As a consequence, the antitumor activity of anti-CTLA-4 antibodies is reduced by anti-CTLA-4-induced activation of PD-1/PD-L1 signalling in tumour-specific T effector cells, and, on the other side, the efficacy of PD-1 inhibition is limited by incomplete activation of cytotoxic T cells due to anti-PD-1 induced CTLA-4 overexpression [41]. This evidence concerns the gene PDCD1 and neoplasm.