Women with breast cancer without local metastasis to the axillary lymph nodes (axillary lymph node-negative, ANN) have a good prognosis. However, 20 to 30% of patients with ANN breast cancer will still experience recurrence and distant metastases. Lymphatic invasion (LVI) is an important prognostic factor for ANN breast cancer. Zinc fingers and homeoboxes 1 (ZHX1) was identified as a candidate gene involved in LVI and associated with early recurrence of ANN breast cancer. I examined expression of ZHX1 in breast cancer cell lines and ANN breast tumour samples and discovered that it is expressed at variable levels. I also investigated ZHX1 copy number and determined that amplification does not appear to be a mechanism of its over-expression. From bioinformatic and proteomic analyses, ZHX1 was discovered to potentially be phosphorylated. Overall, these studies suggest that ZHX1 may be involved in ANN breast cancer.

Programmed Cell Death 4 (PDCD4) is a known tumour suppressor, lost in carcinomas of the breast, prostate, colon, lung and ovary. This study found significantly reduced levels of PDCD4 mRNA and protein in both primary patient oral squamous cell carcinomas (OSCCs) and OSCC cell lines. Moreover, lower PDCD4 mRNA levels were significantly correlated with nodal metastasis (P=0.019). To determine the functional significance of PDCD4 down-regulation in OSCC we asked whether PDCD4 played a role in invasion. In fact, over-expression of PDCD4 decreased invasion of OSCC lines. We then sought to determine a mechanism for PDCD4 down-regulation in OSCC. Previous studies in breast and colon carcinomas suggested that reduced PDCD4 expression was due to over-expression of miR-21. Interestingly, miR-21 was inversely correlated to PDCD4 mRNA (P=0.002) and PDCD4 protein (P<0.001) levels in OSCC patient samples. Moreover, we found that miR-21 directly regulated PDCD4 protein expression in OSCC cell lines. This is the first report in OSCC that demonstrates that PDCD4 is down-regulated by miR-21 and may play a role in OSCC invasion.

Women with breast cancer without local metastasis to the axillary lymph nodes (axillary lymph node-negative, ANN) have a good prognosis. However, 20 to 30% of patients with ANN breast cancer will still experience recurrence and distant metastases. Lymphatic invasion (LVI) is an important prognostic factor for ANN breast cancer. Zinc fingers and homeoboxes 1 (ZHX1) was identified as a candidate gene involved in LVI and associated with early recurrence of ANN breast cancer. I examined expression of ZHX1 in breast cancer cell lines and ANN breast tumour samples and discovered that it is expressed at variable levels. I also investigated ZHX1 copy number and determined that amplification does not appear to be a mechanism of its over-expression. From bioinformatic and proteomic analyses, ZHX1 was discovered to potentially be phosphorylated. Overall, these studies suggest that ZHX1 may be involved in ANN breast cancer.

The establishment of exotic species in novel environments is a major environmental concern, however, few long-term studies have examined the effects of these species on their host environment and community, especially in forest ecosystems. The arrival and subsequent spread of the greater European pine shoot beetle, Tomicus piniperda (L.) (Coleoptera: Curculionidae, Scolytinae), into southern Ontario pine forests provided a natural experiment to assess biotic interactions between an exotic species and its new community over several years. Reproductive success of Tomicus piniperda colonies of various ages was studied between 2001 and 2004. The size and composition of competitor and natural enemy complexes present in these communities were also quantified over time. The impact of the natural enemy complexes on T. piniperda reproduction was assessed, Brood production (no. eggs and galleries/female) by T. piniperda populations rapidly approached those reported from its native range in Europe, with lower densities of parental adults. Thus, reproduction remained consistently above the replacement level for this beetle over all four years of study suggesting that these recently-introduced populations were growing rapidly and at a greater rate than in their country of origin. Tomicus piniperda successfully integrated into a large bark beetle community, and appeared to be capable of displacing native beetles to more marginal bark habitats, however, these competitors were not eliminated during the course of the study. The long-term effect of this marginalization on populations of native beetles is uncertain. Tomicus piniperda rapidly acquired natural enemies in the introduced areas, however, natural enemy-caused mortality did not show a regulating effect on its populations. It seems that intraspecific competition, rather than predation, regulates T. piniperda populations following introduction. The implications of these findings for the establishment and spread of exotic species in forest systems are examined, especially with reference to a prominent theory for success, the Enemy Release Hypothesis. In short, the Enemy Release Hypothesis is not applicable to an exotic species that is not regulated by natural enemies in its native range, and assessments of the Enemy Release Hypothesis should always include a determination of enemy regulation of the exotic in its native range.

L'OMS estime que d'ici 2030, le nombre de décès par cancer devrait poursuivre sa progression et atteindre 12 millions de personnes annuellement. À ce jour, le modèle des cellules souches cancéreuses (CSC) prend de plus en plus d'ampleur. Les CSC ont été j'objet de plusieurs hypothèses portant sur leurs propriétés de résistance à l'apoptose, à de nombreux médicaments ainsi qu'à l'irradiation. Ce modèle propose qu'une petite sous-population seulement de cellules au sein de la tumeur dispose d'une capacité significative de proliférer et de régénérer une nouvelle tumeur analogue à la tumeur primaire. Vu que le marqueur CD133 (prominine-1) a été identifié comme un des plus puissants marqueurs des CSC et que son expression est hautement significative dans les tumeurs récurrentes, nous avons voulu investiguer le phénotype invasif et inflammatoire associé à ce marqueur dans trois lignées cellulaire triées. La recherche présentée dans ce mémoire s'articule autour de trois axes de recherche principaux. Le premier concerne le potentiel invasif des CSC en réponse à des facteurs plaquettaires circulants, le S1P (sphingosine-1-phosphate) et le LPA (acide lysophosphatidique). Cette étude suggère la contribution de MT1-MMP au cours de la signalisation induite par le S1P. Le deuxième axe de recherche s'intéresse davantage à la modulation de l'expression des LRPs (low density lipoprotein receptor-associated protein), de Cox-2 et d'IkB dans un environnement inflammatoire, carcinogénique et hypoxique ; conditions qui miment l'environnement tumoral. Nos données expérimentales suggèrent que les différents traitements peuvent autant moduler l'expression génique des LRPs dans les cellules de la masse tumorale qu'affecter le niveau d'activité de liaison de ces récepteurs au sein des CSC CD133+. Notre étude nous amènent à proposer un modèle global dans lequel LRP apparaît comme un récepteur versatile au niveau de chaque condition engendrée et semble être également moduler dans le développement. Les fonctions de MT1-MMP ont également été investigué entre autre dans le phénotype inflammatoire des CSC CD133+. Les données de notre étude soutiennent la participation des fonctions de MT1-MMP dans l'expression de Cox-2 et cette contribution est impliquée à d'autres niveaux, autre que NFkB, dans la transcription de Cox-2. Finalement, le dernier volet de notre recherche traite du marqueur CD133, de son expression et de la corrélation entre le phénotype CD133 et la prolifération tumorale, Les difficultés rencontrées dans la détection et dans la purification des cellules CD133+ amène un questionnement à ce qui attrait à l'utilisation de CD133 comme marqueur exclusif de CSC cérébrales. L'ensemble de nos recherches vise donc à identifier de nouvelles voies de signalisation et des partenaires moléculaires influençant le phénotype invasif et inflammatoire des CSC. L'identification de MT1-MMP ou des axes MT1-MMP/S1P ou MT1-MMP/Cox-2 sont des cibles thérapeutiques prometteuses dans le traitement du cancer et également des CSC CD133+, De plus, cette étude nous permet d'affirmer qu'une investigation plus spécifique de l'expression des LRPs au sein de chaque type de cancer doit être effectuée afin de discerner le rôle versatile de ces récepteurs dans la progression tumorale et dans le développement. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : cellule souche cancéreuse, CD133, MMP, LRP, Cox-2, invasion, inflammation.

Cancer is a complex, multi-scale disease marked by unchecked cellular growth and proliferation. As a tumor grows, it is known to lose its capacity to maintain a compact structure. This stage of development, known as invasion, is marked by the disaggregation and dispersion of peripheral cells, and the formation of finger-like margins. This thesis provides an overview of three multi-scale models of tumor growth and invasion. The hybrid discrete-continuum (HDC) model couples a cellular automaton approach, which is used to direct the behavior and interactions of individual cells, with a system of reaction-diffusion-chemotaxis equations that describe the micro-environment. The evolutionary hybrid cellular automaton (EHCA) model maintains the core of the HDC approach, but employs an artificial response network to describe cellular dynamics. In contrast to these two, the immersed boundary (IBCell) model describes cells as fully deformable, viscoelastic entities that interact with each other using membrane bound receptors. As part of this thesis, the HDC model has been modified to examine the role of the ECM as a barrier to cellular expansion. The results of these simulations will be presented and discussed in the context of tumor progression.

<p>Basement membranes are dense, sheet-like forms of extracellular matrix that</p><p>surround the epithelial tissues of metazoan organisms. While these structures are</p><p>critical for epithelial support and tissue organization, basement membranes also pose</p><p>formidable barriers to most cells. However, certain specialized cells are able to breach</p><p>these barriers and move between tissues. Acquisition of cell invasive behavior by some</p><p>tumor cells is thought be an important step in cancer progression. Due to the clear basic</p><p>and clinical importance of understanding the mechanisms underlying cell invasion</p><p>through basement membranes, cell invasive behaviors has been an area of intense study.</p><p>In this work I examine a developmentally regulated model of cell invasive behavior in</p><p>the nematode worm, C. elegans. In this system a single proto-epithelial cell remodels</p><p>basement membrane to connect two epithelial tissues, the uterus and vulva. Using this</p><p>model I identify a novel role for UNC-6/Netrin signaling during this process through basement membranes. I show that Netrin signaling is a third regulatory input for AC invasion that functions partially in parallel to fos-1a and the vulval signal. Further I link netrin signaling to the formation of invasive protrusions that penetrate basement membrane.</p> / Dissertation

The mammalian intestine contains a dense and diverse community of microorganisms. The resident microbiota makes contributions to host to promote proper immune system development and limit pathogen colonization. In this study, the effects of microbiota disruption with or without TLRs stimulation on intestinal permeability and immunity were examined in C57BL/6 mice receiving antibiotic treatment for 6 days and in antibiotics-treated mice received dead E. coli or S. aureus at day 4. The results showed that antibiotic treatment significantly decreased the total number of bacteria including specific aerobic group Enterobacteriaceae and Enterococcus, and specific anaerobic group Lactococcus/Bifidobacterium in intestinal mucosa and lumen. Although only a slight increase in the intestinal permeability and no change in caspase-3 activity of intestinal mucosa were observed after antibiotic treatment, the bacterial translocation (BT) to mesenteric lymph nodes (MLN) increased significantly. Subsequent experiments showed that antibiotic treatment decreased the mucosal killing activity and the expression of non-defensin family including RegIII£], RegIII£^, CRP-ductin and RELM£] but not the defensin family, and increased the translocation of pathogen K. pneumoniae significantly, suggesting that the increase of BT to MLN after antibiotic treatment is likely due to a reduction in gut immunity rather than an increase of intestinal permeability. Moreover, stimulation of TLR4 reversed the effect of antibiotic treatment, suggesting that the functioning of TLR4 in intestinal epithelium is required to prevent pathogenic invasion and maintain intestinal homeostasis.

Zugl.: Berlin, Humboldt-Univ., Diss., 2009

Glioblastoma (GB) is the highest grade and most common form of primary adult brain tumors, characterized by a highly invasive cell population. GB tumors develop treatment resistance and ultimately recur; the median survival is nearly fifteen months and importantly, the invading cell population is attributed with having a decreased sensitivity to therapeutics. Thus, there remains a necessity to identify the genetic and signaling mechanisms that promote tumor spread and therapeutic resistance in order to develop new targeted treatment strategies to combat this rapidly progressive disease. TWEAK-Fn14 ligand-receptor signaling is one mechanism in GB that promotes cell invasiveness and survival, and is dependent upon the activity of multiple Rho GTPases including Rac1. Here, we show that Cdc42 is essential in Fn14-mediated Rac1 activation. We identified two guanine nucleotide exchange factors (GEFs), Ect2 and Trio, involved in the TWEAK-induced activation of Cdc42 and Rac1, respectively, as well as in the subsequent TWEAK-Fn14 directed glioma cell migration and invasion. In addition, we characterized the role of SGEF in promoting Fn14-induced Rac1 activation. SGEF, a RhoG-specific GEF, is overexpressed in GB tumors and promotes TWEAK-Fn14-mediated glioma invasion. Moreover, we characterized the correlation between SGEF expression and TMZ resistance, and defined a role for SGEF in promoting the survival of glioma cells. SGEF mRNA and protein expression are regulated by the TWEAK-Fn14 signaling axis in an NF-kB dependent manner and inhibition of SGEF expression sensitizes glioma cells to TMZ treatment. Lastly, gene expression analysis of SGEF depleted GB cells revealed altered expression of a network of DNA repair and survival genes. Thus TWEAK-Fn14 signaling through the GEF-Rho GTPase systems which include the Ect2, Trio, and SGEF activation of Cdc42 and/or Rac1 presents a pathway of attractive drug targets in glioma therapy, and SGEF signaling represents a novel target in the setting of TMZ refractory, invasive GB cells.