PDCD1 and neoplasm: Our data indicate that NANOG induction in tumor cells switched the immune phenotypes in the TME from an immune-stimulatory to an immune-refractory feature by blocking the antitumor immunity cycle via restriction of T cell trafficking to tumors and by cytotoxic T lymphocyte–mediated (CTL-mediated) killing of tumor cells, thereby driving resistance to PD-1 blockade.