CAR-T cells must overcome cancer’s many defenses in order to mount an effective attack. Lulu Perez, CC BY-SA You might think of cancer as a mass of rogue cells that grow uncontrollably. But cancer is more organized and strategic than that. Rather, cancer is a tightly controlled cellular neighborhood that can keep the body’s defenses out or weaken them once they get in. Cancer behaves like a gated community. It has its own residents, rules and security systems. Together, these features create wha