As shown in Fig. 2b, we detected increased concentrations of L-serine and glycine in bile from tumour bearing rats, ascribable to the activity of the serine-glycine synthesis pathway, a glycolytic side-branch frequently triggered in cancer cells in which phosphoglycerate dehydrogenase (Phgdh) catalyzes the first and rate-limiting step [24]. The gene discussed is PHGDH; the disease is neoplasm.