| dc.description.abstract |
<p>Tumor angiogenesis is critical to tumor growth and metastasis, yet much is unknown
about the role vascular cells play in the tumor microenvironment. A major outstanding
challenge associated with studying tumor angiogenesis is that existing preclinical
models are limited in their recapitulation of in vivo cellular organization in 3D.
This disparity highlights the need for better approaches to study the dynamic interplay
of relevant cells and signaling molecules as they are organized in the tumor microenvironment.
In this thesis, we combined 3D culture of lung adenocarcinoma cells with adjacent
3D microvascular cell culture in 2-layer cell-adhesive, proteolytically-degradable
poly(ethylene glycol) (PEG)-based hydrogels to study tumor angiogenesis and the impacts
of neovascularization on tumor cell behavior. </p><p>In initial studies, 344SQ cells,
a highly metastatic, murine lung adenocarcinoma cell line, were characterized alone
in 3D in PEG hydrogels. 344SQ cells formed spheroids in 3D culture and secreted proangiogenic
growth factors into the conditioned media that significantly increased with exposure
to transforming growth factor beta 1 (TGF-β1), a potent tumor progression-promoting
factor. Vascular cells alone in hydrogels formed tubule networks with localized activated
TGF-β1. To study cancer cell-vascular cell interactions, the engineered 2-layer tumor
angiogenesis model with 344SQ and vascular cell layers was employed. Large, invasive
344SQ clusters developed at the interface between the layers, and were not evident
further from the interface or in control hydrogels without vascular cells. A modified
model with spatially restricted 344SQ and vascular cell layers confirmed that observed
344SQ cluster morphological changes required close proximity to vascular cells. Additionally,
TGF-β1 inhibition blocked endothelial cell-driven 344SQ migration. </p><p>Two other
lung adenocarcinoma cell lines were also explored in the tumor angiogenesis model:
primary tumor-derived metastasis-incompetent, murine 393P cells and primary tumor-derived
metastasis-capable human A549 cells. These lung cancer cells also formed spheroids
in 3D culture and secreted proangiogenic growth factors into the conditioned media.
Epithelial morphogenesis varied for the primary tumor-derived cell lines compared
to 344SQ cells, with far less epithelial organization present in A549 spheroids. Additionally,
344SQ cells secreted the highest concentration of two of the three angiogenic growth
factors assessed. This finding correlated to 344SQ exhibiting the most pronounced
morphological response in the tumor angiogenesis model compared to the 393P and A549
cell lines. </p><p>Overall, this dissertation demonstrates the development of a novel
3D tumor angiogenesis model that was used to study vascular cell-cancer cell interactions
in lung adenocarcinoma cell lines with varying metastatic capacities. Findings in
this thesis have helped to elucidate the role of vascular cells in tumor progression
and have identified differences in cancer cell behavior in vitro that correlate to
metastatic capacity, thus highlighting the usefulness of this model platform for future
discovery of novel tumor angiogenesis and tumor progression-promoting targets.</p>
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