Cell cycle arrest enhances CD8+ T cell effector function by potentiating glucose metabolism and IL-2 signaling

Cell cycle-inhibiting chemotherapeutics are widely used in cancer treatment. Although their primary aim is to block tumor cell proliferation, their clinical efficacy also involves specific effector CD8+ T cells that undergo synchronized proliferation and differentiation. How CD8+ T cells are programmed when these processes are uncoupled as occurs during cell cycle inhibition is unclear. Here, we demonstrate that activated CD8+ T cells arrested in their cell cycle can still undergo effector differentiation. Cell-cycle arrested CD8+ T cells become metabolically reprogrammed into a highly energized state, enabling rapid and enhanced proliferation upon release from arrest. This metabolic imprinting is driven by increased nutrient uptake, storage, and processing, leading to enhanced glycolysis in cell cycle-arrested cells. The nutrient sensible mTORC1 pathway, however, was not crucial. Instead, elevated IL-2 production during arrest activates STAT5 signaling, which supports expansion of the energized CD8+ T cells following arrest. Transient arrest in vivo enables superior CD8+ T cell-mediated tumor control across models of immune checkpoint blockade, adoptive cell transfer, and therapeutic vaccination. Thus, transient uncoupling of CD8+ T cell differentiation from cell cycle progression programs a favorable metabolic state that supports the efficacy of effector T cell-mediated immunotherapies. Overall design: To investigate the mechanisms underlying enhanced cell cycle progression after temporal cell cycle arrest, we characterized the transcriptional activity in unstimulated, arrested, released and non-arrested CD8+ T cells. To this end, we made single cell suspensions from pooled spleen samples from mice. CD8 T cells were enriched and we had 4 different conditions: unstimulated (60 hours), blocked (60 hours stimulated with aCD3 and aCD28 in the presence of hydroxyurea), non-arrested (60 hours stimulated with aCD3 and aCD28) or released (stimulated with aCD3 and aCD28 in the presence of hydroxyurea which was washed away. These cells could proliferate for 60 hours. Next, live CD8 T cells were sorted (BD FACS aria). For the "non-arrested" and "released" conditions only the cells that had at least 1 cell division were selected on the basis of CFSE dilution. Next, gene expression profiling analysis was performed using data obtained from RNA-seq of the four different conditions.