MYC is essential for the formation and maintenance of germinal centers

Germinal centers (GC) are sites of intense B cell proliferation, central for T cell dependent antibody responses. However, the role of MYC, a key cell cycle regulator, in this process has been questioned. Here, we identified MYC positive B cell subpopulations in immature and mature GCs, and show through genetic ablation of Myc that they play indispensable roles in GC formation and maintenance. The identification of these functionally critical cellular subsets has important implications for human B cell lymphomagenesis, which mostly originates from GC B cells and frequently involves MYC chromosomal translocations. As these translocations are generally dependent on transcription of the recombining partner loci, the MYC positive GC subpopulations may be at a particularly high risk for malignant transformation

Next-Generation cDNA Screening for Oncogene and Resistance Phenotypes

There is a pressing need for methods to define the functional relevance of genetic alterations identified by next-generation sequencing of cancer specimens. We developed new approaches to efficiently construct full-length cDNA libraries from small amounts of total RNA, screen for transforming and resistance phenotypes, and deconvolute by next-generation sequencing. Using this platform, we screened a panel of cDNA libraries from primary specimens and cell lines in cytokine-dependent murine Ba/F3 cells. We demonstrate that cDNA library-based screening can efficiently identify DNA and RNA alterations that confer either cytokine-independent proliferation or resistance to targeted inhibitors, including RNA alterations and intergenic fusions. Using barcoded next-generation sequencing, we simultaneously deconvoluted cytokine-independent clones recovered after transduction of 21 cDNA libraries. This approach identified multiple gain-of-function alleles, including KRAS G12D, NRAS Q61K and an activating splice variant of ERBB2. This approach has broad applicability for identifying transcripts that confer proliferation, resistance and other phenotypes in vitro and potentially in vivo

MLL-rearranged B lymphoblastic leukemias selectively express the immunoregulatory carbohydrate-binding protein galectin-1

Leukemias with 11q23 translocations involving the Mixed Lineage Leukemia (MLL) gene exhibit unique clinical and biological features and have a poor prognosis. In a screen for molecular markers of MLL rearrangement, we identified the specific overexpression of an immunomodulatory lectin Galectin-1 (Gal1) in MLL-rearranged B lymphoblastic leukemias (B-ALL) compared to other MLL-germline ALLs. To assess the diagnostic utility of Gal1 expression in identifying MLL-rearranged B-ALLs, we performed Gal1 immunostaining on a large series of primary ALLs with known MLL status. All 11 MLL-rearranged B-ALLs had abundant Gal1 expression; in marked contrast, only 1 of 42 germline-MLL B-ALLs expressed Gal1. In addition, Gal1 was readily detected in diagnostic samples of MLL-rearranged B-ALLs by intracellular flow cytometry. Since deregulated gene expression in MLL-rearranged leukemias may be related to the altered histone methyltransferase activity of MLL fusion protein complex, we analyzed histone H3 lysine 79 (H3K79) dimethylation in the Gal1 promoter region using chromatin immunoprecipitation. Gal1 promoter H3K79diMe was ≈ 5 fold higher in a MLL-rearranged B-ALL cell line than in a B-ALL line without the MLL translocation. Furthermore, the Gal1 promoter H3K79 was significantly hypermethylated in primary MLL-rearranged B-ALLs compared to MLL-germline B-ALLs and normal pre-B cells, implicating this epigenetic modification as a mechanism for Gal1 overexpression in MLL B-ALL.Fil: Juszczynski, Przemyslaw. Dana Farber Cancer Institute; Estados UnidosFil: Rodig, Scott J.. Brigham & Women; Estados UnidosFil: Ouyang, Jing. Dana Farber Cancer Institute; Estados UnidosFil: O´Donnell, Evan. Dana Farber Cancer Institute; Estados UnidosFil: Takeyama, Kunihiko. Dana Farber Cancer Institute; Estados UnidosFil: Mlynarski, Wojciech. Dana Farber Cancer Institute; Estados UnidosFil: Mycko, Katarzyna. Dana Farber Cancer Institute; Estados UnidosFil: Szczepanski, Tomasz. Dana Farber Cancer Institute; Estados UnidosFil: Gaworczyk, Anna. Medical University of Lodz; PoloniaFil: Krivtsov, Andrei. Medical University of Lodz; PoloniaFil: Faber, Joerg. Medical University of Silesia; PoloniaFil: Sinha, Amit U.. Medical University of Lublin; PoloniaFil: Rabinovich, Gabriel Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); Argentina; ArgentinaFil: Armstrong, Scott A.. Children; Estados UnidosFil: Kutok, Jeffery. Children; Estados UnidosFil: Shipp, Margaret A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); Argentina; Argentin

Microbial colonization influences early B-lineage development in the gut lamina propria

The RAG1/RAG2 endonuclease ("RAG") initiates the V(D)J recombination reaction that assembles Ig heavy (IgH) and light (IgL) chain variable region exons from germline gene segments to generate primary antibody repertoires1. IgH V(D)J assembly occurs in progenitor (pro-) B cells followed by that of IgL in precursor (pre-) B cells. Expression of IgH μ and IgL (Igκ or Igλ) chains generates IgM, which is expressed on immature B cells as the B cell antigen-binding receptor ("BCR"). Rag expression can continue in immature B cells2, allowing continued Igκ V(D)J recombination that replaces the initial VκJκ exon with one that generates a new specificity3–5. This “receptor editing” process, which also can lead to Igλ V(D)J recombination and expression3,6,7, provides a mechanism whereby antigen-encounter at the Rag-expressing immature B cell stage helps shape pre-immune BCR repertoires. As the major site of post-natal B cell development, the bone marrow is the principal location of primary Ig repertoire diversification in mice. Here, we report that early B cell development also occurs within the mouse intestinal lamina propria (LP), where the associated V(D)J recombination/receptor editing processes modulate primary LP Ig repertoires. At weanling age in normally housed mice, the LP contains a population of Rag-expressing B lineage cells that harbor intermediates indicative of ongoing V(D)J recombination and which contain cells with pro-B, pre-B, and editing phenotypes. Consistent with LP-specific receptor editing, Rag-expressing LP B-lineage cells have similar VH repertoires, but significantly different Vκ repertoires, compared to those of Rag2-expressing BM counterparts. Moreover, colonization of germ-free mice leads to an increased ratio of Igλ-expressing versus Igκ-expressing B cells specifically in the LP. We conclude that B cell development occurs in the intestinal mucosa, where it is regulated by extra-cellular signals from commensal microbes that influence gut Ig repertoires

Pre-diagnosis plasma immune markers and risk of non-Hodgkin lymphoma in two prospective cohort studies

Inflammation and B-cell hyperactivation have been associated with non-Hodgkin lymphoma development. This prospective analysis aimed to further elucidate pre-diagnosis plasma immune marker profiles associated with non-Hodgkin lymphoma risk. We identified 598 incident lymphoma cases and 601 matched controls in Nurses\u27 Health Study and Health Professionals Follow-up Study participants with archived pre-diagnosis plasma samples and measured 13 immune marker levels with multiplexed immunoassays. Using multivariable logistic regression we calculated odds ratios and 95% confidence intervals per standard deviation unit increase in biomarker concentration for risk of non-Hodgkin lymphoma and major histologic subtype, stratifying additional models by years ( \u3c 5, 5 to \u3c 10, \u3e /=10) after blood draw. Soluble interleukin-2 receptor-alpha, CXC chemokine ligand 13, soluble CD30, and soluble tumor necrosis factor receptor-2 were individually positively associated, and B-cell activating factor of the tumor necrosis factor family inversely associated, with all non-Hodgkin lymphoma and one or more subtypes. The biomarker combinations associated independently with lymphoma varied somewhat by subtype and years after blood draw. Of note, the unexpected inverse association between B-cell activating factor and chronic lymphocytic leukemia/small lymphocytic lymphoma risk (odds ratio: 95% confidence interval: 0.51, 0.43-0.62) persisted more than 10 years after blood draw (odds ratio: 0.70; 95% confidence interval: 0.52-0.93). In conclusion, immune activation precedes non-Hodgkin lymphoma diagnosis by several years. Decreased B-cell activating factor levels may denote nascent chronic lymphocytic leukemia many years pre-diagnosis

Tet1 and Tet2 Regulate 5-Hydroxymethylcytosine Production and Cell Lineage Specification in Mouse Embryonic Stem Cells

SummaryTET family enzymes convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) in DNA. Here, we show that Tet1 and Tet2 are Oct4-regulated enzymes that together sustain 5hmC in mouse embryonic stem cells (ESCs) and are induced concomitantly with 5hmC during reprogramming of fibroblasts to induced pluripotent stem cells. ESCs depleted of Tet1 by RNAi show diminished expression of the Nodal antagonist Lefty1 and display hyperactive Nodal signaling and skewed differentiation into the endoderm-mesoderm lineage in embryoid bodies in vitro. In Fgf4- and heparin-supplemented culture conditions, Tet1-depleted ESCs activate the trophoblast stem cell lineage determinant Elf5 and can colonize the placenta in midgestation embryo chimeras. Consistent with these findings, Tet1-depleted ESCs form aggressive hemorrhagic teratomas with increased endoderm, reduced neuroectoderm, and ectopic appearance of trophoblastic giant cells. Thus, 5hmC is an epigenetic modification associated with the pluripotent state, and Tet1 functions to regulate the lineage differentiation potential of ESCs

Antileukemic Activity of Nuclear Export Inhibitors that Spare Normal Hematopoietic Cells

Drugs that target the chief mediator of nuclear export, chromosome region maintenance 1 protein (CRM1) have potential as therapeutics for leukemia, but existing CRM1 inhibitors show variable potencies and a broad range of cytotoxic effects. Here, we report the structural analysis and antileukemic activity of a new generation of small-molecule inhibitors of CRM1. Designated selective inhibitors of nuclear export (SINE), these compounds were developed using molecular modeling to screen a small virtual library of compounds against the nuclear export signal (NES) groove of CRM1. The 2.2-Å crystal structure of the CRM1-Ran-RanBP1 complex bound to KPT-251, a representative molecule of this class of inhibitors, shows that the drug occupies part of the groove in CRM1 that is usually occupied by the NES, but penetrates much deeper into the groove and blocks CRM1-directed protein export. SINE inhibitors exhibit potent antileukemic activity, inducing apoptosis at nanomolar concentrations in a panel of 14 human acute myeloid leukemia (AML) cell lines representing different molecular subtypes of the disease. When administered orally to immunodeficient mice engrafted with human AML cells, KPT-251 had potent antileukemic activity with negligible toxicity to normal hematopoietic cells. Thus, KPT-SINE CRM1 antagonists represent a novel class of drugs that warrant further testing in AML patients

A Novel Clinically Relevant Strategy to Abrogate Autoimmunity and Regulate Alloimmunity in NOD Mice

OBJECTIVE - To investigate a new clinically relevant immunoregulatory strategy based on treatment with murine Thymoglobulin mATG Genzyme and CTLA4-Ig in NOD mice to prevent alloand autoimmune activation using a stringent model of islet transplantation and diabetes reversal. RESEARCH DESIGN AND METHODS - Using allogeneic islet transplantation models as well as NOD mice with recent onset type 1 diabetes, we addressed the therapeutic efficacy and immunomodulatory mechanisms associated with a new immunoregulatory protocol based on prolonged low-dose mATG plus CTLA4-Ig. RESULTS - BALB/c islets transplanted into hyperglycemic NOD mice under prolonged mATG+CTLA4-Ig treatment showed a pronounced delay in allograft rejection compared with untreated mice (mean survival time: 54 vs. 8 days, P < 0.0001). Immunologic analysis of mice receiving transplants revealed a complete abrogation of autoimmune responses and severe downregulation of alloimmunity in response to treatment. The striking effect on autoimmunity was confirmed by 100% diabetes reversal in newly hyperglycemic NOD mice and 100% indefinite survival of syngeneic islet transplantation (NOD.SCID into NOD mice). CONCLUSIONS - The capacity to regulate alloimmunity and to abrogate the autoimmune response in NOD mice in different settings confirmed that prolonged mATG+CTLA4-Ig treatment is a clinically relevant strategy to translate to humans with type 1 diabetes