Mice were anesthetized with 2% isoflurane inhalation, and immobilized in a dedicated mouse holder with a lead shield that allowed for selective thoracic irradiation. Based on the published literatures (16 (link),23 (link)), we administrated the thoracic irradiation using a linear accelerator (Varian Medical Systems, Palo Alto, CA, USA) on the mice at a dose rate of 3 Gy/min with the regimen of 8 Gy ×3 on days 0, 1 and 2. The source-surface distance was 100 cm. The irradiation field was 4 cm × 2 cm. Mice were randomly assigned to different groups with the numbers of 5–12 for each time-point per group. Control mice underwent the same procedure and exposed to 0 Gy.