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Gene expression profile in myeloproliferative neoplasms

ABSTRACT: Myeloproliferative neoplasms (MPN) are clonal hematopoietic diseases that include essential thrombocytosis (ET), polycythemia vera (PV) and primary myelofibrosis (PMF) as well as BCR-ABL+ chronic myelogenous leukemia (CML). In the past several years, studies with cDNA microarrays have defined patterns of gene expression corresponding to specific molecular abnormalities, oncologic phenotypes, and clinical outcomes in hematologic malignancies. This study was aimed at the description of a gene expression signature in MPN which would eventually present a new pathogenetic approaching and also diagnostic as well as prognostic information. Using cDNA microarray analysis, involving 25,100 unique genes, we studied the gene expression profile of the pluripotent hematopoietic CD34+ stem cells and mature granulocytes obtained from peripheral blood of ET, PV, PMF and CML patients compared with healthy individuals. The average number of CD34+ cells (cells/µl) in peripheral blood was approximately 6 in PV and ET, 111 in PMF and 2880 in CML as measured by flow cytometry. A somatic point mutation JAK2V617F was detected in 93% of PV, 73% of PMF and 55% of ET patients within genetically homogenous population. The homozigosity for JAK2V617F mutation was the highest in PV (60%), less prominent in PMF (42%) and low in ET (11%) patients. The JAK2V617F mutation negative patients were also negative for exon 12 mutations. Approximately 420, 680 and 1130 genes had unique expression among CD34+ cells of ET, PV and PMF patients, respectively. In addition comparing to healthy controls, ET, PV, PMF and CML patients showed difference in 840, 1180, 1160 and 2050 expressed genes, respectively. Furthermore, we studied EPO and JAK-STAT signaling pathways related genes expression in MPN. The FOS, RAF1 and JAK2 gene expression, related to EPO signaling pathway, was elevated in ET, PV, PMF and reduced in CML comparing to healthy controls. Related to these genes, the JAK2V617F mutation homozygous and heterozygous patients generally displayed more significant differences comparing to patients with no mutation. STAT5 gene expression was decreased in all MPN patients. CSF3R, STAT1 and STAT3 gene expression, related to JAK-STAT signaling pathway, was elevated in ET, PV, PMF and reduced in CML comparing to healthy controls. CREBBP gene expression was reduced in CD34+ cells of ET, PV and PMF patients, but during maturation it enhanced expression in granulocytes. In conclusion, molecular profiling of CD34+ cells and granulocytes revealed a certain number of genes with changed expression that, beyond their recognized function in disease pathogenesis, can be related to patients’ clinical characteristics and may have an imminent prognostic relevance.

ORGANISM(S): Homo sapiens

PROVIDER: GSE55976 | GEO | 2015/03/14

SECONDARY ACCESSION(S): PRJNA241491

REPOSITORIES: GEO

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Project description:Even though mutations in epigenetic regulators frequently occur in myeloproliferative neoplasms, their effects on the epigenome have not been well studied. Furthermore, even though primary myelofibrosis (PMF) has a markedly worse prognosis compared to essential thrombocytosis (ET) or polycythemia vera (PV), the molecular distinctions between these subgroups are not well elucidated. We performed the HELP (HpaII tiny fragment enriched by LM-PCR) assay to study genome-wide methylation in PV, ET and PMF samples compared with healthy controls. We determined that PV and ET are characterized by aberrant promoter hypermethylation while PMF is an epigenetically distinct subgroup characterized by both aberrant hyper and hypomethylation. Aberrant hypomethylation in PMF was seen to occur in non CpG island loci, demonstrating further qualitative differences between the disease subgroups. The differentially methylated genes in PV and ET were involved predominantly in cell signaling pathways and were enriched for binding sites of GATA1 and other transcription factors. In contrast, aberrantly methylated genes in PMF were involved in inflammatory pathways and were enriched for NF1 (NFI), LEF1 and other transcription factors. Within the PMF subgroup, cases with ASXL1 disruptions formed an epigenetically distinct subgroup with relatively increased methylation. Cases of MPNs with TET2 mutations demonstrated decreased levels of hydroxymethylation and distinct set of hypermethylated genes. In contrast, the JAK2V617F mutation did not drive epigenetic clustering within MPNs. Finally, the significance of aberrant methylation was demonstrated by sensitivity of MPN derived cell lines to decitabine. These results demonstrate epigenetic differences between PMF and PV/ET and reveal methylomic signatures of ASXL1 and TET2 mutations. The study population consisted of 26 MPN patients (6 cases of ET, 8 cases of PV and 12 cases of PMF) and 3 healthy controls. Individual HpaII restriction digest profiles were compared to an internal MspI digest control, to yield differentially methylated fragments for every sample. The purpose of this study was to assess genome wide patterns of DNA methylation across the MPN stratified by disease class.

Project description:Primary mielofibrosis (PMF) is a rare chronic myeloproliferative disorder characterized by the accumulation of abnormal megakaryocytes (Mks) in the bone marrow (BM), variable degrees of BM fibrosis, osteosclerosis and angiogenesis, immature myeloid and erythroid cells, and tear-drop erythrocytes in the peripheral blood (PB), and extramedullary hematopoiesis. The identification of the JAK2V617F mutation represented a seminal discovery in the field of Philadelphia-chromosome–negative chronic myeloproliferative neoplasms (MPNs), providing clues to the pathogenesis, prompting a revision of the diagnostic criteria, and culminating in the development of clinical trials with JAK2 (and JAK1) inhibitors. The JAK2V617F mutation occurs in almost all patients with polycythemia vera (PV) and in 50%-70% of those with essential thrombocythemia (ET) and primary myelofibrosis (PMF). Soon after the identification of the JAK2V617F mutation, mutations in JAK2 exon 12 were described in rare patients with JAK2V617F-negative PV and mutations in MPL were reported in 5%-10% of ET or PMF subjects. The complexity of the molecular pathogenesis of MPNs is reinforced by discovery of additional mutations in TET2, ASXL1, CBL, IDH1/IDH2, EZH2 and IKZF1. These mutations are detected in a minority of patients at different phases of the disorder, including leukemic transformation, and are variably associated each other and with JAK2 or MPL mutations. In order to better characterize biological differences between mutated and wild-type PMF cell populations we performed a gene expression profiling on 9 samples carrying at least one mutation in ASXL1, SRSF2 or EZH2 genes and 11 wild-type samples using the Affymetrix GeneChip technology. After data preprocessing and filtering a supervised analysis approach was used to define a gene expression signature for mutated samples. PMF samples carrying at least one mutation in ASXL1, SRSF2 or EZH2 genes exhibit a specific molecular signature as compared with WT samples. Gene expression profile (GEP) of CD34+ cells from 20 PMF patients (1 replicate for each sample). In particular, GEP was performed on 9 samples carrying at least one mutation in ASXL1, SRSF2 or EZH2 genes and 11 wild-type samples.

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Gene expression profile in myeloproliferative neoplasms

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