immunophenotypic analysis revealed the presence of the immature hematopoietic cell antigen CD34, the myelomonocytic maturation antigens CD13 and CD33, in association with the B-cell related surface marker CD19 on the leukemic cells. Immunoglobulin mu and T-cell receptor beta-genes in the leukemic cells were in germline configuration. Upon incubation in colony culture, clonogenic cells were capable of producing progeny showing eosinophilic or neutrophilic maturation following stimulation with IL-5 or G-CSF, respectively. It is concluded that IL-5 responsive AML represents a subgroup of leukemia with distinct immunotypic and cytogenetic features.

Antigens, CD↗