CGAS and breast cancer: The cGAS‐STING pathway is the major innate immune pathway that senses cytosolic DNA and activates interferon signaling.[23] To determine whether the cGAS‐STING pathway is altered in endocrine‐resistant breast cancer cells, we initially transfected herring testis DNA (HT‐DNA) into MCF7/ZR75.1 cells and R‐MCF7/R‐ZR75.1 cells.