Scientific Resources

Tumors are composed of phenotypically heterogeneous cancer cells that often resemble various differentiation states of their lineage of origin. Within this hierarchy,it is thought that an immature subpopulation of tumor-propagating cancer stem cells (CSCs) differentiates into non-tumorigenic progeny,providing a rationale for therapeutic strategies that specifically eradicate CSCs or induce their differentiation. The clinical success of these approaches depends on CSC differentiation being unidirectional rather than reversible,yet this question remains unresolved even in prototypically hierarchical malignancies,such as acute myeloid leukemia (AML). Here,we show in murine and human models of AML that,upon perturbation of endogenous expression of the lineage-determining transcription factor PU.1 or withdrawal of established differentiation therapies,some mature leukemia cells can de-differentiate and reacquire clonogenic and leukemogenic properties. Our results reveal plasticity of CSC maturation in AML,highlighting the need to therapeutically eradicate cancer cells across a range of differentiation states. View Publication

Laminin and fibronectin are glycoproteins that influence cell behavior and mediate cell/substratum adhesion. We have examined the interaction of these macromolecules with the serine protease plasminogen activator (PA) in two types of extracellular matrices; one produced by the murine Engelbreth-Holm-Swarm (EHS) tumor (Matrigel),and another by normal kidney epithelial cells in culture. Matrigel was found to contain significant quantities of tissue-type PA (tPA). Two of the major components of Matrigel,laminin and type IV collagen,were also examined. Tissue-type PA was associated with purified preparations of laminin; however,it was not found associated with type IV collagen. Normal kidney epithelial cells in culture secrete large amounts of urokinase (UK) and deposit a subepithelial matrix containing both laminin and fibronectin. These matrix macromolecules were isolated from the deposited matrix by immunoprecipitation,examined by zymography,and found to contain UK. The potential role of this interaction in the mechanisms of cell migration and matrix remodeling is discussed. View Publication

Inflammatory bowel disease (IBD) is characterized by severe and recurrent inflammation of the gastrointestinal tract,associated with altered patterns of cytokine synthesis,excessive reactive oxygen species (ROS) production,and high levels of the innate immune protein,lipocalin-2 (LCN-2),in the mucosa. The major source of ROS in intestinal epithelial cells is the NADPH oxidase NOX1,which consists of the transmembrane proteins,NOX1 and p22PHOX,and the cytosolic proteins,NOXO1,NOXA1,and Rac1. Here,we investigated whether NOX1 activation and ROS production induced by key inflammatory cytokines in IBD causally affects LCN-2 production in colonic epithelial cells. We found that the combination of TNFalpha and IL-17 induced a dramatic upregulation of NOXO1 expression that was dependent on the activation of p38MAPK and JNK1/2,and resulted into an increase of NOX1 activity and ROS production. NOX1-derived ROS drive the expression of LCN-2 by controlling the expression of IkappaBzeta,a master inducer of LCN-2. Furthermore,LCN-2 production and colon damage were decreased in NOX1-deficient mice during TNBS-induced colitis. Finally,analyses of biopsies from patients with Crohn's disease showed increased JNK1/2 activation,and NOXO1 and LCN-2 expression. Therefore,NOX1 might play a key role in mucosal immunity and inflammation by controlling LCN-2 expression. View Publication

Soybeans are a rich source of isoflavones that have been linked with anti-inflammatory processes and various health benefits. However,specific mechanisms whereby soy bioactives impact immune cell subsets are unclear. Isoflavones,such as genistein and daidzein,are metabolized by microbes to bioactive metabolites as O-desmethylangolensin (O-DMA) and equol,whose presence has been linked to health benefits. We examined how soy isoflavones and metabolites impact natural killer (NK) cell signaling and function. We observe no impact of isoflavones on viability of healthy donor peripheral blood mononuclear cells (PBMCs) or NK cells,even at high (25 µM) concentrations. However,pre-treatment of PBMCs with physiologically-relevant concentrations of genistein (p = 0.0023) and equol (p = 0.006) decreases interleukin (IL)-12/IL-18-induced interferon-gamma (IFN-gamma) production versus controls. Detailed cellular analyses indicate genistein and equol decrease IL-12/IL-18-induced IFN-gamma production by human NK cell subsets,but do not consistently alter cytotoxicity. At the level of signal transduction,genistein decreases IL-12/IL-18-induced total phosphorylated tyrosine,and phosphorylation MAPK pathway components. Further,genistein limits IL-12/IL-18-mediated upregulation of IL-18Ralpha expression on NK cells (p = 0.0109). Finally,in vivo studies revealed that C57BL/6 mice fed a soy-enriched diet produce less plasma IFN-gamma following administration of IL-12/IL-18 versus control-fed animals (p {\textless} 0.0001). This study provides insight into how dietary soy modulates NK cell functions. View Publication

Exposure to Mycobacterium tuberculosis (Mtb) results in heterogeneous clinical outcomes including primary progressive tuberculosis and latent Mtb infection (LTBI). Mtb infection is identified using the tuberculin skin test and interferon-gamma (IFN-gamma) release assay IGRA,and a positive result may prompt chemoprophylaxis to prevent progression to tuberculosis. In the present study,we report on a cohort of Ugandan individuals who were household contacts of patients with TB. These individuals were highly exposed to Mtb but tested negative disease by IFN-gamma release assay and tuberculin skin test,'resisting' development of classic LTBI. We show that 'resisters' possess IgM,class-switched IgG antibody responses and non-IFN-gamma T cell responses to the Mtb-specific proteins ESAT6 and CFP10,immunologic evidence of exposure to Mtb. Compared to subjects with classic LTBI,'resisters' display enhanced antibody avidity and distinct Mtb-specific IgG Fc profiles. These data reveal a distinctive adaptive immune profile among Mtb-exposed subjects,supporting an expanded definition of the host response to Mtb exposure,with implications for public health and the design of clinical trials. View Publication

BACKGROUND Cytotoxic T lymphocyte antigen-4 (CTLA-4) limits T-cell activation and is expressed on T-regulatory cells. Human CTLA-4 deficiency results in severe immune dysregulation. Abatacept (CTLA-4 Ig) is approved for the treatment of rheumatoid arthritis (RA) and its mechanism of action is attributed to effects on T-cells. It is known that CTLA-4 modulates the expression of its ligands CD80 and CD86 on antigen presenting cells (APC) by transendocytosis. As B-cells express CD80/CD86 and function as APC,we hypothesize that B-cells are a direct target of abatacept. OBJECTIVES To investigate direct effects of abatacept on human B-lymphocytes in vitro and in RA patients. METHODS The effect of abatacept on healthy donor B-cells' phenotype,activation and CD80/CD86 expression was studied in vitro. Nine abatacept-treated RA patients were studied. Seven of these were followed up to 24 months,and two up to 12 months only and treatment response,immunoglobulins,ACPA,RF concentrations,B-cell phenotype and ACPA-specific switched memory B-cell frequency were assessed. RESULTS B-cell development was unaffected by abatacept. Abatacept treatment resulted in a dose-dependent decrease of CD80/CD86 expression on B-cells in vitro,which was due to dynamin-dependent internalization. RA patients treated with abatacept showed a progressive decrease in plasmablasts and serum IgG. While ACPA-titers only moderately declined,the frequency of ACPA-specific switched memory B-cells significantly decreased. CONCLUSIONS Abatacept directly targets B-cells by reducing CD80/CD86 expression. Impairment of antigen presentation and T-cell activation may result in altered B-cell selection,providing a new therapeutic mechanism and a base for abatacept use in B-cell mediated autoimmunity. View Publication

Circulating Tumor Cells (CTCs) represent an easy,repeatable and representative access to information regarding solid tumors. However,their detection remains difficult because of their paucity,their short half-life,and the lack of reliable surface biomarkers. Flow cytometry (FC) is a fast,sensitive and affordable technique,ideal for rare cells detection. Adapted to CTCs detection (i.e. extremely rare cells),most FC-based techniques require a time-consuming pre-enrichment step,followed by a 2-hours staining procedure,impeding on the efficiency of CTCs detection. We overcame these caveats and reduced the procedure to less than one hour,with minimal manipulation. First,cells were simultaneously fixed,permeabilized,then stained. Second,using low-speed FC acquisition conditions and two discriminators (cell size and pan-cytokeratin expression),we suppressed the pre-enrichment step. Applied to blood from donors with or without known malignant diseases,this protocol ensures a high recovery of the cells of interest independently of their epithelial-mesenchymal plasticity and can predict which samples are derived from cancer donors. This proof-of-concept study lays the bases of a sensitive tool to detect CTCs from a small amount of blood upstream of in-depth analyses. View Publication

Microglia are highly plastic immune cells which exist in a continuum of activation states. By shaping the function of oligodendrocyte precursor cells (OPCs),the brain cells which differentiate to myelin-forming cells,microglia participate in both myelin injury and remyelination during multiple sclerosis. However,the mode(s) of action of microglia in supporting or inhibiting myelin repair is still largely unclear. Here,we analysed the effects of extracellular vesicles (EVs) produced in vitro by either pro-inflammatory or pro-regenerative microglia on OPCs at demyelinated lesions caused by lysolecithin injection in the mouse corpus callosum. Immunolabelling for myelin proteins and electron microscopy showed that EVs released by pro-inflammatory microglia blocked remyelination,whereas EVs produced by microglia co-cultured with immunosuppressive mesenchymal stem cells promoted OPC recruitment and myelin repair. The molecular mechanisms responsible for the harmful and beneficial EV actions were dissected in primary OPC cultures. By exposing OPCs,cultured either alone or with astrocytes,to inflammatory EVs,we observed a blockade of OPC maturation only in the presence of astrocytes,implicating these cells in remyelination failure. Biochemical fractionation revealed that astrocytes may be converted into harmful cells by the inflammatory EV cargo,as indicated by immunohistochemical and qPCR analyses,whereas surface lipid components of EVs promote OPC migration and/or differentiation,linking EV lipids to myelin repair. Although the mechanisms through which the lipid species enhance OPC maturation still remain to be fully defined,we provide the first demonstration that vesicular sphingosine 1 phosphate stimulates OPC migration,the first fundamental step in myelin repair. From this study,microglial EVs emerge as multimodal and multitarget signalling mediators able to influence both OPCs and astrocytes around myelin lesions,which may be exploited to develop novel approaches for myelin repair not only in multiple sclerosis,but also in neurological and neuropsychiatric diseases characterized by demyelination. View Publication

Clonal hematopoiesis (CH) is a common aging-associated condition with increased risk of hematologic malignancy. Knowledge of the mechanisms driving evolution from CH to overt malignancy has been hampered by a lack of in vivo models that orthogonally activate mutant alleles. Here,we develop independently regulatable mutations in DNA methyltransferase 3A (Dnmt3a) and nucleophosmin 1 (Npm1),observed in human CH and AML,respectively. We find Dnmt3a mutation expands hematopoietic stem and multipotent progenitor cells (HSC/MPPs),modeling CH. Induction of mutant Npm1 after development of Dnmt3a-mutant CH causes progression to myeloproliferative disorder (MPD),and more aggressive MPD is observed with longer latency between mutations. MPDs uniformly progress to acute myeloid leukemia (AML) following transplant,accompanied by a decrease in HSC/MPPs and an increase in myeloid-restricted progenitors,the latter of which propagate AML in tertiary recipient mice. At a molecular level,progression of CH to MPD is accompanied by selection for mutations activating Ras/Raf/MAPK signaling. Progression to AML is characterized by additional oncogenic signaling mutations (Ptpn11,Pik3r1,Flt3) and/or mutations in epigenetic regulators (Hdac1,Idh1,Arid1a). Together,our study demonstrates that Npm1 mutation drives evolution of Dnmt3a-mutant CH to AML and rate of disease progression is accelerated with longer latency of CH. View Publication

The flow cytometric crossmatch (FCXM) assay,which detects the presence of donor specific HLA antibodies in patient sera,is a cornerstone of HLA compatibility testing. Since relatively long FCXM assay turnaround times may contribute to transplant delays and increased graft ischemia time,we developed and validated two modified crossmatch procedures,namely the Halifax and Halifaster FCXM protocols. These protocols reduce FCXM assay time >60{\%} and simplify their set-up without compromising quality or sensitivity. Optimization of the FCXM (the Halifax protocol) includes a 96-well tray platform,reduced wash times,increased serum to cell suspension volume ratio,shortened incubations and higher incubation temperature. The Halifaster protocol is a further modification,employing methods that improve lymphocyte purity compared to density gradient centrifugation (96 ± 2.63{\%} vs 69 ± 19.06{\%}),reduce cell isolation time (by ∼40{\%}) and conserve FCXM assay reagents. Importantly,linear regression analysis of the median channel fluorescence shift (MCFS) values revealed excellent concordance (R2 of 0.98-0.99) among all three FCXM protocols (standard vs Halifax vs Halifaster). Finally,a retrospective review of 2013 crossmatches performed using the Halifax protocol demonstrated excellent correlation with the virtual crossmatch (95.7{\%} and 96.8{\%} specificity and sensitivity,respectively) regarding the identification of donor specific antibodies (HLA-A/B/DR) assigned based on the single antigen bead (SAB) assay testing with a 2000 mean fluorescence intensity (MFI) cutoff. Implementation of the Halifax or Halifaster protocols will expedite pre-transplantation work-up and improve patient care. View Publication

BACKGROUND The goal of antiretroviral therapy (ART) is to suppress HIV-1 replication and reconstitute CD4+ T cells. Here,we report on HIV-infected individuals who had a paradoxical decline in CD4+ T cells despite ART-mediated suppression of plasma HIV-1 load (pVL). We defined such an immunological outcome as extreme immune decline (EXID). METHODS EXID's clinical and immunological characteristics were compared to immunological responders (IRs),immunological nonresponders (INRs),healthy controls (HCs),and idiopathic CD4+ lymphopenia (ICL) patients. T cell immunophenotyping and assembly/activation of inflammasomes were evaluated by flow cytometry. PBMC transcriptome analysis and genetic screening for pathogenic variants were performed. Levels of cytokines/chemokines were measured by electrochemiluminescence. Luciferase immunoprecipitation system and NK-mediated antibody-dependent cellular cytotoxicity (ADCC) assays were used to identify anti-lymphocyte autoantibodies. RESULTS EXIDs were infected with non-B HIV-1 subtypes and after 192 weeks of consistent ART-mediated pVL suppression had a median CD4+ decrease of 157 cells/mul,compared with CD4+ increases of 193 cells/mul and 427 cells/mul in INR and IR,respectively. EXID had reduced naive CD4+ T cells,but similar proportions of cycling CD4+ T cells and HLA-DR+CD38+CD8+ T cells compared with IR and INR. Levels of inflammatory cytokines were also similar in EXID and INR,but the IL-7 axis was profoundly perturbed compared with HC,IR,INR,and ICL. Genes involved in T cell and monocyte/macrophage function,autophagy,and cell migration were differentially expressed in EXID. Two of the 5 EXIDs had autoantibodies causing ADCC,while 2 different EXIDs had an increased inflammasome/caspase-1 activation despite consistently ART-suppressed pVL. CONCLUSIONS EXID is a distinct immunological outcome compared with previously described INR. Anti-CD4+ T cell autoantibodies and aberrant inflammasome/caspase-1 activation despite suppressed HIV-1 viremia are among the mechanisms responsible for EXID. View Publication

TET enzymes are dioxygenases that promote DNA demethylation by oxidizing the methyl group of 5-methylcytosine to 5-hydroxymethylcytosine (5hmC). Here,we report a close correspondence between 5hmC-marked regions,chromatin accessibility and enhancer activity in B cells,and a strong enrichment for consensus binding motifs for basic region-leucine zipper (bZIP) transcription factors at TET-responsive genomic regions. Functionally,Tet2 and Tet3 regulate class switch recombination (CSR) in murine B cells by enhancing expression of Aicda,which encodes the activation-induced cytidine deaminase (AID) enzyme essential for CSR. TET enzymes deposit 5hmC,facilitate DNA demethylation,and maintain chromatin accessibility at two TET-responsive enhancer elements,TetE1 and TetE2,located within a superenhancer in the Aicda locus. Our data identify the bZIP transcription factor,ATF-like (BATF) as a key transcription factor involved in TET-dependent Aicda expression. 5hmC is not deposited at TetE1 in activated Batf-deficient B cells,indicating that BATF facilitates TET recruitment to this Aicda enhancer. Our study emphasizes the importance of TET enzymes for bolstering AID expression and highlights 5hmC as an epigenetic mark that captures enhancer dynamics during cell activation. View Publication