Of note, the augmented anti-tumor immune response in Nr2f6−/− mice were linked to a markedly higher PD-1 and PD-L1 expression on CD8+ and CD4+ T-cell subsets in vitro when compared to wild-type animals (Supplementary Fig. 1A–D), suggesting a potential resistance mechanism via upregulation of T-cell exhaustion markers. This evidence concerns the gene PDCD1 and neoplasm.