Percent tumor free (A), survival curve (B) and percent with lung metastasis (C) for MT, IL-15 KO/MT and IL-15 TG/MT mice. Mice were palpated and tumors were measured once per week to determine date of first palpation or endpoint. (A) The median age of tumor palpation and number of mice per group was as follows; MT 95 (n = 30), IL-15 KO/MT 78 (n = 30) and IL-15 TG/MT 93 (n = 36). There is a statistical difference between the IL-15 KO/MT mice and the MT or IL-15 TG/MT mice (p < .0001). (B) The median age of endpoint and number of mice per group was as follows; MT 153 (n = 30), IL-15 KO/MT 136.5 (n = 30) and IL-15 TG/MT 157 (n = 28). In comparison to MT mice IL-15 TG/MT mice have increased survival (p = .0051), whereas IL-15 KO/MT mice have decreased survival (p = .002). (C) Percentage of mice with lung metastasis at 120 days of age (MT n = 13, IL-15 KO/MT n = 11 and IL-15 TG/MT n = 14). *p < 0.05, **p < 0.01.