Molecular profiling of CD34⁺ cells in idiopathic myelofibrosis identifies a set of disease-associated genes and reveals the clinical significance of Wilm's tumor gene (WT1)

¹ Department of Hematology, Azienda Ospedaliera-Universitaria Careggi, University of Florence, Florence, Italy
² Department of Biomedical Sciences, Biological Chemistry Section, University of Modena and Reggio Emilia, Modena, Italy
³ INSERM U602, University Paris 11, Institut André Lwoff, Villejuif Cedex, France
⁴ Unit of Clinical Epidemiology, IRCCS Policlinico S. Matteo, Pavia, Italy
⁵ Department of Hematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy; Department of Pathology, University of Illinois at Chicago, Chicago, Illinois

^* To whom correspondence should be addressed. E-mail: amvannucchi{at}unifi.it.

	Abstract

This study was aimed at the characterization of a gene expression signature of the pluripotent hematopoietic CD34⁺ stem cell in idiopathic myelofibrosis (IM) that would eventually provide novel pathogenetic insights and/or diagnostic/prognostic information. Aberrantly regulated genes were revealed by transcriptome comparative microarray analysis of normal and IM CD34⁺ cells; selected genes were assayed also in granulocytes. Two-hundred eighteen differentially expressed genes were identified and in part validated by quantitative PCR. Altered gene expression was corroborated by the detection of abnormally high CD9 or CD164, and low CXCR4, membrane protein expression in IM CD34⁺ cells. According to class prediction analysis, a set of eight genes (CD9, GAS2, DLK1, CDH1, WT1, NFE2, HMGA2, CXCR4) properly recognized IM from normal CD34⁺ cells. These genes were aberrantly regulated also in IM granulocytes, that could be reliably differentiated from control, polycythemia vera and essential thrombocythemia granulocytes in 100% and 81% of cases, respectively. Abnormal expression of HMGA2 and CXCR4 in IM granulocytes was dependent on the presence and the mutational status of JAK2^V617F mutation. The expression levels of both CD9 and DLK1 were associated to the platelet count, while higher WT1 expression levels identified IM patients with more active disease, as revealed by elevated CD34⁺ cell count and higher severity score. In conclusion, molecular profiling of IM CD34⁺ cells uncovered a limited number of genes with altered expression that, beyond their putative role in disease pathogenesis, are associated with patients' clinical characteristics and may have potential prognostic application.

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