PDCD1 and neoplasm: In addition, the OC environment damages the anti-tumor function of CD8+ T cells through the inhibition of signaling pathways, including checkpoints triggered by cytotoxic T lymphocyte antigen 4 (CTLA-4), programmed cell death protein 1 (PD1), lymphocyte activation gene 3 protein (LAG-3), and T-cell immunoglobulin and mucin-domain containing protein 3 (TIM-3) [157,158,159,160].