Browsing by Subject "Masonic Cancer Center"
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Item Co-Targeting the mTOR and MAPK Pathways is Effective in a Novel Mouse Model of Malignant Peripheral Nerve Sheath Tumors(2012-04-18) Anderson, LeahMalignant Peripheral Nerve Sheath Tumors (MPNSTs) are soft tissue sarcomas with low 5-year survival rates and no targeted therapies available. Data suggest that the mTOR and MAPK pathways may be involved in the formation and progression of MPNSTs, and both of these pathways can be inhibited with drugs that are currently in use for other tumor types. In vitro, RAD001 and PD-901, inhibitors of the mTOR and MAPK pathways, respectively, are effective at inhibiting proliferation of human MPNST cells, while having little effect on normal human Schwann cells. To better study their therapeutic potential, we tested these drugs in a mouse model of MPNSTs. This model closely resembles genetic changes (Pten loss, EGFR overexpression) and histological feature of human MPNSTs. RAD001 or PD-901 treatment moderately reduced tumor burden and size, and extended lifespan in this model. However, when one pathway is inhibited, there is an increase in signaling through the other pathway, suggesting that these pathways feedback on one another, and that targeting both pathways in combination may be more effective. We found synergistic effects on reducing tumor burden and size, and a significant increase in lifespan when RAD001 and PD-901 are given in combination. The synergy seen is due to the combination therapy allowing for persistent and prolonged reduction in signaling through both pathways, without a subsequent increase in signaling through one pathway, as seen in single agent treatments. These data suggest that co-targeting the mTOR and MAPK pathways could potentially be an effective treatment for patients with MPNSTs.Item Cytogenetics Worldwide(2012-04-18) Selinger, JessieWith the advance of molecular technology in the past thirty years, cytogenetic analysis has become essential for making an appropriate diagnosis, prognosis, and treatment plan for children with acute leukemia. It is now a regular practice to document the frequencies of chromosomal translocations that are found in children with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL), but a comparison of the different frequencies of chromosomal translocations throughout the world has not yet been undertaken. Differing frequencies of chromosomal translocations in pediatric leukemia in populations worldwide could have large implications for the study of genetics and pediatric leukemia.Item Exploring the Mechanism of Ara-C Resistance in Acute Myeloid Leukemia(2010-04-21) Ellingson, Alexandra M.Acute myeloid leukemia (AML) is the most common and most deadly type of leukemia in adults, affecting approximately 3 people per 100,000. AML is typically treated with a cocktail of chemotherapeutic drugs, most often involving the pharmaceutical agent cytosinearabinoside (Ara-C). Treatment with Ara-C will almost always cause remission in AML patients. However, developed resistance to Ara-C becomes a problem for many patients suffering from the disease, and many relapse within a few years of remission. We are using an in vitro system to model the Ara-C resistance in AML cell lines.Item Gene expression differences between hemangiosarcoma cells in monolayer and non-adherent sphere culture(2011-04-13) Sahli, NathanaelThe cancer stem cell (CSC) theory argues that tumors have a subset of cells that initiate, maintain, and expand cancer in an affected patient. Experimental support for this theory comes from studies that identified sub-populations of cells in a tumor that have the capacity to evade common cancer treatments such as chemotherapy and radiation. Additionally, these same cells exclusively retain the capacity to initiate new disease in xenograft studies. The study of these evasive cells was initially challenging as they differentiate in standard serum-containing culture medium where they grow as a monolayer. In the past decade, methods for culturing stem cells using a serum-free medium has allowed CSCs to be maintained, where they form non-adherent multicellular spheres. Here, we cultured canine hemangiosarcoma (HSA) in both a multicellular sphere and standard monolayer system to compare gene expression using real time qRT-PCR. In our system, the monolayer cultures are a useful surrogate for differentiated tumor cells (the bulk of the tumor), while the serum-free sphere-derived cells are a surrogate for in vivo CSC. Here, we investigate differences in gene expression between these two cultures systems. The genes chosen for study have been shown to be up-regulated in CSCs from various other cancers, or normal stem cells, with minimal expression in differentiated cells. We found gene expression differences between cultures conditions which will allow it to be utilized in the study of hemangiosarcoma as well as possibly other cancers with a CSC.Item Identification of a Novel p53 Regulated Endogenous Retrovirus MMERGLN(2012-04-18) Singhal, SurbhiWith roughly half of all tumors with mutations in the TP53 gene, TP53 undoubtedly is a tumor suppressor gene that plays a critical role in the prevention of cancer. TP53 responds to cellular stress in cells, either metabolic disorder or genetic damage for example, and becomes transcriptionally activated to produce the p53 protein. Several genes that are directly targeted by p53 have been studied extensively and their role in cellular apoptosis and senescence are well documented. However, whether p53 can also regulate expression of repetitive elements that comprise a significant part of the genome, and their possible consequence, is not known. The mouse genome, in addition to known genes, also has several endogenous retroviruses, short DNA sequences derived from ancient viral infections that are now part of the genome. In my thesis work, I characterize one specific endogenous retrovirus, MMERGLN, and explore MMERGLN’s relationship with the p53 protein. Not only does MMERGLN show p53 regulation according to RNA Sequence data, MMERGLN also possesses p53-binding sites. Here we have identified MMERGLN transcripts that are present in a p53-dependent manner and MMERGLN is expressed body-wide in mouse. Furthermore, we demonstrate that multiple copies of MMERGLN contain all the components necessary for retrotranspostion or infection suggesting this genomic element may still be active. In order to determine a potential function for this genomic element, we investigated the ability of MMERGLN to act as an enhancer by identifying genes with differential transcription near MMERGLN insertion sites in p53 wild type and p53 null mice. Finally, with the purpose of understanding how MMERGLN is prevented from spreading throughout the genome, we investigated the mechanism by which MMERGLN is restricted, and see evidence for cytosine deamination mediated by the Apobec proteins. Our results demonstrate a paradigm shift in how transposable elements are regulated by p53 and suggest a new role for MMERGLN in tumor suppression. We anticipate these studies to shed light on the potential role of transposable elements in preventing disease.Item Mechanisms of Androgen-Mediated Repression of the Maspin Tumor Suppressor Gene in Prostate Cancer(2009-04-08) Bader, DavidIt is estimated that one in six men in North America will be diagnosed with prostate cancer (PCa) during his lifetime. Localized PCa is often treated using surgery and radiation. Advanced and metastatic PCa can be treated by blocking the production or action of androgens, the male sex hormones. This androgen depletion therapy is only temporarily successful because PCa frequently returns in an androgen-refractory form that is resistant to hormonal manipulations and capable of growing in an androgen-depleted environment. Androgen receptor (AR) is a nuclear receptor transcription factor necessary for normal prostate cell growth and function as well as for growth of PCa. Androgens activate the AR, which translocates to the nucleus where it transcriptionally activates or represses target genes. One such gene is the Maspin tumor suppressor. Maspin is a proteinase inhibitor that serves to prevent proteinase degradation of the extracellular matrix, which is prerequisite to tumor invasion and metastasis. Androgens transcriptionally repress Maspin, but the mechanisms have not yet been fully characterized. To investigate the mechanisms of Maspin repression, a plasmid containing the luciferase reporter gene under the control of the Maspin promoter was constructed and transfected into VCaP and LNCaP PCa cell lines. Transfected cells were treated with dihydrotestosterone (a natural androgen) or mibolerone (a synthetic androgen) for 24 hours. Luciferase activity was subsequently measured by dual luciferase assay. These experiments have indicated that the AR may not directly repress Maspin transcription. Ongoing research will utilize real time PCR to determine whether AR inhibits Maspin transcription via a direct or indirect mechanism.Item MiRNA-155 Regulates IL-12 Expression by Targeting SOCS-1 in Human Dendritic Cells(2010-04-21) Roensch, KristinDendritic cells (DCs) are the most potent type of white blood cells that regulate the immune response. DCs’ antigen processing activities are controlled in response to inflammatory stimuli. DCs play a unique role in the immune activation to pathogens and transformed cells. MicroRNAs (miRNAs) are small, single-stranded non-coding RNAs that function through stem-loop binding to the 3’ untranslated regions (UTRS) of target mRNAs, usually silencing its protein’s production and degrading the mRNA itself. Aims of the study: 1. Understand miR-155’s role during monocyte-derived dendritic cell maturation. 2. Understand mechanism by which miR-155 functions during dendritic cell development.Item Spin Embryoid Bodies as an Improved Method of Blood Cell Differentiation in Human Embryonic Stem Cells and Induced Pluripotent Stem Cells(2010-04-21) Armstrong, RebeccaTwo types of cells have been characterized as pluripotent stem cells: human embryonic stem cells (hESCs) and the more recently described induced pluripotent stem cells (iPSCs). Pluripotency means that these cells have the ability to form all the cells and tissues of the human body. hESC and iPSC differentiation into blood cells is particularly useful in studying the mechanisms of blood diseases and cell transfusion therapies. To better understand the potential of these cells to specifically produce blood cells, it is necessary to define an efficient and reproducible system of differentiation. Previously, our and other groups have used a stromal cell co-culture method to support blood development from hESCs. In these current studies, we are employing a stromal-free and serum-free differentiation method that may facilitate clinical translation of hESC- and iPSC-derived cells. This method involves forced aggregation of defined numbers of undifferentiated hESCs or iPSCs in 96-well plates by centrifugation to form embryoid bodies (spin EBs) of a uniform size. We examine this method’s potential to derive blood precursor cells and mature blood lineage cells from both hESCs and iPSCs.