PDCD1 and neoplasm: Our findings indicated that immune checkpoints (PDCD1, ENTPD1 and TIGIT), the T-cell exhaustion state-associated transcription factor TOX, and the gene DDX58 (transcriptional protein RIG-I) are co-expressed in tumour-infiltrating CD8+ T cells (Figs. 1A–D; Fig. EV1A–D).