PDCD1 and neoplasm: Our results from xenotransplantation of PANC-1 cells with stably transfected PD-1 shRNA2 into NOD/SCID mice showed significantly smaller tumor volumes in PD-1 knockdown tumors (N = 3 mice, N = 6 tumors) compared to scramble/control shRNA tumors (N = 3 mice, N = 6 tumors) (P < 0.01) (Fig. 5a).