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R Delwel

Publications and source records attributed to R Delwel.

51 records · Page 3Linked to original sources
PubMed1989

Granulocyte colony-stimulating factor receptors in human acute myelocytic leukemia.

The binding of granulocyte colony-stimulating factor (G-CSF) to normal and human acute myeloid leukemia (AML) cells was investigated with radiolabeled recombinant human G-CSF (rhG-CSF). In all 14 cases of primary AML specific receptors for G-CSF were demonstrated on purified blast cells. The average numbers of G-CSF receptors ranged from very low to 428 receptors per cell (mean). Normal granulocytes showed G-CSF binding sites on their surface at higher densities (703 to 1,296 sites per cell). G-CSF receptors appeared to be of a single affinity type with a dissociation constant (kd) ranging between 214 and 378 pmol/L for AML blasts and 405 to 648 pmol/L for granulocytes. In 12 of 14 cases, including those with relatively low specific binding, G-CSF was a potent inducer of DNA synthesis of blasts in vitro; therefore, apparently relatively few receptors are required to permit activation of AML cell growth. However, in two cases cell cycling was not activated in response to G-CSF despite G-CSF receptor availability. The results show that G-CSF receptors of high affinity are frequently expressed on the blasts of human AML, but their presence may not be a strict indicator of the proliferative responsiveness of the cells to G-CSF.

Cell Division↗
PubMed1988

Human AML colony growth in serum-free culture.

Here we report experiments dealing with the development of a fully serum-free culture system for AML cell proliferation. A number of compounds were tested for the requirements of AML colony formation and DNA synthesis in vitro in an attempt to replace serum with an artificial mixture. The results indicate that bovine serum albumin (BSA, 15 mg/ml), cholesterol (7.8 micrograms/ml), transferrin (7.7 X 10(-6) M) and insulin (1 microgram/ml) were essential for AML cell proliferation. Linoleic acid, 2-mercaptoethanol and selenite contributed only moderately beneficial effects. This mixture obviated the need for adding exogenous fetal calf or horse serum to the cultures and permitted equivalent and frequently superior AML colony formation and DNA synthesis. This is the first serum-free culture method for human AML that may allow for in-vitro studies of the growth regulation by recombinant growth factors under exactly defined and standardized conditions.

Cell Division↗
PubMed1988

Effects of recombinant multi-CSF, GM-CSF, G-CSF and M-CSF on the proliferation and maturation of human AML in vitro.

To investigate the relative role of the individual hematopoietic growth factors in stimulating AML cell growth we compared the effects of recombinant (r) Multi-CSF (IL-3), rGM-CSF, rG-CSF and rM-CSF on DNA synthesis of AML blasts in culture. In order to establish the interrelationship between the proliferative effects exerted by these CSFs on AML cells, the ability of these factors to induce progressive monocytic or granulocytic maturation in AML blasts was also assessed. The studies were conducted in 25 cases of AML. They show that AML blasts often are responsive to at least one of the physiologic regulators but the patterns of response reveal a considerable heterogeneity among patients with AML. Although the cells react to these factors, they are usually inert in their capacity to mature, which indicates their intrinsic maturation defect.

Cell Division↗
PubMed1988

In vivo uptake of daunorubicin by acute myeloid leukemia (AML) cells measured by flow cytometry.

Monitoring of daunorubicin (DNR) concentrations in leukemic cells in blood and bone marrow in vivo of patients with acute myeloid leukemia may yield insight into the interindividual variations of the clinical response to treatment. We evaluated the applicability of flow cytometry for measuring DNR uptake in direct comparison with high performance liquid chromatography (HPLC). In vitro studies revealed good correlations between the mean cellular fluorescence measured by flow cytometry and the cellular DNR concentrations determined with HPLC. In vivo cell measurements were then obtained in 17 evaluable patients during their first remission induction treatment with DNR and cytosine arabinoside. The results indicate that: (a) DNR fluorescence of leukemic blast cells is intermediate between the smaller lymphocytes and the approximately equally large granulocytes; (b) DNR fluorescence of peripheral blast cells and bone marrow blast cells correlate well (p less than 0.001); and (c) patients reaching complete remission show a tendency of higher DNR fluorescence of leukemic blast cells than do partial responders.

Adolescent↗
PubMed1988

Phenotyping of acute myelocytic leukemia (AML) progenitors: an approach for tracing minimal numbers of AML cells among normal bone marrow.

Previous studies have shown that the phenotypes of progenitors of human AML (AML-CFU) are variable, reflecting arrests at different stages of maturation. We were interested to seek discrepancies between the surface properties of AML precursors and normal bone marrow colony formers in order to detect minimal numbers of AML cells among normal bone marrow cells in remission bone marrow. Therefore, we selected two surface markers, the MoAb CD34, reactive with blast cells, and Vim-2, a surface marker reactive with mature myeloid cells, and determined the antigen density of these markers (relative fluorescence intensity using fluorescence-activated cell sorting) for normal marrow and AML progenitors. While these markers defined an identical phenotype (CD34++/Vim-2-/+) for a broad spectrum of normal progenitors, i.e., CFU-GEMM, BFU-e, day 15 CFU-GM, and day 7 CFU-GM, referred to as the "normal" progenitor phenotype, AML progenitors frequently exhibited different phenotypes. In 12 of 20 cases the phenotypes of the majority of AML progenitors were discrepant from the normal surface profile, i.e., according to one marker in 8 cases (CD34-/+/Vim-2-/+ or CD34++/Vim-2++) and two markers in 4 cases (CD34-/+/Vim-2++). Since these data indicate that AML and normal progenitors were frequently distinguishable, we then determined the potential utility of these phenotypic dissimilarities for detection of minimal disease. Artificial mixtures of normal bone marrow and minimal numbers (0.1-1%) of AML cells were prepared. Based upon the phenotypic discrepancies, AML metaphases were successfully demonstrated in these mixtures following cell sorting and culture. Thus, it appears that minimal numbers of AML mitoses can be identified with an approximate 10(-2) to 10(-3) sensitivity by taking advantage of differential coexpression of surface antigens.

Antibodies, Monoclonal↗
PubMed1988

Growth regulation of human acute myeloid leukemia: effects of five recombinant hematopoietic factors in a serum-free culture system.

The response of human acute myeloid leukemia (AML) cells to the distinct hematopoietic growth factors (HGFs), ie, recombinant interleukin-3 (IL-3), granulocyte-macrophage-CSF (GM-CSF), granulocyte-CSF (G-CSF), macrophage-CSF (M-CSF), and erythropoietin (Epo) was investigated under well-defined serum-free conditions. Proliferative responses to these factors, when added separately as well as in combinations, were analyzed in 25 cases of human AML using 3H-thymidine incorporation and colony assays. The 3H-thymidine uptake data revealed that IL-3, GM-CSF, G-CSF, and M-CSF were stimulators of AML proliferation in 19, 15, 13, and 4 cases, respectively. Epo only stimulated DNA synthesis in the cells of the single erythroleukemia case. GM-CSF stimulation was seen only in IL-3 reactive cases and GM-CSF, when combined with IL-3, could not further elevate the DNA synthesis evoked by IL-3 alone. On the other hand, in six cases, G-CSF enhanced the IL-3- or GM-CSF-stimulated thymidine uptake. These results suggest that subpopulations of AML cells that are activated by distinct CSFs (eg, IL-3/GM-CSF-responsive cells and G-CSF-responsive cells) coexist. The 3H-thymidine incorporation assay was more sensitive for measuring CSF responses than methylcellulose colony cultures, since activation of DNA synthesis was more frequently seen than induction of colony formation. DNA synthesis experiments revealed eight different CSF response patterns among these 25 cases. CSF phenotyping may be a useful addition to the morphologic classification of AML, since these patterns directly reflect the ability of the proliferating subsets of AML cells to respond to the CSFs.

Cell Division↗
PubMed1987

Characterization of a human multilineage-colony-stimulating factor cDNA clone identified by a conserved noncoding sequence in mouse interleukin-3.

Blood-cell production is regulated by hemopoietic growth factors, which act at specific stages of hemopoietic cell differentiation. Murine interleukin-3 (mIL-3)/multilineage colony-stimulating factor (multi-CSF) has been shown to stimulate colony formation in vitro by multipotent hemopoietic cells and production of spleen colony-forming units (CFU-S) in suspension cultures. The molecular cloning of the human counterpart of mIL-3 is described here. Hybridization of radiolabeled mIL-3 cDNA with a cDNA library obtained from mRNA of stimulated human lymphocytes resulted in the identification of a human (h)multi-CSF cDNA clone. Sequence homology (73%) in the 3'-noncoding region of mIL-3 enabled the detection of the hmulti-CSF cDNA clone. Whereas only 45% sequence homology was found in the coding region, specific A + T-rich domains in the 3'-noncoding region were highly conserved (93%). As far as we know, this is the first example of gene identification by sequence homology occurring only within the 3'-noncoding region. The protein encoded by this hmulti-CSF cDNA stimulates in vitro colony formation by multipotent human hemopoietic stem cells. In addition, the growth factor strongly stimulates the in vitro proliferation of human leukemic blast cells.

Animals↗
PubMed1987

Human recombinant multilineage colony stimulating factor (interleukin-3): stimulator of acute myelocytic leukemia progenitor cells in vitro.

Acute myeloid leukemia colony forming cells (AML-CFU) require the addition of colony stimulating factors (CSFs) for in vitro proliferation. Recently, we isolated a human recombinant multilineage CSF (hMulti-CSF). We investigated the ability of hMulti-CSF to stimulate AML clonogenic cells in seven patients in direct comparison with the effects of human granulocyte CSF (hG-CSF), human granulocyte-macrophage CSF (hGM-CSF), and feeder leukocytes. We show that hMulti-CSF is an efficient stimulator of AML colony formation in four of seven cases. In these patients, hGM-CSF was also capable of stimulating AML colonies in vitro. In two of seven cases hMulti-CSF appeared to be a weak stimulus of AML-CFU proliferation. In these latter two cases, however, hG-CSF and in one case hGM-CSF effectively stimulated AML-CFU growth. In one patient none of the hCSFs, either alone or in combination, induced AML colony formation, whereas AML colonies consistently appeared in the phytohemagglutinin (PHA) leukocyte feeder assay. This finding suggests that PHA stimulated leukocytes produce components other than the tested hCSFs that may have a role in the proliferation of AML cells in vitro. Multi-CSF, like hGM-CSF, revealed a limited capacity to induce progressive maturation during AML colony growth, ie, not beyond the promyelocytic stage. On the other hand, in one case, hG-CSF stimulated the growth of AML colonies containing (meta)myelocytes and granulocytes. We conclude that hMulti-CSF is a regulator of AML-CFU proliferation in a significant number of cases. The patterns of responsiveness of AML precursors to the three hCSFs in different patients show a striking variability, which may indicate that AML-CFU are the neoplastic representatives of normal bone marrow progenitors at different stages of maturation and with distinct CSF requirements.

Adult↗
PubMed1987

Membrane receptors for interleukin 2 on hematopoietic precursors in chronic myeloid leukemia.

In this report we present data on the expression of IL2 receptors on chronic phase CML cells. Using an anti IL2 receptor monoclonal antibody (McAb aIL2r) in indirect immunofluorescence we found significant proportions (42.2% +/- 19.7 SD) of the CML cells (previously depleted of E rosetting T cells) to be IL2 receptor positive following incubation in suspension for 18 hours at 37 degrees C. Noninduced cells did not express IL2 receptors. After induction the aIL2r positive and negative cell subpopulations were sorted and analyzed separately for morphology, lineage specific cell surface markers, and clonogenic cell numbers. The IL2 receptor positive CML subpopulations mainly contained blast cells and monocytes and revealed reactivity with myeloid McAbs but not with T cell, B cell, platelet, or erythroid markers. Clonogenic cells (CFU-GEMM, BFUe, and CFU-GM) were selectively recovered from aIL2r positive CML cells and thus were IL2 receptor positive. The addition of recombinant IL2 (rIL2) to CFU-GM and BFUe cultures, in concentrations from 50 to 500 U/mL, did not influence the efficiency of colony formation. Binding of a radiolabeled IL2 preparation to the in vitro activated CML cells indicated the presence of low affinity receptors for IL2. In contrast to CML, normal human marrow cells were consistently aIL2r nonreactive. Thus, IL2 receptor inducibility is a characteristic feature of CML clonogenic cells, which they share with AML, but not with normal marrow progenitors. The role of IL2 receptors in the regulation of proliferation of CML cells requires further investigation.

Antibodies, Monoclonal↗
PubMed1987

Mutations in N-ras predominate in acute myeloid leukemia.

Using synthetic oligomers we investigated fresh samples of acute myeloid leukemia (AML) for the presence of mutated ras oncogenes. Our original results showed that five of eight samples contained a mutation in codon 13 of the N-ras gene. In a subsequent study involving 37 samples, we found only one N-ras-13 mutation, and, in addition, mutations in codon 61 of the N-ras gene in four cases and a mutation in codon 12 of the Ki-ras gene in two cases. Amplification of ras genes was not observed. We conclude that in approximately 20% to 25% of AML cases, a mutated ras oncogene is present, predominantly the N-ras gene. The occurrence of mutations does not correlate with the cytological features of the leukemia.

Base Sequence↗
PubMed1987

Vim-2, candidate monoclonal antibody for purging autologous marrow grafts in acute myeloblastic leukaemia.

In this report we present a method for purging acute myeloid leukaemia progenitors (AML-CFU) from autologous marrow grafts. Previous studies using flow cytometry and cell sorting had indicated that the monoclonal antibody (MCA) Vim-2 reacts strongly with AML-CFU in a significant number of cases, whereas the majority of normal bone marrow precursors are Vim-2 negative. To investigate the applicability of Vim-2 for selective purging, we performed complement-dependent cytotoxicity experiments and determined the specific lysis of AML-CFU. In 11 of 17 patients, 97.5 +/- 4% (mean +/- SD) of AML-CFU were killed following immune-mediated lysis. Multi-lineage normal haematopoietic progenitors (CFU-GEMM) were not significantly affected by the MCA Vim-2-mediated complement lysis. These data suggest that the MCA Vim-2 is a useful reagent for the elimination of residual AML progenitor cells from remission bone marrow in patients subjected to autologous marrow transplantation.

Antibodies, Monoclonal↗
PubMed1986

Acute lymphoblastic leukemia and non-Hodgkin's lymphoma of T lineage: colony-forming cells retain growth factor (interleukin 2) dependence.

The regulatory role of interleukin 2 (IL 2) in the proliferation of T acute lymphoblastic leukemia (T-ALL) and T non-Hodgkin's lymphoma (T-NHL) cells from six individual patients was analyzed in a colony culture system to which pure recombinant IL 2, and the lectin phytohemagglutinin (PHA) or the phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (TPA), had been added. The proliferative response was correlated with the inducibility of receptors for IL 2 on the surface membrane of T-ALL and T-NHL cells by incubation with TPA or PHA for 18 hours. Leukemic T cell colonies, identified by immunophenotyping or cytogenetic analysis, appeared in vitro following TPA and IL 2 stimulation in all six cases. Accordingly, receptors for IL 2, initially absent from the cell surface, were found on high proportions of the T-ALL and T-NHL cells after in vitro exposure to TPA. In contrast, colony formation stimulated by PHA and the induction of IL 2 receptors by PHA were limited to the one case of T-NHL with the mature thymocyte immunophenotype. The cells from the other patients, expressing common or prothymocyte phenotypes, did not respond to PHA. No colonies were formed in any of these cases when PHA or TPA was withheld from the IL 2-containing cultures. Although colony growth depended absolutely on exogenous IL 2 in three cases (ALL), in the three other cases (one ALL, two NHL) some colonies grew also when no IL 2 had been added to the cultures. Upon further analysis of the cells of one of the latter patients, it was found that the cells produced IL 2 and proliferated in response to this endogenous IL 2. The results from this study indicate that the requirements of endogenous v exogenous IL 2 for cell proliferation in T-ALL and T-NHL and IL 2 receptor activation by PHA and TPA vary from patient to patient. In addition, they support the notion that T-ALL and T-NHL cells have not lost dependence on IL 2 and IL 2 receptor activation for in vitro growth.

Adult↗
PubMed1986

Fucose binding lectin for characterizing acute myeloid leukemia progenitor cells.

The reactivity of acute myeloid leukemia cells (AML) was determined in 29 patients using the fucose binding lectin Ulex europaeus agglutinin (UEA) as surface marker. We show a marked heterogeneity in the UEA-binding abilities of the cells in these patients as determined by fluorescence analysis of the blasts labeled with the UEA coupled to the fluorescent molecule FITC. The results suggest a correlation between the capability of AML blast cells to bind UEA and cytologic maturation, because in 1 of 10 M1, 3 of 8 M2, 6 of 8 M4, and 1 of 3 M5 cytology types UEA binding to the leukemic cells was apparent. In 13 cases, the cells gave rise to colonies in vitro. The amount of UEA binding to AML colony-forming cells (AML-CFU) was determined by cell sorting and subsequent colony culture of UEA-negative, intermediately positive, and highly fluorescent cells. AML-CFU from none of the four patients with M1 cytology were UEA positive, whereas they showed intense reactivity with the lectin in 1 of 4 cases with M2 cytology and in all 4 cases of M4. In these five cases with strongly UEA positive AML-CFU, the fluorescence distribution of the colony formers differed from that of the total leukemia population, indicating that AML-CFU represent a subpopulation of AML cells with specific UEA-binding properties. Normal bone marrow myeloid and multipotential colony-forming cells (CFU-GM, CFU-GEMM) showed low or no binding of UEA. UEA-FITC appears a useful reagent for membrane analysis of AML-CFU. In certain cases, UEA-FITC labeling may be applied to discriminate AML-CFU from normal hematopoietic progenitors.

Colony-Forming Units Assay↗
PubMed1985

Common and pre-B acute lymphoblastic leukemia cells express interleukin 2 receptors, and interleukin 2 stimulates in vitro colony formation.

The role of interleukin 2 (IL 2) as a possible regulator of in vitro proliferation and differentiation of non-T acute lymphoblastic leukemia (ALL) cells was investigated. For this purpose, leukemic cells from the blood or bone marrow of eight untreated patients with common or pre-B ALL were analyzed using the anti-Tac monoclonal antibody (reactive with the IL 2 receptor) in indirect immunofluorescence. The receptors for IL 2, which were initially absent from the cell surface, were induced on high percentages of the ALL cells after the in vitro exposure to the lectin phytohemagglutinin or the phorbol ester 12-O-tetradecanoylphorbol-13-acetate in six patients, suggesting that the cells had become sensitive to IL 2. In colony cultures to which feeder leukocytes and IL 2 had been added, colony growth was obtained in five of eight cases. Whereas the cells from one patient formed colonies in the absence of exogenous stimuli, the cells from others were dependent on the addition of feeder leukocytes plus IL 2. In the latter cases, feeder leukocytes alone, releasing some IL 2, stimulated growth suboptimally at different cell concentrations. Their stimulative effect was significantly enhanced when leukocyte-derived IL 2 or pure recombinant IL 2 was supplemented. Alone, IL 2 (up to 500 U/mL) did not support colony formation. Apparently, IL 2 and feeder leukocytes are both required for the induction of colonies in these cases of ALL. From cell sorting of fluorescent anti-common ALL antigen (CALLA) stained cells it appeared that colonies descended from cells with high as well as low or negative CALLA expression. Immunophenotyping demonstrated the presence of the original leukemia markers on colony cells, but was not indicative of maturation of ALL toward more differentiated B cells. We suggest that IL 2 can stimulate the in vitro proliferation of certain neoplastic B lymphocyte progenitors.

Adolescent↗