The clinical importance of IFN-γ expression in cancer was described by Higgs et al. (2018) [57], who found that patients with small-cell lung carcinoma and advanced-stage urothelial carcinoma had a better response to checkpoint inhibitors (PD-L1), indicating that IFN-γ expression may be considered a predictive marker of response to checkpoint-blocking immunotherapies [58]. This evidence concerns the gene IFNG and small cell lung carcinoma.