Because PD-1 pathway blockade acts mainly on Tpex cells, causing them to generate Ttrex cells with strong cytolytic activity (11), an administration of IL-15 that increases the population of Tpex cells combined with αPD-1 therapy could lead to a powerful synergistic effect that might be applied to more patients and different types of cancer that are resistant or refractory to current therapies. This evidence concerns the gene PDCD1 and cancer.