Interferon regulatory factor-1 (IRF1) can function as a tumor suppressor in breast cancer by regulating the balance of prosurvival and proapoptotic factors. Loss of IRF1 is an important characteristic of breast cancer cells that have acquired resistance to antiestrogen therapy, a phenotype that often develops in estrogen receptor-α positive (ER+) breast cancers. Interferon gamma (IFNγ), a type II interferon, can rescue IRF1 expression in antiestrogen-resistant breast cancer cells and restore their sensitivity to antiestrogen-mediated apoptosis. For details, see article by Ning and colleagues on page 1274.