title: Distinct signal transduction abnormalities and erythropoietin response in bone marrow hematopoietic cell subpopulations of myelodysplastic syndrome patients.
abstract: OBJECTIVE
  Myelodysplastic syndromes (MDS) are heterogeneous clonal diseases characterized by cytopenias as a result of ineffective hematopoiesis. Little is known about alterations in signal transduction pathways in MDS.
  
  
  METHODS
  Multiparameter flow cytometry was used to evaluate the proteolytic activation of caspase-3 and the phosphorylation of extracellular signal-regulated kinase (ERK)1/2, p38 mitogen-activated protein kinase (MAPK), and STAT5 specifically in defined CD34(+), CD45(+), or CD71(+)CD45(-) bone marrow (BM) cells from 60 MDS cases and normal controls, both at baseline and following stimulation with granulocyte colony-stimulating factor (G-CSF) and erythropoietin.
  
  
  RESULTS
  In CD71(+)CD45(-) cells from a subpopulation of 36 MDS cases who were predicted to be responsive by clinical parameters (endogenous erythropoietin levels, transfusion dependency, percentage of blasts in the BM), erythropoietin failed to activate ERK1/2 or STAT5 in 23 of 36 cases, but it was effective in 13 of 36 cases, although to a significantly lower degree than in CD71(+)CD45(-) cells from healthy donor BM. The erythropoietin response in vivo correlated with in vitro erythropoietin-dependent STAT5 activation in 20 of 22 cases. STAT5 was significantly activated at baseline in MDS cells compared with normal controls, whereas caspase-3 was activated in CD34(+) and CD45(+) MDS cells, and was activated more often in the RA and RAEB-1 MDS subtypes. G-CSF stimulation activated ERK1/2 and STAT5 equally in MDS and normal CD34(+) cells.
  
  
  CONCLUSIONS
  Abnormalities in the response to growth factors are restricted to erythropoietin stimulation in CD71(+)CD45(-) cells and correlate with the clinical response to erythropoietin. Activation of baseline signal transduction for proliferative and apoptotic signals is altered in MDS but with different patterns among the various BM subpopulations.
authors.affiliation: FU Hematology and Department of Laboratory Medicine, Azienda Ospedaliero Universitaria (AOU) Careggi, University of Florence, Florence, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Spinelli
authors.forename: Roberto
authors.initials: R
authors.lastname: Caporale
authors.forename: Francesca
authors.initials: F
authors.lastname: Buchi
authors.forename: Erico
authors.initials: E
authors.lastname: Masala
authors.forename: Antonella
authors.initials: A
authors.lastname: Gozzini
authors.forename: Alessandro
authors.initials: A
authors.lastname: Sanna
authors.forename: Francesca
authors.initials: F
authors.lastname: Sassolini
authors.forename: Ana
authors.initials: A
authors.lastname: Valencia
authors.forename: Alberto
authors.initials: A
authors.lastname: Bosi
authors.forename: Valeria
authors.initials: V
authors.lastname: Santini
mesh_terms: D000368:Aged; D017209:Apoptosis; D001854:Bone Marrow Cells / Q000378:metabolism*; D049109:Cell Proliferation; D004921:Erythropoietin / Q000494:pharmacology*; D005260:Female; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D006801:Humans; D008297:Male; D009190:Myelodysplastic Syndromes / Q000378:metabolism*
chemical_list: D004921:Erythropoietin