PDCD1 and melanoma: Ishizuka et al. (2019) utilized an in vivo clustered regularly interspaced short palindromic repeats (CRISPR) screen for the unbiased identification of targets that synergize with ICB therapy and revealed ADAR1 as the top candidate gene selectively depleted in B16 murine melanoma in immunocompetent mice plus anti-PD-1 treatment as compared to mice lacking T cells.