PDCD1 and melanoma: In order to rule out the possibility that the therapeutic effect of combined anti-PD-1 antibody and miR-21–3p-AuNp is related to a direct effect on melanoma cells whereas not mediated by the immune system, we have performed animal experiments in C57BL/6 mice in which CD8+ T cells are systemically eliminated by intraperitoneal CD8α antibody injection (online supplemental figure S4E).