Project Summary Breast cancer (BC) is the most frequently diagnosed cancer in women. In addition, metastatic BC has a 5-year survival rate of only 27% and metastases are associated with the vast majority of cancer-related deaths. Recent research has highlighted a complex dynamic between cancer cells and the tumor microenvironment as essential for the formation of macrometastases. Within this field, tissue stiffening through matrix accumulation and altered matrix organization were recently linked with sustained proliferation and increased migration of tumor cells. Elevated levels of the glycoprotein fibronectin (FN) have been correlated to poor patient survival in BC and are linked to enhanced seeding of disseminated tumor cells at metastatic sites. My previous work has indicated several mechanisms through which accumulated FN impacts the metastatic potential of BC cells. Foremost, I helped identify a transient increase in extracellular FN in the lungs, which peaked before overt metastasis, coupled with a non-transient increase in total lung volume. I further found that cyclic mechanical force acted as a suppressor of cancer cell growth in a biomimetic lung model, implicating the accumulation of extracellular matrix (ECM) as an attempt by the cancer cells to alter the mechanical properties of the lung tissue and resist entering dormancy. However, my results showed that BC cells could not organize FN into ECM independently. Instead, BC cells altered the accumulation and architecture of FN by conditioning resident fibroblasts through soluble factors and extracellular vesicles. I observed that the FN produced by conditioned fibroblasts varied not only based on the phenotype of the BC cell, but also from the method of conditioning which tested paracrine and endocrine signaling. These preliminary results indicate that unique subtypes of cancer associated fibroblasts (CAFs) may develop based on the BC cell conditioning mechanism, where unique subtypes may be associated with the specific needs of the various stages of the metastatic cascade. Therefore, Aim 1 of the proposed studies during my Ph.D. research will define the contribution of cyclic strain on BC cell phenotype and dormancy using our novel actuating platform. Aim 2, which I will undertake during my postdoctoral research, will seek to better define the varied roles of CAFs in metastatic progression through the development of a foundation of subtypes after conditioning with media, isolated extracellular vesicles, and contact from BC cancer cells, including metastatic and non-metastatic BC cells with epithelial and mesenchymal phenotypes. These findings will enable advanced interaction studies and promote the development of novel targets for fibroblasts, which may be a more consistent target than genetically unstable cancer cells and lead to more effective treatment. In addition, the proposed studies and training plan will expand my current tissue engineering skillset to include advanced understanding of mechanotransduction pathways and CAF formation as well as improve my communication, mentoring, and teaching. Together, these skills will place me as a competitive candidate for an independent principle investigator position in a research university at the intersection of cancer biology and engineering.

Project Narrative After metastasis to the lungs, breast cancer cells are exposed to unique forces and matrix proteins that are not present at the primary tumor. My previous findings indicate that cyclic stretching, mimicking breathing dynamics within a 3D model of the early metastatic niche, can drive tumor cells into a state of growth arrest without widespread cell death. Because stromal cells are the key contributor of matrix composition and architecture, my goal is to evaluate the unique fibroblast subtypes conditioned by breast cancer cells at different stages of the metastatic cascade and characterize how the tissue changes they produce alter the metastatic progression of disseminated breast cancer cells.