PHGDH and breast cancer: Notably, all serine synthesis pathway (SSP) enzymes, i.e., phosphoglycerate dehydrogenase (PHGDH), PSAT1, phosphoserine phosphatase (PSPH), were reduced upon mutp53 silencing in both BC cells with low (MDA-MB-231)13,29,30 and high (MDA-MB-468; SUM-149PT)29,30,35 serine synthesis capability (Fig. 1c).