Citraconate preserves T cell stemness and antitumor immunity.

Metabolic perturbations in the tumor microenvironment profoundly compromise the stemlike properties and effector functions of CD8 T cells. Deciphering the metabolic circuitry that sustains T cell stemness is critical for reinvigorating tumor-infiltrating lymphocytes and augmenting immunotherapeutic efficacy. Here, we identify citraconate, an itaconate isomer, as a metabolite markedly depleted in CD8 T cells subjected to chronic antigen stimulation or hypoxic conditions. Citraconate supplementation preserves stemlike characteristics, attenuates ferroptosis, and potentiates T cell-mediated antitumor immunity. Mechanistically, citraconate maintains intracellular cyclic adenosine monophosphate (cAMP) concentrations by suppressing phosphodiesterase1A/C (PDE1A/C) expression and preserving mitochondrial integrity, thereby activating protein kinase A (PKA) signaling. This activation transcriptionally represses arachidonate-5-lipoxygenase (ALOX5), consequently reducing arachidonic acid peroxidation. Clinically, diminished ALOX5 or PDE1A expression correlates with reduced T cell exhaustion and improved responses to immune checkpoint blockade (ICB) therapy. Our findings reveal the citraconate-mediated PDE1-cAMP-ALOX5 axis as a potential therapeutic target for enhancing cancer immunotherapy.