OXYGEN GRADIENTS AND EXTRACELULLAR MATRIX INTERACTIONS SYNERGISTIC EFFECT ON SARCOMA CELL MIGRATION
LEWIS-DISSERTATION-2018.pdf (12.35Mb) (embargoed until: 2021-05-01)
Lewis, Daniel Matthew
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Soft tissue sarcomas are a heterogeneous group of malignant cancers derived from transformed cells of mesenchymal origin. Approximately 13,000 new cases per year are diagnosed in the US alone, with 25–50% of patients developing recurrent and metastatic disease. Current clinical data suggest that undifferentiated pleomorphic sarcoma (UPS) is one of the most aggressive sarcoma subtypes, which frequently results in lethal pulmonary metastases that are insensitive to radio/chemotherapy. It has recently become apparent that sarcoma progression and metastasis are regulated by microenvironmental cues such as extracellular matrix (ECM) remodeling, cell-to-cell/matrix interactions, signaling factors, and spatial gradients. Current hydrogel platforms to study the tumor microenvironment do not fully capture complexity of the tumor microenvironment. Addressing the need for hydrogel platforms that more closely mimic the tumor microenvironment, we developed a new class of hydrogels to study oxygen gradients, collagen architecture, as well as stress relaxation as how it effects sarcoma cell migration. First we utilized a novel gelatin based hydrogel to create a fast forming hypoxic gradient to explore the effect of varying oxygen tensions on sarcoma cell migration. To accurately model the effect of the O2 gradient, we examined individual sarcoma cells embedded in the O2-controllable hydrogel. We observed that hypoxic gradients guide sarcoma cell motility and matrix remodeling through hypoxia inducible factor one alpha (HIF–1α) activation. We further found that in the three-dimensional hypoxic gradient, individual cells migrate quicker, across longer distances, and in the direction of increasing O2 tension. Treatment with minoxidil, an inhibitor of hypoxia-induced sarcoma metastasis, abrogated cell migration and matrix remodeling in the hypoxic gradient. To determine the impact of collagen fiber density and hypoxic gradient on sarcoma cell migration, we then generated hypoxic collagen gels. Sarcoma cells encapsulated in high fiber density hypoxic gels migrated faster and degraded the matrix more rapidly compared to the low fiber density hypoxic constructs. Finally, we explored the effect of stress relaxation in the hypoxic collagen platform. From this study we can conclude that a quicker stress relaxation in hypoxic gradients lead to an increase in cell migration due to an increase procollagen-lysine,2-oxoglutarate 5-dioxygenase 2 (PLOD2) expression. We determined the quicker stress relaxation increases PLOD2 via transforming growth factor beta (TGF-). Indeed, In-vivo we found an increase in tumor growth in the quicker stress relaxation hydrogels as well as an increase in collagen secretion and PLDO2 expression. Analyzing data from the cancer genome atlas (TCGA), we found a significant decrease in patient survival with an increase in PLOD2. Finally, when sarcoma from primary patient tissue was encapsulated in the system the cells demonstrated the same predicted phenotype as the mouse sarcoma line.