PDCD1 and cancer: Myeloid‐derived suppressor cells presence is known to be associated with T cell exhaustion and senescence via PD‐1 up‐regulation on effector T cells, establishing the rationale for PD‐1/PD‐L1 signalling blockade as an effective immune therapy for many cancers (Huang, Francois, McGray, Miliotto, & Odunsi, 2017).