PDCD1 and melanoma: Compared with B16-Ova, the non-immunogenic B16-F10 melanoma was significantly less responsive to monotherapy treatments; however, TLR9 agonist (p = 0.0054), anti-CTLA-4 (p = 0.0125) and anti-PD-1 (p = 0.0283) all showed a modest capacity to extend survival (Fig. 2a).