Search

The activating mutations in JAK2 (including JAK2V617F) that have been described in patients with myeloproliferative neoplasms (MPNs) are linked directly to MPN pathogenesis. We developed R723, an orally bioavailable small molecule that inhibits JAK2 activity in vitro by 50% at a concentration of 2nM, while having minimal effects on JAK3, TYK2, and JAK1 activity. R723 inhibited cytokine-independent CFU-E growth and constitutive activation of STAT5 in primary hematopoietic cells expressing JAK2V617F. In an anemia mouse model induced by phenylhydrazine, R723 inhibited erythropoiesis. In a leukemia mouse model using Ba/F3 cells expressing JAK2V617F, R723 treatment prolonged survival and decreased tumor burden. In V617F-transgenic mice that closely mimic human primary myelofibrosis, R723 treatment improved survival, hepatosplenomegaly, leukocytosis, and thrombocytosis. R723 preferentially targeted the JAK2-dependent pathway rather than the JAK1- and JAK3-dependent pathways in vivo, and its effects on T and B lymphocytes were mild compared with its effects on myeloid cells. Our preclinical data indicate that R723 has a favorable safety profile and the potential to become an efficacious treatment for patients with JAK2V617F-positive MPNs.

Optical breakdown has been generated by focusing YAG laser radiation in the air. The laser radiation itself was scattered due to laser-induced air optical breakdown. Angular distributions of scattered radiation at 1064, 532, and 355 nm were measured. Analysis of the distributions has been performed in terms of Mie scattering. It has been assumed that scattering of laser radiation is due mainly to highly ionized plasma balls in the initial phase of air optical breakdown. The wavelength-dependent angular distribution has been analyzed with two parameters. The mean radius and the plasma frequency of the plasma balls have been determined by a least-squares fit procedure. Observed wavelength-dependent angular distributions are in good agreement with ones calculated by Mie theory.

Information about several topics discussed at a symposium titled "The 21st Century Family Portrait" during the 19th Tokyo International Women's Film Festival held on October 22-26, 2006 in Tokyo, Japan. It centered on the outcomes of low birth rates and the different roles of family members in the society. The event presented 15 films from the participating countries and some speeches delivered by its directors.

An acquired JAK2 V617F mutation has been detected in up to 90% of patients with polycythemia vera (PV) and in a sizeable proportion of patients with other myeloproliferative disorders such as essential thrombocythemia (ET) and idiopathic myelofibrosis (IMF). However, how a single mutation may be responsible for such different clinical phenotypes is unknown. Mice transplanted with bone marrow cells in which V617F JAK2 was retrovirally expressed developed PV-like features, but not ET or IMF. To address the contribution of this mutation to the pathogenesis of these three MPDs, we generated transgenic mice expressing V617F JAK2 driven by the murine H2Kb promoter. We established two lines. The expression of V617F JAK2 mRNA in bone marrow cells was 0.45 and 1.35 that of endogenous wild-type JAK2 in the two lines. One line showed leukocytosis after 4 months of age, with a predominance of granulocytes. Among 43 mice, examined after 3 months of age, 8 (19%) showed polycythemia and 14 (33%) showed thrombocythemia. Two polycythemia cases also showed thromobocytosis. The other line showed extreme leukocytosis and thromobocytosis at one month of age. The leukocytosis progressed as the animals aged, but the thrombocytosis tended to resolve at 8 months. They showed anemia that means Hb value from 9 to 10 g/dL at one month old. Myeloid cells and megakaryocytes were predominant in the bone marrow of these animals, and splenomegaly with myeloid cell and megakaryocyte invasion was observed. We conclude that in vivo expression of V617F JAK2 results in ET-like, IMF-like, and PV-like disease.