Human CD34+ cells are capable of generating normal and JAK2V617F positive endothelial like cells in vivo.

Endothelial like cells (ELCs) are thought to originate from either a hierarchy of endothelial progenitor cells (EPC), monocytes or monocyte derived multipotent progenitor cells (MOMCs). In this report, the ability of CD34(+) cells to generate ELC in vivo was examined using an immunodeficient mouse transplant assay system. The Philadelphia chromosome negative (Ph(-)) myeloproliferative neoplasms (MPN) are associated with the acquired mutation, JAK2V617F.

Correction of the abnormal trafficking of primary myelofibrosis CD34+ cells by treatment with chromatin-modifying agents.

The abnormal trafficking of CD34+ cells is a unique characteristic of primary myelofibrosis (PMF). We have further studied the behavior of PMF CD34+ cells by examining their homing to the marrow and the spleens of nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. Following the infusion of PMF and normal granulocyte colony-stimulating factor-mobilized peripheral blood (mPB) CD34+ cells into NOD/SCID mice, reduced numbers of PMF CD34+ cells and granulocyte-macrophage colony-forming unit (CFU-GM) compared with mPB were detected in the marrow of these mice, whereas similar numbers of PMF and mPB CD34+ cells and CFU-GM homed to their spleens.

Pivotal role of mast cells in pruritogenesis in patients with myeloproliferative disorders.

Pruritus is a common symptom in patients with Philadelphia chromosome-negative myeloproliferative disorders (MPDs). The pathophysiology of MPD-associated pruritus is unclear. We have demonstrated that MPD mast cells (MCs) are involved by the malignant process.

MNX1-ETV6 fusion gene in an acute megakaryoblastic leukemia and expression of the MNX1 gene in leukemia and normal B cell lines.

Patients with infant acute myeloid leukemia (AML) who carry a t(7;12)(q36;p13) translocation have been reported to have a poor clinical outcome. MNX1-ETV6 fusion transcripts (previously HLXB9-ETV6) were rarely detected in AML patients having t(7;12)(q36;p13). A 23-month-old girl with acute megakaryoblastic leukemia (AMKL) exhibited chromosome abnormalities, including add(7)(q22), and del(12)(p12p13).

Circulating angiogenic monocyte progenitor cells are reduced in JAK2V617F high allele burden myeloproliferative disorders.

The clinical course of patients with Philadelphia chromosome negative myeloproliferative disorder is frequently complicated by thrombotic events. Post-natal vasculogenesis has been proposed to play a critical role in angiogenesis by acting through a hierarchy of endothelial progenitor cells. Some endothelial progenitor cells have been shown to share a number of features associated with monocytes while other more primitive progenitor cells produce endothelial cells in vitro exclusively.

Behavior of CD34+ cells isolated from patients with polycythemia vera in NOD/SCID mice.

Objective: We investigated if polycythemia vera (PV) peripheral blood (PB) CD34+ cells contain cells capable of engrafting nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice and if the JAK2V617F mutational burden of these cells alters their behavior in NOD/SCID mice.

Materials And Methods: CD34+ cells isolated from patients with PV, idiopathic myelofibrosis (IM), or granulocyte colony-stimulating factor-mobilized normal donors were transplanted into sublethally irradiated NOD/SCID mice. Cells engrafted into the NOD/SCID mice were analyzed flow cytometrically using lineage-specific antibodies.

Effects of chromatin-modifying agents on CD34+ cells from patients with idiopathic myelofibrosis.

Idiopathic myelofibrosis (IM) is likely the consequence of both the acquisition of genetic mutations and epigenetic changes that silence critical genes that control cell proliferation, differentiation, and apoptosis. We have explored the effects of the sequential treatment with the DNA methyltransferase inhibitor, decitabine [5-aza-2'-deoxycytidine (5azaD)], followed by the histone deacetylase inhibitor, trichostatin A (TSA), on the behavior of IM CD34(+) cells. Unlike normal CD34(+) cells where 5azaD/TSA treatment leads to the expansion of CD34(+) cells and marrow-repopulating cells, treatment of IM CD34(+) cells results in a reduction of the number of total cells, CD34(+) cells, and assayable hematopoietic progenitor cells (HPC).

Pivotal contributions of megakaryocytes to the biology of idiopathic myelofibrosis.

In order to investigate the biologic processes underlying and resulting from the megakaryocytic hyperplasia that characterizes idiopathic myelofibrosis (IMF), peripheral blood CD34+ cells isolated from patients with IMF, polycythemia vera (PV), and G-CSF-mobilized healthy volunteers were cultured in the presence of stem cell factor and thrombopoietin. IMF CD34+ cells generated 24-fold greater numbers of megakaryocytes (MKs) than normal CD34+ cells. IMF MKs were also shown to have a delayed pattern of apoptosis and to overexpress the antiapoptotic protein bcl-xL.

Erlotinib effectively inhibits JAK2V617F activity and polycythemia vera cell growth.

JAK2(V617F), a mutant of tyrosine kinase JAK2, is found in most patients with polycythemia vera (PV) and a substantial proportion of patients with idiopathic myelofibrosis or essential thrombocythemia. The JAK2 mutant displays a much increased kinase activity and generates a PV-like phenotype in mouse bone marrow transplant models. This study shows that the anti-cancer drug erlotinib (Tarceva) is a potent inhibitor of JAK2(V617F) activity.

Treatment with candesartan combined with angiotensin-converting enzyme inhibitor for immunosuppressive treatment-resistant nephrotic syndrome after allogeneic stem cell transplantation.

Most cases of nephrotic syndrome following stem cell transplantation (SCT) occur 6 months after SCT. The patients are treated with immunosuppressive therapies; however, in some cases treatment is not effective. We used enalapril, an angiotensin-converting enzyme inhibitor (ACEI) and candesartan, an angiotensin II receptor blocker (ARB), for the control of proteinuria in a case of immunosuppressive treatment (IST)-resistant nephrotic syndrome.

Involvement of various hematopoietic-cell lineages by the JAK2V617F mutation in polycythemia vera.

The JAK2(V617F) mutation has been shown to occur in the overwhelming majority of patients with polycythemia vera (PV). To study the role of the mutation in the excessive production of differentiated hematopoietic cells in PV, CD19+, CD3+, CD34+, CD33+, and glycophorin A+ cells and granulocytes were isolated from the peripheral blood (PB) of 8 patients with PV and 3 healthy donors mobilized with G-CSF, and the percentage of JAK2(V617F) mutant allele was determined by quantitative real-time polymerase chain reaction (PCR). The JAK2(V617F) mutation was present in cells belonging to each of the myeloid lineages and was also present in B and T lymphocytes in a subpopulation of patients with PV.