Arc Institute Sep 5 2025 Cancer immunotherapy, which primes the body's immune system to fight off tumors, has historically focused on harnessing T cells' natural ability to recognize and attack cancer cells. While this approach has saved the lives of patients with melanoma, as well as certain lung cancers and blood cancers, it has been less effective against solid tumors, which tend to be "cold" environments, where anti-cancer immune responses are inactive and cancer-killing T cells are not