In multiple pathogen infections and cancers, activated NK cells have been shown to express the immune checkpoints programmed cell death protein 1 (PD1), cytotoxic T lymphocyte-associated antigen 4 (CTLA4), and T cell immunoreceptor with Ig and ITIM domains (TIGIT) [109,110,111,112,113]. This evidence concerns the gene CTLA4 and cancer.