The NAD+ Salvage Pathway Supports PHGDH-Driven Serine Biosynthesis

NAD + is a key metabolic redox cofactor that is regenerated from nicotinamide through the NAD + salvage pathway. Here, we find that inhibiting the NAD + salvage pathway depletes serine biosynthesis from glucose by impeding the NAD + -dependent protein, 3-phosphoglycerate dehydrogenase (PHGDH). Importantly, we find that PHGDH high breast cancer cell lines are exquisitely sensitive to inhibition of the NAD + salvage pathway. Further, we find that PHGDH protein levels and those of the rate-limiting enzyme of NAD + salvage, NAMPT, correlate in ER-negative, basal-like breast cancers. Although NAD + salvage pathway inhibitors are actively being pursued in cancer treatment, their efficacy has been poor, and our findings suggest that they may be effective for PHGDH-dependent cancers.