Here, a TME associated with higher densities of CD8+ tumor-infiltrating lymphocytes (TILs) with a Th1 phenotype and more clonal T-cell receptor (TCR) repertoire, higher levels of interferon (IFN), IFN-γ-inducible genes, and IFN-stimulated chemokines such as CXCL9, CLCL10, and CXCL11, and high levels of immune checkpoints such as cytotoxic T-lymphocyte antigen 4 (CTLA-4), PD-L1/PD-L2, PD-1, and indoleamine 2,3-dioxygenase (IDO) may predict benefit from anti-PD-1 and anti-PD-L1 therapy [12, 60, 62]. The gene discussed is IDO2; the disease is neoplasm.