PD-L1 (Programmed death-ligand 1) is expressed on several types of tumor cells, mediating the tumor-induced immune suppression (immune checkpoint) by binding with the receptor PD-1 (programmed cell death protein 1), which is highly expressed in activated T cells, B cells, dendritic cells, and natural killer cells (Dermani et al., 2019). Here, PDCD1 is linked to neoplasm.