Browsing by Author "Kurz, Ebba"

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    Characterization of Salicylates as Novel Catalytic Inhibitors of Human DNA Topoisomerase II Alpha
    (2014-06-23) Bau, Jason; Kurz, Ebba
    Topoisomerase II (topo II) is a ubiquitous enzyme required for the maintenance of DNA topology. Due to its essential nature, many pharmaceuticals have been found to or developed to target the enzyme for both laboratory and clinical uses. Topo II poisons, such as doxorubicin and etoposide, are commonly used in cancer chemotherapy regimens and are cytotoxic due to their ability to covalently trap topo II on cleaved DNA, leading to the accumulation of DNA double-stranded breaks. In contrast, compounds that inhibit topo II catalytic activity without generating DNA double-stranded breaks are classified as catalytic inhibitors and impair enzyme function at a number of stages in the catalytic cycle, including DNA binding, DNA cleavage, ATP hydrolysis, and enzyme dissociation. Some catalytic inhibitors have been found to counter the DNA damaging effects of topo II poisons. This thesis describes work identifying salicylate as a novel catalytic inhibitor of topo II. It demonstrates that pretreatment of cells with salicylate, prior to treatment with topo II poisons, attenuates poison-induced DNA damage signaling mediated by the ATM protein kinase. This is associated with a concomitant loss of poison-induced DNA double- stranded breaks and consequently decreased cytotoxicity following treatment with topo II poisons. This work also demonstrates that salicylate does not block topo II-DNA binding, or trap the enzyme as a closed clamp on DNA. Rather, salicylate blocks DNA cleavage and enzyme-mediated ATP hydrolysis is impaired in a non-competitive manner. Furthermore, salicylate-mediated inhibition of topo II catalytic activity is selective for the alpha isoform of topo II. In investigating the structural determinants modulating potency of topo II inhibition, many compounds with structural similarities to salicylate, including the salicylate-based pharmaceuticals sulfasalazine and diflunisal, were found to also act as catalytic inhibitors of topo II. It was determined that potency is determined by modifications at the 2’-position that are electronegative and capable of donating a hydrogen bond, but that these effects are further influenced by substitutions at the 5’-position. Considered together, the data presented in this thesis establish a new role for a long-established drug.
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    Characterization of the In Vivo Consequences of Salicylate Co-Administration on the Efficacy of Topoisomerase II Poison-Based Chemotherapy in a Model of Human Breast Cancer
    (2017) Crovetto, Gina Marie Alexandra; Kurz, Ebba; Lees-Miller, Susan; Morris, Donald
    Human DNA topoisomerase IIα (TOP2A) is an essential enzyme that resolves the topological complexities of DNA, via transient DNA double-strand breaks (DSBs), during replication, transcription, and mitosis. Several gold-standard chemotherapeutics used for treating breast cancer are TOP2 poisons, which act by covalently trapping TOP2-DNA complexes leading to an accumulation of cytotoxic DNA DSBs. Salicylate, the primary metabolite of aspirin, catalytically inhibits DNA cleavage by TOP2A and is known to attenuate TOP2 poison cytotoxicity in MCF-7 breast cancer cells. Given, the widespread use of aspirin and other salicylate derivatives, determining their effects on chemotherapeutic efficacy could have far-reaching implications. To address this, a panel breast cancer cell lines was compiled to further characterize the effect of salicylate on TOP2 poison cytotoxicity. Following the in cyto work, a murine xenograft model of human breast cancer was used to evaluate the in vivo consequences of salicylate co-administration on TOP2 poison-based chemotherapy.
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    Fostering Deep Learning, Engagement, and Critical Thinking
    (2015-05-13) Benoit, Wendy; Mah, Megan; Kurz, Ebba; Kemp, Taylor; Finn, Patrick; de Groot, Anton
    Three student-faculty teams will share their perspectives and experiences that address the components of the conference theme: fostering deep learning, engagement, and critical thinking. The Faculty of Science team will explore reflective practice for deep learning. Reflective practices lead us to recognize our own deep learning experiences. We can then foster such experiences in our students by examining what we find to be most meaningful, and then using ongoing communication to know how students view and use these ideas. The team will discuss strategies for fostering deep learning in a second-year organic chemistry course: scaffolding class content around student work, and using worksheets to frame a cycle of practice and feedback. The Faculty of Medicine team will investigate six “high-impact” practices have been defined and positively linked with student learning, retention and engagement. These include learning within a community of learners, engaging in research with faculty mentors, international experiences and culminating capstone experiences. The team will discuss how these ‘high-impact’ practices have been integrated within and facilitated by the Bachelor of Health Sciences program and share their impact from the student perspective. The team will also suggest ways in which these approaches can be incorporated across a diverse array of disciplines. The School of Creative and Performing Arts team will explore the critical thinking aspect of designing for learning. What exactly is critical thinking? Universities uniformly promote the idea that they must turn students into “critical thinkers.” What does that mean? Are we currently experiencing a shortage of critical thinkers that we must address? Are governments, not for-profits and businesses clamoring for more critical thinkers? Do parents dream of raising critical thinkers? The team will explore the value of critical thinking and ask how best to address its position in academic pedagogy.
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    Incorporating Universal Design for Learning in Disciplinary Contexts in Higher Education
    (University of Calgary, 2021) Abegglen, Sandra; Aparicio-Ting, Fabiola; Arcellana-Panlilio, Mayi; Behjat, Laleh; Brown, Barbara; Clancy, Tracy; DesJardine, Patricia; Din, Cari; Ferreira, Carla; Hughson, E. Anne; Kassan, Anusha; Klinke, Chelsea; Kurz, Ebba; Neuhaus, Fabian; Pletnyova, Ganna (Anna); Paul, Robyn Mae; Peschl, Houston; Peschl, Rosalynn; Squance, Rod; Dyjur, Patti
    Universal Design for Learning (UDL) is a set of principles that can be used to guide course design and delivery with the goal of enhancing the learning for the greatest number of students. Incorporating UDL in higher education is complex, varied and nuanced work that instructors are doing to meet the learning needs of students in their classes. In this guide we illuminate different ways in which UDL principles have been implemented across disciplines and in different ways to enhance student learning. Each chapter offers a case of how UDL has been incorporated into learning experiences in higher education. Our goal is to provide discipline-based examples of courses that illustrate how UDL can be incorporated into a higher education context. Along the way, we hope you will be inspired by the work of others. We wish you great success in your journey to teach courses that are increasingly accessible and inclusive!
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    Molecular Targets of Atropine- and Mamba Toxin 3-Mediated Inhibition of Form-Deprivation Myopia in the Chick: A Case of Mistaken Receptor Identity?
    (2017) Carr, Brittany Jane; Stell, William Kenyon; Hollenberg, Morley Donald; Kurz, Ebba; Gordon, Grant
    Myopia is a refractive disorder characterized by the inability to see distant objects clearly. It is the most common childhood vision disorder, and the leading cause of adult visual impairment world-wide. Myopia prevalence is rising rapidly; it is estimated that 2.5 billion people will be affected by 2030, and any degree of myopia increases the risk of blindness-inducing comorbidities. There are no universally accepted pharmaceutical therapies to slow myopia progression, but some success has been found with the muscarinic acetylcholine receptor (mAChR) antagonist atropine. There remains a paucity of investigations into the ocular signalling cascades modulated by atropine-treatment. Research in this area has been based on the assumption that because atropine, and a few other mAChR antagonists, inhibit myopia at extremely high concentrations, mAChRs must regulate myopia progression. Regulation of eye growth by mAChRs has never been proven conclusively. Here, I report that myopia-inhibition by atropine is dependent on induction of nitric oxide (NO), and that exogenous NO is sufficient to inhibit experimentally-induced form-deprivation myopia (FDM) on its own. In addition, I provide evidence that disproves the assumption that mAChRs are responsible for atropine- and mamba toxin 3-mediated myopia-inhibition in the chick. First, I demonstrate that alpha2-adrenoceptor (ADRA2) agonists can dose-dependently inhibit FDM. Second, I show that myopia-inhibiting mAChR antagonists can bind to, and block signalling by, human alpha2A-adrenoceptors (ADRA2A). Furthermore, I show that the relative inhibitory potencies (pIC50’s) of myopia-inhibiting mAChR antagonists at ADRA2A correlate better with their reported abilities to inhibit FDM in the chick than their relative pIC50’s at human and chicken mAChR M4. My data further our understanding of how the eye may know how large to grow. They provide two novel alternative targets for anti-myopia therapies (NO & ADRA2s), both of which would eliminate the most significant side-effects of atropine-treatment. They provide a range in which mAChR antagonists should be expected to act in a “specific” manner at human and chicken mAChR M4, and reinforce the need for caution in attributing the effects of high concentration drug to a specific receptor target.
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    Myxoma Virus Treatment for Brain Tumour Initiating Cells: Interrogating and Enhancing Myxoma-Mediated Cell Death
    (2012-12-20) McKenzie, Brienne Alexandra; Forsyth, Peter; Kurz, Ebba
    Brain tumour initiating cells (BTICs) are stem-like cells hypothesized to mediate recurrence in high-grade gliomas. Preclinical success has been demonstrated in treating patient-derived BTICs with oncolytic virotherapy, using replication-competent viruses to target and kill malignant cells. Myxoma virus (MyxV) is an oncolytic candidate, which is highly effective in conventional glioma models, but only modestly effective in BTICs. The objective of this study was to improve MyxV efficacy in BTICs in vitro, combining chemotherapeutics and virotherapy. Using a pharmacoviral screen, eleven compounds that enhance MyxV-mediated cell death were identified. A lead compound, axitinib, was validated in multiple BTIC models. It was demonstrated that a virally encoded protein, M011L, prevents MyxV-induced apoptosis in BTICs, and M011L disruption was shown to greatly improve MyxV-mediated cell death through apoptosis induction. These studies have elucidated multiple strategies for improving MyxV efficacy in a preclinical glioma model, with implications for the future clinical development of MyxV.
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    Targeting Selective Receptor Tyrosine Kinases in Refractory Embryonal Tumors of Childhood
    (2016) Singh, Anjali; Narendran, Aru; Kurz, Ebba; Krawetz, Roman; Bahlis, Nizar
    Embryonal tumors are a collection of biologically heterogeneous malignancies and the exact cellular origin of these tumors is not known. Neuroblastoma (NB) and atypical teratoid/rhabdoid tumor (AT/RT) are highly malignant tumors of embryonal origin that primarily affect infants and young children. Neuroblastoma is the most common type of extra cranial solid tumor in children. In the case of AT/RT, the survival rate of children affected by this disease is the lowest when compared to all embryonal tumors. Despite intensifying multimodal treatments, children affected with refractory AT/RT and NB have unacceptably high treatment failure and mortality rates. To improve the clinical outcome of these malignancies, it is important to identify the key molecules and cellular pathways responsible for tumor progression, survival and invasion. Many childhood cancers have high activation levels of selective receptor tyrosine kinase signaling pathways. Activation of these signaling pathways promotes cell proliferation, differentiation and cell survival. Therefore, receptor tyrosine kinases (RTKs) have become attractive therapeutic targets and the use of small molecule kinase inhibitors to block their signal transduction functions has led to the discovery of a number of novel therapeutics agents. This research presents the relevant background information on two pediatric neoplasms that we have selected to study and aims to provide the rationale for the development of useful new therapies for their treatment. Presented in details are the data with respect to the establishment of a screening approach to identify effective therapeutic agents with information on target validation and target modulation activities that can be utilized to design future clinical trials for these cancers.