Biomedical subjects

J Birkmann

Publications and source records attributed to J Birkmann.

21 records · Page 2Linked to original sources

PubMedDate not supplied

Sequential versus alternating chemotherapy for high grade non-Hodgkin's lymphomas: a randomized multicentre trial.

In a multicentre phase III trial 146 previously untreated patients with high grade non-Hodgkin's lymphomas stage II-IV were randomized to receive either four cycles of CHOEP (cyclophosphamide 750 mg/m2 iv d 1, doxorubicin 50 mg/m2 iv d 1, vincristine 2 mg iv d 1, etoposide 100 mg/m2 iv d 3-5, prednisolone 100 mg po d 1-5) (treatment arm A), or four cycles of chemotherapy with hCHOP (cyclophosphamide 1200 mg/m2 iv d 1, doxorubicin 40 mg/m2 iv d 1 + 2, vincristine 2 mg iv d 1, prednisolone 100 mg po d 1-5) alternating with IVEP (ifosfamide 1500 mg/m2 iv d 1-5, vindesine 3 mg/m2 iv d 1, etoposide 120 mg/m2 iv d 3-5, prednisolone 100 mg po d 1-5) (treatment arm B). After four cycles of chemotherapy an involved field irradiation with a total dose of 35 Gy was given to all patients in complete or partial remission without persisting extranodal disease. A complete response (CR) was seen in 124/146 patients (86 per cent) with 87 per cent CR in arm A versus 83 per cent CR in arm B. During a median follow-up of 17 months (range 2-40) 30 patients relapsed (16 patients arm A, 14 patients arm B). The overall survival at 40 months is projected to be 71 per cent versus 70 per cent for arm A and B, respectively. Disease-free survival is projected to be 68 per cent in arm A and 59 per cent in arm B at 40 months. So far, the differences in CR, survival and disease-free survival are not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMedDate not supplied

Granulocyte-macrophage colony-stimulating factor (GM-CSF) reduces the density of stem cell factor receptors (c-kit oncogene product) on a GM-CSF-dependent human myeloid cell line.

By employing a monoclonal antibody against the stem cell factor receptor (SCF-R), c-kit oncogene product, we analysed in flow cytometric technique the density of SCF-R on GM/SO cells which were incubated under various culture conditions. These experiments revealed that there is an inverse correlation between the SCF-R density on the cells and the doses of granulocyte-macrophage colony-stimulating factor (GM-CSF) in culture medium; the lower the dose, the higher the density of SCF-R on the cells. More detailed analyses showed that, in contrast to SCF which rapidly downregulates its own receptor, GM-CSF does not alter the measurable level of SCF-R in an exposition period of 60 minutes, which suggests that the internalization or shedding of the receptor is not the mechanism of action. Since the most striking difference regarding density of SCF-R between GM-CSF-treated and untreated cells was observed on day 2, the modulation of c-kit oncogene protein by GM-CSF likely occur prior to expression of protein onto the cell surface. In order to exclude the possibility that altered cell viability due to insufficient GM-CSF content in culture medium might be responsible for the increased SCF-R densities on GM-CSF-dependent cells, we subsequently generated a GM-CSF-independent subclone which still responded to GM-CSF as well as the dependent did. The experiments carried out with this subclone confirmed the results presented above. Thus our data suggest that GM-CSF is directly involved in the regulation of SCF receptor density on GM/SO cells.

Antibodies, Monoclonal↗

PubMedDate not supplied

Regulation of the density of the stem cell factor receptor (c-kit) by tumor necrosis factor alpha on a human myeloid cell line.

The GM/SO cell line bears a high level of stem cell factor receptors (SCF-R) i.e. c-kit protein, and therefore constitutes a potential model for studying the regulation of this crucial receptor on myeloid cells. In this study we evaluated the effect of tumor necrosis factor alpha (TNF-alpha) on the expression of SCF-R by flow cytometry. In contrast to 1 hour of preincubation, the experiments carried out after 24 hours preincubation revealed that TNF-alpha, if added alone, reduced the density of SCF-R on GM/SO cells in a dose-dependent manner. However, if combined with GM-CSF, which per se downregulates the SCF-R on these cells as well, TNF-alpha antagonized the effect of GM-CSF and slightly increased the density of SCF-R. Yet the cells incubated for 24 hours in medium without cytokines invariably expressed a higher level of SCF-R than the cells incubated in the presence of TNF-alpha and GM-CSF, either alone or in combination. In contrast to these cytokines, stem cell factor (SCF), which was also tested simultaneously in all experiments, downregulated its own natural receptor on these cells also after a preincubation of 1 hour. Furthermore, prolonged exposure of GM/SO cells to TNF-alpha for 5-7 days yielded a monocyte-macrophage-like morphology of some cells as these cells displayed an apparent glass and plastic adherence. In contrast, no such morphological changes could be observed in the presence of GM-CSF or SCF.

Cell Differentiation↗