PDCD1 and cancer: Checkpoint inhibitors (such as programmed cell death protein 1 (PD‐1) or Cytotoxic T‐Lymphocyte Associated protein 4 (CTLA‐4) inhibitors) present one avenue of immunotherapy that aim to circumvent the immunosuppression inherent to many cancers and thus, enable immune cells to carry out their ‘anti‐tumour’ roles.2