PRF1 and cancer: Within the early cancer setting, ILCs are extremely efficient at eliminating malignant cells through the expression of perforin and granzyme, as well as death ligands, such as TNF‐regulated apoptosis‐inducing ligand (TRAIL) and Fas ligand [132, 133, 134] ILCs comprise the cytotoxic NK cells, and the more recently discovered ‘helper’ ILC subsets.