The understanding of tumour-induced immune tolerance has led to the development of innovative treatments based on inhibition of negative immune regulation through targeting immune checkpoint molecules, including cytotoxic T lymphocyte antigen 4 (CTLA-4), programmed cell death protein 1 (PD-1) and programmed cell death ligand 1 (PD-L1) [1]. Here, PDCD1 is linked to neoplasm.