PDCD1 and neoplasm: Given the potential of tumor cell HR defects, including BRCAness, to increase susceptibility to ICI through enhanced immune activation and expression of PD-1 or PD-L1 (103), ICI response is being studied in cancers, including breast cancers, with germline mutations in BRCA1 or BRCA2 (NCT01772004, NCT03025035).