First, the publically available METABRIC dataset (37) was used to interrogate PDCD1 (PD-1), PDCDLG1 (PD-L1), and PDCDLG2 (PD-L2) gene expression in 1,896 human BC stratified by molecular subtype using PAM50 (38). This evidence concerns the gene PDCD1LG2 and breast cancer.