Identification of a novel BET bromodomain inhibitor-sensitive, gene regulatory circuit that controls Rituximab response and tumour growth in aggressive lymphoid cancers.: CYCLON-induced Rituximab resistance

International audienceImmuno-chemotherapy elicit high response rates in B-cell non-Hodgkin lymphoma but heterogeneity in response duration is observed, with some patients achieving cure and others showing refractory disease or relapse. Using a transcriptome-powered targeted proteomics screen, we discovered a gene regulatory circuit involving the nuclear factor CYCLON which characterizes aggressive disease and resistance to the anti-CD20 monoclonal antibody, Rituximab, in high-risk B-cell lymphoma. CYCLON knockdown was found to inhibit the aggressivity of MYC-overexpressing tumours in mice and to modulate gene expression programs of biological relevance to lymphoma. Furthermore, CYCLON knockdown increased the sensitivity of human lymphoma B cells to Rituximab in vitro and in vivo. Strikingly, this effect could be mimicked by in vitro treatment of lymphoma B cells with a small molecule inhibitor for BET bromodomain proteins (JQ1). In summary, this work has identified CYCLON as a new MYC cooperating factor that autonomously drives aggressive tumour growth and Rituximab resistance in lymphoma. This resistance mechanism is amenable to next-generation epigenetic therapy by BET bromodomain inhibition, thereby providing a new combination therapy rationale for high-risk lymphoma

Proteomic strategy for the identification of critical actors in reorganization of the post-meiotic male genome

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A six gene expression signature defines aggressive subtypes and predicts outcome in childhood and adult acute lymphoblastic leukemia

International audienceAbnormal gene expression in cancer represents an under-explored source of cancer markers and therapeutic targets. In order to identify gene expression signatures associated with survival in acute lymphoblastic leukemia (ALL), a strategy was designed to search for aberrant gene activity, which consists of applying several filters to transcriptomic datasets from two pediatric ALL studies. Six genes whose expression in leukemic blasts was associated with prognosis were identified:three genes predicting poor prognosis (AK022211, FASTKD1 and STARD4) and three genes associated with a favorable outcome (CAMSAP1, PCGF6 and SH3RF3). Combining the expression of these 6 genes could successfully predict prognosis not only in the two discovery pediatric ALL studies, but also in two independent validation cohorts of adult patients, one from a publicly available study and one consisting of 62 newly recruited Chinese patients. Moreover, our data demonstrate that our six gene based test is particularly efficient in stratifying MLL or BCR.ABL negative patients. Finally, common biological traits characterizing aggressive forms of ALL in both children and adults were found, including features of dormant hematopoietic stem cells, suggesting new therapeutic strategies

Receptor-Independent Ectopic Activity of Prolactin Predicts Aggressive Lung Tumors and Indicates HDACi-Based Therapeutic Strategies

International audienceAims: Ectopic activation of tissue-specific genes accompanies malignant transformation in many cancers. Prolactin (PRL) aberrant activation in lung cancer was investigated here to highlight its value as a biomarker.Results: PRL is ectopically activated in a subset of very aggressive lung tumors, associated with a rapid fatal outcome, in our cohort of 293 lung tumor patients and in an external independent series of patients. Surprisingly PRL receptor expression was not detected in the vast majority of PRL-expressing lung tumors. Additionally, the analysis of the PRL transcripts in lung tumors and cell lines revealed systematic truncations of their 5' regions, including the signal peptide-encoding portions. PRL expression was found to sustain cancer-specific gene expression circuits encompassing genes that are normally responsive to hypoxia. Interestingly, this analysis also indicated that histone deacetylase (HDAC) inhibitors could counteract the PRL-associated transcriptional activity.Innovation and Conclusion: Altogether, this work not only unravels a yet unknown oncogenic mechanism but also indicates that the specific category of PRL-expressing aggressive lung cancers could be particularly responsive to an HDAC inhibitor-based treatment

Bromodomain-dependent stage-specific male genome programming by Brdt: Brdt: a master regulator of spermatogenesis

International audienceMale germ cell differentiation is a highly regulated multistep process initiated by the commitment of progenitor cells into meiosis and characterized by major chromatin reorganizations in haploid spermatids. We report here that a single member of the double bromodomain BET factors, Brdt, is a master regulator of both meiotic divisions and post-meiotic genome repackaging. Upon its activation at the onset of meiosis, Brdt drives and determines the developmental timing of a testis-specific gene expression program. In meiotic and post-meiotic cells, Brdt initiates a genuine histone acetylation-guided programming of the genome by activating essential genes and repressing a ‘progenitor cells’ gene expression program. At post-meiotic stages, a global chromatin hyperacetylation gives the signal for Brdt's first bromodomain to direct the genome-wide replacement of histones by transition proteins. Brdt is therefore a unique and essential regulator of male germ cell differentiation, which, by using various domains in a developmentally controlled manner, first drives a specific spermatogenic gene expression program, and later controls the tight packaging of the male genome.</p

1q12 chromosome translocations form aberrant heterochromatic foci associated with changes in nuclear architecture and gene expression in B cell lymphoma.

International audienceEpigenetic perturbations are increasingly described in cancer cells where they are thought to contribute to deregulated gene expression and genome instability. Here, we report the first evidence that a distinct category of chromosomal translocations observed in human tumours--those targeting 1q12 satellite DNA--can directly mediate such perturbations by promoting the formation of aberrant heterochromatic foci (aHCF). By detailed investigations of a 1q12 translocation to chromosome 2p, in a case of human B cell lymphoma, aberrant aHCF were shown to be localized to the nuclear periphery and to arise as a consequence of long range 'pairing' between the translocated 1q12 and chromosome 2 centromeric regions. Remarkably, adjacent 2p sequences showed increased levels of repressive histone modifications, including H4K20me3 and H3K9me3, and were bound by HP1. aHCF were associated to aberrant spatial localization and deregulated expression of a novel 2p gene (GMCL1) that was found to have prognostic impact in diffuse large B cell lymphoma. Thus constitutive heterochromatin rearrangements can contribute to tumourigenesis by perturbing gene expression via long range epigenetic mechanisms

Chromatin-to-nucleoprotamine transition is controlled by the histone H2B variant TH2B.

International audienceThe conversion of male germ cell chromatin to a nucleoprotamine structure is fundamental to the life cycle, yet the underlying molecular details remain obscure. Here we show that an essential step is the genome-wide incorporation of TH2B, a histone H2B variant of hitherto unknown function. Using mouse models in which TH2B is depleted or C-terminally modified, we show that TH2B directs the final transformation of dissociating nucleosomes into protamine-packed structures. Depletion of TH2B induces compensatory mechanisms that permit histone removal by up-regulating H2B and programming nucleosome instability through targeted histone modifications, including lysine crotonylation and arginine methylation. Furthermore, after fertilization, TH2B reassembles onto the male genome during protamine-to-histone exchange. Thus, TH2B is a unique histone variant that plays a key role in the histone-to-protamine packing of the male genome and guides genome-wide chromatin transitions that both precede and follow transmission of the male genome to the egg

Chromatin-to-nucleoprotamine transition is controlled by the histone H2B variant TH2B.

International audienceThe conversion of male germ cell chromatin to a nucleoprotamine structure is fundamental to the life cycle, yet the underlying molecular details remain obscure. Here we show that an essential step is the genome-wide incorporation of TH2B, a histone H2B variant of hitherto unknown function. Using mouse models in which TH2B is depleted or C-terminally modified, we show that TH2B directs the final transformation of dissociating nucleosomes into protamine-packed structures. Depletion of TH2B induces compensatory mechanisms that permit histone removal by up-regulating H2B and programming nucleosome instability through targeted histone modifications, including lysine crotonylation and arginine methylation. Furthermore, after fertilization, TH2B reassembles onto the male genome during protamine-to-histone exchange. Thus, TH2B is a unique histone variant that plays a key role in the histone-to-protamine packing of the male genome and guides genome-wide chromatin transitions that both precede and follow transmission of the male genome to the egg

The prognostic Role of hepatic venous pressure gradient in cirrhotic patients undergoing elective extrahepatic surgery

Background & aims: Surgery in cirrhosis is associated with a high morbidity and mortality. Retrospectively reported prognostic factors include emergency procedures, liver function (MELD/Child-Pugh scores) and portal hypertension (assessed by indirect markers). This study assessed the prognostic role of hepatic venous pressure gradient (HVPG) and other variables in elective extrahepatic surgery in patients with cirrhosis. Methods: A total of 140 patients with cirrhosis (Child-Pugh A/B/C: 59/37/4%), who were due to have elective extrahepatic surgery (121 abdominal; 9 cardiovascular/thoracic; 10 orthopedic and others), were prospectively included in 4 centers (2002-2011). Hepatic and systemic hemodynamics (HVPG, indocyanine green clearance, pulmonary artery catheterization) were assessed prior to surgery, and clinical and laboratory data were collected. Patients were followed-up for 1 year and mortality, transplantation, morbidity and post-surgical decompensation were studied. Results: Ninety-day and 1-year mortality rates were 8% and 17%, respectively. Variables independently associated with 1-year mortality were ASA class (American Society of Anesthesiologists), high-risk surgery (defined as open abdominal and cardiovascular/thoracic) and HVPG. These variables closely predicted 90-, 180- and 365-day mortality (C-statistic >0.8). HVPG values >16 mmHg were independently associated with mortality and values ≥20 mmHg identified a subgroup at very high risk of death (44%). Twenty-four patients presented persistent or de novo decompensation at 3 months. Low body mass index, Child-Pugh class and high-risk surgery were associated with death or decompensation. No patient with HVPG 0.63 developed decompensation. Conclusions: ASA class, HVPG and high-risk surgery were prognostic factors of 1-year mortality in cirrhotic patients undergoing elective extrahepatic surgery. HVPG values >16 mmHg, especially ≥20 mmHg, were associated with a high risk of post-surgical mortality.Supported in part by grants from Ministerio de Educacion yCiencia (SAF-2016-75767-R), and from Instituto de Salud CarlosIII (PIE 15/00027). CIBERehd is funded by Instituto de Salud Car-los III. ER was recipient of a Río Hortega award (2012–2014),Instituto de Salud Carlos III