Seido Oku

Development of ET, primary myelofibrosis and PV in mice expressing JAK2 V617F

An acquired JAK2 V617F mutation is found in most patients with polycythemia vera (PV), and about half of patients with essential thrombocythemia (ET) or primary myelofibrosis (PMF). Mice transplanted with bone marrow cells in which JAK2 V617F was retrovirally expressed developed PV-like features, but not ET or PMF. To address the contribution of this mutation to the pathogenesis of these three MPDs, we generated two lines of JAK2 V617F transgenic mice. One line showed granulocytosis after 4 months of age. Among 43 mice, 8 (19%) showed polycythemia and 15 (35%) showed thrombocythemia. The second line showed extreme leukocytosis and thromobocytosis. They showed anemia that means Hb value from 9 to 10 g per 100 ml when 1 month old. Myeloid cells and megakaryocytes were predominant in the bone marrow of these animals, and splenomegaly was observed. The expression of JAK2 V617F mRNA in bone marrow cells was 0.45 and 1.35 that of endogenous wild-type JAK2 in the two lines, respectively. In vitro analysis of bone marrow cells from both lines showed constitutive activation of ERK1/2, STAT5 and AKT, and augmentation of their phosphorylations by cytokine stimulation. We conclude that in vivo expression of JAK2 V617F results in ET-, PMF- and PV-like disease.

JAK2 V617F uses distinct signalling pathways to induce cell proliferation and neutrophil activation

The acquired JAK2 V617F mutation is observed in the majority of patients with BCR‐ABL1 negative chronic myeloproliferative neoplasms (MPN). BCR‐ABL1 negative MPN displays myeloproliferation with an elevated leucocyte alkaline phosphatase (LAP) activity, a neutrophil activation marker. We tried to separate the downstream signalling of JAK2 V617F to stimulate myeloproliferation and LAP activity. NB4, a myeloid lineage cell line, was transduced with Jak2 V617F mutation or wild‐type Jak2. We found that Jak2 V617F mutation, but not wild‐type Jak2 enhanced LAP expression in NB4‐derived neutrophils and proliferation of NB4 cells. JAK2 V617F induces constitutive phosphorylation of STAT3 and STAT5, and uses signalling targets such as Ras/MEK/ERK and PI3K/Akt pathways. By using MEK1/2 inhibitor U0126, PI3K inhibitor LY294002, and STAT3 or STAT5 siRNAs, JAK2 V617F was found to specifically use the STAT3 pathway to enhance LAP expression, while STAT5, Ras/MEK/ERK and PI3K/Akt, but not STAT3 pathways, were able to stimulate cell proliferation. These data strongly suggest that JAK2 V617F uses distinct signalling pathways to induce typical pathological features of MPN, such as high LAP activity and enhanced cell proliferation.

Different Risk Factors Related to Adenovirus- or BK Virus-Associated Hemorrhagic Cystitis following Allogeneic Stem Cell Transplantation

Virus-associated hemorrhagic cystitis (HC) is a major cause of morbidity and mortality following allogeneic hematopoietic stem cell transplantation (HSCT). Although numerous studies have attempted to identify factors that predispose patients to viral HC, its causes remain controversial. We analyzed retrospectively the results of 266 allogeneic HSCTs to identify factors associated with HC. Of this group, 42 patients (15.8%) were diagnosed with viral HC, because of either adenovirus (ADV; n = 26; 9.8%) or BK virus (BKV; n = 16; 6.0%). ADV-HC was frequently associated with T cell purging, and was less common in patients with acute graft-versus-host-disease (GVHD). Conversely, BKV-HC was more frequently observed in patients with excessive immune reactions such as GVHD, preengraftment immune reaction, and hemophagocytic syndrome. These observations indicate that ADV- and BKV-HC may differ significantly in their risk factors and pathogenesis. Profound immune deficiency is more likely to be associated with ADV-HC, whereas immune hyperactivity might play a key role in BKV-HC.

Reduced-intensity conditioning followed by cord blood transplantation in a patient with refractory folliculotropic mycosis fungoides

Advanced-stage mycosis fungoides (MF) has a generally poor prognosis. Allogeneic hematopoietic stem cell transplantation improves the outcome of advanced-stage MF. Recently, cord blood has been used as an alternative stem cell source; however, there are few reports of MF patients treated using cord blood transplantation. Here, we report a rare case of refractory folliculotropic MF, which was treated with reduced-intensity conditioning followed by cord blood transplantation.

Successful Stem Cell Transplantation without Cryopreservation from a Microchimeric Haploidentical Sibling for Refractory Acute Myeloid Leukemia Complicated with Critical Thrombophlebitis and Cellulitis

We describe the case of a 38-year-old male patient who had acute myeloid leukemia and developed prolonged neutropenia after induction chemotherapy. He developed thrombotic complications at multiple sites. Thrombophlebitis of the hemorrhoidal plexus became exacerbated and developed into critical cellulitis. Because the patient had no human leukocyte antigen-identical sibling, we considered an alternative donor. Because of the necessity for early neutrophil recovery to resolve the critical infection, we proceeded with allogeneic peripheral blood stem cell transplantation (PBSCT) from a microchimeric haploidentical sibling donor.We infused peripheral blood mononuclear cells directly into the patient without cryopreservation and thawing procedures. We aimed for the contaminating granulocytes to act as a granulocyte transfusion. Actually, the neutrophils increased to 1.6 X 109/L on day 1, when the patient showed a temporary resolution of infection. Engraftment was achieved shortly after neutropenic nadir, and acute graft-versus-host disease (GVHD) has been well controlled. Although the patient experiences extensive chronic GVHD, he has been well as an outpatient with a 90% Karnofsky performance status score.The leukemia has been in complete remission for more than 1 year.These findings suggest the clinical utility of a salvage therapy with allogeneic PBSCT from a microchimeric haploidentical donor to treat refractory leukemia concurrent with life-threatening infection.