PDCD1 and cancer: For example, chemotherapy regimens, FLOT (5-FU, oxaliplatin, docetaxel) and CROSS (carboplatin and paclitaxel) could promote an immune-resistant phenotype through upregulation of inhibitory immune checkpoint ligands and receptors, such as PD-1/PD-L1 [19]; PARP inhibitor could enhance cancer-associated immunosuppression by upregulating PD-L1 expression [20]; MAP kinase inhibitor is able to potentiate antitumor T cells by blocking TCR-driven apoptosis [21].