PDCD1 and neoplasm: A previous study showed that activation of PERK-eIF2α signalling could inhibit CD8+ T-cell infiltration and promote tumour growth, while inhibition of PERK-eIF2α signalling decreased the number of infiltrating CD8+ T cells, increased tumour clearance, and enhanced the efficacy of anti-PD-1 therapy in sarcoma [167] (Fig. 3).