PDCD1 and lung cancer: Furthermore, bioinformatic analyses of lung cancer patient datasets from the Gene Expression Comprehensive Database (GEO) and the Cancer Genome Atlas (TCGA) by Yundi Zhang et al. revealed a correlation between SOD3 expression and immune checkpoint molecules, such as PD-1 and Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) [19].