PDCD1 and neoplasm: Moreover, KLRB1 expression exhibited a positive correlation with the expression of PDCD1 (r = 0.624), CD274 (r = 0.317), and CTLA4 (r = 0.541) under condition of tumor purity, and PDCD1 (r = 0.731), CD274 (r = 0.441), and CTLA4 (r = 0.643) under condition of age in BRCA.