To determine whether intracellular IL-15 also requires IL-15Rα to function, we used anti-IL-15 antibodies to immunoprecipitate cancer cell-intrinsic IL-15 and found that IL-15 was associated with IL-15Rα (Fig. 9C and D) but not with the IL-2/IL-15Rβ or IL-2Rγ chains. This evidence concerns the gene IL15 and cancer.