To date, others have reported that accumulation of the 2HG enantiomers L-2HG or D-2HG can occur under certain conditions as pathological metabolites in hypoxic cancer cells produced by lactate dehydrogenase (LDH) or malate dehydrogenase (MDH) [30, 37, 38] or as so-called “oncometabolites” as a result of gain-of-function mutations in the genes encoding for isocitrate dehydrogenase 1 or 2 (IDH1 or IDH2) [39, 40]. The gene discussed is PHGDH; the disease is cancer.