Indoleamine 2,3-dioxygenase (IDO), which is overexpressed in tumors (e.g., pancreatic cancers and NSCLC) and associated with poor prognosis in cancer patients, has been identified as a motivator for cancer immunosuppression via suppressing local CLTs and NKs, thus making IDO a potential target [94]. This evidence concerns the gene IDO1 and non-small cell lung carcinoma.