PDCD1 and central nervous system cancer: Given that mPD-L1 interacts with hPD-1 and forms a functional immune checkpoint [58] and that the hPD-1HA ectodomain more potently blocks mPD-L1 on murine B16-F10 cells than does the wild-type hPD-1 ectodomain [30], further in vivo experiments are needed to confirm the efficacy of Ad5Δ24RGD_IIIa-IgGκ-hPD1HA (L3-23K) in murine models, including CT-2A and GL-261 gliomas.