Ex vivo stimulation of ILC1s isolated from human patient RCC exerted direct cytotoxicity against tumour cells in a dose-dependent manner in response to IL-15 stimulation in experimental killing assays, and targeted deletion of cancer cell-derived IL-15 in experimental animal models in vivo impaired ILC1 cytotoxic effector function, evident through a reduction in GzmB and GzmC expression and enhanced tumour burden. Here, IL15 is linked to neoplasm.