The expression of IDO1 and Ki-67 in tumor tissues was detected by immunohistochemical staining, and the results showed that the expression of IDO1 and Ki-67 in the tumor tissues of mice in the IFN-γ group was significantly upregulated compared with that in the tumor tissues of mice in the NSCLC group (Fig. 6D). Here, IDO1 is linked to neoplasm.