In terms of mechanism, PD-L1 expressed on tumor cells promotes immune evasion (Topalian et al., 2015; Sanmamed and Chen, 2018), and therapeutic blockade of the PD-1 pathway theoretically requires the expression of PD-L1 on antigen-presenting cells and tumor cells (Yamaguchi et al., 2022). This evidence concerns the gene PDCD1 and neoplasm.