Since we have previously demonstrated that Ido-1 expression is highly correlated with other immune-suppressive markers in NSCLC (such as PD-1 and PD-L1) [3] and that NSCLC tumors undergone to epithelial-mesenchymal-transition (EMT) are enriched for those markers [12], we hypothesized that NSCLC with EMT features could be the best models to explore Ido-1 signaling. This evidence concerns the gene PDCD1 and non-small cell lung carcinoma.