Oncogène | EPFL Graph Search

Les oncogènes (du grec onkos, signifiant vrac, masse ou tumeur et génos signifiant génération, naissance, origine) sont une catégorie de gènes dont l'expression favorise la survenue de cancers. Ce sont des gènes qui commandent la synthèse d'oncoprotéines, protéines stimulant la division cellulaire ou inhibant la mort cellulaire programmée (apoptose), ce qui déclenche une prolifération désordonnée des cellules. Le terme oncogène peut désigner aussi des virus qui provoquent l'apparition de cancers. On parle d'oncovirus. Introduction Notre organisme est composé d'environ 10 cellules réparties dans plus de 200 types cellulaires différents qui composent les tissus (cellules sanguines, nerveuses, germinales, etc.). La prolifération cellulaire au sein de ces tissus est rigoureusement contrôlée au cours de notre vie ; certaines cellules (les neurones) ne nécessitant pas un renouvellement constant, d'autres étant perpétuellement en cours de multiplication (cellules sanguines ou

Organoid Profiling Identifies Common Responders to Chemotherapy in Pancreatic Cancer

Candice Megan T Young

Pancreatic cancer is the most lethal common solid malignancy. Systemic therapies are often ineffective, and predictive biomarkers to guide treatment are urgently needed. We generated a pancreatic cancer patient-derived organoid (PDO) library that recapitulates the mutational spectrum and transcriptional subtypes of primary pancreatic cancer. New driver onco-genes were nominated and transcriptomic analyses revealed unique clusters. PDOs exhibited heterogeneous responses to standard-of-care chemotherapeutics and investigational agents. In a case study manner, we found that PDO therapeutic profiles paralleled patient outcomes and that PDOs enabled longitudinal assessment of chemosensitivity and evaluation of synchronous metastases. We derived organoid-based gene expression signatures of chemosensitivity that predicted improved responses for many patients to chemotherapy in both the adjuvant and advanced disease settings. Finally, we nominated alternative treatment strategies for chemorefractory PDOs using targeted agent therapeutic profiling. We propose that combined molecular and therapeutic profiling of PDOs may predict clinical response and enable prospective therapeutic selection. SIGNIFICANCE: New approaches to prioritize treatment strategies are urgently needed to improve survival and quality of life for patients with pancreatic cancer. Combined genomic, transcriptomic, and therapeutic profiling of PDOs can identify molecular and functional subtypes of pancreatic cancer, predict therapeutic responses, and facilitate precision medicine for patients with pancreatic cancer. (C) 2018 AACR.

2018

RNA-Protein interactions at AU-rich elements

Ramona Pauchard-Batschulat

The expression of many proto-oncogenes, nuclear transcription factors and cytokines is regulated post-transcriptionally by specific interactions between distinct cis-elements within the mRNA and trans-acting factors that bind to these elements and thereby either promote or inhibit the rapid decay of the mRNA. This kind of regulation enables the cell to rapidly respond to changes in the cellular environment. These elements are usually located within the 3’UTR of the mRNA, rich in adenylate and uridylate and called AU-rich elements or AREs. To date, many of these trans-acting factors have been determined and among the best studied are the stabilizing HuR, the rather destabilizing AUF1 and the destabilizing KSRP and TTP. Previous studies have suggested that these ARE-BPs as well as yet unidentified factors might have overlapping target specificities and bind either in a concurrent, concomitant or maybe an even cooperative fashion to their targets to regulate mRNA half-life. However, the exact manner of how these factors might interact and how these interactions might be influenced, is largely unknown. Thus, my first project aimed to study the interactions between AUF1, KSRP and HuR in the context of the 3’UTRs of RANKL and Bcl-6 that were recently identified as AUF1 targets with a short half-life. By combining ARE-BP immunoprecipitations with qRT-PCR analysis of co-precipitated reporter RNAs, we were able to gain interesting insight into the RNA-protein interactions at AU-rich elements. However, this approach is very laborious and can study RNA-protein interactions only within a limited context. Yet, the pools of mRNA targets as well as binding factors are very multifaceted and likely depend on the cell type and condition as well as the cellular environment. Thus, a much broader approach is necessary to reveal the entire network of RNA-protein and protein-protein interactions at AU-rich elements. A promising technique is the combination of ARE-BP immunoprecipitation and high-throughput sequencing to analyze co-precipitated RNA. This approach allows for the extraction of a lot of important data from a single experiment as for example the virtually complete pool of target mRNAs under the studied conditions, the binding sites within these mRNAs as well as the frequency with which these sequences were detected. Based on these data, it would be possible to make suggestions about the binding specificities as well as potential, yet un-identified targets. If accumulating data sets for different cellular or environmental conditions, we might gain insight into the regulation of these RNA-protein interactions. In a similar way, the comparison of data sets for different ARE-binding proteins would give us further insight into the protein-protein interactions at and around AU-rich elements. Therefore, my second project focused on the development of a novel protocol that allows for the rapid, reliable and reproducible generation of high-throughput sequencing samples based on co-immunoprecipitated RNA fragments.

EPFL2013

Identification of genetic insulator elements to increase the safety of viral gene therapy vectors

Armelle Gaussin

Haematopoeitic system diseases, both acquired and inherited, can be currently cured by allogeneic haematopoietic stem cell transplantation. This treatment provides highly successful immune function recovery for patients receiving grafts of HLA-compatible donors but has still a great risk of complications and even failure if no suitable donor is available. Among the alternative therapeutic options, ex vivo retrovirus-mediated gene transfer into haematopoietic progenitor cells has been shown to be an efficient strategy for a substantial number of severe combined immunodeficiency-suffering patients. A recent gene therapy trial has been remarkably effective for the immunological reconstitution of patients suffering from X-linked severe combined immunodeficiency. This treatment was able to provide full correction of disease phenotype and thus, clinical benefit. However, the appearance of leukemia in several patients has put in question the safety of the procedure. This severe adverse event has been attributed to the integration of the therapeutic transgene-carrying viral vector into a known T-cell oncogene, LMO2, thereby contributing to the development of T-cell leukemia by causing aberrant expression of LMO2. Further studies mentioned the possible retroviral-mediated cis-activation of the LMO2 promoter underlying the potential ability of retroviral regulatory elements to influence neighboring gene transcription. This project aimed at decreasing the risk associated with the use of viral vectors for gene therapy through the identification of genetic insulator elements capable of isolating the vector regulatory elements in order to prevent the activation of chromosomal genes by the viral enhancers. We have established a standardized screening procedure whereby the potency of insulators can be assessed quantitatively on relevant vector elements. This assay system consists of a series of plasmids containing two reporter genes: one mimicking a therapeutic gene under the control of strong viral long terminal repeat (LTR) enhancer, and the other one standing for an endogenous gene close to the chromosomal vector integration site. The assay allowed the quantification of the enhancer blocking activity of the well-characterized chicken beta-globin 5'HS4 insulator (cHS4) in cultured cells. We assessed the insulator activity of novel synthetic elements, constructed from optimized binding sites for the insulator protein CTCF. In addition, we demonstrated the enhancer blocking activity of the nuclear factor 1 protein family (CTF/NF1) and showed that it also displays barrier properties, protecting transgene expression from silencing. We showed that both CTCF and CTF/NF1 binding sites act as insulators that mediate potent enhancer-blocker activity, resulting in a commensurate reduction of genotoxicity when implemented in viral gene therapy vectors. Finally, we used the same approach to analyze the enhancer blocking activity of well-known chromatin domain delimiters, matrix attachment regions (MAR), mainly characterized by their barrier properties. We could demonstrate the enhancer blocking ability of the 1-68 MAR that is mainly harbored by an A-T rich core sub-region.