The expression of LncRNA MEG3, miR-543, and IDO (IDO1, IDO2, and TDO proteins) in the lung tissue of rats using IDO inhibitor was also evidently elevated, while miR-543 was declined compared with that of lung carcinoma model rats, suggesting that IDO inhibitor can obviously reduce the activity of carcinoma cells. The gene discussed is IDO2; the disease is lung carcinoma.