Using Extracellular Matrix Hydrogels to Evaluate the Normal Tissue Radiation Response

Breast cancer, affecting over 280,000 Americans every year, has a multitude of treatments including surgery, chemotherapy, and radiotherapy, however, locoregional recurrence still occurs. Previous studies have established that normal tissue irradiation induces fibrosis, the deposition of extracellular matrix components such as collagen I that leads to increased tissue stiffness. In addition, the irradiated normal tissue microenvironment has been shown to encourage circulating tumor cell recruitment, which emphasizes the significance of the tissue microenvironment in cancer recurrence. In this study, we hypothesized that stiffness and irradiation of collagen I hydrogels may impact breast cancer cell behavior. To test this hypothesis, we encapsulated GFP-labeled 4T1 murine TNBC breast cancer cells in irradiated and unirradiated collagen I hydrogels at low (2.5 mg/mL) and high (5.0 mg/mL) concentrations representing normal tissue and tumor microenvironments, respectively. We evaluated cell morphology through phalloidin staining of F-actin and migration using live cell imaging 48 hours post-encapsulation. All images were quantified using ImageJ. 4T1 cells exhibited increased elongation and migration speeds in stiffer, irradiated hydrogels, suggesting that the irradiated tissue microenvironment may be a driving factor of breast cancer recurrence. Future experiments will focus on cell behavior in irradiated extracellular matrix hydrogels from tissue samples. This work may lead to improvements in breast cancer treatment strategies to reduce recurrence and increase survival in TNBC patients.