Natural Killer cell kills the cancer cell in two simple ways: 1. “Death signal” way (extrinsic apoptosis) NK cell shows a special key (FasL or TRAIL). The cancer cell has a lock (death receptor). Key fits lock → instant message inside: “self-destruct now.” The cancer cell calmly chops itself into small, tidy pieces and dies without making a mess. 2. “Bullet poison” way (granule pathway) NK cell shoots tiny holes with perforin. Poison enzymes (granzymes) slip through the holes. Poison turns on th