It is worth noting that the high expression of indoleamine 2,3-dioxygenase 2 (IDO2), an analog of IDO1, has been reported to significantly correlate with high PD-L1 levels and poor prognosis in NSCLC patients, indicating it will be another innovative target in the future (36, 37). The gene discussed is IDO1; the disease is non-small cell lung carcinoma.