nitrophenols and Polycythemia-Vera

The activating mutation JAK2 V617F plays a central role in the pathogenesis of polycythemia vera, essential thrombocythemia, and primary myelofibrosis. Inhibition of JAK2 activity leads to growth inhibition and apoptosis in cells with mutated JAK2. However, the proapoptotic proteins involved in JAK2 inhibition-induced apoptosis remain unclear. In this study, we show that JAK2 inhibition-induced apoptosis correlated with up-regulation of the nonphosphorylated form of the BH3-only protein Bim in hematopoietic cell lines bearing JAK2 mutations. Knockdown of Bim dramatically inhibited apoptosis induced by JAK2 inhibition, which was reversed by the BH3 mimetic agent ABT-737. In addition, ABT-737 enhanced the apoptosis induced by JAK2 inhibition in JAK2 V617F(+) HEL and SET-2 cells. The combination of JAK inhibitor I and ABT-737 reduced the number of erythroid colonies derived from CD34(+) cells isolated from JAK2 V617F(+) polycythemia vera patients more efficiently than either drug alone. These data suggest that Bim is a key effector molecule in JAK2 inhibition-induced apoptosis and that targeting this apoptotic pathway could be a novel therapeutic strategy for patients with activating JAK2 mutations.

Topics: Apoptosis; Apoptosis Regulatory Proteins; Bcl-2-Like Protein 11; Biomimetic Materials; Biphenyl Compounds; Erythroid Cells; Female; Humans; Janus Kinase 2; K562 Cells; Male; Membrane Proteins; Mutation; Nitrophenols; Piperazines; Polycythemia Vera; Proto-Oncogene Proteins; Sulfonamides

Polycythemia vera (PV) treatment with interferon α (IFNα) is frequently limited by dose-related toxicity. PV CD34(+) cells are characterized by overexpression of Bcl-xL, which can be antagonized by ABT-737 leading to apoptosis. We explored the effects of ABT-737 and IFNα on PV hematopoiesis. Both IFNα and ABT-737 alone or in combination had a modest effect on normal hematopoiesis but each individually were able to markedly induce PV CD34(+) cell apoptosis and suppress hematopoietic colony formation. The inhibitory activities of these agents in combination were greater against PV hematopoiesis than either agent alone. The exposure of PV CD34(+) cells to low doses of IFNα and ABT-737 in combination resulted in the reduction of the proportion of JAK2V617F(+) colonies similar to that observed with higher doses of IFNα. These data provide the rationale for combination therapy with low doses of IFNα and a BH3 mimetic for patients with PV.

Topics: Amino Acid Substitution; Antigens, CD34; bcl-X Protein; Biphenyl Compounds; Bone Marrow Cells; Colony-Forming Units Assay; Drug Synergism; Fetal Blood; Hematopoietic Stem Cells; Humans; Interferon alpha-2; Interferon-alpha; Janus Kinase 2; Nitrophenols; Piperazines; Polycythemia Vera; Polyethylene Glycols; Recombinant Proteins; Sulfonamides

An increased expression of antiapoptotic molecules is often found in malignant cells, where it contributes to their clonal expansion by conferring an improved survival ability. We found that erythroid precurors derived from patients with polycythemia vera (PV) with medium and high JAK2V617F mutation rates often express elevated levels of the antiapoptotic molecules Bcl-2 and Bcl-X(L) (5 of 12 patients with 3 to 7 times Bcl-2 and 3 of 12 patients with 4 to 7 times Bcl-X(L) than average normal controls) and are more resistant to myelosuppressive drugs than normal erythroblasts. ABT-737, a small-molecule inhibitor of Bcl-2, Bcl-X(L), and Bcl-W, induced apoptosis preferentially in JAK2V617F-high PV erythroid precursors as compared with JAK2V617F-low or normal erythroblasts. ABT-737 inhibited also the proliferation of PV erythroblasts and interfered with the formation of endogenous erythroid colonies by PV hematopoietic progenitors. Altogether, these results suggest that small-molecule inhibitors of Bcl-2/Bcl-X(L) may be used in the treatment of patients with PV with high JAK2V617F allele burden.

Topics: Apoptosis; bcl-X Protein; Biphenyl Compounds; Cell Division; Cells, Cultured; Erythroid Precursor Cells; Erythropoiesis; Gene Expression; Humans; Molecular Mimicry; Nitrophenols; Piperazines; Polycythemia Vera; Proto-Oncogene Proteins c-bcl-2; Sulfonamides

Topics: Acid Phosphatase; Blood Platelets; Bone Marrow; Bone Marrow Cells; Chromatography, DEAE-Cellulose; Chromatography, Ion Exchange; Electrophoresis, Disc; Fluorides; Gaucher Disease; Histocytochemistry; Humans; Isoenzymes; Leukemia; Leukemia, Lymphoid; Leukemia, Myeloid; Leukemia, Myeloid, Acute; Leukocytes; Lymphatic Diseases; Lymphocytes; Lymphoma, Non-Hodgkin; Molecular Weight; Monocytes; Nitrophenols; Polycythemia Vera; Staining and Labeling; Tartrates