Due to the powerful antitumor effect of type I interferon in immune microenvironment, the blockade of cGAS‐STING signaling in endocrine‐resistant breast cancer promoted the tolerance to dsDNA‐induced cell death and inhibited the maturation of DCs and the cytotoxicity of PBMC immune cells, which could promote the formation of immunosuppressive microenvironment, tending to “cold” tumor. Here, STING1 is linked to breast carcinoma.