| dc.description.abstract | The majority of breast cancer patients receive radiation therapy. Although this treatment improves overall outcomes, patients with triple negative breast cancer (TNBC) have a significantly higher risk of distant and locoregional recurrence, especially if they are immunocompromised. An emerging body of literature suggests that normal tissue damage caused by radiation may contribute to recurrence through the recruitment of circulating tumor cells. Many steps in the tumor reseeding process are not well characterized, and current in vitro models available for studying the effects of normal tissue damage are limited in their efficacy. Therefore, there is a significant need to design robust in vitro models that better replicate biology. Three-dimensional (3D) co-culture models are multicellular constructs that retain relevant architecture and biological properties, making them an attractive alternative to monolayer cultures that do not mimic complex in vivo characteristics. In this dissertation, we first describe the development and characterization of an irradiated mammary epithelial organoid model. This model retains epithelial cell characteristics and allows for studying macrophage and tumor-stromal interactions. We then build on this work by developing a novel fibroblast spheroid model to evaluate macrophage-mediated tumor cell recruitment in immunocompromised microenvironments. We characterized radiation-induced macrophage infiltrates (RIMI) in vivo via flow cytometry and immunohistochemical staining. We then used our knowledge of RIMI phenotypes to engineer a biologically relevant model, consisting of primary fibroblasts isolated from mouse mammary glands. Using this model, we establish that the irradiated stroma and RIMI facilitate secretion of IL-6, which drives tumor cell recruitment. Finally, we explore the role of CD8+ T cells in the normal tissue radiation damage response. Using murine co-cultures of fibroblasts, macrophages, and primary CD8+ T cells, we discover that the CD8+ T cells regulate the fibroblast damage response. These results provide evidence that immunocompromised patients suffer from aberrant inflammation post-radiation that may lead to tumor cell recruitment. Looking forward, 3D co-culture models will be crucial for biological discovery and complementing in vivo studies, having significant implications for TNBC patients. | |
