Browsing by Subject "Cancer"

Now showing 1 - 20 of 63
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    Adrenergic antagonists disrupt lipid and cholesterol homeostasis resulting in canine hemangiosarcoma cell death
    (2019-11) Korpela, Derek
    The beta-adrenergic receptor (-AR) antagonist, propranolol, has been identified as an effective adjunct therapy for angiosarcoma patients. Why angiosarcomas are susceptible to propranolol remains unknown. The objectives of this dissertation were to characterize the mechanisms behind the susceptibility of these tumors to the lethal effect of propranolol and to identify other drugs classed as AR antagonists that could further improve patient outcomes. In addition, translation of these findings could be used to treat a virtually indistinguishable tumor in dogs known as canine hemangiosarcoma. Using a panel of hemangiosarcoma cell lines, we found that propranolol reduced tumor cell viability through an AR-independent mechanism. Further investigation showed that propranolol inhibited endocytosis, limiting the uptake and processing of extracellular lipids. To restore lipid homeostasis, hemangiosarcoma cells rapidly increased the activation of metabolically costly cholesterol and lipid synthesis pathways, leading to ER stress, reduced mitochondrial activity, and cell death. Screening assays identified the mixed-acting 1-, -AR antagonist, carvedilol, as a more effective inhibitor of endocytosis, lipid homeostasis, and mitochondrial metabolism. We conclude that propranolol and carvedilol disrupt lipid homeostasis and tumor cell metabolism to kill hemangiosarcoma cells. Repurposing propranolol or its AR-inactive R-(+) enantiomer may provide a readily translatable and clinically safe strategy for the treatment of canine hemangiosarcoma. Related drugs, such as carvedilol, may further improve outcomes for angiosarcoma patients with less side effects.
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    Advancing Focal Therapies for Cancer and Neural Targets
    (2023-04) Ranjbartehrani, Pegah
    Focal therapies (FT), including cryosurgery, thermal ablation and irreversible electroporation (IRE) have been widely used in the treatment of cancer and other diseases, with the aim to expose cells to extreme physical conditions, leading to cell death. The use of FT has increased recently due to advantages such as being minimally invasive and having lower costs, shorter recovery periods, and lower morbidity. The advent of imaging tools has also helped FT gain more attention among surgeons. However, limited understanding of the energy field around the FT probes might cause undertreatments, which would lead to recurrence of the disease, or overtreatment, which would lead to damages to the surrounding sensitive organs such as nerves and create severe side effects. Moreover, choosing the most suitable FT modality for treating a special organ target is essential.Our first objective for a successful focal therapy treatment is to have a clear understanding of the energy field distribution around the probes, both in clinical and preclinical applications. In preclinical cancer research, syngeneic tumors and xenograft tumors in rodent models are often used to define pre-clinical thresholds and outcomes for focal therapy modalities alone and with adjuvant approaches. Nevertheless, application of clinical-sized focal therapy probes in rodent tumor models can be difficult to control or characterize for this purpose. This, in turn, affects our understanding of the energy dose necessary to destroy diseased tissue. The fact that tumors in small animals come in different sizes and shapes and have thermal properties raises the need for a computational model capable of visualizing the temperature and electric field distribution within the tumor during the process of focal ablation. Understanding the interaction between the energy field and the tissue affects our understanding of the actual role of those ablation modalities in creating the tissue damage and enables us to predict and optimize the outcome of the procedure. Our second objective for a successful focal therapy treatment is to propose methods for preventing the damage to the surrounding organs, especially neural targets that are in close proximity to the treated area. In this work, we focus on preventing neural damage during prostate cancer cryosurgery. One major complication associated with prostate cancer cryosurgery is erectile dysfunction, caused by cryoinjury to the cavernous nerve in the neurovascular bundle, which is in close proximity to the prostate and is therefore directly exposed to freezing temperatures during cryosurgery. The use of cryoprotective agents (CPAs) to protect nerves against freezing temperatures is a method that has been used in nerve cryopreservation. While existing literature has established the idea of using CPAs to prevent nerve damage, there is still a lack of experimental data and quantitative models to study the effect of CPAs in preventing nerve cryoinjury during prostate cryosurgery. Moreover, no comprehensive study has assessed both the toxicity and the cryoprotective effectiveness of CPA exposure to the nerve within a repeatable and relevant biological model. Choosing a suitable FT modality is also crucial for a successful FT treatment. Certain modalities have better outcomes for specific organ targets than others. In this work, we propose a novel approach for renal denervation using Iron-oxide nanoparticle heating for treating hypertension. The most common ablation technique currently used in clinic for renal denervation is radiofrequency. However, this approach suffers from several disadvantages due to heating from inside of the renal artery which would result in damage to the artery wall, limited nerve ablation depth and inconsistent and unpredictable denervation. The use of iron-oxide nanoparticles, however, will alleviate some of the disadvantages mentioned by providing a repeatable treatment that can be used in combination with alcohol or other neurolytic agents as well. Using iron-oxide nanoparticles can also benefit from image guidance. This work will advance the application of FT by helping to better understand the energy field around the probe and helping to prevent unwanted damage to surrounding organs such as nerves.
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    APOBEC3B-driven mutagenesis in breast and other human cancers
    (2013-08) Burns, Michael Bradley
    Cancer is a disease that results from alteration of the cellular genome. The sources of these changes are multifarious, and in many cases unknown. This thesis focuses on the polynucleotide cytosine deaminase, APOBEC3B, as a newly discovered source of mutation in multiple human cancers. As a deaminase, APOBEC3B converts cytosines to uracils in single-stranded DNA. These uracil lesions are mutagenic as failure to properly repair them can result in a wide variety of mutation types. The initial discovery of this mutational phenomenon was described mechanistically using a variety of biochemical, genetic, and cellular assays in breast cancer cell lines. Follow-up work using publicly available next generation sequencing and clinical data indicated that this effect is operating in a large proportion of breast cancers. Expanded bioinformatic analysis that assessed APOBEC3B's potential impact was expanded to include 18 other human cancer types in addition to breast. This work shows that APOBEC3B is likely a significant contributor to the genetic heterogeneity in breast, head & neck, bladder, cervical, and lung (adeno- and squamous cell) carcinomas as evidenced by differential levels of expression in cancer tissues, increased mutation load, mutation clusters (kataegis), and an APOBEC3B mutation signature in tumors expressing high levels of this enzyme. Taken together, this thesis is a body of work describing a previously unappreciated source of genetic heterogeneity in several human cancers.
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    Association of opioid requirement and cancer pain with survival in advanced non-small cell lung cancer
    (2017-05) Zylla, Dylan
    Background: Pain is associated with shorter survival in non-small cell lung cancer (NSCLC). Lung cancer cells express opioid receptors. Opioids promote angiogenesis, tumor growth and metastases, and shorten survival in animal models. Methods: To examine if long-term opioid requirement, independently of chronic pain, is associated with survival, we studied 209 patients treated with chemotherapy for stage IIIB/IV NSCLC. Pain was stratified by proportion of time patients reported specific levels of pain. Opioids were converted to oral morphine equivalents (OME) for comparison. The effects of pain, opioid requirement, and known prognostic variables on survival were analyzed in univariable and multivariable models. Results: Both severity of pain and greater opioid requirement in first 90 days after starting chemotherapy were strongly predictive of shorter survival on univariable analysis. Patients with no/mild chronic pain and requiring <5 mg/day OME during first 90 days had nearly 12 months longer median survival compared to patients requiring ≥5 mg/day OME and/or experiencing more pain. Differences in survival remained remarkably similar when chronic pain and opioid requirement were assessed over the entire clinical course (until death or last follow-up). In multivariable models, both opioid requirement and chronic pain remained independent predictors of survival, after adjustment for age, stage and performance status. Conclusions: Severity of chronic cancer-related pain or greater opioid requirement are associated with shorter survival in advanced NSCLC, independently of known prognostic factors. While pain adversely influences prognosis, controlling it with opioids does not improve survival. Prospective studies should determine if achieving pain control using opioid-sparing approaches improves outcomes.
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    Bisphosphonate-related osteonecrosis of the jaw
    (2013-05) Thumbigere Math, Vivek
    Bisphosphonates (BP), potent osteoclast inhibitors, play a key role in managing patients with osteoporosis, Paget’s disease, bone metastasis, and multiple myeloma. BP’s anti-resorptive activity substantially reduce fracture risk by 40%-70% in osteoporosis patients, and improve quality of life in cancer patients by preventing skeletal complications. However, prolonged BP use is associated with a significant dental complication termed “Bisphosphonate-Related Osteonecrosis of the Jaw (BRONJ)”. To date, the true incidence, etiology, and risk factors that contribute to BRONJ pathogenesis are unknown. In this dissertation, we assessed the frequency, etiology and risk factors that contribute to BRONJ pathogenesis. We noted that the BRONJ frequency in cancer patients is around 3.1%. Factors such as poor periodontal status, diabetes, smoking, prolonged duration of BP therapy, and higher numbers of BP infusions significantly increase the risk of developing BRONJ. In addition, long-term BP administration adversely affects jawbone mechanical properties that could result in increased microdamage accumulation within the jaw bones. Furthermore, using proteomic analysis we identified 200 salivary proteins that were differentially expressed in BRONJ subjects. A majority of the differentially expressed proteins were predicted to have a role in dermatological diseases, genetic disorders, immunological diseases, and inflammatory responses. Finally, analysis of serum samples revealed that VEGF levels are significantly suppressed in patients undergoing BP therapy. In summary, results from this dissertation provide insight into the pathogenesis of BRONJ development.
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    Bivalent Ligand MMG22 Reduces Bone Cancer Pain without Tolerance or Sedation
    (2022-07) Shueb, Sarah
    Pain is among the most common symptoms in cancer and approximately 90% of patients experience end-stage cancer pain. The management of cancer pain is challenging due to the significant side effects associated with opioids, and novel therapeutic approaches are needed. MMG22 is a bivalent ligand containing MOR agonist and mGluR5 antagonist pharmacophores joined by a 22-atom spacer. MMG22 exhibited extraordinary analgesia following intrathecal administration in a mouse model of bone cancer pain. Here, we assessed the effectiveness of systemic administration of MMG22 in reducing cancer pain and evaluated whether MMG22 displays side effects associated with opioids. Fibrosarcoma cells were injected into and around the calcaneus bone in C3H mice. Mechanical hyperalgesia was defined as an increase in the paw withdrawal frequencies (PWFs) evoked by the application of a von Frey monofilament (3.9 mN bending force) applied to the plantar surface of the hind paw.Subcutaneous (s.c.), intramuscular (i.m.), and oral (p.o.) administration of MMG22 produced robust dose-dependent antihyperalgesic, whose ED50 was orders of magnitude lower than morphine. Moreover, the ED50 for MMG22 decreased with disease progression. Importantly, s.c. administration of MMG22 did not produce acute (24 h) or long-term (9 days) tolerance, was not rewarding (conditioned place preference test), and did not produce naloxone-induced precipitated withdrawal or altered motor function. A possible mechanism of action of MMG22 is discussed in terms of inhibition of spinal NMDAR via antagonism of its co-receptor, mGluR5, and concomitant activation of neuronal MOR. We suggest that MMG22 may be a powerful alternative to traditional opioids for managing cancer pain.
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    Breast Cancer Screening: Your Guide To Health
    (2010-07-22) Flaten, Dean B
    Mammography has consistently been proven to be an effective and safe method of screening women 50 and older for breast cancer. However, this study found that annual screening with mammography for women in their 40’s was not effective at reducing breast cancer mortality compared with women who undergo usual care with breast physical examination and breast self-examination. In general then, universal screening mammography for women in their 40’s should not be mandate, but rather an informed, personal decision between the physician and patient based on individual concerns, family history and acceptable risk/benefit profiles.
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    Cancer and the medicare disabled.
    (2008-11) Habermann, Elizabeth Anne
    This dissertation examines relationships between cancer in working-age adults and enrollment in Medicare due disability. We examine whether cancer diagnosis and treatments affect enrollment in Medicare due to disability, whether there is pent-up demand for cancer diagnosis during the 29-month waiting period between application and receipt of Medicare benefits, and whether disabled working-age adults receive quality cancer care when enrolled in Medicare.
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    Cancer gene discovery using somatic transposon mutagenesis in the mouse and systems for validation of identified candidate cancer genes and pathways.
    (2012-07) Moriarity, Branden Scott
    The conditional Sleeping Beauty (SB) transposon mutagenesis system has proven to be a successful method for cancer gene identification in solid tumors. Using tissue specific Cre recombinases (TSP-Cre) to selectively activate SB mediated mutagenesis in tissues of interest has yielded numerous novel candidate cancer genes in leukemia/lymphoma, colorectal, liver, and pancreatic cancers. We implemented the SB system for the identification of genes involved in osteosarcoma (OS). OS is the most common cancer of the bone and third most common cancer in children and adolescents. The 5-year survival rate of OS patients is 60-70%, though with metastatic disease it drops to less than 20%-30%. Identification of genes responsible for OS development and metastasis has been difficult due to its genomic instability and subsequent complexity. Consequently, there is a pressing need to identify the genes and pathways governing OS development and metastasis. To this end, we performed a forward genetic screen utilizing the conditional Sleeping Beauty (SB) transposase and mutagenic T2/Onc transposon system in Osx-Cre mice on a predisposing Trp53LSL-R270H/+ or wild type background to induce random somatic mutations that induce OS development and metastasis. One hundred and nineteen OSs were isolated from 96 predisposed and 20 wild type mice undergoing SB mutagenesis, with a subset of animals harboring metastases to the liver and/or lungs. Over 100 candidate cancer genes, both known and novel, were identified by analysis of recurrent T2/Onc insertion sites. In order to validate the candidate cancer genes identified in our screen, we developed a recombinase-based system for efficient assembly of vectors to over express or knock down 1-6 genes in mammalian cells. Further, these vectors were constructed in Piggybac transposons to allow for stable and reversible integration of the vector via transposition. In addition to cDNA over expression or shRNA knock down, we also developed methods for generation and selection of candidate cancer gene knock out cell lines using TAL effector nucleases (TALENs).
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    CAROTID ARTERY ELASTICITY: Describing Elasticity in Healthy Children and Adults, and the Use of Atorvastatin to Modulate Elasticity in Adult Survivors of Childhood Cancer
    (2015-06) Marlatt, Kara
    Carotid artery elasticity has become a commonly assessed non-invasive marker of arterial health that is relatively easy to administer. Indeed, the loss of elastic properties within the larger and more elastic arteries like the carotid artery contributes substantially to the increase in systolic blood pressure as well as pulse pressure, which are known independent risk factors for the development of cardiovascular disease (CVD). Such risk factors can lead to compensatory remodeling of the carotid artery and nearby arterial beds, as well as create synergistic detriments to the arterial tree in the presence of other risk independent risk factors. Decreased carotid arterial elasticity and increased stiffness has been reported with advanced aging in both men and women; however, little research has examined artery elasticity measures by sex in otherwise healthy young adults, as well as children and adolescents. The purpose of the following dissertation was to examine the potential influences of sex, pubertal development, and age, on measures of carotid arterial elasticity in otherwise healthy children, adolescents, and adults, to lend further insight to the already existing body of research surrounding arterial elasticity and stiffness. Additionally, a separate study was further employed using HMG coenzyme A reductase inhibitors, or statins, to assess whether individuals at increased risk of CVD like childhood cancer survivors could potentially benefit from the known therapeutic effects of statins and subsequently improve carotid artery elasticity and stiffness. Given vascular dysfunction is considered an early manifestation of atherosclerosis, potential therapeutic remedies that dampen cardiovascular risk in populations that are at increased risk for vascular dysfunction are critical to explore.
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    Characterization Of TM9SF2 And WAC As Novel Colorectal Cancer Driver Genes
    (2018-10) Clark, Christopher
    The studies performed in this dissertation focused on the characterization of two candidate cancer genes, TM9SF2 and WAC, and their role in colorectal cancer (CRC). Interest in these two genes stems from their discovery as frequently mutated genes in a mouse-based CRC mutagenesis screen. The first chapter will discuss CRC and provide an historical overview of the methods used to discover novel CRC driver genes. The chapter will also cover modern strategies to identify exciting new CRC driver genes before it ends with a thorough overview of the transposon based forward mutagenesis screen used for CRC gene discovery. The second chapter describes my work demonstrating that the transmembrane protein TM9SF2 is a novel CRC oncogene. Here, we have shown that TM9SF2 is a significant driver gene in murine CRC tumors and, with multiple approaches, that TM9SF2 is overexpressed in approximately one-third of human CRC samples. We provide functional data demonstrating that shRNA-mediated reduction of TM9SF2 or complete knockout by CRISPR/Cas9 drastically reduces tumor fitness in human CRC cell lines. Finally, we provide evidence that high TM9SF2 expression is correlated with poor patient prognosis. The third chapter focuses on the WAC gene and its potential tumor suppressor activity in CRC. We have shown that WAC is frequently mutated in murine CRC mutagenesis screens and that reduction in WAC expression reduces cell growth. This chapter also discusses our finding that loss of WAC is detrimental to mouse embryonic development. The final chapter in this dissertation provides a discussion of the significance of these findings and how these results will impact the CRC research community.
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    Characterizing the migration and therapeutic potential of CD8 tumor-infiltrating lymphocytes
    (2023-06) Gavil, Noah
    Beginning in the 19th century, immunologists slowly uncovered the mechanisms ofcancer immunosurveillance, ultimately identifying thymic-dependent “T” lymphocytes (T cells), and not antibodies, as the primary mediators of cancer cell elimination and control. T cell surveillance is performed by diverse subsets. After antigen encounter, T cells differentiate, adopting many phenotypic fates. In settings of acute infection, T cells diversify into ‘effector’ and long-lived ‘memory’ states. While some memory T cells circulate throughout the body, others remain resident, patrolling tissues locally. The migration and function of memory T cells has been well studied, providing a systemic view of immune surveillance for microbial pathogens. In settings of chronic antigen, such as cancer, antigen-specific T cells diverge from the memory program, existing along a spectrum of differentiation and exhibiting restrained functional capabilities. While the early stages of cancer immunosurveillance mirror immune responses to microbial pathogens, the T cell surveillance of progressive malignant tumors is poorly understood. Many studies describe the heterogeneity of tumor-infiltrating T cells (TILs). Generally, the density of CD8+ TILs correlates with improved prognosis, but the density of CD8+ TILs with resident-memory (TRM) phenotypes better predicts patient outcomes and responsiveness to immunotherapies. These TRM-like cells may directly control tumor growth, but their migration properties have not been directly studied, leaving their direct function unknown. Importantly, newer data shows that many CD8+ TILs are bystanders, specific for microbial pathogens, not tumors. Reactivation of these bystander T cells with cognate peptide can orchestrate potent anti-tumor immune responses. In this thesis, I study the migration properties of tumor-specific and virus-specific CD8+ T cell subsets. Distinct resident populations of CD8+ TILs exist, differing based on the presence or absence of chronic antigen. Resident CD8+ TILs do not recapitulate the resident T cell programs of healthy tissues. I also investigated the anti-tumor immune mechanisms initiated by antiviral CD8+ TILs reactivation. Cytokine production and innate immune mechanisms were the predominant source of tumor killing. Taken together, T cell immunosurveillance is characterized by the coexistence of T cell subsets that represent lineages associated with chronic antigen exposure and memory T cells, which possess potent therapeutic potential (e.g. TRM).
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    Comparative and molecular approaches to improve identification, classification, and therapeutic approaches to cancer
    (2013-01) Frantz, Aric M.
    A major area of contemporary research in cancer is focused on improving tumor classification into clinically relevant subgroups of disease. To achieve this, it is important to understand the molecular events that driver tumor heterogeneity both at the cellular level and at the tissue level. I initially tested the hypothesis that canine lymphoma is composed of a group of molecularly distinct entities with prognostic significance. The results show that canine lymphoma can be stratified into molecular subgroups that have prognostic value and can assist to guide therapy. Next, I tested the hypothesis that canine hemangiosarcoma (HSA) is organized hierarchically with a cancer stem cell (CSC)-like population of cells at the apex. The data show that variable numbers of CSC-like cells are invariably present in HSA. These CSC-like cells retain the capacity to differentiate into vascular, inflammatory, or adipogenic tissue, suggesting that their multipotency is a contributing factor to the observed heterogeneity in this disease. Finally, I tested the hypothesis that CSCs, or CSC-like cells from three histologically distinct types of canine cancer (HSA, osteosarcoma, and glioblastoma) share molecular and functional properties. Using a system that allowed me to eliminate tumor-specific culture conditions, I showed that despite extensive heterogeneity in CSC-like cells from these tumors, they all showed reduced activity of pathways associated with proliferation and development. In summary, my results confirm that cellular heterogeneity exists both within and among tumors. A better understanding of the mechanisms that drive this will improve patient stratification and guide efforts to develop rational, more effective therapies.
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    Comparison of quality of life and health behaviors between melanoma survivors and controls
    (2016-01) Vogel, Rachel
    Unlike most cancer types, melanoma incidence has been increasing over the past 30 years in the United States. The unique characteristics of melanoma argue for research that captures the specific issues faced by melanoma survivors. Studies of long-term melanoma survivors are lacking, and the survivorship research to date has been limited by the inability to make comparisons with a population control group. The goal of this dissertation was to document the long-term effects of a melanoma diagnosis and treatment on survivors and compare their quality of life and health behaviors with population controls. First, a series of focus groups were conducted to describe the breadth of experiences among melanoma survivors, focusing on the experience at diagnosis, ongoing physical, emotional and social concerns, and behavioral changes since diagnosis (Manuscript 1). Based on these data, a comprehensive questionnaire to address the quality of life issues faced by melanoma survivors was designed and tested. Finally a cross-sectional study of melanoma survivors and population controls was conducted. The goal was to collect data to evaluate the impact of melanoma on long-term survivorship focusing on quality of life (Manuscript 2) and sun exposure and protection behaviors (Manuscript 3). A total of 592 melanoma survivors and 518 controls completed the survey. Results indicate that long-term survivors of melanoma reported similar general physical and emotional quality of life as controls. In addition, while they generally reported greater use of sun protection behaviors than controls, a significant subgroup experienced sunburn in the past year, putting them at elevated risk for future melanomas. The data presented in this dissertation suggest that long-term melanoma survivors reported similar quality of life as controls, though opportunities exist to improve their sun exposure and protection behaviors.
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    Computational methods to explore chemical and genetic interaction networks for novel human therapies
    (2013-11) Deshpande, Raamesh
    Model organisms are often used as a test-bed for the development of new genomic technologies and computational approaches. For example, the yeast Saccharomyces cerevisiae was the first eukaryote to have its entire genome sequenced, paving the way for the sequencing of the human genome. Beyond genome sequencing, yeast and other model organisms have been extensively used for reverse genetics technology development. Reverse genetics is a general approach for studying biology where the genome is perturbed in precise ways (e.g. targeted gene deletion), to gain functional information about the perturbed genes from the resulting phenotypic changes. With developments of new genomic technologies, reverse genetics at a genome-wide scale has become a reality. This dissertation focuses on the development of several computational methods for scaling up the reverse genetics experiments in model organisms as well as for exploring the generated genomics data with the ultimate goal of understanding and translating these data for use in applications for human therapeutics. One such method I developed is COMPRESS-GI which compresses the deletion collection by 95% such that the compressed set still remains highly informative for drug discovery analyses. This compression is critical for conducting chemical genomics experiments on natural products available in extremely limited quantities. I also conducted a systematic comparison of different profile similarity measures for genetic interaction networks which was crucial in discovering dot product as one of the most robust similarity measure. Enabled by these methods, we have conducted chemical genomics experiments for more than 10,000 natural products in yeast and now aim to discover therapeutically interesting compounds for human diseases. For this problem and a more general problem of translating and comparing genomic data across species, we developed a computational method neXus. Furthermore, we have started working on applications that could benefit from discovery of large number of drug-targets. One application is discovery of cancer targets using synthetic lethal interactions; however, very few synthetic lethal interactions are known in human so we developed a novel approach of discovering cancer relevant synthetic lethal interactions by translating the wealth of genetic interactions in model organisms to human.
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    Conceptual Modeling of Adaptive Therapy Dosing for Chemotherapeutic Administration in Cancer Allows for the Direct Comparison of Continuous and Adaptive Dosing Regimes
    (2022-05) McGehee, Cordelia
    Adaptive therapy of cytotoxic (cell killing) chemotherapy has been proposed as a method to prolong progression-free survival in certain cancers when underlying cell-cell competition between sensitive and resistant cancer cells is present. Traditionally, cytotoxic chemotherapy dosing is administered at the maximal tolerated dose with the goal of rapidly shrinking tumor growth. In the case of a tumor where underlying intratumoral cell-cell competition between a drug sensitive and drug resistant population leads to competition for resources, it is hypothesized that maximally killing the sensitive cell population allows for competitive release of the resistant cell population and outgrowth of a chemotherapy resistant tumor. In adaptive therapy, chemotherapy is administered when a tumor reaches a certain upper threshold and then is discontinued when the tumor shrinks to a specified lower threshold. The purpose of this strategy is to use the sensitive cell population to inhibit the growth of the resistant cell population and increase the length of time to competitive release and outgrowth of the resistant cell population. In this thesis, a modified Lotka-Volterra competition model is explored across competition parameters in order to analytically address 1) the optimality of continuous fixed dose versus adaptive dosing schedules and 2) the role of drug dose and mechanism of action in the choice of dosing regime. Using this model, several novel results are shown. First, for certain parameters, complete tumor eradication can be achieved in the presence of a resistant subpopulation under adaptive cytotoxic or continuous antiproliferative (decreasing growth rate) dosing schedules. Second, in this parameter space, fixed dose antiproliferative dosing schedules are more robust than cytotoxic adaptive regimes to uncertainty in initial conditions. Third, in parameter spaces where eradication of the resistant cell population is not feasible, both fixed dose antiproliferative schedules and cytotoxic adaptive therapy schedules may result in delayed resistant cell outgrowth over maximum tolerated dose and are comparable in their benefits. Overall, these results indicate that both antiproliferative continuous fixed dose therapy and cytotoxic adap-tive therapy can be used for tumor management in the case of underlying intratumoral competition between chemotherapy sensitive and chemotherapy resistant cells.
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    CT Scans: What are the Risks?
    (2012-07-26) Zaban, Nick
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    The design and synthesis of constrained AVPI peptidomimetics
    (2008-12) Kending, Cory
    Recent studies have demonstrated that breast cancer cell lines are sensitive to the XIAP (X-linked inhibitor of apoptotic proteins) antagonist Smac (second mitochondrial activator of caspases). Specifically the terminal tetrapeptide, AVPI, inhibits XIAP and thus sensitizes the breast cancer cells to various apoptotic therapeutics. These peptides are poor drug candidates due to their size, hydrophilicity and potential for peptidase cleavage. To address these issues we systematically synthesized peptide mimics that are constrained at various torsion angles along the peptide backbone. The compounds were tested in vivo and in vitro utilizing the laboratories of the Mayo Medical School. One compound, HCl*NH2-(R)-αMe-γ-Lactam-L-Val-L-Pro-L-Ile-OMe (3.1), increased the apoptotic signals above the assay background. Retro-modeling analysis utilizing the Schödinger flexible docking program suite did not provide an easy explanation for why this might be the case. The in silico models suggest that compound 3.1 interacts with only the primary pocket of the AVPI binding site and does not interact, like the native peptide, with both pockets in the active site. The R stereochemistry of the bicyclic compounds is predicted by our models to have a binding efficacy above that of the native peptide presumably due to the interaction with both pockets of the binding site as well as d-orbital interactions of the thiazole ring system with the neighboring tryptophan. The S stereochemistry was also initially proposed as a negative control for the biological assays, however, the instability of the molecule provided several daunting challenges to an already challenging and low yielding synthesis and the negative controls were abandoned when it was clear that the synthesis was futile. Our research shows limited evidence that our AVPI peptidomimetics are a potential scaffold to base other drug-like molecules upon. Future biological data from the bicyclic compounds will hopefully prove our hypothesis and molecular modeling studies correct.
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    Design and synthesis of tubulysin analogs that stabilize and mimic a key acetate important for potent antiproliferative activity against multi-drug resistant cancers
    (2012-10) Peterson, Michael Thomas
    Tubulysins are antimitotic natural products with potent anticancer activity against multidrug-resistant (MDR) cancer cells, acting by inhibition of tubulin polymerization. The marked difference in antiproliferative activity between tubulysins V and U exemplifies the importance of an acetate positioned alpha to the thiazole ring. However, this acetate has been shown to be labile under both acidic and basic conditions, so the effectiveness of this modification may be hindered due to this instability. Hence, the work presented here focuses on the synthesis of analogs that mimic and stabilize the acetate at this position.Heteroatom exchange at the α-thiazole position of tubuvaline was hypothesized to increase molecular stability while maintaining observed activity by bioisosteric replacement of the tubuvaline oxygen with a nitrogen. The nitrogen-containing analogs of tubulysin V and U, N tubulysin V and U, were the most important targets to test the singular modification of heteroatom exchange on bioactivity and to survey molecular stability. The synthetically derived N tubuvaline amino acid residue was generated following a rigorously controlled Mitsunobu reaction, but difficult final stage deprotections to N tubulysin V suggests a lowered stability compared to tubulysin V. N-acylation of a penultimate tetrapeptide intermediate led to generation of N tubulysin U and other acylated N tubulysin analogs to establish a more robust SAR at the α-thiazole position. N Tubulysin U was found to be more stable than tubulysin U under strongly basic conditions, and upcoming biochemical evaluation will determine the effect that these modifications have on antiproliferative activity.Investigations into the SAR at the tubuvaline α-thiazole position also included oxygen-based analogs, where two methods for acylation of tubulysin V were exploited to generate O-acylated analogs with various alkyl groups. Biochemical evaluation of antiproliferative activity, along with the use of two electrophilic analogs to act as affinity labels, will survey important interactions within the tubulysin-tubulin binding site.
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    Determining the Effect of Cell Culture Methods on the Polarization and Phenotype of Macrophages
    (2024) Lambrecht, Daniel; Chiu, Maggie; Provenzano, Paolo P.
    Macrophages play an important role in the regulation of cancer tumor microenvironments (TME). The specific role they play depends on their polarization, which is divided into two general phenotypes: M1, a pro-inflammatory phenotype, and M2, an anti-inflammatory phenotype known to support tumor growth. As the field of cancer research develops, there is an increased focus on understanding the role of the macrophage in the TME and how it can be manipulated to limit the growth of the tumor. Thus, it is important for researchers who are studying the macrophage’s role in the TME to know the phenotype of the macrophages that they are culturing in their research. The goal of this study was to observe the differentiation and polarization of macrophages during the standard cell culture protocol. We expected the macrophages to be fully differentiated after 7 days of culture with M-CSF and that cell passaging would result in a higher abundance of M1 polarized macrophages in culture. However, we found that macrophages are fully polarized after only 5 days of exposure to M-CSF and that passaging has no significant effect on macrophage polarization. This implies that macrophage differentiation protocols can be shortened with no loss in macrophage yield and that passaging is a suitable cell culture method for macrophages.