PDCD1 and cancer: Anti-PD-1 blockade has been successfully used as an immunotherapy for a variety of advanced cancers, including melanoma.35 Finally, we investigated whether the antitumor effect of Lsp1 deficiency can be further improved by the administration of anti-PD-1 Ab since the two approaches have different antitumor mechanisms: improvement of T cell trafficking versus blockade of inhibitory immune checkpoints, respectively.