Interestingly, in vitro, irradiation of 4T1 carcinoma cells in the absence of the tumor stroma showed upregulation of ISGs, except Ifnb1 (Figure S1a, Supporting Information), suggesting that the cGAS‐STING pathway may be variant in 4T1 cells and that tumor stromal cells play a critical role in RT‐activated immune responses. Here, CGAS is linked to carcinoma.