The NCOR-HDAC3 co-repressive complex modulates the leukemogenic potential of the transcription factor ERG

The ERG (ETS-related gene) transcription factor is linked to various types of cancer, including leukemia. However, the specific ERG domains and co-factors contributing to leukemogenesis are poorly understood. Drug targeting a transcription factor such as ERG is challenging. Our study reveals the critical role of a conserved amino acid, proline, at position 199, located at the 3' end of the PNT (pointed) domain, in ERG's ability to induce leukemia. P199 is necessary for ERG to promote self-renewal, prevent myeloid differentiation in hematopoietic progenitor cells, and initiate leukemia in mouse models. Here we show that P199 facilitates ERG's interaction with the NCoR-HDAC3 co-repressor complex. Inhibiting HDAC3 reduces the growth of ERG-dependent leukemic and prostate cancer cells, indicating that the interaction between ERG and the NCoR-HDAC3 co-repressor complex is crucial for its oncogenic activity. Thus, targeting this interaction may offer a potential therapeutic intervention

Role of ETS1 in The Transcriptional Network of Diffuse Large B Cell Lymphoma of The Activated B Cell-like Type

Le lymphome diffus à grandes cellules B (DLBCL) est le type de lymphome le plus commun, représentant 25-30% de tous les cas dans les pays occidentaux. C'est une maladie hétérogène avec diverses présentations cliniques, biologiques et génétiques. On distingue au moins deux sous-groupes moléculaires principaux dans les lymphomes DLBCL caractérisés selon les différents stades de différenciation des cellules B: DLBCL à cellules germinales à centre germinatif (GCB) et DLBCL à cellules B activées (ABC). ABC-DLBCL est un sous-type agressif avec un faible pronostic vital pour le patient et ressemble génétiquement à des cellules B activées par BCR arrêtées au cours de la différenciation plasmacytique. Nous avons précédemment caractérisé un gain au locus chllq24.3 se produisant dans près d'un quart des cas de DLBCL. Le gain est associé à la surexpression de deux gènes appartenant à la famille ETS : ETS1 et FLI1. Le facteur de transcription ETS1 est un effecteur en aval de la signalisation de la kinase activée par les mitogènes et est connu pour réguler des caractéristiques biologiques telles que les métastases, la croissance et la différenciation dans le cancer. Nous avons également observé que ETS1 arborant la thréonine 38 phosphorylée, est principalement détecté dans le sous-type ABC de DLBCL, ce qui suggère que son activité transcriptionnelle est favorisée. Dans cette étude, nous avons trouvé que l'expression de ETS1 dans les lignées cellulaires ABC-DLBCL contribue à des caractéristiques telles que la signalisation des cellules B, le blocage de la différenciation des lymphocytes B, les voies réactives immunitaires et la régulation du cycle cellulaire. Parmi les gènes différemment exprimés, nous avons observé une diminution de l'expression des gènes HCST, CD52, FAIM3, RGS1.ARHGAP9 etSASH3 lorsque l'expression de ETS1 est diminuée par petit ARN interférant et ce dans cinq lignées cellulaires ABC-DLBCL. L'intégration des donnés avec les profils de chromatine disponibles au public pour ETS1, a permis l'identification de gènes cibles de ETS1 parmi nos résultats. FAIM3, un récepteur Fc IgM, module l'activité de la voie de signalisation BCR et détermine potentiellement le destin cellulaire dans les cellules B, nous amenant à étudié son expression en relation avec DLBCL et ETS1. La stimulation IgM des lignées cellulaires exprimant un mutant ETS1 introduit par voie rétrovirale et dépourvu de la phosphorylation de la thréonine 38, couplé au knockdown de ETS1 endogène, a montré une diminution de l'induction de l'ARNm FAI M 3 par rapport au control. Dans un échantillon clinique de patients atteints de DLBCL, l'expression de FAI M 3 était plus élevée dans le sous-type ABC, conformément aux données sur les lignées cellulaires. Enfin, nous avons confirmé que les protéines SF3B1, THOC4, NOP56 et DDX21, principalement impliquées dans la biogenèse de l'ARN, étaient de nouveaux partenaires interagissant avec ETS1. À partir de notre profil d'expression génique, nous avons également observé que ETS1 supprimait principalement les ensembles de gènes impliqués dans la biogenèse et le traitement de l'ARN, suggérant que ETS1 pourrait avoir une fonction inhibitrice sur les protéines précédemment mentionnés. En conclusion, l'expression de ETS1 influence les réseaux de gènes préalablement reconnus comme des caractéristiques importantes définissant le sous-type ABC-DLBCL. Le gène FAIM3 a été identifié comme une nouvelle cible du facteur de transcription ETS1. Tandis qu'une étude plus approfondie de la fonction biologique exacte de FAIM3 dans DLBCL est nécessaire, il a été démontré que ce dernier modifie la différenciation des cellules B et l'activation des cellules B, deux caractéristiques dérégulées dans le sous-type ABC-DLBCL. -- Diffuse large B cell lymphoma [DLBCL) is the commonest type of lymphoma, accounting for 25-30% of ail cases in Western countries. It is a heterogeneous disease with diverse clinical, biological and genetic présentations. At least two main subsets/molecular entities are distinguished within DLBCL lymphomas that represent their cell of origin at différent stages of B cell differentiation: germinal center B cell (GCB)-like DLBCL and activated B cell (ABC)-like DLBCL. ABC-DLBCL is an aggressive subtype with poor patient outcome and resembles genetically BCR-activated B cells arrested during plasmacytic differentiation. We have previously characterized a gain at chllq24.3 that occurs in up to a fourth of DLBCL cases. The gain is associated with the overexpression of two ETS genes, ETS1 and FLI1. The transcription factor ETS1 is a downstream effector of mitogen activated kinase signaling and known to regulate such biological features as metastasis, growth and differentiation in cancer. We have also observed that threonine 38 phosphorylated ETS1 is mainly detected in the ABC subtype of DLBCL, suggesting that its transcriptional activity is promoted. In this study we saw that ETS1 expression in ABC-DLBCL cell lines contributes to features such as B cell signaling, block of B cell differentiation, immune responsive pathways, and cell cycle régulation. Among our differently expressed genes we observed HCST, CDS2, FAIM3, RGS1, ARHGAP9 and SASH3 to be downregulated after ETS1 knock down by small interfering RNA in five ABC-DLBCL cell lines. Intégration with publicly available chromatin profiles for ETS1 allowed the identification of direct ETS1 target genes among our findings. FAIM3, an IgM Fc receptor, modulâtes the activity of the BCR signaling pathway and potentially détermines cell fate in B cell, as such we investigated its expression in relation to DLBCL and ETS1. IgM stimulation of cell lines expressing a retrovirally introduced ETS1 mutant lacking the threonine 38 phosphorylation while endogenous ETS1 was knocked down, showed a reduced induction of FAI M 3 mRNA expression compared to controls. In clinical specimen of DLBCL patients, FAI M 3 expression was higher in the ABC subtype, in accordance with cell line data. Lastly, we confirmed SF3B1, TH0C4, NOP56 and DDX21, proteins mainly involved in RNA biogenesis, as new interaction partners of ETS1. From our gene expression profiling we also observed that ETS1 mainly suppressed gene sets involved in RNA biogenesis and processing, suggesting that ETS1 could have an inhibitory function over the mentioned protein interactors. In conclusion ETS1 expression influenced the gene networks that have already been recognized as prominent features defining ABC-DLBCL. The FAIM3 gene was identified as a novel target of the ETS1 transcription factor. While fùrther investigation of the exact biological fonction of FAIM3 in DLBCL is needed, it is known to modify B cell differentiation and B cell activation two defining features deregulated in ABC-DLBCL

Role of ETS1 in the transcriptional network of diffuse large B cell lymphoma of the activated B cell-like type

Diffuse large B cell lymphoma (DLBCL) is a heterogenous disease that has been distinguished into at least two major molecular entities, the germinal center-like B cell (GCB) DLBCL and activated-like B cell (ABC) DLBCL, based on transcriptome expression profiling. A recurrent ch11q24.3 gain is observed in roughly a fourth of DLBCL cases resulting in the overexpression of two ETS transcription factor family members, ETS1 and FLI1. Here, we knocked down ETS1 expression by siRNA and analyzed expression changes integrating them with ChIP-seq data to identify genes directly regulated by ETS1. ETS1 silencing affected expression of genes involved in B cell signaling activation, B cell differentiation, cell cycle, and immune processes. Integration of RNA-Seq (RNA sequencing) data and ChIP-Seq (chromatin immunoprecipitation sequencing) identified 97 genes as bona fide, positively regulated direct targets of ETS1 in ABC-DLBCL. Among these was the Fc receptor for IgM, FCMR (also known as FAIM3 or Toso), which showed higher expression in ABC- than GCB-DLBCL clinical specimens. These findings show that ETS1 is contributing to the lymphomagenesis in a subset of DLBCL and identifies FCMR as a novel target of ETS1, predominantly expressed in ABC-DLBCL

Antitumor activity of the dual BET and CBP/EP300 inhibitor NEO2734

Bromodomain and extra-terminal domain (BET) proteins, cyclic adenosine monophosphate response element-binding protein (CBP), and the E1A-binding protein of p300 (EP300) are important players in histone acetylation. Preclinical evidence supports the notion that small molecules targeting these proteins individually or in combination can elicit antitumor activity. Here, we characterize the antitumor activity of the pan BET/CBP/EP300 inhibitor NEO2734 and provide insights into its mechanism of action through bromodomain-binding assays, in vitro and in vivo treatments of cancer cell lines, immunoblotting, and transcriptome analyses. In a panel of 60 models derived from different tumor types, NEO2734 exhibited antiproliferative activity in multiple cell lines, with the most potent activity observed in hematologic and prostate cancers. Focusing on lymphoma cell lines, NEO2374 exhibited a pattern of response and transcriptional changes similar to lymphoma cells exposed to either BET or CBP/EP300 inhibitors alone. However, NEO2734 was more potent than single-agent BET or CBP/EP300 inhibitors alone. In conclusion, NEO2734 is a novel antitumor compound that shows preferential activity in lymphomas, leukemias, and prostate cancers

The NCOR-HDAC3 co-repressive complex modulates the leukemogenic potential of the transcription factor ERG

Abstract The ERG (ETS-related gene) transcription factor is linked to various types of cancer, including leukemia. However, the specific ERG domains and co-factors contributing to leukemogenesis are poorly understood. Drug targeting a transcription factor such as ERG is challenging. Our study reveals the critical role of a conserved amino acid, proline, at position 199, located at the 3’ end of the PNT (pointed) domain, in ERG’s ability to induce leukemia. P199 is necessary for ERG to promote self-renewal, prevent myeloid differentiation in hematopoietic progenitor cells, and initiate leukemia in mouse models. Here we show that P199 facilitates ERG’s interaction with the NCoR-HDAC3 co-repressor complex. Inhibiting HDAC3 reduces the growth of ERG-dependent leukemic and prostate cancer cells, indicating that the interaction between ERG and the NCoR-HDAC3 co-repressor complex is crucial for its oncogenic activity. Thus, targeting this interaction may offer a potential therapeutic intervention