PDCD1 and neoplasm: Immune checkpoint inhibitors targeting the Programmed Cell Death Protein-1/Programmed Cell Death Protein Ligand-1 (PD1/PDL1) axis or Cytotoxic T-Lymphocyte Associated protein-4 (CTLA-4) have been the predominant successes in the field of cancer immunotherapy but the tumour microenvironment has been a major obstacle to their success in many solid organ tumours (Labani-Motlagh et al., 2020).