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Silverman, Lewis

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Silverman

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Lewis

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Silverman, Lewis
Author's Publications: search.filters.isAuthorOfPublication.7f977a4a-a219-4814-a361-fb7d9d02f48b

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    Repression of BIM mediates survival signaling by MYC and AKT in high-risk T-cell acute lymphoblastic leukemia
    (2014) Reynolds, Christine; Roderick, Justine E.; LaBelle, James L.; Bird, Gregory; Mathieu, Ronald; Bodaar, Kimberly; Colon, Diana; Pyati, Ujwal; Stevenson, Kristen E.; Qi, Jun; Harris, Marian; Silverman, Lewis; Sallan, Stephen; Bradner, James E; Neuberg, Donna; Look, A.; Walensky, Loren; Kelliher, Michelle A.; Gutierrez, Alejandro
    Treatment resistance in T-cell acute lymphoblastic leukemia (T-ALL) is associated with PTEN deletions and resultant PI3K-AKT pathway activation, as well as MYC overexpression, and these pathways repress mitochondrial apoptosis in established T-lymphoblasts through poorly defined mechanisms. Normal T-cell progenitors are hypersensitive to mitochondrial apoptosis, a phenotype that is dependent on expression of proapoptotic BIM. In a conditional zebrafish model, MYC downregulation induced BIM expression in T-lymphoblasts, an effect that was blunted by expression of constitutively active AKT. In human T-ALL cell lines and treatment- resistant patient samples, treatment with MYC or PI3K-AKT pathway inhibitors each induced BIM upregulation and apoptosis, indicating that BIM is repressed downstream of MYC and PI3K-AKT in high-risk T-ALL. Restoring BIM function in human T-ALL cells using a stapled peptide mimetic of the BIM BH3 domain had therapeutic activity, indicating that BIM repression is required for T-ALL viability. In the zebrafish model, where MYC downregulation induces T- ALL regression via mitochondrial apoptosis, T-ALL persisted despite MYC downregulation in 10% of bim wild-type zebrafish, 18% of bim heterozygotes, and in 33% of bim homozygous mutants (P = 0.017). We conclude that downregulation of BIM represents a key survival signal downstream of oncogenic MYC and PI3K-AKT signaling in treatment-resistant T-ALL.
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    Triplication of a 21q22 region contributes to B cell transformation through HMGN1 overexpression and loss of histone H3 lysine 27 trimethylation
    (2014) Lane, Andrew; Chapuy, Bjoern; Lin, Charles Y.; Tivey, Trevor; Li, Hubo; Townsend, Elizabeth C.; van Bodegom, Diederik; Day, Tovah; Wu, Shuo-Chieh; Liu, Huiyun; Yoda, Akinori; Alexe, Gabriela; Schinzel, Anna; Sullivan, Timothy J.; Malinge, Sébastien; Taylor, Jordan E.; Stegmaier, Kimberly; Jaffe, Jacob D.; Bustin, Michael; te Kronnie, Geertruy; Izraeli, Shai; Harris, Marian; Stevenson, Kristen E.; Neuberg, Donna; Silverman, Lewis; Sallan, Stephen; Bradner, James E; Hahn, William; Crispino, John D.; Pellman, David; Weinstock, David
    Down syndrome confers a 20-fold increased risk of B cell acute lymphoblastic leukemia (B-ALL)1 and polysomy 21 is the most frequent somatic aneuploidy amongst all B-ALLs2. Yet, the mechanistic links between chr.21 triplication and B-ALL remain undefined. Here we show that germline triplication of only 31 genes orthologous to human chr.21q22 confers murine progenitor B cell self-renewal in vitro, maturation defects in vivo, and B-ALL with either BCR-ABL or CRLF2 with activated JAK2. Chr.21q22 triplication suppresses H3K27me3 in progenitor B cells and B-ALLs, and “bivalent” genes with both H3K27me3 and H3K4me3 at their promoters in wild-type progenitor B cells are preferentially overexpressed in triplicated cells. Strikingly, human B-ALLs with polysomy 21 are distinguished by their overexpression of genes marked with H3K27me3 in multiple cell types. Finally, overexpression of HMGN1, a nucleosome remodeling protein encoded on chr.21q223–5, suppresses H3K27me3 and promotes both B cell proliferation in vitro and B-ALL in vivo.
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    Childhood Leukemia: Electric and Magnetic Fields as Possible Risk Factors
    (Environmental Health Perspectives, 2003) Brain, Joseph; Kavet, Robert; McCormick, David L.; Poole, Charles; Silverman, Lewis; Smith, Thomas; Valberg, Peter A.; Van Etten, R. A.; Weaver, J
    Numerous epidemiologic studies have reported associations between measures of power-line electric or magnetic fields (EMFs) and childhood leukemia. The basis for such associations remains unexplained. In children, acute lymphoblastic leukemia represents approximately three-quarters of all U.S. leukemia types. Some risk factors for childhood leukemia have been established, and others are suspected. Pathogenesis, as investigated in animal models, is consistent with the multistep model of acute leukemia development. Studies of carcinogenicity in animals, however, are overwhelmingly negative and do not support the hypothesis that EMF exposure is a significant risk factor for hematopoietic neoplasia. We may fail to observe effects from EMFs because, from a mechanistic perspective, the effects of EMFs on biology are very weak. Cells and organs function despite many sources of chemical "noise" (e.g., stochastic, temperature, concentration, mechanical, and electrical noise), which exceed the induced EMF "signal" by a large factor. However, the inability to detect EMF effects in bioassay systems may be caused by the choice made for "EMF exposure." "Contact currents" or "contact voltages" have been proposed as a novel exposure metric, because their magnitude is related to measured power-line magnetic fields. A contact current occurs when a person touches two conductive surfaces at different voltages. Modeled analyses support contact currents as a plausible metric because of correlations with residential magnetic fields and opportunity for exposure. The possible role of contact currents as an explanatory variable in the reported associations between EMFs and childhood leukemia will need to be clarified by further measurements, biophysical analyses, bioassay studies, and epidemiology.