Animal & Avian Sciences Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2741
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Item Lineage reprogramming of tumor-infiltrating cytotoxic T lymphocytes using protein stem cell transcription factors(2015) BhaduriHauck, Anjuli Lucija; Xiao, Zhengguo; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Adoptive cell transfer therapy (ACT) is one of the most promising immunotherapies against cancer. However, this treatment regimen requires the expansion of a small population of effector cells, known as tumor infiltrating lymphocytes, into the billions in order to overcome the immunosuppressive tumor microenvironment. The cytotoxic T lymphocytes (CTLs) within this invading immune cell population are the most critical components to kill the growing cancer cells. Nonetheless, the rapid expansion of already exhausted tumor-infiltrating cytotoxic T lymphocytes (TICTLs) may further push them to a terminally differentiated state that reduces their proliferative response upon antigen stimulation. Recently, induced pluripotent stem cells (iPSCs) generated from TICTLs have been suggested as a way to create a renewable source of rejuvenated tumor-specific CTLs, but retroviral reprogramming is inefficient, and can lead to an increased chance of tumorigenesis. To improve the expansion of TICTLs, we used transient protein exposure to SOX2, OCT4, and NANOG (SON) in order to push these exhausted TICTLs to a less differentiated stage, preferably stem cell-like memory CTLs (Tscm). These three transcription factors were transiently delivered using a nuclear protein delivery system. We found only the TICTLs treated with SON (STICTLs) exhibited an increased proliferation rate and extended survivability, independent of additional cytokines and antigen stimulation both in vitro and in vivo; effector CTLs did not respond to the SON regimen. These highly proliferative STICTLs could be associated with up regulation of certain genes related in cell cycle control, such as cyclin D1. Though these STICTLs still express a T cell receptor (TCR), as well as many critical downstream components, they were unable to elicit a reaction against antigen exposure. Though clearly not iPSCs, it is possible that the SON treatment had pushed the TICTLs into a state similar to an early double negative thymocyte. Our findings indicate that TICTLs are uniquely responsive to protein SON compared to naïve and effector CTLs; suggesting TICTLs may also be sensitive to regulation by other more lineage specific transcription factors, thus present new avenue for cancer immune therapy.Item MOLECULAR MECHANISMS UNDERLYING CADHERIN-6B INTERNALIZATION IN PREMIGRATORY CRANIAL NEURAL CREST CELLS DURING THEIR EPITHELIAL-TO-MESENCHYMAL TRANSITION(2015) Padmanabhan, Rangarajan; Taneyhill, Lisa A; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The generation of migratory cells from immotile precursors occurs frequently throughout development and is crucial to the formation and maintenance of a functioning organism. This phenomenon, called an epithelial-to-mesenchymal transition (EMT), involves the disassembly of intercellular adhesions and cytoskeletal rearrangements in order to promote migration. Importantly, aberrant EMTs and cell migration can lead to devastating human conditions including cancer metastasis and fibrosis. How cells accomplish EMT to become migratory is still an unanswered question in the biomedical field. To this end, we use chick neural crest cells as an in vivo model to elucidate the molecules and pathways that regulate EMT and migration. Neural crest cells are a population of embryonic cells that are originally stationary within the dorsal neural tube but later migrate to form a variety of adult derivatives, such as the craniofacial skeleton, skin pigment cells and portions of the heart. To facilitate EMT, chick premigratory neural crest cells lose intercellular contacts mediated, in part, by the transmembrane cell adhesion protein Cadherin-6B (Cad6B). While Cad6B mRNA is transcriptionally repressed in premigratory neural crest cells, loss of Cad6B protein does not directly follow and instead occurs ~90 minutes later, just prior to migration. This rapid depletion of Cad6B is all the more striking given that the half-life of most cadherins, including Cad6B, is ~6-8 hours in vitro. As such, unique post- translational mechanisms must exist to remove Cad6B from premigratory neural crest cell plasma membranes to facilitate neural crest EMT. Since cadherins are known to be downregulated through internalization mechanisms (e.g., endocytosis, macropinocytosis) in other in vitro systems, the hypothesis of this dissertation is that Cad6B is internalized, and that this process plays a critical function to enable neural crest EMT. To this end, we document the existence of Cad6B cytoplasmic puncta in cultured cells, cultured neural crest cells and transverse sections of chick embryos. We subsequently identified a p120-catenin binding motif in the Cad6B cytoplasmic tail and demonstrated its functionality through site-directed mutagenesis, revealing a role in enhancing Cad6B internalization and reducing the stability of membrane-bound Cad6B. Furthermore, we uncover for the first time that Cad6B is removed from premigratory cranial neural crest cells through cell surface internalization events that include clathrin-mediated endocytosis and macropinocytosis. Both of these processes are dependent upon the function of dynamin, and inhibition of Cad6B internalization abrogates neural crest cell EMT and migration. Collectively, our findings provide a molecular blueprint for how cadherins are dynamically regulated during the formation of migratory cell types required for normal embryonic development and tissue repair as well as those generated during human diseases and cancers. Importantly, our research is multi-disciplinary, integrating cell biology and physiology to reveal how a cellular event, the active downregulation of a membrane protein, results in a physiological event, neural crest EMT and migration.