PSAT1 and cancer: The metabolic features of NRF2-addicted cancers rely on both direct NRF2 targets (metabolic enzymes involved in glutathione synthesis, the pentose phosphate pathway (PPP) and NADPH production), and indirect NRF2 targets, of which ATF4 regulated serine biosynthetic enzymes, (PHGDH—Phosphoglycerate Dehydrogenase, PSAT1—Phosphoserine Aminotransferase 1 and SHMT2—Serine Hydroxymethyltransferase 2) correlate with poor prognosis in NSCLC [105].