Since ENKTL tumor cells secrete interferon (IFN)-γ which is known to induce PD-L1 expression in macrophages, it is postulated that ENKTL may utilize the PD-L1/PD-1 pathway to inhibit immune suppression via the upregulation of PD-L1 expression either on tumor cells or on macrophages [115]. This evidence concerns the gene PDCD1 and neoplasm.