PDCD1 and neoplasm: As the first-line (chemo- and radio-therapy are still mainstay) therapies for various solid and liquid tumors, three types of ICIs, CTLA-4, PD-1 interact with ligand PD-L1 and PD-L2, and anti-PD-L1 antibodies, have been approved by the FDA [231], even though the therapeutic effects are limited in most tumor patients.