Metabolic profiling reveals pyrimidine synthesis enzyme CAD as a central carbon metabolism signaling node in cancer cell proliferation.

Rapid cancer cell proliferation requires extensive macromolecular biosynthesis, yet how distinct anabolic pathways are coordinated remains incompletely understood. Here, we report that the trifunctional carbamoyl-phosphate synthase, aspartate transcarbamoylase, and dihydroorotase (CAD) activates key glycolytic enzymes to support biosynthesis and cancer cell proliferation. When cancer proteomics datasets were queried, a CAD activation signature was identified in diverse tumors. Metabolomics analysis revealed that CAD fuels central carbon metabolism, specifically the pentose phosphate pathway (PPP) and serine synthesis pathway (SSP). Mechanistically, CAD deamidates and activates glucose-6-phosphate dehydrogenase (G6PD) and phosphoglycerate dehydrogenase (PHGDH), rate-limiting enzymes of the PPP and SSP, respectively, which are fully recapitulated by the glutaminase domain of CAD. Functional interrogation of cancer-associated CAD mutations and human hepatocellular carcinoma tumors predicts the metabolic signature endowed by G6PD and PHGDH deamidation. Simultaneous inhibition of G6PD and PHGDH effectively impeded tumor formation. This work identifies CAD as a central carbon metabolism signaling node and a potential therapeutic target.