Tumor cells expressed PD-L1 (programmed cell death protein ligand 1) or PD-L2 (programmed cell death protein ligand 2) ligands that match the T-cell PD-1 protein, preventing them from finding the tumor and sending signals to the immune system to attack the tumor, directly leading to T-cell failure [34]. The gene discussed is PDCD1LG2; the disease is neoplasm.