Microarray and Proteomic Analysis of Myeloproliferative Neoplasms,

Abstract 3856

The gene and protein expression profiles in myeloproliferative neoplasms (MPN) may reveal gene markers of a potential clinical function in diagnosis and prediction of response to therapy. Using cDNA microarray analysis, involving 25,100 unique genes, we studied the gene expression profile of hematopoietic CD34⁺ progenitor cells and granulocytes obtained from peripheral blood of patients with essential thrombocythemia (ET), polycythemia vera (PV) and primary myelofibrosis (PMF) compared with healthy individuals. The microarray analyses of the hematopoietic progenitor cells and granulocytes have been performed on 9 patients with ET, 8 patients with PV, 4 patients with PMF and 8 healthy donors. The granulocytes for proteomic studies have been pooled in 4 groups: PV with JAK2 mutant allele burden above 80%, ET with JAK2 mutation, PMF with JAK2 mutation and ET/PMF with no JAK2 mutation. We focused our analysis to hematopoiesis related genes. In the collected patient samples, the increased number of granulocytes allowed for further validation by protein analysis of microarray gene expression suggested from less differentiated hematopoietic progenitor cells. Folate receptor 3 (FOLR3), constitutively secreted in hematopoietic tissues, has increased protein levels in granulocytes of JAK2V617F homozygous PV as well as mRNA levels in hematopoietic progenitor cells of patients with PV. The enzyme matrix metallopeptidase 9 (MMP9), involved in IL-8-induced mobilization of hematopoietic progenitor cells from bone marrow, also has significantly increased protein levels in granulocytes of PV patients with increased JAK2 mutation allele burden. In addition, Ras-related C3 botulinum toxin substrate 2 (RAC2) protein level, essential for erythropoiesis, is increased specifically in PV granulocytes with JAK2V617F homozygosity. Moreover, RAC2 gene expression is significantly increased in hematopoietic progenitor cells of PV, with no changes in its granulocytes. Although, like PV, RAC2 gene expression was also increased in ET and PMF hematopoietic progenitor cells compared to healthy individuals, in granulocytes of ET and PMF patients with JAK2 mutation RAC2 protein levels were decreased, contrary to the elevated level in PV. Furthermore, inconsistent with JAK2V617F homozygous PV patients, granulocytes of ET and PMF with the JAK2 mutation exhibit FOLR3 protein at levels lower than the ET and PMF with no JAK2 mutation. Investigating the extent to which these genes participate in the complex molecular and cellular mechanisms of MPN will likely lead to new insights of malignancy development. In conclusion, molecular profiling of hematopoietic progenitor cells and granulocytes of MPN patients revealed gene expression patterns that are beyond their recognized function in disease pathogenesis and can be related to patients' clinical characteristics with imminent prognostic relevance.