Browsing by Subject "glioblastoma"

Now showing 1 - 4 of 4
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    Characterization of Glioblastoma and T Cell Migration in Brain Tissue
    (2023-07) Anderson, Sarah
    Glioblastoma (GBM) is an aggressive malignant brain tumor with extremely low 5-year survival rates. One key characteristic of the disease is the ability of glioblastoma cells to migrate rapidly and spread throughout healthy brain tissue. To develop treatments that effectively target cell migration, it is important to understand the fundamental mechanism driving cell migration in brain tissue. In the first part of this dissertation, we utilized confocal imaging to measure traction dynamics and migration speeds of glioblastoma cells in mouse organotypic brain slices to identify that the cells are using a motor-clutch mode of migration. In addition, both integrins and CD44, as well as myosin motors, were found to play an important role in constituting the adhesive clutch. In developing a treatment that targets migration of glioblastoma cells, it is critical to take into account how this could impact T cell migration and the resulting ability of T cells to kill cancer cells. A hallmark of glioblastoma is the suppression of the immune response, allowing the tumor to grow and spread faster, and infiltration of cytotoxic CD8+ T cells into the tumor has been shown to be an important indicator of disease progression and survival. In the second part of this dissertation, we use mouse organotypic brain slices co-cultured with CD8+ T cells to image migrating CD8+ T cells in healthy brain tissue in response to cell migration targeting drugs and antibodies. We find an increase in migration speed in response to targeting CD44, which is a critical deviation between cancer cell and T cell phenotype, implicating CD44 as a potential target for improving glioma outcomes by slowing cancer cell migration and speeding up CD8+ T cells.
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    Delivery and efficacy of targeted therapeutics and imaging agents for brain tumors
    (2018-11) Kim, Minjee
    The treatment of both primary and secondary brain tumors is a serious unmet medical need in the field of neuro-oncology. Despite advances in developing molecularly-targeted anti-cancer therapeutics in treating peripheral tumors, there is no effective therapeutic for brain tumors that demonstrated dramatic improvement in patient survival. One of the major reasons of having lack of efficacy in central nervous system may be related to the delivery of therapeutic agents across the blood-brain barrier (BBB). The BBB expresses various transporters as well as unique junctional proteins that selectively permeate molecules into the brain from systemic circulation. Many molecularly-targeted therapeutic agents are found to be substrates of these efflux transporters at the BBB including P-glycoprotein (P-gp) and Breast cancer resistance protein (Bcrp). The current dissertation examined the multiple challenges in the treatment of brain tumors including non-specific protein binding, brain distributional kinetics, and role of efflux transporters on the distribution of various molecules such as molecularly-targeted anti-cancer drugs and tumor imaging agents.
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    Delivery And Efficacy Of CDK4/6 Inhibitors In The Treatment Of Brain Tumors
    (2016-01) Parrish, Karen
    Primary and metastatic brain tumors have limited treatment options and long term survival is rare. Cyclin-dependent kinases (CDKs) are major regulators of the cell cycle and are commonly altered in tumors. The CDK4/6 pathway regulates the checkpoint between G1 and S phase of the cell cycle. When altered, cells are able to proliferate rapidly and independent of this checkpoint. The blood-brain barrier (BBB) is a network of cells and proteins that prevent the paracellular and transcellular passage of many therapeutic agents from systemic circulation into the brain. The efflux transporters P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) actively transport substrates back into systemic circulation. Previous studies have demonstrated that numerous molecularly-targeted agents are substrates of P-gp and/or BCRP and that these transporters are responsible for the limited brain delivery. The objective of this work was to evaluate the role of efflux transport at the BBB in the brain delivery of CDK4/6 inhibitors and assess the relationship between brain delivery and efficacy in a glioblastoma (GBM) patient-derived xenograft. There are three CDK4/6 inhibitors, palbociclib, ribociclib and abemaciclib, currently in clinical development for the treatment of a variety of solid tumors. We show that palbociclib has limited brain delivery to active efflux transport by P-gp and BCRP at the BBB. Furthermore, we demonstrate that the concentrations of palbociclib reaching the brain are also subtherapeutic in the treatment of a subcutaneous GBM tumor. We then used a pharmacological inhibitor of efflux transport and improved the brain delivery of palbociclib in tumor-naïve and tumor-bearing mice. We demonstrated that chronic use of this combination therapy was well tolerated and significantly improved the brain delivery of palbociclib in an intracranial tumor model to the same levels that were achieved in the subcutaneous GBM model. Despite improving the brain delivery of palbociclib, there was no improvement in efficacy. Using the in situ brain perfusion technique, we compared the brain delivery of palbociclib, ribociclib and abemaciclib and the data suggest that abemaciclib may saturate efflux at lower concentrations that palbociclib or ribociclib and have improved brain delivery. These studies show that improving the brain delivery of palbociclib alone is not sufficient to improve survival in the intracranial GBM model. Future studies that reveal other factors besides delivery that are altered in subcutaneous models of brain tumors will be essential in understanding the use of preclinical models to study experimental GBM therapies.
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    Experimental and simulated cell migration in 1D and 2D nanofiber microenvironments
    (2017-03) Estabridis, Horacio
    Understanding how cells migrate in fibrous environments is important in wound healing, immune function, and cancer progression. A key question is how fiber orientation and network geometry influence cell movement. Here we describe a quantitative, modeling-based approach toward identifying the mechanisms by which glioblastoma cells migrate in fibrous geometries having well controlled orientation. Specifically, U251 glioblastoma cells were seeded onto STEP Fiber substrates that consist of networks of suspended 400 nm diameter nanofibers. Cells were classified based on the local fiber geometry and live cell migration was tracked, quantified and parameterized. Cells were found in three distinct geometries: adhering two a single fiber, adhering to two parallel fibers, and adhering to a network of orthogonal fibers. Cells adhering to a single fiber or two parallel fibers can only move in one dimension along the fiber axis, whereas cells on a network of orthogonal fibers can move in two dimensions. We found that cells move faster and more persistently in 1D geometries than in 2D, with cell migration being faster on parallel fibers than on single fibers. To explain these behaviors mechanistically, we simulated cell migration in the three different geometries using a motor-clutch based model for cell traction forces. Using nearly identical parameter sets for each of the three cases, we found that the simulated cells naturally replicated the reduced migration in 2D relative to 1D geometries. In addition, the modestly faster 1D migration on parallel fibers relative to single fibers was captured using a modest increase in the number of clutches to reflect increased surface area of adhesion on parallel fibers. Overall, the integrated modeling and experimental analysis indicates that cell migration response to varying fibrous geometries can be explained by a simple mechanical readout of geometry via a motor-clutch mechanism.