PDCD1 and neoplasm: Consistently, GSK-3β knockout or in vivo inhibition in mice results in decreased PD-1 expression in CD8 T cells; increased expression of T-bet, granzyme B, and IFN-γ; enhanced CTL function ex vivo; increased tumor infiltration; and reverted T cell exhaustion in an LCMV model (94, 101, 113).