We have shown in the B16 melanoma model that hetIL-15 enhances the survival, proliferation and antitumor effects of adoptively transferred Pmel-1 cells without the need for lymphodepletion preconditioning, resulting in improved tumor control and survival.47 Overall, hetIL-15 administration is associated with increased proliferation of effector memory T lymphocytes and NK cells expressing the cytotoxic serine protease Granzyme B (GzmB).47 However, the mechanism(s) underlying promotion of antitumor responses by IL-15 is still not completely understood. The gene discussed is GZMB; the disease is melanoma.