Tumor NK cells downregulated canonical NK activation markers, such as FASLG, TNFSF10, KLRK1, GZMB, and KLRD1, the latter having both inhibitory and activator capabilities but being a marker of favorable prognosis in human cancers if present in either the serum or tumor (29, 30) (Figure 1F). This evidence concerns the gene KLRD1 and cancer.