Dysregulated Myelomonocytic Signaling in Response to Colony Stimulating Factor Is Common in Myelodysplastic Syndrome
Juehua Gao, Suchitra Swaminathan, Yi-Hua Chen, LoAnn Peterson, Charles Goolsby. Northwestern University Feinberg School of Medicine, Chicago, IL
Background: Myelodysplastic syndromes (MDS) are clonal disorders characterized by peripheral cytopenias, dysplasia and ineffective hematopoiesis. Genetic alterations are often observed in MDS, but many cases lack an easily detectable abnormality. Little is known about the signaling pathways in hematopoietic subpopulations in MDS.
Design: Multiparameter flow cytometric analysis was performed on bone marrow (BM) aspirates obtained from MDS, non-clonal cytopenias and negative lymphoma staging BM. The phosphorylation of signal-regulated kinases Erk (p-Erk) and Stat5 (p-Stat5) were measured at baseline and after stimulation with 4 cytokine/growth factors important in myeloid maturation: stem cell factor (SCF), Flt3 ligand, GM-CSF and G-CSF. The fraction of responding cells and the median fluorescent intensity at peak response were recorded for distinct subpopulations of the myeloid lineages based on surface immunophenotype. This was compared with our published data from a cohort of normal BM (Malvin et al, Blood 2011).
Results: BM cells were obtained from 9 newly diagnosed MDS or MDS/MPN, 2 AML transformed from MDS, 6 non-clonal cytopenias, and 5 lymphoma staging BM. Cytogenetic analysis on the MDS cases showed normal karyotype (3/9), +8 (2/9), del(Yq) (1/9), complex karyotype (1/9), -13q (1/9) and t(11;22) (1/9). Abnormal phosphoprotein expression was not observed in any of the cytopenias and 4/5 staging BM; 1 staging BM lacked response to GM-CSF stimulation in granulocytes. In contrast, mature granulocytes or monocytes from all 9 MDS cases showed abnormal pErk (7/9) and/or pStat5 (4/9) responses after G-CSF or GM-CSF stimulation that fall into 3 categories: lack of response (6/9), increased response (3/9) and constitutive activation (1/9). CD34+CD117+ or CD34-CD117+ progenitor cells from MDS cases did not show significant signaling difference compared to normal counterpart in response to SCF and Flt3 stimuli. Progenitor cells in 1 AML showed lack of response to GM-CSF.
Conclusions: Abnormal signaling response to G-CSF and GM-CSF in mature granulocytes and monocytes is common in MDS but rare in cytopenias or lymphoma staging BM. Interestingly, although MDS is a clonal stem cell disorder, the progenitor cells do not demonstrate significant signaling abnormalities for stimuli and endpoints analyzed. The abnormal myelomonocytic signaling pattern may help in distinguishing MDS from non-clonal cytopenias.
Tuesday, March 5, 2013 9:30 AM
Poster Session III # 172, Tuesday Morning