PDCD1 and neoplasm: Thus, a further combinational approach by applying immune checkpoint antibodies, such as anti-CTLA-4 for Treg suppression or anti-PD-1/PD-L1 to restore exhausted CTLs, could be used for the synergistic oncotherapy to eliminate primary tumor and inhibit tumor metastasis, or even to generate a robust immunological memory for tumor recurrence prevention without noticeable systemic toxicity (78, 80).