PDCD1 and cancer: The PD-1 receptor and its ligand, PD-L1, form a crucial immune checkpoint pathway that plays a significant role in immune evasion.270,271 The PD-1/PD-L1 pathway is a crucial regulatory mechanism that maintains immunological homeostasis, preventing excessive immune activation and autoimmunity.272 However, cancers frequently use this pathway to escape immune monitoring, contributing to tumor development and resistance to treatments.273 Understanding the PD-1/PD-L1 signaling pathway is crucial for developing targeted therapies aimed at enhancing anti-tumor-immune responses (Fig. 5a).