PDCD1 and cancer: An example of this is the paramount success of immune checkpoint therapy (ICT) based on antibody-dependent targeting of T cell functional modulators like cytotoxic T lymphocyte antigen 4 (CTLA-4) and programmed cell death protein 1 (PD-1) that relies on cancer restriction through the activation of the host immune system and resulted in significant improved clinical benefits in many type of solid tumours [1–3].