Xenograft Model of Breast Cancer Metastasis

NOD scid gamma (NSG) mice were purchased from Jackson Laboratory. Eight week old female mice were injected unilaterally with 2.5×10⁶ cells in 200 µL of 50∶50 Matrigel/Collagen I into the fourth abdominal fat pad by subcutaneous injection at the base of the nipple. Tumor growth was monitored externally using vernier calipers for up to 30 weeks and animals sacrificed when tumors reached 10% of body weight. Necropsies were performed to identify macro-metastases. Primary tumors and organs were harvested, paraffin embedded, sectioned and stained with hematoxylin and eosin or antibodies against cytokeratin 18 (CK18), epidermal growth factor receptor (EGFR), and Her2. Pathology processing and staining of harvested mouse tissues was performed at the Lombardi Comprehensive Cancer via Science Exchange, Inc. Slides were analyzed by a pathologist to confirm the presence of metastases. RNA was isolated from three independent metastases and primary xenograft tumors for analysis. Note: No estrogen pellets were required for growth of estrogen receptor alpha positive cell lines, MCF7 and BT474.