Metabolic checkpoint CPS1 sustains TCA anaplerosis via urea cycle in IDH-mutant gliomas

Isocitrate dehydrogenase-mutant (IDH-MUT) gliomas exhibit distinct metabolic profile marked by 2-hydroxyglutarate (2-HG) accumulation at the expense of α-ketoglutarate. How these tumors maintain the tricarboxylic acid (TCA) cycle, however, remained unclear. We conducted comprehensive metabolomic profiling using clinical cohorts, cell lines, and patient-derived organoids (PDOs). The metabolic dynamics of TCA and urea cycles were interrogated using stable isotope tracing with ¹³C-aspartate, U5-¹³C-¹⁵N-aspartate, ¹⁵NH₄Cl and ¹⁵N-glutamate. The functional role of carbamoyl-phosphate synthase 1 (CPS1), the key enzyme of the urea cycle, was validated through inhibition experiments in vitro, in vivo and in PDO model, followed by seahorse respirometry and electron microscopy. Metabolomic profiling of two glioma cohorts consistently showed elevated urea cycle metabolites in IDH-MUT tumors. We identified CPS1 as a metabolic checkpoint sustaining TCA cycle through half urea cycle (from ammonia to arginine). Of note, CPS1 upregulation drove fumarate anaplerosis to sustain TCA flux in IDH-MUT gliomas. Thus, CPS1 inhibition not only reduced fumarate levels but also decreased oncometabolite 2-HG both in vitro and in vivo. Consistently, CPS1 inhibition impaired mitochondrial respiration and suppressed tumor growth in vitro, in vivo and in PDOs. Taken together, metabolic checkpoint CPS1 orchestrates half urea cycle to replenish the TCA cycle in IDH-MUT gliomas. Targeting CPS1 represents a promising metabolic therapeutic target for this glioma subtype.