We were intrigued to see that the PD-1 ligands PD-L1(CD274 gene) and PD-L2 (PDCD1LG2 gene) mRNA were among top significant genes that were positively correlated with IDO1 mRNA in lung adenocarcinoma tumors (Fig. 5A, B). This evidence concerns the gene IDO1 and lung adenocarcinoma.