335 NEOPLASMA 56, 4, 2009 Differential gene expression of bone marrow CD34+ cells in early and advanced myelodysplastic syndrome A. VASIKOVA 1 , E. BUDINSKA 3 , M. BELICKOVA 1 , J. CERMAK 2 , H. BRUCHOVA 1* 1 Institute of Hematology and Blood Transfusion, Department of Molecular Genetics, U Nemocnice 1, 128 20 Prague 2, Czech Republic, e-mail: hana.bruchova@uhkt.cz; 2 Institute of Hematology and Blood Transfusion, Inpatient Department, U Nemocnice 1, 128 20 Prague 2, Czech Re- public; 3 Institute of Biostatistics and Analyses, Masaryk University, Kamenice 3, 625 00 Brno-Bohunice, Czech Republic Received October 1, 2008 Myelodysplastic syndrome (MDS) is a hematopoietic stem cell disorder characterized by ineffective hematopoiesis and dysplasia in one or more blood cell lines. Because it ofen progress to poor outcome stages or acute leukemia we searched for candidate genes associated with disease progression. Using microarrays we performed gene expression profiling in CD34+ cells of 4 early and 4 advanced MDS patients and identified 286 significantly differentially expressed genes between these two categories. Out of these, 136 genes were up-regulated and 150 down-regulated in early MDS compared to advanced MDS. Using clustering analysis those two patient categories were clearly differentiated. Further, we selected three genes (ADAM8, BIRC5, MPL) for gene expression validation by qRT-PCR in an additional set of 29 MDS and sAML patients. We confirmed decreasing trend for BIRC5 expression from early to advanced stages of MDS, with the lowest levels in sAML patients. On the contrary, higher ADAM8 and MPL expression was observed in most advanced MDS patients compared to the early MDS patients. Association between gene expression levels and bone marrow blast proportion was tested, but only BIRC5 expres- sion showed negative correlation (r=-0.83 at p<0.001). Tis study demonstrates stage-specific expression of some genes that may have potential prognostic significance. Key words: gene expression profiling, myelodysplastic syndrome, CD34+ cells * Corresponding author Myelodysplastic syndrome (MDS) is a clonal stem-cell disorder characterized by ineffective hematopoiesis, dysplasia of at least one blood cell lineage, peripheral cytopenia and increased potential progress to acute myeloid leukemia (AML) [1, 2, 3]. Etiology of MDS is still unclear; however, several environmental risk factors are known (smoking, benzene, pesticides, toluene, cytotoxic agents or ionizing radiation) [4, 5, 6]. Multistep pathogenesis involves several subsequent processes including development and expansion of mutant clone of a hematopoietic progenitor cell, and transformation into AML in 1/3 of MDS cases. Two classification systems for MDS have been adopted: the classification according to the French-American-British (FAB) Cooperation Group of 1982 [1] that was recently modified by the World Health Organization (WHO) [7]. Early stages of MDS – refractory anemia (RA), refractory cytopenia with multilineage dysplasia (RCMD) and also the subtypes with the presence of ring sideroblasts (RARS, RCMD-RS) are character- ized by better overall survival (~59 months) and lower risk of leukemic development (21%) [8]. In this initial phase, excessive apoptosis in marrow hematopoietic cells leads to ineffective hematopoiesis and peripheral cytopenia in spite of increased proliferation of hematopoietic elements [9]. Advanced MDS subtypes, refractory anemia with excess of blasts (RAEB-1 and 2), are associated with higher probability of leukemic transformation (>50%) and shorter survival of patients (~16 months) [8]. Subtype stratification in MDS is crucial for fur- ther treatment management and prognosis. Microarray assays revealed that the MDS subtypes are considerably different at the molecular level and thus gene expression profiling may contribute to diagnosis and/or prognosis specification. Moreover, MDS represents a useful in vivo model of malignant clone development due to frequent leukemic transformation. Comparison of patients with MDS and sAML resulted in definition of several parameters, which correlated with risk of leukemic transformation: age under 40 years, pancytopenia in 3 lineages, >15% bone marrow (BM) blasts, ≥2 abnormal karyotypes and treatment with combined doi:10.4149/neo_2009_04_335