PDCD1 and neoplasm: Blockage of PD-1/PD-L1 pathways has been the most successful strategy as it promotes the programmed death of tumor cells, with various anti-PD-1/PD-L1 antibodies approved for first- and second-line settings with manageable toxicity profiles, improved efficacy, and longer durations of response compared to standard chemotherapy [59,67,68].