PD-1 blockade reversed the increased expression of PD-1 and PD-L1 on human melanoma antigen-specific CTL by Tregs, rescued INF-γ expression by melanoma antigen-specific CTL that were diminished by Tregs, and resulted in the downregulation of intracellular FoxP3 expression by Tregs [90]. This evidence concerns the gene PDCD1 and melanoma.