Date of Award

Spring 2022

Document Type

Dissertation

Degree Name

Doctor of Engineering (DEng)

Department

Biomedical Engineering (ENAS)

First Advisor

Mak, Michael

Abstract

Tumors are often described as ”wounds that do not heal”. Tumor progression and woundhealing both feature sustained proliferative signaling, evasion from immune destruction, cell death resistance, inflammation, angiogenesis, extracellular matrix(ECM) remodeling, and activated cell migration. Unlike normal wound healing which often ends up with restored tissue homeostasis, pathological ECM remodeling is frequently implicated in fibrotic diseases and solid tumors. In addition, the dysregulated ECM signatures are directly associated with poor prognosis and also immunotherapy failure in certain types of cancers. In this dissertation, we used 3D in vitro cocultures to understand how tumor cells co-op with stromal/immune components, how ECM remodeling is hijacked, and how ECM architecture impacts tumor progression. We first investigated the impact of fibroblasts. Fibroblasts are the most abundant cell types in the tumor stroma. The density of cancer-associated fibroblasts(CAFs) has been shown directly correlated with poor prognosis in some types of solid tumors. To uncover potential mechanisms behind the quantitative relationship between CAFs and tumor dissemination, we developed our coculture model by varying the density ratios between normal human lung fibroblasts and breast cancer cells(MDA-MB-231s). We found that fibroblasts increase tumor cell motility and facilitate the transition from confined to diffusive tumor cell motions, indicative of an uncaging effect. Furthermore, the ECM is globally and locally remodeled substantially with the presence of fibroblasts. Moreover, these fibroblast-mediated phenomena are in part dependent on matrix metalloproteinases. We then investigated the impact of macrophages. In this study, we developed a 3D collagen co-culture system to mimic the melanoma microenvironment and investigate how interactions between melanoma cancer cells, fibroblasts, and macrophages shape the early stages of macrophage immune activity. In this in vitro model, we captured the macrophage immunosuppressive transition. Macrophages in the model displayed increased motility and acquired a phenotype that was similar to tumor-associated macrophages(TAMs) from melanoma tumors. This model may provide a platform for further studies on TAMs targeted immune therapy in melanoma. In the end, we investigated the impact of ECM architecture in tumor progression. Reconstruction of a biomimetic scaffold is critical in 3D in vitro models. Here we introduce a new type of thick collagen bundles that highly mimic in vivo ECM structure. We fabricated this type of thickened collagen bundles by introducing mechanical agitation during the transient gelation process. Thickened collagen patches are interconnected with a loose collagen network, highly resembling collagen architecture in human skin scars. This type of thickened collagen bundles promotes tumor cell dissemination. The effect is significantly augmented in the presence of fibroblasts. The application of this type of collagen triggers different morphology and migration behaviors of tumor cells and highlights the importance of mesoscale architectures. Overall, this dissertation investigated the roles of stromal and non-stromal components in tumor progression through 3D in vitro models. The coculture models established in this dissertation may be further extended to test novel therapeutics targeted at CAFs, TAMs or ECM architecture.

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