Dissertation
The role of NetrinG1 in stroma-derived extracellular vesicle-mediated survival of pancreatic ductal adenocarcinoma during nutrient-deprivation
Doctor of Philosophy (Ph.D.), Drexel University
Dec 2021
DOI:
https://doi.org/10.17918/00000902
Abstract
Pancreatic Ductal Adenocarcinoma (PDAC) is a devastating disease which is, in part, driven and supported by changes in its microenvironment or stroma. These changes occur early, yet the majority of PDAC cases are undiagnosed until after the disease has metastasized, causing survival rates to drop tenfold. Therefore, there exists a grave importance to detect this disease as early as possible and understand its progression. This dissertation investigates the intercellular communication that exists between the primary stromal component, cancer associated fibroblasts (CAFs) and PDAC cells. Specifically, this study focuses on the mechanism by which CAF-secreted extracellular vesicles (EVs) promote PDAC survival. EVs are heterogeneous populations of membrane structures used to transfer material between cells. This investigation highlights specific populations of EVs including exosomes and exomeres. An additional goal of this work aims to identify potential EV-biomarkers suitable to generate a noninvasive "liquid biopsy" test for early PDAC detection and prognosis assessment. This study reports distinct types of CAF-derived EVs containing unique surface receptors. One novel surface protein, NetrinG1, is expressed on the plasma membrane of pancreatic CAFs, but absent in nonpathogenic fibroblasts. Functional assays designed to test PDAC viability under nutrient deprivation show CAF EVs can protect PDAC cells from the induction of apoptosis. Analysis of CAF EV cargo suggest that this EV-mediated survival benefit is caused by NetG1-dependent changes in proteins and metabolites being transferred to nutrient-stressed PDAC cells. This work also identifies distinct subtypes of CAF-derived EVs containing unique cargo and surface receptors including NetrinG1; these CAF-derived EVs localize to novel exomere subpopulations, suggesting the secretion mechanism is distinct from canonical exosome trafficking. An additional protein receptor, Integrin [alpha]5, was observed in exosome structures, supporting previous reports of its subcellular localization in CAFs being associated with a pathological state. Supporting the potential for disease detection, NetrinG1 and Integrin [alpha]5 in EVs from human plasma were shown to be significantly enriched in PDAC patients. Additionally, this investigation provides early evidence that the extracellular matrix differentially binds subpopulations of EVs based on surface markers. This suggests that the extracellular matrix can play an important role in determining the biodistribution of secreted EVs in vivo, which has significant implications for what EV subpopulations maybe be found circulating systemically in blood or acting locally in a paracrine manner within the tumor microenvironment. Altogether, this research elucidates a novel mechanism of tumor-stroma communication and introduces functional EV subpopulations potentially capable of identifying PDAC occurrence in humans.
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Details
- Title
- The role of NetrinG1 in stroma-derived extracellular vesicle-mediated survival of pancreatic ductal adenocarcinoma during nutrient-deprivation
- Creators
- Kristopher S. Raghavan
- Contributors
- Edna Cukierman (Advisor)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xvii, 233 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Biochemistry and Molecular Biology; College of Medicine; Drexel University
- Other Identifier
- 991016457359504721