PDCD1 and cancer: An additional recent approach to inhibit the PD-1/PD-L1 axisrelieson the use of the recombinant PD-1 ectodomain to address the PD-L1protein on the surface of cancer cells.16 In fact, the formation of a complex between recombinant PD-1 andPD-L1 on cancer cells hampers the interaction of the latter with PD-1exposed on T-cells and circumvents the main issue of the immune systemsuppression.17,18