In particular, the inflammatory tumour microenvironment can upregulate ligands for T‐cell inhibitory receptors such as programmed cell death protein‐1 (PD‐1) on tumour cells to inhibit T‐cell signalling and promote the tolerisation or exhaustion of T cells (Pardoll, 2012; Ribas & Wolchok, 2018). This evidence concerns the gene PDCD1 and neoplasm.