However, tumors exploit these pathways by expressing checkpoint proteins like CTLA-4, PD-1, and its ligand (PD-L1), which help cancer cells evade immune detection and promote T-cell exhaustion.9, 10, 11 ICIs targeting checkpoint proteins have shown significant success in cancers such as melanoma, non-small-cell lung cancer (NSCLC), and bladder cancer (BC).12, 13, 14 Despite these successes, response rates remain variable, and not all patients benefit from these therapies. Here, PDCD1 is linked to breast cancer.