PDCD1 and cancer: The use of immune checkpoints protein inhibitors, such as antibodies against PD-L1 (anti-PD-L1) and PD-1 (anti-PD-1), has shown notable long-term clinical benefits in a wide number of cancer types [135,136,137,138,139,140,141,142,143,144,145], even if the patient response rate is still low [146,147,148].