IN VITRO MODELS AND IMAGING TOOLS TO ASSESS ROLES OF OBESITY ASSOCIATED STROMAL MICROENVIRONMENT ON BREAST CANCER PROGRESSION

Abstract

Cancer is a complex disease that is often tissue and context dependent. Tumor microenvironment has been shown to have pivotal roles in regulating tumor initiation, growth and metastasis. Enrichment of cancer associated fibroblasts (CAFs) have been shown to promote cancer cell invasion by modulating physiochemical components of ECM, promoting angiogenic behaviors of endothelial cells (ECs) and shuffling metabolites to satisfy tumor metabolic demands. Obesity worsens the prognosis for breast cancer patients, and adipose stromal cells (ASC)-mediated fibrotic ECM remodeling of breast tissue plays a role in this process. Obese ASCs have been shown to share many similarities to CAFs. Whether or not obese vs. lean ASCs differentially affect the other factors important to progression of premalignant breast cancer, remains unclear. In this dissertation, I proposed the hypothesis that obese vs. lean ASCs can prime the breast tissue microenvironment to be permissive to breast cancer progression by remodeling the surrounding extracellular matrix (ECM), altering angiogenesis and reprogramming metabolism. Leveraging different tissue engineering strategies, I designed numerous physiologically relevant 3D in vitro models and developed advanced imaging tools to investigate 1) how does obese ASC and ECM remodeling mediate breast cancer cell invasion? 2) how does ASC and ECM remodeling contribute to angiogenesis? 3) what is the metabolic interplay between ASC and tumor cells during cancer invasion? Results from these studies suggest that 1) direct cell-cell contact with ASCs enables collective tumor cell migration and obese ASCs are more effective than their lean counterparts. Both matrix metalloproteinase-dependent proteolytic activity and ASC contractility are important during obese ASC mediated collective cancer migration. 2) Obese ECMs promote the proangiogenic behavior of ECs by altering their proliferative, secretory, and invasive capacities as compared to lean ECMs. 3) A label free multiphoton anisotropy imaging platform can be used to measure NAD(P)H dynamics as an indirect readout for cell metabolism. Combining with gold standard seahorse analysis, it is a powerful tool to allow us to monitor the metabolic states of ASCs and tumor cells in various culture platforms. In summary, tools and models developed in this dissertation provide novel insights into how different aspects of obesity associated microenvironmental changes are functionally related to breast cancer cell invasion, which increase the understanding of how obesity promotes breast cancer.