Importantly, the regulation of cell fate by PHGDH is unrelated to the rates of serine synthesis, at least in HEK293 cells and in HCCs, consistent with the study showing that the enzymatic activity of PHGDH is dispensable for the development of HCC.71 Therefore, we have found a non-catalytic function of PHGDH, in tumor suppression, as opposed to the previously established tumor-promoting role of PHGDH, which depends on its catalytic function to upregulate serine synthesis (reviewed in refs. 72,73). The gene discussed is PHGDH; the disease is hepatocellular carcinoma.