Moreover, using flow cytometry, we analyzed the PBMCs of patients with advanced cancer, and the results suggested that the population of Casp8‐ NK cells (NK cells with low Casp8 expression) had a lower ability to produce IFN‐γ and CD107a than Casp8+ NK cells (NK cells with high Casp8 expression), but Casp8‐ NK cells had a higher expression of PD‐1 and CTLA‐4. Here, CTLA4 is linked to cancer.