GSK-3 regulates CD4-CD8 cooperation needed to generate super-armed CD8+ cytolytic T cells against tumors

While immune checkpoint inhibitor therapy has transformed cancer treatment, the signaling pathways underlying T-cell function optimization remain incompletely understood. While glycogen synthase kinase-3 (GSK-3) is a negative regulator and CD4+ T-cells provide help for CD8+ T-cell development, the signaling events controlling CD4-CD8 T-cell cooperation are unclear. Here, using GSK-3 knock-down mice (GSK-3KD), we show that GSK-3 is the central regulator of CD4-CD8 cooperation, specifically in enhancing the expression of granzymes necessary for CD8+ CTL killing. GSK-3KD induced metabolic reprogramming toward glycolysis in T-cells and, when combined with PD-1 blockade, overcame tumor checkpoint resistance characterized by reduced Treg TILs and increased effector-memory CD8+ TILs. GSK-3KD with anti-PD-1 therapy induced unprecedented expression of seven out of nine granzymes in CD8+ TILs through enhanced CD4+ T-cell help. These findings identify GSK-3 as a key regulator of CD4+ T-cell help in generating highly cytotoxic CD8+ T-cells, presenting a promising therapeutic strategy for cancer treatment.