Unregulated activation of STAT-5, ERK1/2 and c-Fos may contribute to the phenotypic transformation from myelodysplastic syndrome to acute leukaemia.
Myelodysplastic syndrome (MDS) is characterised by ineffective erythropoiesis and poor progenitor response to erythropoietin (Epo). The aim of this study was to determine the role of the Epo-R mediated signalling in the rise of MDS and whether alteration of signalling pathways contribute to the leukeamogenesis from MDS to acute leukaemia. We analysed Epo and GM-CSF induced ERK1/2 activation, c-Fos expression, STAT-5 and AP-1 DNA binding activities in mononuclear cells of umbilical cord blood (UCBMNC), normal marrow (NBMMNC) or marrow with MDS, AML with prior MDS and de novo AML. In UCBMNC and NBMMNC, Epo and GM-CSF induced the activation of STAT-5 DNA binding and ERK 1/2 activation (n = 6). In contrast, in MDS RA, both signalling pathways were activated only by GM-CSF but not by Epo (n = 7). In acute leukaemia, elevated basal activity of STAT-5 DNA binding appeared in 8/8 cases, which was independent of Epo or GM-CSF treatment. In normal and MDS samples, c-Fos and Egr-1 proteins were not detectable and the expression levels were not increased by Epo or GM-CSF treatment. In contrast, we found an elevated level of c-Fos expression in 5/8 acute leukemia cases, which was not further increased in the presence of Epo or GM-CSF. The elevated c-Fos expression was accompanied by an extremely high blast number in 5/5 cases. These results suggest that impaired ERK/MAPK activation, similarly to impaired STAT-5 activation in Epo-R signalling, may be responsible for the apoptotic process and the block of maturation in MDS RA. The results also suggest that the appearance of the constitutively activated STAT-5 DNA binding and c-Fos expression may be used as a predictor of the blastic transformation.
Kolonics
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Department of Cell Metabolism, National Institute of Haematology and Immunology, Budapest, Hungary.
Apáti
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A
Nahajevszky
S
S
Gáti
R
R
Brózik
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Magócsi
M
M
D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000368:Aged; D001854:Bone Marrow Cells / Q000473:pathology; D016022:Case-Control Studies; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects* / Q000502:physiology; D004921:Erythropoietin / Q000494:pharmacology; D005260:Female; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006801:Humans; D007938:Leukemia / Q000201:enzymology / Q000209:etiology* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D008894:Milk Proteins; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009190:Myelodysplastic Syndromes / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D010641:Phenotype; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D050799:STAT5 Transcription Factor; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D015534:Trans-Activators / Q000378:metabolism
D004268:DNA-Binding Proteins; D008894:Milk Proteins; D016760:Proto-Oncogene Proteins c-fos; D050799:STAT5 Transcription Factor; D015534:Trans-Activators; D004921:Erythropoietin; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases