IDO1 and lung cancer: Patients in HRG had high expression of 11 kinds of immune checkpoint genes, including immunotherapy targets that have been proved effective in the treatment of lung cancer, such as PDCD1 (PD-1), TNFRSF8 (CD30), IDO1 and LAG3. This discovery provides new possibilities for HRG patients to provide more effective immunotherapy strategies (Fig. 6D).