Immune checkpoint inhibitors, which include programmed cell death protein 1 (PD-1)/cell death protein ligand 1 (PD-L1), have substantially improved treatment outcomes and achieved a breakthrough in adult cancers in the past few years.1–3 The PD-1 receptor, a transmembrane glycoprotein, plays a crucial role in the immune evasion mechanism which downregulates T-cell activation. Here, PDCD1 is linked to cancer.