SUMMARY Activated T cells engage aerobic glycolysis and anabolic metabolism for growth, proliferation, and effector functions. We propose that a glucose-poor tumor microenvironment limits aerobic glycolysis in tumor-infiltrating T cells, which suppresses tumoricidal effector functions. We discovered a new role for the glycolytic metabolite phosphoenolpyruvate (PEP) in sustaining T cell receptor-mediated Ca2+-NFAT signaling and effector functions by repressing sarco/ER Ca2+-ATPase (SERCA) activity. Tumor-specific CD4 and CD8 T cells could be metabolically reprogrammed by increasing PEP production through overexpression of phosphoenolpyruvate carboxykinase 1 (PCK1), which bolstered effector functions. Moreover, PCK1-overexpressing T cells restricted tumor growth and prolonged the survival of melanoma-bearing mice. This study uncovers new metabolic checkpoints for T cell activity and demonstrates that metabolic reprogramming of tumor-reactive T cells can enhance anti-tumor T cell responses, illuminating new forms of immunotherapy.

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Receptor-mediated gene transfer has been used to introduce genes into tissues ofanimals in vivo. The genes introduced by this approach have been transiently expressed at low levels in animal tissues. Hi levels ofexpression, for longer periods, have been attaine by the induction of cell division (i.e., partial hepatectomy) or disruption of lysosomal degradation of the DNA. We have studied the correlation of specific structural features on the DNA/ligand complexes with their ability to efficiently introduce DNA into the livers of intact animals. A chimeric gene contain the phosphoenolpyruvate carboxykinase gene promoter (nucleotides -460 to +73) linked to the structural gene for human factor IX (PEPCK-hFIX gene) was condensed with galctlated poly(L-lysine) by titration with NaCl, resulting in complexes of defined size (10-12 nm in diameter) and shape. The PEPCK-hFIX gene complex was injected into the caudal vena cava ofadult rats and the conjugated DNA was specifically targeted to the livers ofthe animals; no detectable DNA was noted in other tissues. The plaid containing the PEPCK-hFIX gene was found as an episome in the livers of the rats 32 days after inection of the DNA complex. Human factor IX DNA, mRNA, and functional protein were deed up to 140 days after administration ofthe DNA complex (the duration of the experiment). Transcription from the PEPCK promoter could be induced over the entire course of the experiment by feeding the rats a high-protein, carbohydrate-free diet. We conclude that the structure of the DNA/ligand complexes is of key importance for the successful introduction of genes into the tissues of animals by receptormediated endocytosis.