Imipramine blue sensitively and selectively targets FLT3-ITD positive acute myeloid leukemia cells.

Aberrant cytokine signaling initiated from mutant receptor tyrosine kinases (RTKs) provides critical growth and survival signals in high risk acute myeloid leukemia (AML). Inhibitors to FLT3 have already been tested in clinical trials, however, drug resistance limits clinical efficacy. Mutant receptor tyrosine kinases are mislocalized in the endoplasmic reticulum (ER) of AML and play an important role in the non-canonical activation of signal transducer and activator of transcription 5 (STAT5). Here, we have tested a potent new drug called imipramine blue (IB), which is a chimeric molecule with a dual mechanism of action. At 200-300 nM concentrations, IB is a potent inhibitor of STAT5 through liberation of endogenous phosphatase activity following NADPH oxidase (NOX) inhibition. However, at 75-150 nM concentrations, IB was highly effective at killing mutant FLT3-driven AML cells through a similar mechanism as thapsigargin (TG), involving increased cytosolic calcium. IB also potently inhibited survival of primary human FLT3/ITD+ AML cells compared to FLT3/ITDneg cells and spared normal umbilical cord blood cells. Therefore, IB functions through a mechanism involving vulnerability to dysregulated calcium metabolism and the combination of fusing a lipophilic amine to a NOX inhibiting dye shows promise for further pre-clinical development for targeting high risk AML

Inhibition of the Gab2/PI3K/mTOR signaling ameliorates myeloid malignancy caused by Ptpn11 (Shp2) gain-of-function mutations

Activating mutations, such as E76K and D61Y, in PTPN11 (SHP2), a protein tyrosine phosphatase implicated in multiple cell signaling processes, are associated with 35% of patients with juvenile myelomonocytic leukemia (JMML), an aggressive childhood myeloproliferative neoplasm (MPN). Here we show that the interaction between leukemia-associated mutant Shp2 and Gab2, a scaffolding protein important for cytokine-induced PI3K/Akt signaling, was enhanced, and that the mTOR pathway was elevated in Ptpn11E76K/+ leukemic cells. Importantly, MPN induced by the Ptpn11E76K/+ mutation was markedly attenuated in Ptpn11E76K/+/Gab2-/- double mutant mice-overproduction of myeloid cells was alleviated, splenomegaly was diminished and myeloid cell infiltration in nonhematopoietic organs was decreased in these double mutants. Excessive myeloid differentiation of stem cells was also normalized by depletion of Gab2. Acute leukemia progression of MPN was reduced in the double mutant mice and, as such, their survival was much prolonged. Furthermore, treatment of Ptpn11E76K/+ mice with Rapamycin, a specific and potent mTOR inhibitor, mitigated MPN phenotypes. Collectively, this study reveals an important role of the Gab2/PI3K/mTOR pathway in mediating the pathogenic signaling of the PTPN11 gain-of-function mutations and a therapeutic potential of Rapamycin for PTPN11 mutation-associated JMML

Psoriasis-associated variant Act1 D10N with impaired regulation by Hsp90

Act1 is an essential adaptor molecule in IL-17-mediated signaling and is recruited to the IL-17 receptor upon IL-17 stimulation. Here, we report that Act1 is a client protein of the molecular chaperone, Hsp90. The Act1 variant (D10N) linked to psoriasis susceptibility is defective in its interaction with Hsp90, resulting in a global loss of Act1 function. Act1-/- mice modeled the mechanistic link between Act1 loss of function and psoriasis susceptibility. Although Act1 is necessary for IL-17-mediated inflammation, Act1-/- mice exhibited a hyper TH17 response and developed spontaneous IL-22-dependent skin inflammation. In the absence of IL-17-signaling, IL-22 is the main contributor to skin inflammation, providing a molecular mechanism for the association of Act1 (D10N) with psoriasis susceptibility

Walkable Neighborhoods: Linkages Between Place, Health, and Happiness in Younger and Older Adults

Problem, research strategy, and findings: We examined whether living in a walkable neighborhood influenced the happiness of younger and older city residents. The data for this study came from a comprehensive household population survey of 1,064 adults living in 16 neighborhoods in Dublin City (Ireland) and its suburbs. We used multigroup structural equation modeling to analyze the direct and indirect effects of walkability on happiness, mediated by health, trust, and satisfaction with neighborhood appearance. We found living in a walkable neighborhood was directly linked to the happiness of people aged 36 to 45 (p¼.001) and, to a lesser extent, those aged 18 to 35 (p¼.07). For older adults, we found that walkable places mattered for happiness indirectly. Such built environments enhanced the likelihood that residents felt more healthy and more trusting of others, and this in turn affected the happiness of older people living in walkable neighborhoods. Takeaway for practice: We found that the way neighborhoods are planned and maintained mattered for happiness, health, and trust. Our findings suggest that mixed-use neighborhood designs that enable residents to shop and socialize within walking distance to their homes have direct and indirect effects on happiness. We call for an ongoing dialogue and evaluation of the way our urban and suburban neighborhoods are planned, designed, and developed, so that people can live in walkable places that better enable health and wellbeing

Gab2 Promotes Hematopoietic Stem Cell Maintenance and Self-Renewal Synergistically with STAT5

Grb2-associated binding (Gab) adapter proteins play major roles in coordinating signaling downstream of hematopoietic cytokine receptors. In hematopoietic cells, Gab2 can modulate phosphatidylinositol–3 kinase and mitogen associated protein kinase activities and regulate the long-term multilineage competitive repopulating activity of hematopoietic stem cells (HSCs). Gab2 may also act in a linear pathway upstream or downstream of signal transducer and activator of transcription-5 (STAT5), a major positive regulator of HSC function. Therefore, we aimed to determine whether Gab2 and STAT5 function in hematopoiesis in a redundant or non-redundant manner.), reduced HSC survival, and dramatic loss of self-renewal potential as measured by serial transplantation.These data demonstrate new functions for Gab2 in hematopoiesis in a manner that is non-redundant with STAT5. Furthermore, important synergy between STAT5 and Gab2 was observed in HSC self-renewal, which might be exploited to optimize stem cell-based therapeutics

Repercussion of megakaryocyte-specific Gata1 Loss on megakaryopoiesis and the hematopoietic precursor compartment

During hematopoiesis, transcriptional programs are essential for the commitment and differentiation of progenitors into the different blood lineages. GATA1 is a transcription factor expressed in several hematopoietic lineages and essential for proper erythropoiesis and megakaryopoiesis. Megakaryocyte-specific genes, such as GP1BA, are known to be directly regulated by GATA1. Mutations in GATA1 can lead to dyserythropoietic anemia and pseudo gray-platelet syndrome. Selective loss of Gata1 expression in adult mice results in macrothrombocytopenia with platelet dysfunction, characterized by an excess of immature megakaryocytes. To specifically analyze the impact of Gata1 loss in mature committed megakaryocytes, we generated Gata1-Lox|Pf4-Cre mice (Gata1cKOMK). Consistent with previous findings, Gata1cKOMK mice are macrothrombocytopenic with platelet dysfunction. Supporting this notion we demonstrate that Gata1 regulates directly the transcription of Syk, a tyrosine kinase that functions downstream of Clec2 and GPVI receptors in megakaryocytes and platelets. Furthermore, we show that Gata1cKOMK mice display an additional aberrant megakaryocyte differentiation stage. Interestingly, these mice present a misbalance of the multipotent progenitor compartment and the erythroid lineage, which translates into compensatory stress erythropoiesis and splenomegaly. Despite the severe thrombocytopenia, Gata1cKOMK mice display a mild reduction of TPO plasma levels, and Gata1cK-OMK megakaryocytes show a mild increase in Pf4 mRNA levels; such a misbalance might be behind the general hematopoietic defects observed, affecting locally normal TPO and Pf4 levels at hematopoietic stem cell niches. © 2016 Meinders et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

The Antioxidant Protein Peroxiredoxin 4 Is Epigenetically Down Regulated in Acute Promyelocytic Leukemia

The antioxidant peroxiredoxin (PRDX) protein family comprises 6 members, which are implicated in a variety of cellular responses, including growth factor signal transduction. PRDX4 resides in the endoplasmic reticulum (ER), where it locally controls oxidative stress by reducing H2O2levels. We recently provided evidence for a regulatory function of PRDX4 in signal transduction from a myeloid growth factor receptor, the granulocyte colony-stimulating factor receptor (G-CSFR). Upon activation, the ligand-induced G-CSFR undergoes endocytosis and routes via the early endosomes where it physically interacts with ER-resident PRDX4. PRDX4 negatively regulates G-CSFR mediated signaling. Here, we investigated whether PRDX4 is affected in acute myeloid leukemia (AML); genomic alterations and expression levels of PRDX4 were investigated. We show that genomic abnormalities involving PRDX4 are rare in AML. However, we find a strong reduction in PRDX4 expression levels in acute promyelocytic leukemia (APL) compared to normal promyelocytes and different molecular subtypes of AML. Subsequently, the possible role of DNA methylation and histone modifications in silencing of PRDX4 in APLs was investigated. We show that the reduced expression is not due to methylation of the CpG island in the promoter region of PRDX4 but correlates with increased trimethylation of histone 3 lysine residue 27 (H3K27me3) and lysine residue 4 (H3K4me3) at the transcriptional start site (TSS) of PRDX4, indicative of a bivalent histone code involved in transcriptional silencing. These findings suggest that the control of G-CSF responses by the antioxidant protein PRDX4 may be perturbed in APL