PHGDH and lung carcinoma: In human lung cancer cells, NRF2 regulates serine biosynthesis via activating transcription factor 4 (ATF4) and phosphoglycerate dehydrogenase (PHGDH) to support GSH and nucleotide production and coordinately activates the pentose phosphate pathway (PPP) to supply ribose for nucleic acid biosynthesis (29, 107).