2.4.1. Breast Cancer Metastases Murine Model

Twenty BALB/c mice (female, 12-week-old, Charles River Laboratories, Wilmington, MA, USA) were orthotopically injected with 5 × 10⁴ 4T1 cells into the #4 mammary fat pad of the mice. Once the tumors measured ~100 mm³, 10 mice received sham irradiation and the other 10 received focal irradiation (6.5 Gy) to the primary tumor. The mice were monitored until the tumor volume reached 2000 mm³, and were then sacrificed, with primary tumors and lung metastases collected in RNA later (Qiagen, Germantown, MD, USA).