PHGDH and Ewing sarcoma: The upregulation of the rate-limiting enzyme of serine biosynthesis, 3-phosphoglycerate dehydrogenase (PHGDH), has been identified in a large subset of cancers, including melanoma (Mullarky et al., 2011), Ewing’s sarcoma (Issaq et al., 2020), breast (Locasale et al., 2011; Possemato et al., 2011), colorectal (Jia et al., 2016), pancreatic (Song et al., 2018), and non-small cell lung cancers (Zhu et al., 2016).