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Yes / The NAD(+)-dependent deacetylase SIRT1 is involved in diverse cellular processes, and has also been linked with multiple disease states. Among these, SIRT1 expression negatively correlates with cancer survival in both laboratory and clinical studies. Active regulator of SIRT1 (AROS) was the first reported post-transcriptional regulator of SIRT1 activity, enhancing SIRT1-mediated deacetylation and downregulation of the SIRT1 target p53. However, little is known regarding the role of AROS in regulation of SIRT1 during disease. Here, we report the cellular and molecular effects of RNAi-mediated AROS suppression, comparing this with the role of SIRT1 in a panel of human cell lines of both cancerous and non-cancerous origins. Unexpectedly, AROS is found to vary in its modulation of p53 acetylation according to cell context. AROS suppresses p53 acetylation only following the application of cell damaging stress, whereas SIRT1 suppresses p53 under all conditions analysed. This supplements the original characterization of AROS but indicates that SIRT1 activity can persist following suppression of AROS. We also demonstrate that knockdown of AROS induces apoptosis in three cancer cell lines, independent of p53 activation. Importantly, AROS is not required for the viability of three non-cancer cell lines indicating a putative role for AROS in specifically promoting cancer cell survival.

<p dir="ltr">Given the relatively poor visual acuity of compound eyes, many insects have developed alternative means for navigating their environment. For example, insects often rely on chemosensation to find food, mates, and inter- and intraspecific communication. Eusocial insects in particular have developed complex systems of pheromone communication to organize their colonies, enabling them to partition labor for foraging, brood care, and colony defense tasks to different portions of the colony. A variety of genes coding for proteins are involved in detecting these chemicals, including gustatory receptors, ionotropic receptors, and odorant receptors (ORs). Eusocial insects, and especially ants, have evolved an expanded clade of ORs in their genome, likely due to an increased reliance on pheromones compared to other insects. The ability to recognize nestmates from non-nestmates is one of the vital functions performed by these ORs, which detect hydrocarbons present on the cuticle to distinguish friend from foe. However, research into the details of nestmate recognition has been stymied due to difficulties in manipulating OR genes. Despite advances in genetic sequencing and manipulation technologies, strict reproductive divisions within most ant lineages make generating transgenic ants nearly impossible, and so we have been left with limited options to further investigate these receptors. To narrow down the ORs that could be involved in nestmate recognition in the Argentine ant (Mayr, 1868), I took a multi-pronged approach of generating tissue transcriptomes to identify ORs that are selectively upregulated in the antennae, as well as conducting a phylostratigraphic analysis to identify which OR genes arose more recently in the Argentine ant genome. While conducting these analyses, it became necessary to reannotate the set of Argentine ant OR genes, due to current published annotations not containing the full breadth of <i>L. humile</i> ORs. Finally, I orally administered fluorescently-labelled dsRNA to workers, and tracked the extent to which ingested dsRNA is capable of traversing the tissues of ant workers, to investigate whether RNAi is a viable method for investigating gene function for genes showing tissue-selective expression. I discovered a subset of OR genes that are highly expressed in the antennae and confirmed that dsRNA is able to reach the antennae and knock down OR gene expression through ingestion, meaning that RNA interference is a viable method for the practical study of ant OR genes and can be used to further explore how individual ORs regulate nestmate recognition.</p>

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Durch den Transfer der Gene des heterodimeren T-Zellrezeptors (TZR) mithilfe viraler Vektoren können T-Zellen programmiert werden, ein ausgewähltes Antigen spezifisch zu erkennen. In klinischen Studien wurden solche T-Zellen bereits mit Erfolg zur Immuntherapie von Krebs und viralen Infektionen eingesetzt. Genmodifizierte T-Zellen unterscheiden sich jedoch von normalen T-Zellen, weil sie neben den beiden zelleigenen auch die zwei übertragenen TZR-Gene exprimieren. Diese Situation erlaubt die Bildung vier verschiedener TZR-Heterodimere: der zelleigene TZR, der übertragene TZR und zwei gemischte TZR, bestehend aus je einer übertragenen und einer zelleigenen TZR-Kette. Gemischte TZR bergen das Risiko von Nebenwirkungen, weil sie durch Zufall gesundes Körpergewebe erkennen und so Autoimmunität auslösen könnten. In dieser Arbeit wurden deshalb virale Vektoren entwickelt, die gleichzeitig mit der Übertragung von neuen TZR-Genen den zelleigenen TZR durch RNA Interferenz (RNAi) unterdrücken. Mikro-RNA (miRNA), die in den Vektor MP71 eingefügt wurden, reduzierten den zelleigenen TZR in Maus-T-Zellen um mehr als 85%. Dies hatte zur Folge, dass beide Ketten des übertragenen P14-TZR in gleicher Menge auf der Zelloberfläche exprimiert wurden und die Bildung von gemischten TZR reduziert wurde. In einem Mausmodell der adoptiven T-Zelltherapie verhinderte die Unterdrückung des zelleigenen TZR die Entstehung von Autoimmunität, die andernfalls durch gemischte TZR verursacht wurde. Im Gegensatz dazu führte die Anwendung von gentechnisch optimierten P14-TZR-Genen weder zur angeglichenen Oberflächenexpression der P14-TZR Ketten noch zu weniger Autoimmunität im Mausmodell. Ein anderes Tierexperiment zeigte, dass die miRNA die Funktion der genmodifizierten T-Zellen nicht beeinträchtigte. Schließlich wurde ein viraler Vektor entwickelt und getestet, der die Expression des zelleigenen TZR in menschlichen T-Zellen effektiv unterdrückte und die Bildung von gemischten TZR reduzieren konnte. / T cells can be genetically modified using viral vectors. The transfer of genes encoding both chains of the heterodimeric T cell receptor (TCR) programs T cells to specifically react towards an antigen of choice. Such TCR gene-modified T cells were already successfully applied in clinical studies to treat cancer and viral infections. However, in contrast to nonmanipulated T cells these cells express the transferred TCR in addition to the endogenous TCR and this situation allows the assembly of four different TCR heterodimers: the endogenous TCR, the transferred TCR, and two mixed TCR dimers, composed of one endogenous and one transferred TCR chain. The formation of mixed TCR dimers represents a safety issue because they may by chance recognize self-antigens and thereby cause autoimmune side effects. To overcome this problem, an RNAi-TCR replacement vector was developed that simultaneously silences the endogenous TCR and expresses an RNAi-resistant therapeutic TCR. The expression of miRNA encoded by a retroviral MP71 vector in transduced mouse T cells reduced the surface levels of the endogenous TCR by more than 85%. The knockdown of the endogenous TCR in turn resulted in equal surface expression levels of both transferred P14 TCR chains and prevented the formation of mixed TCR dimers. Accordingly, the development of lethal mixed TCR dimer-dependent autoimmunity (TI-GVHD) in a mouse model of adoptive T cell therapy was dramatically reduced by the knockdown of the endogenous TCR. In contrast, the usage of genetically optimized TCR genes neither resulted in equal surface levels of both P14 TCR chains nor in reduced autoimmunity. A second mouse model demonstrated that the in vivo functionality of the transduced T cells was not negatively influenced by the expression of the miRNA. Finally, an RNAi-TCR replacement vector for human T cells was developed that effectively reduced the expression of the endogenous TCR and prevented the formation of mixed TCR dimers.

Mehrere Studien haben gezeigt, daß die Cyclooxygenase-2 (COX-2) eine bedeutende Rolle sowohl bei Entstehung als auch Progression maligner Tumoren spielt. COX-2-Inhibitoren werden bereits in klinischen Studien zur Krebstherapie getestet. COX-2 ist die induzierbare Isoform der Cyclooxygenase - dem Schlüsselenzym der Synthese von Prostaglandinen und anderen Eicosanoiden. Im Tier- und Zellkulturmodell konnten COX-Hemmer anti-Tumor-Effekte hervorrufen. Es ist jedoch unklar, ob diese Effekte durch Hemmung des COX-Enzyms oder durch COX-unabhängige Mechanismen vermittelt werden. Wir untersuchten daher die Auswirkung der COX-Inhibition zum einen durch den selektiven COX-2-Hemmer NS-398 sowie zum anderen durch COX-Isoform-spezifische RNA-Interferenz (RNAi) in zwei humanen Ovarialkarzinomzellinien (OVCAR-3 und SKOV-3). OVCAR-3 zeigte eine konstitutive COX-1-Expression und eine durch IL-1beta induzierbare COX-2-Expression. SKOV-3 war COX-1- und COX-2-negativ. IL-1beta führte bei OVCAR-3 zu einer vermehrten Produktion von Prostaglandin E2 (PGE2), die durch eine gegen die COX-2 gerichtete siRNA gehemmt werden konnte, wohingegen COX-1-siRNA keinen Effekt hatte. Das deutet darauf hin, daß die COX-2 die Hauptquelle von PGE2 in OVCAR-3 ist. 1mikroM NS-398 waren ausreichend, um die PGE2-Produktion und somit auch die COX-2 in OVCAR-3 zu inhibieren. Höhere Konzentrationen NS-398 (>10mikroM) hatten einen antiproliferativen Effekt. Auch in der COX-2-negativen Zellinie SKOV-3 trat diese Wachstumshemmung auf; sie war nicht durch exogene Zufuhr von PGE2 (10mikroM) reversibel. Durchflußzytometrische Zellzyklusanalyse ergab, daß der Wachstumshemmung in beiden Zellinien ein G0/G1-Zellzyklusarrest zugrunde liegt. Dagegen führten weder COX-1- noch COX-2-Ausschaltung durch RNAi zu ähnlichen Auswirkungen auf Proliferation bzw. Zellzyklus. Diese Ergebnisse zeigen, dass ein COX-2-unabhängiger Mechanismus für den durch NS-398 induzierten G0/G1-Arrest verantwortlich ist. / Several studies have provided evidence that the enzyme Cyclooxygenase-2 (COX-2) plays an important role in tumor development and progression. COX-2-inhibitors are already evaluated in clinical trials as cancer therapeutics. COX-2 is the inducible isoform of cyclooxygenase - the rate-limiting enzyme in the synthesis of prostaglandins and other eicosanoids. COX-inhibitors cause antitumor effects in animal models and in cell culture experiments. However, it is not clear, whether these effects are due to inhibition of the COX-enzyme or mediated via a COX-independent mechanism. We therefore investigated the effects of COX inhibition by the selective COX-2-inhibitor NS-398, as well as by COX-isoform specific RNA interference (RNAi) in the human ovarian carcinoma cell lines OVCAR-3 and SKOV-3. OVCAR-3 cells showed a constitutive expression of COX-1, and an inducible COX-2 expression. COX-2 was induced through stimulation with Interleukin-1beta, leading to production of high levels of Prostaglandin E2 (PGE2). SKOV-3 cells were negative for both COX isoforms. Selective COX-2-suppression by RNAi reduced PGE2 production in OVCAR-3, whereas COX-1-siRNA had no effect on PGE2 synthesis. Thus, COX-2 is the main source of PGE2 in OVCAR-3 cells. In these cells, 1microM NS-398 was sufficient to completely inhibit PGE2-synthesis - and thus the activity of the COX-2 enzyme. Increasing amounts of NS-398 (>10microM) had an antiproliferative effect. This growth inhibition was also observed in the COX-negative cell line SKOV-3, it could not be reverted by exogenous addition of PGE2 (10microM). Flowcytometric analysis of the cell cycle revealed that this growth inhibition was based on a G0/G1-cell-cycle-arrest. In contrast, suppression of COX-1 or COX-2 by RNAi had no effect on proliferation or cell cycle progression. These results suggest that a COX-independent mechanism is responsible for the G0/G1-arrest induced by NS-398.

No description available.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal