LY2109761 is a novel transforming growth factor

by Selleckchem | Jan 04 2013

The JAK2V617F mutated allele is present in virtually all patients with polycythemia vera (PV) and in about 60% of those with essential thrombocythemia (ET) and primary myelofibrosis (PMF), which are the other two main clinical entities included within the group of myeloproliferative LY2109761 neoplasms.1 The presence of the mutation, and/or the burden of JAK2V617F allele, have been found to correlate with defined laboratory abnormalities and clinical features in the different myeloproliferative neoplasms.2 In most of the studies performed in PV patients an allele burden greater than 50% was found to correlate with leukocytosis and higher hemoglobin level, lower platelet count, presence and degree of splenomegaly, occurrence of aquagenic pruritus and higher rate of transformation to myelofibrosis.2 JAK2V617F is a constitutively phosphorylated tyrosine kinase whose expression in cytokine-dependent cell lines confers cytokine independence and cytokine BX-795 hypersensitivity through the constitutive activation of STAT5, Akt and ERK-dependent pathways.3,4 The adoptive transfer of marrow cells transduced with a retrovirus expressing JAK2V617F in irradiated recipient mice invariably resulted in the development of erythrocytosis, 5-9 sometimes accompanied by leukocytosis, splenomegaly and later changes suggestive of myelofibrotic transformation.

6-9 The presence and burden of JAK2V617F correlated with endogenous erythroid colony formation in PV patients10,11 CEP-18770 and the expression of mutated Jak2 in mice induced erythropoietin-independent growth in vitro.7,9 Modification in the design of gene expression in murine models also resulted in an ET-like phenotype,12,13 indicating overall, that the JAK2V617F mutation is an integral component of the myeloproliferative process that underlies the different myeloproliferative neoplasms. A unique gene expression profile has been associated with the presence and/or the burden of the V617F allele in neutrophils; among the genes involved, some were associated with neutrophil activation, such as PRV114,17 and the gene encoding for leukocyte alkaline phosphatase. 18 The constitutively activated status of circulating neutrophils associated with the mutated JAK2, together with enhanced activation of platelets and their hyper-responsiveness to CH5424802 agonists,19,20 may contribute to the thrombotic tendency found in patients with PV.

21 However, there is a current lack of information concerning the functional relevance of the JAK2V617F mutation in other leukocyte subtypes, such as eosinophils and basophils. In this study, we investigated the features of basophils in patients with PV, other myeloproliferative neoplasms and in control subjects. Design and Methods Patients This study involved a total of 78 patients with PV whose diagnosis satisfied the WHO criteria;22 for comparison, we also included 70 patients with ET and 22 with PMF (all diagnosed according to the WHO criteria), and seven subjects with reactive forms of hypoxic erythrocytosis. Most of the patients with PV were being treated with phlebotomy, but none was receving chemotherapy, at the time of blood sampling. Thirtyfour healthy volunteers were included as controls. The study was approved by the local Ethical Committee and informed consent was obtained from all subjects included in the study. Flow cytometry analysis of activated basophils Circulating CD63+/CD123+/HLA-DR? basophils were enumerated using 100 ?L of heparin-anticoagulated peripheral blood, promptly put on ice after sampling; antibodies were obtained from Becton Dickinson (San Jose, CA, USA).

At least 200,000 events were acquired on a FACScan flow cytometer; results are expressed both as the percentage of gated basophils expressing CD63 and as the absolute number of CD63+ basophils by normalizing to total basophil count. CD63 expression level was calculated as the ratio of geometric mean fluorescence intensity (MFI) with isotype BX-912 control antibody. Purification of basophils and granulocytes Basophils were purified from peripheral blood using a negative-depletion immunomagnetic procedure (Miltenyi Biotech; Gladbach, Germany). The purity of the isolated basophil preparations was checked by flow cytometry after labeling with phycoerythrin (PE)- CD123/peridin chlorophyll (PerCP)-HLA-DR monoclonal antibodies (Becton-Dickinson); the median purity was 81% (range, 75 to 86%). Neutrophils were obtained by centrifugation of peripheral blood on a Ficoll density gradient; by visual inspection of cytosmears, neutrophils accounted for 95-97% of the cells while basophils were virtually absent from these cell suspensions.