No description available.

No description available.

No description available.

Despite the global effort to discover and improve ways to detect, treat, and monitor cancer, it still remains the second leading cause of death in the United States and poses a major health and economic burden worldwide. While traditional treatments like surgery, chemotherapy, radiation therapy, and hormone therapy have been successful and have decreased cancer mortality, cancer incidence in all sites continues to rise. Consequently, there is an immediate need to find new therapeutics for the treatment of cancer. In recent years, and with the continuing push towards personalized medicine, cancer biomarkers have become crucial to detect, treat, and monitor cancer. Thymidine kinase 1 (TK1) has been identified as a cancer biomarker with diagnostic, prognostic, and therapeutic potential. TK1 is a nucleotide salvage pathway enzyme responsible for maintaining a balance in the cell nucleotide pool and providing the cell with thymidine monophosphate, which upon further phosphorylation is incorporated into DNA during cell replication. TK1 has been found to be upregulated in the serum of cancer patients. Serum TK1 (sTK1) has been used as an early diagnostic and prognostic biomarker in many types of cancer and has been shown to be a better proliferation biomarker than Ki67. In this dissertation, we described the characterization of TK1 as a cancer biomarker that associates with the plasma membrane of hematological malignancies such as Burkitt's lymphoma, acute lymphoblastic leukemia, acute promyelocytic leukemia, acute T cell lymphoma, and solid malignancies such as lung, breast, and colon cancer. We also describe the different oligomeric TK1 forms that are found on the cell membrane and show that membrane TK1 has activity. We assess the clinical relevance of TK1 in all these malignancies, looking at tissue expression as well as gene expression from patients from The Cancer Genome Atlas database. We find that TK1 is not expressed on the surface of normal cells, whether they are proliferating or not, making TK1 a unique cancer biomarker, with the potential to be used in targeted therapy. We also find that TK1 expressed on the surface may be involved in the invasion potential of cancer cells. The knowledge gained from this study will help researchers working in clinical research and cancer immunotherapeutics to potentially use TK1 as a biomarker and cancer target, and thus providing another weapon against cancer. In this dissertation, we described the characterization of TK1 as a cancer biomarker that associates with the plasma membrane of hematological malignancies such as Burkitt's lymphoma, acute lymphoblastic leukemia, acute promyelocytic leukemia, acute T cell lymphoma, and solid malignancies such as lung, breast, and colon cancer. We also describe the different oligomeric TK1 forms that are found on the cell membrane and show that membrane TK1 has activity. We assess the clinical relevance of TK1 in all these malignancies, looking at tissue expression as well as gene expression from patients from The Cancer Genome Atlas database. We find that TK1 is not expressed on the surface of normal cells, whether they are proliferating or not, making TK1 a unique cancer biomarker, with the potential to be used in targeted therapy. We also find that TK1 expressed on the surface may be involved in the invasion potential of cancer cells. The knowledge gained from this study will help researchers working in clinical research and cancer immunotherapeutics to potentially use TK1 as a biomarker and cancer target, and thus providing another weapon against cancer.

No description available.

Thèse (M.Sc.)--Université Laval, 2005. / Titre de l'écran-titre (visionné le 13 févr. 2008). Bibliogr.

Thesis (Ph.D.)(Genetics)--University of Pretoria, 2006. / Includes summary. Available on the Internet via the World Wide Web.

We describe a simple, sensitive, nonradioactive, relatively rapid and relatively inexpensive protocol to measure DNA synthesis in cultured cells by a chemiluminescent bromodeoxyuridine (BrdU) enzyme-linked immunosorbent assay (ELISA). We show that it exhibits similar sensitivity and activity as traditional 3H-thymidine incorporation assays and a commercial chemiluminescent BrdU ELISA kit when tested in commonly used cell lines, such as NIH 3T3 cells, mink lung epithelial cells (Mv1LU), and baby hamster kidney (BHK-21) fibroblasts. This assay also exhibits a wider dynamic range than colorimetric BrdU ELISA methods. Besides being a viable, nonradioactive alternative to 3H-thymidine incorporation assays, our BrdU ELISA is less expensive than a commercial chemiluminescent BrdU ELISA kit.

Résumé : Lors de l’utilisation de la radiation pour le diagnostic et le traitement du cancer, l’ADN est une cible importante due à son rôle dans la division cellulaire. La radiation y dépose de l’énergie par production abondante (10[indice supérieur 5] e[indice supérieur −]/MeV) d’électrons de basse énergie (EBE) (<50 eV) menant à la production de radicaux et à la dissociation de molécules. Une meilleure compréhension de ces phénomènes physico-chimiques mènera au développement de nouvelles stratégies en radioprotection et en radiothérapie. Il est primordial d’identifier et de quantifier ces dommages initiaux. Suite à des résultats obtenus par des expériences récentes (Li et al., 2010) sur des couches minces d’ADN irradiées par des EBE dans le vide, nous suggérons que certains produits désorbent en quantité significative. Nous proposons une méthode pour mesurer cette perte de matière en utilisant une balance à quartz pour mesurer in situ les changements de masse totale. Ce mémoire présentera la conception et la construction de l’appareil ainsi que les résultats d’irradiation de la thymine et de la thymidine. À 25 ◦ C, le taux de perte de masse spontanée des échantillons joue un rôle important pour les petites molécules comme la thymine (126 uma). L’irradiation augmente d’abord ce taux qui diminue d’un facteur 5 à 15 après une exposition prolongée, signe de modifications notables de l’échantillon. Pour des molécules plus imposantes comme la thymidine (242 uma), il n’y a pas de désorption spontanée et le taux de désorption induite par des électrons de 50 eV est de 0,4 ± 0,1 uma/e[indice supérieur -]. Cette méthode, nécessaire à la calibration d’autres expériences réalisées par HPLC et spectrométrie de masse, permet de compléter la quantificationdes fragments, qui peuvent aussi être l’origine de lésions subséquentes. / Abstract : DNA is the principle target of radiotherapy (RT) due to its crucial role in cellular growth and function. Ionizing radiation (IR) delivers its energy into the cell and its nucleus via sequential ionization events that produce many low-energy electrons (LEE)(10[superscript 5]e[superscript −] per MeV) which drive subsequent molecular dissociations and the formation of radicals and other reactive species. Since a better understanding of these mechanisms is needed to develop new strategies for radioprotection and RT, it is essential to identify and to quantify the initial damage induced by IR. Recent chromatographic (HPLC) analysis of short oligonucleotide irradiated with LEE in vacuo (Li et al., 2010) revealed that only ∼30 % of the loss of intact molecules could be explained by the formation of identifiable radiation products. We hypothesize that electron stimulated desorption (ESD) may account for some of the unexplained loss of the missing molecules. Here we propose a new experimental method to quantify this loss using a quartz crystal microbalance to measure in situ the total mass change due to ESD. This thesis describes the design and the construction of the novel apparatus and presents results for LEE irradiated thymine (thy) and thymidine (dT). We find that at 25 ◦ C, the thermal-induced mass loss is important for small molecules such as thy (126 amu). Upon irradiation at 50 eV, the rate of mass loss initially increases, but then decreased by factors between 5 and 15 indicating structural changes occurring at the sample surface. For larger molecules such as dT (242 amu), there is no thermal evaporation at 25 ◦ C and the LEE induced rate of desorption at 50 eV is 0.4 ± 0.1 amu/e[superscript -]. This work is needed to calibrate HPLC and mass spectrometry experiments allowing us to quantify the fragment species produced by LEE that are expected to induce further and biologically significant damage.

Cells die when they are starved of thymidine, one of the four DNA nucleotides. Since the discovery of this killing phenomenon, termed thymineless death (TLD), researchers have been trying to understand why. The goal of the work presented here is to use systems level approaches to shed light on this process. Because DNA synthesis is the only cellular process that requires thymidine, it is logical that the focus has been mainly on DNA stability and damage. My work expands the focus to new frontiers: acetate metabolism, the cytoplasm and the inner membrane. I generated thymidine auxotrophs in two genetic backgrounds by inactivating the thymidylate synthase enzyme, thyA. These mutants need supplementation with exogenous thymidine in order to survive. I used these strains in three experimental approaches to explore the mechanisms of TLD. Fitness profiling of a transposon insertion library in a thyA- strain, long-term laboratory evolution during thymidine-limitation, and RNA sequencing of TLD-sensitive and TLD-resistant strains identified genes in previously known processes as well as genes in novel processes. These approaches allowed me to gather rich data sets that identified many contributing genes. 52 genes showed consistent effects across approaches. My work confirms that ROS is a key contributor to killing during thymidine starvation and reveals that putrescine biosynthesis enzymes, an acetate overflow kinase, and the proton-transporting ATP synthase are novel players in TLD. I suggest that these three novel players contribute through their shared role in modulating cytoplasmic pH and propose a model in which DNA damage, ROS accumulation, and cytoplasmic acidification converge on the killing process during thymidine starvation. My findings expand the sites of critical action during TLD from the DNA to the cell’s inner and outer membranes and the cytoplasm. Theories on active vs. passive and specific vs. general bacterial death pathways will be discussed at the end.